a few CG tweaking ponderances :)

[tahrey]

So, having passed my test, and finding the CG will actually go a fair bit faster - certainly "fast enough" on the motorway - without the red & white baffles, I'm considering keeping it a bit longer. But some stuff may have to change.

First up, top gear needs to be longer, so I don't end up ruining the engine. I just don't have the self control to keep it in the truck lane, and it's definitely got the power to stay in contention (quite plainly going out the top of the power band on a regular basis).
Options are changing sprockets - was going to do them in a couple thou' miles anyway - or maybe the whole box itself.

I've done the maths on what sprocket sets would change the gearing by certain amounts, and roughly figured what would give both a higher top speed, lower revs and maybe better economy... BUT as I may want a stock (or even slightly shorter - 1st already requires a lot of slipping at full chat) setup in reserve, is it quicker/easier to swap out the front sprocket or the rear one? I'm thinking front, as it's just one cover, and the rear involves dismounting the rear wheel, but I could be wrong.

Also, if e.g. I come up with a couple of alternatives as per the above, that are... say, 13 and 15 tooth front sprocket with *whatever* rear, is there any leeway on chain length? Could I have just a "14-tooth"-spec chain and get away with it being slightly looser, slightly tighter, or does it have to match exactly? I'd have a different chain if I was changing the rear by more than a tooth or two of course, but the front one can change the gearing by a lot with very little actual difference in size.

Also idly looking around stuff on carb tuning and boring out the engine (not going to bother with that for now, if at all), I came across a list of some Honda bikes and their boxes. Now, it looks like one off, say, an XL185 would be a good swap-in for me; there's a 5 speed that widens the 1st-5th range by a bit, and a 6 speed that would give a good starting 1st, high speed 5th and cruising 6th, if I also have different sprockets. But are they, or boxes off other small-block Hondas, in any way interchangable with the CG? If so, is it even conceptually an "easy" job? I know it'll involve getting the clutch on and off for a start.

On that note, I need to learn how to retune the carb. It's not so much flatspot at low RPMs as actually stalling on full/wide throttle below about 3500rpm (another thing to find: revcounter. maybe not for permanent attachment, but diagnostic use). I had thought this was just part of the super-simple carb's characteristics, but further reading suggests it's actually running too lean, and it needs rejetting or something of the ilk. I know NOTHING about this stuff... is it simple enough to learn? It'd really help with pulling away and the like, because I have to slip the clutch to keep it above the point where it dies... launches are occasionally a two-step affair.


Other things I'm wondering about the value, ease and cost of:
* Heated grips (at least, anything more than the £5 ones!)
* Bulb upgrade from 35w - the leccy start model has almost 60w more coming out of its alternator vs the kickstart, so I reckon a 20w brighter bulb is doable...
* Hazard flashers? I can't figure out quite how the indicators work from the wiring diagram, it looks wierd, like the input on one side is the other side's ground or something bizarre like that. Hence if I was to stick in a simple switch that took the flasher relay output and shoved it into both lights, undefined things could happen.
* Crash pegs ... well, it's gone on the ground once and not seen any serious damage, but what of "next time"?
* Bolt-on screen - there's a Givi one that seems to incorporate handlebar deflectors as well. However with the fitting kit it's easily over £120. It'd keep the wind off and bring the speed up even higher... but worth it?
* Side stand + switch, and maybe a kill switch as well. Not really any clear idea how to do this at the moment, least not til I can get the other half of the CBF wiring diagram for a clue how something like that would fit into the whole scheme of things.
(Killswitch presumably goes between crank sensor and CDI unit, but all I can figure so far with the stand is that it feeds into a thing marked "clutch diode", totally crapping on my previous pencil-and-paper attempts to redraw the ignition system to my own ends...)
* Oh yeah ... and sometime when I was adjusting/oiling the clutch, I somehow took out the clock backlights. The left side (speedo) came back when I accidentally knocked the indicator switch (?!) and the telltales work, but the petrol guage remains dark. What the hell might I have done, and how do I fix it, short of pulling them completely and tracing the wires?

Or maybe chop in for a CBF to get the switched stand, H4 lights and PGM-FI (no more carb troubles, AND yet more efficient), then start from the top again

Tips, info, comments? (Other than "sell it and buy a gixxer" )

[P.]

Dont sell and buy another 125..
you will regret it, get shot for about £1000 and buy a 250 if you really want to do motorway and not have much more petrol consumption.

Its essentially a 125 with the bonus of being a bit more suited to motorways.

Ive got a CB250 you can have for a few notes

[tahrey]

mmm, that was another option... but i am kind of in love with the mpg, which is why i went for it in the first place
not looking to change the basic nature that much, just bling it a bit.
(i would have a 149, but they're like rocking horse shit in the uk)

[stevo as b4]

I don't think all the things your asking for or wanting to do are really that achievable tbh! You could possibly go for a +1t front sprocket, if all your riding was mainly motorway, but riding a CG on long distance motorway commutes daily, is a bit committed for the sake of the MPG. You can get nearly 60mpg out of a CB500, and i bet a CB250 or similar would be around 75mpg, so only 10-15mpg less than your CG at best, for a much more useable and safe motorway machine.

If you up gear it too much you will ruin the acceleration and general performance, and i suspect that a +1t front sprocket might not make it much if any more economical, as you'd be in 4th for more time, and struggling on every long hill and headwind in top to stay above 50mph. The std gearing on the CG would for me let me sit at 60mph indicated all the time on the flat. In ideal conditions or without any headwind, then it could at times put 65mph on the clock and keep it up for a bit. Down a long hill flat out and prone, you could just see close on 75mph, but i think you'd be revving it past 9500 to get there, and it's vibey as hell!
The std gearing seems to work ok, as it was very rare on dual tracks, or even slightly hilly A-roads that you'd need to drop to 4th, and it would always maintain 50-55mph, which was sufficiant. Whether that's enough on a congested busy motorway for regular communting is debatable, but then the CG is not the best long distance tool for lots of reasons, and the suggestions of a bigger bike are very well considered IMO!

As for tuning, well it's spending money for little gains as with alot of basic low capacity machines. More cc is a good way to go but then you need to make sure that the bottom end is up to it really. There is i reckon around 13-14bhp to be had from a well modded CG lump at 125cc, and maybe 15-16bhp with a 150/160cc conversion.

The better way to go would be to use a bigger engine if you really want to make a project out of the bike, (not what it sounds like in your post if it's a daily commuter though!). The XLR125 OHC engine would go in fairly easily id say, and you can get a 200cc version of the XLR. The old XL185 engine is doable as well, and it's one of those conversions that i've always heard about, but never seen one for real. The problem is finding a useable XL185 engine now, and i would think most of them would need a major engine re-build to be considered for a reliable daily commuter bike motor. It's around 16bhp, so that would be a nice performance boost but then even though the chassis can probably just cope with 15bhp, the brakes are crap and a late CG125 front end with a disc would be a very sensible mod for safety IMO.

You could definately sell any tidy CG for a fairly decent price, as they are always in demand. Then a small 250cc 4stroke like a CB250, GN250, SR250, or even something a bit more complex like a GPX250 or VTR250, or Hyosung Comet 250, would still be excellent on fuel and running costs.

[Nexus Icon]

https://cgi.ebay.co.uk/1981-SUZUKI-BLACK-GSX-250-/260675540359?pt=UK_Motorcycles&hash=item3cb1791587

Peanuts.

[Teflon-Mike]

If you are of the opinion that removing the rear wheel to change the sprokets is too big a job.... then muggering about with all the rest of the stuff you have suggested is WELL beyond you!

The CG125 has 9bhp. Thats why its ecconomical. Thats why its slow.

You can much about with the gearing to your hearts content, it doesn't have the power to go any faster.... gearing it up will just have the already labouring, tortured motor struggling even more, it would be like riding up a hill the whole time in too high a gear.

You say its a kick-start model... that implies to me its a 6v bike.... in which case the e-start versions generator makes more power becouse its 12v and more powerful to charge the battery for the e-start.

In which case heated grips may not work too well.

The windscreen, also wont do you any favours and it CERTIANLY wont make the bike any more areodynamic, even if it did, that would be virtually NO reccompense for the increase in frontal area, adding drag, reducing mpg and slowing you down.

I have no idea what you are trying to do with the electrics..... but it sounds like a bad idea, and yes, getting a multi-meter and wiring diagram and tracing connections would be the conventional way of finding an e-fault!

As for buying a CBF..... why?

If you want another bike, with better wind protection, 12v electrics, and a bit of speed, then there are plenty to choose from.

If you want mpg, ride it sensibly. My VF1000, which has an unenviable reputation for thirst, used concervatively could, lugging the mass of three CG's around, return 70mpg!

I think your on a fools errand mucking about with the CG... you know enough to be dangerouse, not enough to realise its a bad idea!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[tahrey]

Let's do this in order and I'll TRY to keep it under control. As there's much to reply to, it won't be brief however.

Paddy, unless you ninja edited that, I must have misread. What's the econ like on the CBs, then?
(I'll admit it's not the first time I've been reccomended 250 as about right ... I'm just allergic to the whole going around looking at and buying vehicles thing, but am fairly comfortable tinkering with what I have)


Stevo, don't actually know what mpg I'm getting on a flat out run yet, but lower is lower. I know that running a larger engine at cruise can be more economical than a small one at full throttle, but the motorway stuff isn't all I do (and I haven't even really worked out whether going that way, or through town, is the quickest route into work). Fair amount of city fiddling as well. What I've had so far is about 100 average, pre-test. I'm not really doing "long distance" (to and from my dads, which is Brum to south end of M6, is about the comfortable limit), but it's enough that filling the car is a serious expense and I figured that bike + lessons + gear + insurance would still break even after a couple of years. And when school's in, it's a traffic nightmare.

Still, having those numbers is useful. I wouldn't really want to lose more than... oh... plucking a number out of the air... 15% economy vs what I now get, whatever that will be? Similar in scope to dropping from 36 to 30mpg in the car. Which is actually reasonably significant and requires a change in driving style over the same course, or the start of engine trouble.

If I wasn't confident that it's often undergeared in top, then I wouldn't bother looking to gear up. Besides, if I'm down in 4th... that 4th will be longer. Overall the engine speed and economy should, at worst, be about the same on average, just the shift point changes. And the fairly mild change between 14 and 15 teeth means I wouldn't have been that far off shifting down anyway. The things you describe are why I'm looking to bring it up! I mean, doesn't the fact that you end up being in top gear almost all the time on such a small engine suggest that it could maybe stand, or even benefit from longer legs? The other gears are kind of wasted once you're out of the 30mph zones. I haven't yet found a hill that requires anything lower than 3rd gear to climb (including the steep as f**k Ankerdine in Gloucestershire), and I can't even say that for the cars I've owned.

Not really so keen on major changes, just curious to ask about them as I really don't know that much. I'm comfortable with what is and isn't a major job on a car, but enough of the underlying mechanicals on a bike are alien that I feel like I'm "back at school" almost. I was hoping that a 149cc bore-up wouldn't be too much of a job, but from what I've read, it's iffy and probably not worth it vs the other things I can do cheaper/more easily/at less risk. Certainly dropping a whole different engine in seems counterproductive. But I have a feeling the carb isn't properly set up, and just tweaking that could release an extra mph or two and more low-rev torque.

Though it may be showing my cards, I bought it for a little under £900 and it's certainly not as tidy as it was then, there are things that would drop the selling price and I've had difficulty keeping the chrome up to snuff.


CHR15 - thanks for that. I really had no idea at all whether it would be easy or hard.
But, if a 250 is just as economical, why do the 125s, and this one in particular, have a reputation as being very light on fuel, almost as good as a C90?


Teflon-Mike - Hey now... I don't think removing the rear wheel is too hard. I've had to do it enough times over the past year! It's just a pain, particularly getting it back on without an assistant or paddock stands, and if I was having to do it... say... twice a week (maybe friday and sunday) in order to alter the gear range, that'd be the end of that crazy idea. But if swapping the front one was an easier prospect, then I might just give it a go.

My tech level is good enough to do cambelt/gasket and gearbox swaps on the ol' cage, but I'm both a coward and a lazy bugger when it comes to potentially ruinous or slog-type things on a regular basis

Can you tell me how altering the gearing so it's doing maybe 72mph at a touch over 9000rpm, rather than 70 at closer to 10000 (when the peak power is somewhere around 8500-9000, and limiter 10500-11000) would be causing it to strain harder and labour like going uphill in too high a gear? On the current sprockets it's not even down to peak torque til you're below 50, and not labouring until 40mph or less, so I think I've got plenty of revs and sloggability in hand, particularly as I'm only envisaging a fairly mild ratio change, less than +/- 10% (4th to 5th is 18%). 4th is useless past about 55 on the clock, so if it's having trouble I could shift down. Having that extra power come in at a speed that would save unladen trucks from overtaking me/the engine going pop at an indicated 60 up a moderate hill is another advantage I'd like.

[size=small](The biggest hill on my motorway commute sees the speed level out at 59~60 in 5th right now btw. Going back the other way i've seen 79, probably almost on the limiter, but I dare not do that again. I figure max power - or what would be the 5-6 change point at same rpms as 4-5 - is about 65-66mph indicated but it'll easily exceed that on the flat. As it's an old, 8v design, the power - about 11hp actually, big whoop I know - noticably drops off from peak rpms towards the redline, in fact I don't shift up anywhere near the limiter in any gear... so dropping the engine speed from this down into the power band WOULD make it faster, as well as putting less wear on the engine. This is why overdrives were originally developed.)[/size]

I have actually thought about this a bit and figured how not to overdo it, not to mention doing a similar thing before with an almost as gutless car. Personal experience from someone who's actually tried similar and can actually say yay/nay would be useful

I never said it was a kickstart. It's an electric-start-only 2006 model. This is why I'm confident that there's [s]volts[/s] [s]amps[/s] watts to spare as well as horses. It's got a significantly more powerful alternator than the kick model, almost twice as much. As best as I can make out there's as much as 50w spare with all the lights on (and sparks firing) at 5000rpm (under 40mph in top). Much of that will be just getting shoved out the rectifier heatsink as charging a small lead-acid battery at that rate would be downright dangerous. It's only got about 60Wh total capacity.

What you say about the screen directly contradicts what I've been told from other quarters (well... ok, the awardspace site, which is my only other source, whether or not it's full of BS I don't know). I figure a smooth surface pushing the air around my lumpy body, much as the fairing on a supersports (or the Mallard, which looked like a normal steam train when the swoopy bit was taken off the front for servicing) should help reduce drag, even if the frontal area is slightly larger (unlikely, as I'm almost certainly wider, and taller bars-to-crown than any available screen). In any case, it may be worth it to get the cold, noisy wind off my body, helmet, and by the look of the most appealing design, my hands.

I haven't got a fault with my electrics, or at least didn't before you wrote this (light has now gone wierd). Not sure you're actually paying attention. I have a multimeter, and can take the bike apart to find the stuff if I want, but it seems counterproductive doing all that if either a/ someone else already knows, b/ I can just figure it out in a couple of minutes by tracing my pen around a drawing.

What I'm actually looking at is whether it's possible to plug a side stand switch straight in anywhere, if I get a stand with a switch. There's a mystery unused connector shown on the diagram after all. I could probably go to Maplins and put a breadboard together in a project box that would allow the same functionality, but that's just over the top when there's so many other things to do in life. And would be pricey once all the bits have been bought.
(that said, I have a diagram for the CG itself, and I really can't figure out WTF is going on with the indicator switch wiring... it's either crazy, or genius, maybe both)

Why CBF? It's much the same bike but has 1. fuel injection - a Good Thing for many reasons, 2. slight fairing and small screen which probably helps the aero, 3. slightly more power and torque over a better range, 4. built in, switched side stand, 5. if it doesn't have better lights, it should at least be easier to fit them, 6. still cheap on tax, insurance, fuel, etcetera. Though it does sound tinnier for some reason. (I can't remember whether its 5 or 6 speed though)
Why CBF diagram? It's reasonably similar to the CG, save for the FI, but has the switched stand. It may offer clues. Might not. Don't know til I look.

Ride sensibly ... haha OK. That's going to happen. Not. And will I get similar MPG from a larger machine doing much the same speeds as I would from upgearing and improving the aero of this one? Well... jury's out at the moment. Unless someone can bring me figures rather than conjecture, it might be that I'm the one who has to actually go and do the goddamn fieldwork. (As ever)

And if I only knew enough to be dangerous and was fool enough to run off and do it without considering the implications, would I be asking about all this in here?

All these things btw were looked at as being cheap and - apart from the gearbox proper and engine/carb - hopefully fairly easy mods. I'm not rich of either money or time. Hence not coming back on to this til two weeks after first post. And spending more on a different bike is certainly off the cards, unless it'll cover all the bases for less than the additions/alterations would. (Note that the sprockets were only going to be done when they needed changed as service items anyway). Coulda kicked myself when I overlooked one on ebay originally... because it was a little rusty... but it had topbox, hotgrips and revcounter. Gah.


Anyway I think what I need to concentrate on for now is getting my light working, maybe investigating better tyres, possibly fork gaiters, and some of those cheap & cheerful hotgrips, as the first flush of this cold snap turned my fingers purple. OK, didn't have any undergloves on, but they can only do so much, and the alternative (for me) is winter handroids, which are a whole lot more expensive.

DONE ... I'm SO splitting a query like this in to seperate one-question posts in future BTW. This is crazy even for me

[Paxovasa]

TMI for me.

I have a very short attention spam..

Just get a bigger bike
____________________
Suzuki GSF600 K3 (in the fastest colour, black).

[The Shaggy D.A.]

[P.]

A CB250 was my brothers daily commute before a CB400.
The 250 did the motorway munching all day, sat at 85mph. 70/80 was more than comfy, but hes a *go as fast as I can* guy.

In terms of fuel, £12 a week maybe £15... but its was only really 7 miles there and 7 miles back, half town/half motorway.

I was going to have his old 250, but i'd rather get a bigger bike, so i bought a 500, which in reality is faster than his 250 and returns a bit less on the mpg side...but was much more fun.

[N cee thirty]

cbf's are rubbish compared to the cg

to quiet and slow,+ they look ghey
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[tahrey]

So... let's math. 15 miles, 5 times a week, at about £15. 75 miles for 15 litres. 6 miles per litre. That's 27mpg. Are you sure about that? I had a car that topped out at 90 which pulled 30mpg flat out...

And let's say for the sake of argument the "bigger bike" thing isn't happening, or I will make my judgement of whether to do it on whether my ideas are possible / affordable.

Plus if I was doing this for fun/speed I'd have just bought a gixxer or something already. I enjoy it, don't get me wrong, but that's not the primary focus. I want to do 125mph or hammer around corners faster than I can reasonably see to stop, I can already do that. OK, I have my DAS, but that's more in light of license changes to come, the unpredictability of the future, and blowing money on renting something silly for a day on holiday.

And yeah ... I know. Ludicrously long. I'm fair tempted to copy-paste, break it up into single issue threads, post em and delete/lock this, looking at it.

[P.]

[Livefast123]

As much as people like to view their their first bike / CG 125 with rose tinted specs I think there is a time when moving on is the best thing to do. Sure tuning the CG might be a fun project but it will also make it less reliable and you will spend £££ for no real gain.

I haven't done it but can't imagine a CG would be much fun on the the motorway messing with all the 44 ton trucks

I've got a Hyosung Comet GT250 which i use for my dual carriageway/ A road and sometimes motorway commute. I'm getting 88 Mpg according to Fuelly and can cruise easily at 85 Mph with speeds into 3 figures possible on a private road.

I think it's a case of getting the right tool for the job.
____________________
Current ride - Yamaha MT-07

[truslack]

[jimspeed]

when I changed the front sprocket on my old Hyosung cruise from a 15t to a 16t it went exactly the same speed on the flat but did less rpms. basically a whole 10lbf of torque is trying its best against wind and weight etc.
The Kawasaki 250 I have now cost a wopping £2 more each week to run (in fuel ) than the 125 did on the same runs to work but does just about the wrong side of 100mph and is happy cruising at 85 all day..
if you want free motoring buy a mobility scooter (and charge it up at work but avoid motorways
____________________
Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[P.]

[tahrey]