Rapidly worsening CG engine noise / hard starting / etc

[tahrey]

Long story short: Horrendous engine noises, which started after the bike was laid up for a month in a damp environment, and rapidly got worse. It seems to have enough oil, hasn't been routinely thrashed to the redline (just the usual medium-high revs/full throttle CGs get) and I can't see what else would be wrong with it. After less than 150 miles of riding since I first started suspecting a problem, it now sounds like the cars do in Grand Theft Auto just before you nudge that final kerbstone and they explode, and although it's still raucous when stopped in neutral, pulling in the clutch seems to alter the tone or even add extra sounds.

I'm not well set up for home servicing, don't have a trailer or know anyone with one, and I don't know anywhere within reasonable wheeling/limping distance that would be able to have a look at it, now the Honda garage that used to be on my local high street shut down, so could do with some educated guesses at WTF is wrong and whether I have a snowball's of being able to DIY a fix.

But, really, there is the aforementioned long story in order to fill in all the details and the usual questions that get asked, so, here goes...


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So, I'm currently looking at a litany of Bad Stuff with the poor old CG (last service, its first "professional" one in my care, was basically abandoned except for the things needed to pass MOT (stand replacement, bar and light alignment) because the garage lacked the time and I lacked the money to have them fixed) - notched headstock, worn tyre, worn wheel bearing, leaky fork seals etc, that I'm building up a "repair fund" for, and was going to come ask about closer to the relevant time - but the worst, most obvious and potentially most damaging has come on unexpectedly and a lot more recently.

It's been stood for a while in a rather damp garage (roof's started to leak with the torrential rain) just being rocked out of the way of the car and back in again for several weeks, because I'd managed to bash my leg up at a party, and because the weather was doing nothing but alternating between "the surface is ok but good luck seeing where you're going" and "visibility's alright but you may as well be riding on ice". Not exactly prime rush hour commuting conditions.

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Came to ride it again once both issues had improved slightly, and it unexpectedly needed a heck of a lot of cajoling to get going again - full choke, lots of cranking and a fair bit of throttle blipping for a couple of minutes before it would even idle on half choke. Didn't think it'd actually keep running for me to get to work and considered driving the car with all my gear on...

Still, it did work, and gradually improved as I rode it that day and the following ones, eventually getting back to the point where it would start almost immediately with no choke even after standing overnight. Just cobwebs and condensation, then, thinks I. A bit odd, because it's basically never needed anything more than a few seconds on half-choke even in the depths of winter, but these are pretty exceptional conditions.

However it seemed a bit noisy ... sounds were a bit rattly, and a bit abrasive, which puts one in mind of oil lack, and also puts the wind up you. Soon as I got home that same day I parked it on the level, left it a couple hours to settle, and checked the oil level. All fine - rather near the bottom of the dipstick but still showing a decent reserve above the "min" mark. Topped it up a little bit anyway just to be sure. Similar case a couple nights ago when I was more concerned, but this time the level was about halfway up.

Throughout this, the noises are getting gradually worse, with me resolving to have it looked at as soon as was practical. Not doing any serious riding missions, just schlepping 13 miles each way to and from work (with one fairly laid back cruise from Brum up to Derby on the cards for this sunday - not any more!).

Generally, the very definition of "mixed riding conditions": lots of mooching along at 25-40mph in tight traffic punctuated with some winding-on of the throttle in top gear for brief periods on the way in (maybe sustaining 60+ for a full minute if I was lucky) and a number of red light starts after idling for a minute. Return journeys more gentle, generally trundling at 30-35 and peaking around 50-55 in the flow of traffic on a 50 limit road, taking an otherwise slower route but with fewer traffic lights and other stops and rarely dropping out of top gear. Apart from one or two forays to the still sort of conservative zone between max torque and max power in first gear when pulling away, I was deliberately short shifting quite a lot because of the noise, using the grunt instead of fully hammering it, and generally being in top by 40-45, even when in a hurry (and 25-30 when not). Certainly, it's been a pretty long time since it's come anywhere close to the actual redline, let alone the rev limiter - there's no benefit in it.

Then last night, heading home, it was already sounding and feeling a bit rough on startup - quite loud and staccato at tickover and low rpm, even some vibration through the bars, and a definite 8:8 cyclical rhythm going on (very weird for a 1-pot 4-stroke!) particularly as the revs rose. However, I had somewhere to be, so I rode about the same on the way back as I had that morning, including reaching 60-65 for a short while...
...and it really didn't like that.

By the time I reached my destination it sounded like a complete bag of spanners and was making additional strange, atonal noises when I pulled in the clutch with any revs wound on. From there I crawled home at like 20-25mph using absolutely minimum power for pulling away and climbing, and chopping the engine entirely on downhills. Tried quickly diagnosing where it may be coming from on the inside with it parked up and idling, but I hadn't a long-handled screwdriver to hand, so the best I could do was "inside the engine/transmission assembly somewhere" before giving up. It certainly continued both with the clutch pulled in / in neutral whilst moving, and when parked.

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Other details...
Engine power throughout was unaffected, apart from that first start where it refused to run properly (stuttered a lot and stalled a couple times on the road before clearing its throat and continuing as if nothing had happened). Possibly a little better than it's ever been, even, but most likely it's exactly the same and it just sounded rortier at high rpm. Certainly, with sufficient run-up, it'd probably nudge an indicated 70 just fine on the level.

Oil is probably past due a change, but not massively so. To this point, before the aborted service, I'd been changing it decidedly in advance of the official Honda schedule, and it would have been basically bang on target had the professional service actually gone ahead. Not many miles (less than 250) have passed since that point - I think I did one trip in and out of work after that, before it got parked for a month, then a further working week. Assuming the garage didn't get as far as undoing the sump plug, it should have a good litre of Fuchs Comp4 bike-spec semi synthetic-ester 10w40 coating its guts - none of yer cheap crap oil, here. A "mere" 14500 miles on the clock right now, too.

Chain and sprockets are due for replacement, but still in reasonable shape and kept well oiled. No idea about the clutch, but it hasn't been slipping or showing other signs of advanced wear. Gearbox has sometimes been a little whiney under load but I've previously been told that's just a CG "thing", and it's otherwise remarkably well-behaved. Spark plug and lead a bit old now, but basically appear to be made out of adamantium...

Quick restart this morning to check it wasn't just some kind of weird hypochondria or one of these problems that goes away when you show it to the mechanic, and I quickly killed it within about 10 power strokes thanks to the frightening racket it made. The volume was a sign of something being wrong as much as anything (though maybe the exhaust is just falling apart as a side effect?). Definitely gonna have to trailer it to the mechanic if it requires professional help.

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So what the hell could this be, given it came on so quickly? Like, probably within 120-150 miles of that first restart; 5 lots of 26-mile round trips, and one jaunt to the local supermarket with a quick cobweb-clearing scoot up and down the local bypass (~3 miles each way, 55 outbound, flat out return) on the way home; haven't even got more than 2/3rds the way down the full tank of fuel it originally had when parked up.

Potentially fixable at home, by a club-fingered, poorly-tooled (random handtools, basically no power tools, no pit, no paddock stands; all I got is a socket set, torque wrench, haynes manual and a hammer) mechanical disaster zone like myself?

The one thing I sort of suspect is the valve clearance, but I checked and re-set it myself at the last oil change, made sure the locknuts were properly done up and so-on. Would it have drifted that much since?

Also, the service centre said they were going to check and clean the centrifugal oil filter and a few other deep-clean sort of things, it's not possible they might have started on that before discovering the other issues and then shoved things back together wrong is it?

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Further thinking: is it possible even that my dipstick is lying to me and there's actually bugger-all oil in the engine, or it's largely turned to sludge? (The stuff I wiped off before checking was still sort of deep golden brown, certainly not black like old car oil) ... because I bet a lack of oil pressure would definitely knacker all manner of components in very short order.

And ... where might be convenient for someone in northeast Birmingham to get to either pushing/coasting, or riding slowly for a short period, that won't be complete cowboys? Bike garages seem few and far between in my neck of the woods, they're all clustered around work instead - 13 miles away.
(Or, can anyone recommend somewhere that can come collect with a trailer or van for free or at low cost? Unfortunately my AA membership doesn't "yet" cover bikes, so the usual ruse of hobby-horsing it a half mile away and then having them tow it to the nearest garage is off the cards)

I know a wall of text is unhelpful in these situations, so I may see if I can do a quick recording and shove it on youtube or whatever.

Cheers Ta....

[Boxing]

Another bad spark plug I presume.

Unless someone hasn't been letting it warm up before pulling off.

But yeah, bad noises and hard starting do sound like a spark plug issue, take the spark plug out if it's black, try cleaning it first and then see if it improves, still buy a new one and replace it if it's black / dirty.

Usually if you don't let it warm up, the engine plays up when it's warm (won't start / stay running when warm). Learnt my lesson when I was young, on a 49CC Mini Dirt Bike.

[jjdugen]

That level of noise and vibration will be a little more than a plug change, more like a big end or main bearing collapsed. Definitely dont run it until you have had conformation, you coud end up wrecking the whole engine.
Its an easy enough job to take the engine out needing minimal tools and basic common sense. Easy enough to strip too. Might be worth doing that and taking it to a mechanic to repair.
____________________
The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
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[DMCpro]

buy a new spark plug, change your oil, clean the gauze and adjust your valve clearances
____________________
Honda CB-1, TS125X
VW Golf Estate

[Timmeh]

No way will a dirty plug cause horrible noises. That is just bollocks, frankly.

Drop the oil, if it's shiny or has bits of metal in it then you'll have to rebuild it.

If it's a top-end rattle then it might just be a broken valve spring.
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[DMCpro]

[tahrey]

OK, I'll try to write this without taking whatever meds I must have been on for the original post...

Switched the spark plug anyway in-between, as I had one hanging around spare and I was out checking the clearances. Oil level good, didn't change it but have topped up with clean stuff to the max mark on the dipstick. Valve clearances fine - in fact, so spot-on that I didn't even need to adjust them this time. Forgot to check the air filter, but it's always come out pretty much clean as your maiden aunt's tablecloth every other time I've home-serviced the bike so I doubt this is much different - ditto the oil filter.

Put it back together, let it settle, started it ... engine still sounds like someone's put a toaster in a washing machine and put it on a moderate spin cycle. It doesn't even sound brilliant when cranked with the plug disconnected.

Had a look through the Haynes for what it could be (reading up the suspect problems direct instead of using the practically non-existent "fault finder" this time), and their description of a big end or main crank bearing issue looks about spot on. It also gives a method for each - variously "take it to a dealer, they know how to do it" and "hahaha like you're going to have any of those kind of tools if you live in a flat and don't fix bikes for a living", along with a warning that if you suspect such a fault you shouldn't run the engine other than for diagnostic purposes else it could well break the connecting rod and/or crankshaft.

So... hmm. Bollocks. What now?
Anything I can do myself? New engine? Find a local bike garage? (Recommendations? My normal one, as previously stated, is at least a half hour's ride away, probably a full hour if I limp there at 20...)

I maybe wasn't as excruiatingly kind with it as I could be, but I have always used as good a grade of suitable oil as I could get hold of, and changed it well ahead of the schedule. And even just turning it over a few times on the starter with the rocker cover off saw me getting a little oily as it already welled up in the main oilway and started to spill out (and I could very easily blow through the upper galley in the rocker cover itself) ... so even though I was often giving it full throttle within about a half mile of setting off (a twisting access road from the little estate my flat is part of, then an often congested 30mph road, then leading to a difficult right turn onto a 40mph DC), I doubt there would have been much problem of oil pressure build-up or it being poorly lubricated... and I short shift it a hell of a lot.

The only problem is the short top gear and its rather surprising state of tune combine to a rather unfriendly sustained-rpm scenario on quicker roads, but by that point it's definitely warmed through.

It's not exactly like the stories you hear of CGs being run loaded to the gunnels for 50,000 miles with no servicing or warm-ups at all and only needing their centrifugal filters cleaned at the end of it :p

Cheers anyhaps...

Hmm I nearly wrote Gaynes back there. I think that's a more fitting name.

[lukamon]

I too enjoy the famous Haynes optimism of " ideally you need a 5 ton press and lathe to do this job but you can also make a tool out of 2 tin cans and a kerfulffle valve"
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[tahrey]

[russell210276]

hi the hard start could of been or could be water in the tank from the condensation which normally forms when the bike has been stood and the fuel tank has been left half empty.

for the noise while the bike is idling if you can hear the noise get a screw driver and place it at different parts of the engine and put your ear to it to pin point where the noise is coming from bottom of the engine would most likely be the big end bearing, top of the engine could be piston slap,bent valve springs,bent rods.

if you feel comfortable wip the topend off and pull the rods and have a look at the head.

i had the sound like a bag of spanners in my old engine but it was (chinese) stipped the engine down to the cases and had excessive free play on the crank.

if its the same with your bike i wouldn't continue riding it as it can cause the conrod to fracture and break in the engine and cause some really damage from the play in the bearings. good luck russ

[tahrey]

Cheers for the input but that's basically where we're up to already

I did the arsing about with a screwdriver-stethoscope ages ago now and it did very little for me other than scratching the surface ... literally.

Whilst there's half a chance it might be bent rods/valves etc, given that it runs just fine ... no lack of power, no excessive consumption etc, just very noisy... and the clearances came out bang-on spec, I doubt it. Signs at the moment point to it being a crankcase problem, either the big end bearings (something I can't do myself, AFAIK), or the mainbearings (ie your bit of "excessive free play on the crank"). Seeing as the latter will still require pulling all the engine apart to get at the bits and then pratting about with improvised tools and possibly a combination of blowtorches and icepacks, I figure I may as well get a replacement bottom end or crank assembly off fleabay and have a garage do the work for us, even if I have to remove the engine from the frame myself first.
(Or I could even see if they're able to source the parts...)

Of course, my luck being what it is, the Birmingham Used Parts Exclusion Zone is once again in operation, and my current "best bets" are either in Durham, Yeovil, or quite literally Land's End. They're cheap, but of unknown quality, and it's four hours drive each way to check them out and/or collect... because only one of them offers any kind of shipping rather than local pickup.

(Or, I could just buy a replacement, Chinese-made engine for £300-400... O_O)

[russell210276]

what ever you do dont put a chinese engine in i just got rid of my chinese bike had it 3 years and 2 engine later both with the pushrod engine first engine bottom end went after 3000 miles then put the 200cc engine is which was also the pushrod and the bottom end was starting again at been noisey so i got rid a friend of mine is currently going through court as his engine only lasted 600 miles before it shit its self

[tahrey]

Might go put a bid on the spare crankshaft assembly I saw on there, then...!

I've called a few garages and one of them finally bothered to both a/ answer the bloody phone and b/ not fob me off to somewhere twice the distance away ... problem is their mechanic was off on hols and won't back til monday. Feck.

So I guess I'll be coasting down there (it is at least very nearly downhill all the way, with just a couple of small rises and a mile of flatness to deal with) for them to listen to, probably tut and drawn breath through teeth, and then either leave in their care or ride gingerly uphill all the way home after...

Were cheeky enough to ask me to call before I set off in case he was then off on a recovery job, but ummed and ahhed when I asked whether they would be able to come and pick mine up on a trailer as well. Wondering if I might be as well to just remove the engine and truck it down there in a backpack on my pushbike along with the carb and a sippy-cap water bottle with a couple shots of petrol in it...

[karthead]

Depending on how accessible the engine is, you could just whip out the engine and do a whole engine rebuild, which is good because you dont need to keep rebuilding one part of the engine, when the problem lies in a different part. Just take it all apart, replace necessary parts, put it back together, chuck it in, and you're ready. Shouldn't be too much of a task if you have a good idea of what you're doing. Might also do with a tune up after the rebuild.

[Shaft]

You've got enough tools and mechanical wherewithal to do basic servicing (including valve clearances) and a Haynes manual, so why don't you tear the thing down yourself?

4T engines don't get any simpler than the CG, hell, Third World mechanics rebuild them with not much more than a penknife and a nearby handy twig!

You can't make things any worse and, even if you do, the cheap Chinky copy motor is still an option.
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[tahrey]

*sigh*
RTFT

1/ The very Haynes itself says that I cannot replace the big end bearing myself. It's not even that it gives it a rare six-spanner rating and says "we cannot stress highly enough how bad an idea this is, but if you insist, here's how" - it simply declines to give a method and says to take it to a garage. The reason for this, it turns out, is that... well, the bearing can't be replaced and what the garage will most likely do is just replace the whole lot and charge through the nose for it. That or they'll resort to some arcane method involving blowtorches and liquid nitrogen to separate the old crankpin from and then place a new one within the prison between the flywheels... because the tightly-held (pretty much cold-welded) crankpin IS the bearing shell.

2/ I'm mulling over whether to take the engine apart and replace the crankshaft (or crankcase assembly, even) outright, but even so, having tried to follow the method through in the book - which wasn't particularly clear, as it gives plenty of different atomic procedures but doesn't tie them together into any kind of integrated whole, i.e. "if you want to do X, then you will need to do A, B, C, skip to F, and also K and L first"...

ergo I don't properly know what I'd have to do in order to take the old shaft out and fit a "new" one (assuming they're even all interchangeable, which I fear they may not be)... and there are at least a couple parts which demand things like either a slotted spanner thing or the infamous "home made tool", or flywheel pullers et al, which I simply don't have, and wouldn't know what to do if I bought one, as the Haynes doesn't say what to do and on previous inspection of them there's no instructions.

So I'd either be guessing blind at how to use a bulky, specialist tool on a rather crucial bit of the engine of a vehicle which I may soon need as an alternative to the other one I own, which has its own problems, so I can get to work and back during the busy september period where I can NOT (and I mean, seriously, NOT take any leave), or finding myself signing up for a nine month mechanical engineering evening class college course in order to understand what to do when what I really want and need is my bike back on the road within a couple weeks - preferably sometime in the coming week.

3/ Really, if I've got feeler guages and the requisite three or four different spanners and hex bits to change the oil, sparkplug, rear wheel, adjust chain slack/wheel alignment, pop the rocker and inspection covers off, turn the engine to TDC and turn a couple more bolt-heads on the valves, then I've got the necessary tools to do a full strip of the engine including taking off the head, dismantling the crankcase and replacing (or even servicing) the crankshaft assembly, then putting it back together? And I'll be able to do that either in my dinky kitchen, modest bathtub, or unlit garage without a workbench or running water, two minutes walk and two flights of stairs from my flat?

Please enlighten me to the method, because just a cursory flick through that section of the manual suggests not.

Plus I'd have to go get hold of fresh head bolts and a set of gaskets at the very least. And spend a load of time I currently don't have.

I might be up to dropping the engine out of the frame - MAYBE. If I can scrounge up some bits of wood and some bricks from somewhere to serve as a makeshift bike stand and something to stop the engine from dropping to the floor when I undo the final bolt. But after that, I'd prefer to entrust it to a seasoned pro who may, if I'm exceptionally lucky, happen to have a spare CG bottom end hanging around that can be swapped straight on for the price of the part and a couple hours of labour. Then I bolt it back in.

Besides it's not even entirely confirmed what the fault is yet. It's still only a suspicion. Part of the service is having them check it over.

I have indeed buggered about quite heavily with engines before, and when I first started looking it up I was hoping it may be something along the lines of "Drain oil and remove sump. Undo bolts holding big-end clamps to conrods, withdraw clamps, slide out worn bearing shells from clamps, and then from rods after slowly and carefully turning crank to get clearance. Insert new bearing shells. Lubricate well with fresh oil. Turn crank back to where it was and bolt the big ends back onto the conrods. Replace sump. Refill oil. Turn engine by hand a couple times then start and allow to idle for a few minutes. Ride gently for the next 100 miles." - That, I would have had a go at, particularly as it was only one cylinder so I could have set it up on the ignition stroke and not had to worry about valve crash. However the actual method is far more involved, particularly as there is no such thing as a replaceable bearing in these engines.

Also, last time I did such buggerage, it was 13+ months ago, and I had the benefit of a large, lit garage with electrical sockets and good headroom, attached to a house with hot running water on demand, and plenty of room to prat about either indoors or out, including a back garden patio with a table that doubled up as a rather basic bench. Even that is no longer available.

And beside the socket sets and screwdrivers, despite my best efforts to try and intelligently expand it, my toolkit always ends up looking rather sparse when it comes to such things. Partly because I don't have and probably will never have the necessary metalwork drills (though really it'd need a drill press), bandsaw/keyhole hacksaw, vices or welding gear to fabricate the suitable DIY tools it always mentions, because I'd have nowhere to put half of it, wouldn't know how to use the other half, and some of it costs almost as much as a typical trip to the garage in the first place.

Also, the third world mechanics? That's their bloody job, and they've learnt that craft pretty much as an alternative to school as they were growing up. They could do things with that penknife and twig with their eyes shut that would make a westerner weep tears of pure joy and terror all at once. I have a job already, and, unfortunately, it's not fixing bikes or working in any other kind of engineering workshop. My schooling was resolutely dull, including being part of the group which never even got to do any serious metal or woodwork in the school's D&T centre, pretty much because the teacher didn't like our faces as far as I can tell. We were shown the drill press and belt sanders and told to stay the hell away from them, and that was about it.

No I don't know what I'm doing, most of the parts involved here are alien to me other than the piston, upper conrod and piston rings. Oh, and the oil. I've not had to deal with pushrod valves before, with carburettors (the "tuning" thing is quite possibly beyond me, I try to read up the method and my eyes go crossed; FI tuning? Fine), integrated big end flywheels, engines where you might have to dismantle the alternator, clutch and part of the gearbox (all with particular special tools, plus another one for the oil filter/pump combo) in order to get at the crank, and mainbearings that are stuck on the crank itself instead of being stuck in the crankcase, and so require putting the crank in a vice (which I don't have and don't have anywhere to mount, not even a B&D workmate should I have anywhere to put the blessed thing as once the car, motorbike and bicycle are in the garage, and all the existing tools are back on the shelves I already put in, it's full) before whacking it with a leather hammer (also don't have and have never seen for sale).

And somehow it seems I have to often crank out this life story multiple times per question.

I mean, thanks for the positive words of encouragement, and the confidence - seriously, it's pretty neat - but it's just not practical right now. I'd love nothing more than to have a coupla three days stripping the engine out, taking it apart, learning how it works, seeing how all the bits integrate with each other, fixing it myself, and having the joy of hearing it fire back up fully working in the frame knowing that I did that just by myself and with the help of some anonymous lovely people on the internet and behind the typesetting machines of a paperback repair manual - much as I've done an increasingly long time in the past now (EGR clean on the car excepted - but that was a/ fairly simple, b/ rather fruitless, and the eventual repair came after a specialist traced a fault in a part I didn't know existed, and c/ done in the bloody rain in january and I froze my tits off) ... but, it's just not practical, much more so for having looked at the method, and it's not what I'm looking for now.

Like I say I might, might lose a future weekend to swapping the crankshaft in its entirety if I'm desperate and having a garage deal with it seems either super-expensive or a no-go, but that's probably the end of it.

[BigGeeking]

./
____________________
Bendy "Flip front. I can filter down the M4 while shoving a Twix in my face."
honda CG 125 2001 SOLD-- current Bandit 400--SOLD. current SV650s 2000
MOD 1 ON 20/7/2011**passed** MOD 2 ON 17/10/2011***passed***,,

[tomh]

Hi sorry to hear about the problems your having with your CG. Have you got a video of the symptoms? Also does the loud engine noises happen still if the bike is in neutral and on the stand or only when riding?

I also had what I believed where engine issues with my bike which caused grinding noises at high rpm and a horrible vibration through the pegs but there was no effect on performance/acceleration. After considering rebuilding the engine after being scared to ride it any further I found the problem was that the swingarm had no grease on the spindle and that the bolt was too loose. The foot pegs were also only hand tight.

So before considering striping the engine I would check all major fasteners on the bike for looseness, especially the engine mounting bolts. It could also be a leaking exhaust although that is more of a constant tapping/clicking sound.

As for the being unsure on rebuilding the engine, this video will give you a rough idea of what is required: https://www.youtube.com/watch?v=XNX1Im0CBhc&sns=em

Edit: The grinding noise would be the worst when I pulled the clutch, the higher the rpm the louder the noise.

[tomh]

Just seen this on eBay and not to far away from you?

HONDA CG125 BRAZIL 1993 - BOTTOM END OFF ENGINE - CG 125 BRAZIL

https://bit.ly/P8ybgq

[tahrey]

Thanks Tom - I will check those out first and see if you've clocked something both I and two different garages missed (no sarcasm - it's happened before enough times).

As for the bottom end - probably would have been just the thing, unfortunately I was at the other end of europe with no web access when you posted that!

[tahrey]

Very very very late follow up...

In the end, suspicions confirmed - it's some kind of bottom end bearing issue. Whether the big end or the crankshaft itself, I don't know. But I got a replacement one off t'eBay, and just when turning the two of them over by hand the difference in smoothness and noise was stark, the replacement was a lot easier to turn, near silent and almost silky vs the old one.

Did the swap job late october / early november in my mum's garage. Not the smoothest of jobs - broke a few tools, had to modify some part (I forget which ... I think a bit of the generator/gearbox cover?) with a dremel to get it to fit, as well as bend the chainguard mount slightly. Part of the issue was that the new bottom end was off an XR125, the only supposedly compatible part that didn't cost both legs, an arm and a couple of fingers. It mated up almost perfectly ... apart from those two pieces. The reason behind them being that the front sprocket doesn't sit in entirely the same place, but is a few millimetres displaced further out from the frame than the CG one. It also has a different spline, so I now have a spare CG front sprocket (15t) if anyone wants it...

Oh yeah and some other piece needed to be spaced out with about six random washers before it would do up tight, and the engine's only held in with three of the four through-bolts. Still haven't worked out if the problem is down to the hole being blocked with the rusty remains of some other bolt (looks like it?) or that the XR just didn't have a thru-hole in that place (despite having the mouldings for it), but I must have spent two or three hours trying to drill through and getting nowhere.

In any case it's back together, and it works, very nicely. There's still a few things I have to clear up - I think the carb is set a little rich (not really sure how to fix that, but the only problem it really causes is occasional hard starting and the odd backfire on over-run), I -still- need to change the rear sprocket and chain (was going to do it at the same time, but after I got it to turn over I was summarily kicked out of the garage and there's not been a clear oppo to do it since), and the exhaust just fell apart... but that's about it

[tomh]

Nice to see you've nearly got it sorted All the bolts holes are the same on the XR bottom end so it will be the remain of stuck bolt,

Also take note that a few of engine mount holes are a larger diameter on the XR although I cant remember which ones of the top of my head but maybe see if there's room to enlarge to holes in the frame to mount the engine more securely.

[prawny1]

I take it the centrifugal oil filter was never cleaned on the old engine.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[bikenut]

any chance of some pics of the dead engine bits..........and insides....
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nuts about bikes