Gear problems on Honda CM 125 Custom (with history)

[hannadarling]

Hi everyone, (Sorry theres ALOT to read, can skip to last paragraph for problem)
I'm seriously disappointed in my first bike, the 1982 Honda Cm 125 Custom.
Ive had it now since last June and Ive only had 3 decent rides on it from the day I got it to now!

Since the very first day I got this its been nothing but hassle and constant problems, one after the other!
In the first month I had the engine pulled out and in pieces on my kitchen table to replace the camshaft, pistons, rocker arms and gaskets (these were the problems at first).

One ride after The carburetor Packed up with rust and grime from the tank which screwed up the performance not letting the bike go past second gear without dying. So I cleaned the tank out as much as I could and cleaned the carburetor thoroughly so thats not a problem anymore.

Then I had the throttle needle getting stuck which made the bike sound like it was going to explode and made it rev without me touching the throttle, fixed that by taking and the needle and just putting it back in (that was weird?)

Then all of a sudden the bike wouldn't start at all so I guessed the battery needed charging but instead of it charging the battery just dried up and left crystals so I had to replace that.

The bike still wouldnt start even with a new battery and it puzzled me and I gave up on it for afew months.. Came back to it as the sun motivated me, I took out the carburetor again and found the valve needle was stuck in position not letting the fuel in which also starved the engine from fuel.

So I cleaned that again, checked all lights ect and just tried to start it and it started! Carburetor pilot screws needed abit of tweeking but it started!!

I took it out for the third time and it was so smooth! But when I got back oil was leaking and some of the engine screws had loosened themselves even though they was torqued up to the specifications? So I tightened them up and managed to snap one of the bolts on the gearbox casing.. Not only that my amazing ride in 8 months resulted in me having a puncture in my back tyre..

That was yesterday by the way, I went back to it today and fixed the tyre by myself with tyre levers and a bike plaster aha

So I thought It was ready to go again today(atleast to test the tyre).. Started the bike up, sounds sluggish.. Left to warm up, didnt improve.. Thought ok well I'll just take it round the block and see it the bike improves.

I started off, first gear down the road, changed in the second gear, the bike doesnt sound good, went to go in third gear and it wouldnt go? It felt like the gear lever was stuck up, so I kept kicking it up and the bloody thing wouldnt go into third gear so I pushed the lever down abit and up again and then it kinda went into third gear but didnt fully go until I let the clutch out 3 quarters way and then it made the clank noise? And then when I was coming to traffic lights I couldnt get it into 2nd gear? So I had to try and pull away in third and I had lots of time to gear down, it just wouldn't budge?!

annoying thing is its not something simple like the clutch needs adjusting or the gear lever is worn, I think it might be the gear switcher thing but I dont know? Hence why I'm on here asking, its been a loong 10 months with occurring problems and I have left alot of other problems that I have had to deal with out of this as its long wounded to read as it is aha

So does anyone know what to do or what it is with the gears??
They work but I have to let the clutch out by 3 quarters and then it kinda clanks into gear, this is after ive put the lever in the gear I want and the gear lever is also getting stuck..

I just want to bang my head against the wall!!

Please help, I will be very appreciated!!!

You must really love bikes to read all that

[Eddie Hitler]

Sounds like the bike is trolling you, hard.

Could be a bent gear selector fork? Have you tried shifting the gears without using the clutch? (Blipping the throttle then changing up etc), may help diagnose any issues with the clutch cable/adjustment/pushrods/bearings. I don't know that bike at all mechanically, just chucking some ideas.

Might just be easier to buy a new engine, or scrap the bike and start again!

[Teflon-Mike]

Sounds to me like the thing needs a lot more than a little TLC.
Lets start at the beginning.

Starter. Poor starting, killing battery. Strip it. Clean it. Fit new brushes. These bikes have self exited ignition. Sparks get electric from the crank spinning, not the battery, and both plugs are fired together, so they only get half the juice each, so like the motor to spin over nice and quick to get them to 'catch'.

They also like nice clean new spark plugs.

Carbs and fuel. Crud getting to carb, ultimate fix is to treat the tank properly with POR15 tank remedy; About £50 for the full treatment with industrial clean, metal etch preparation, and the actual tank coating. Trick is to not take short cuts and do the full treatment as the instructions tell you. Many folk only add the coating, then dont let it cure, then grumble the stuff gloops up the carbs. But do it properly, follow the instructions, and coating seals tank and you stop getting rust down the pipe.

Float needle on PD24 carb is notoriouse for sticking. New needle can help if seat clean, but expect it to be a bit lazy still. Give float bowl a tap with screw-driver to get it to budge, when its playing up, but fix is use. When bike used and given a bit of a thrashing from time to time, it beds in and does its job.

Other wise, carbs pretty robust and doesn't warrant half the attension so many folk give them. Problems usually down stream, in the manifold seals, the valves or the exhaust.

Did you grind/lap the valves when you rebuilt the top end? Are tappets properly adjusted?

And what state is the exhaust in. These motors dont work well if the pipe is blowing or pin-holed, or rotted through before the silencer, or even in the silencer, and exhausts often cause more carburation faults than faults in the carbs.

Gear selector; start with the simple; Clutch and clutch adjustment. If they dont go into gear, its often because the clutch is dragging and not taking load of the cogs.

What state is the oil in? Is it the right grade? When was it last changed? Too think, and clutch will drag.

Often clutch gets adjusted at the handle-bar lever, not the engine case where it ought to be; also the cam and pressure pin can get worn down, so clutch wont fully dissengage. You have to have the primary drive off to check that, so do so after checking cable.

HOWEVER, little clue in your commentary about broken engine screws; the release mechanism is in the primary drive cover. IF the cover is sat 'cock' on the crank cases, or screws aren't tight, then when you pull in clutch, it pushes primary cover away from clutch, rather than pushes clutch plates apart. I cocked up a clutch once, and noticed when I pulled clutch lever, that the primary casing actually 'bowed' out, against a clutch pack that wouldn't disengage. Maybe an area worth a little investigation.

While you are in there you will be able to see the ratchet mechanism that levers the selector drum round. Its not unknown for the ratchet spring to break, which could give symptoms you suggest; or for the ratchet 'pawl' to get worn so it wont grab the ratchet. You'll be able to see obviouse damage with primary cover off, without splitting cases.

If its more seriouse; will probably be a selector fork not gripping the rod; or selector fork bent or broke; possibly the dogs on the gears worn to bludger or mashed. Thats full case split strip job, and possibly easier / cheaper to do an engine swap. But you wont know till you have dug into it.

For inspiration and help; have a look at my profile. List of photo-how to's on Benley engines, but also link to my G/F's 125 Super-Dream renovation.

Its all fixable, if you take a deep breath; expell the frustration, and tackle it all one step at a time.

Whether its worth it, is another matter; but only you can decide that, when you know full extent of what ought to be done.

This is old bikes. You have to enjoy getting spanners dirty and look on 'problems' as 'added fun' rather than frustration stopping you have any.
____________________
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?'

[dydey90]

Out of interest, how much did you pay for this shed charming example of engineering?
____________________
This post is probably not serious and shouldn't be taken literally.
Past: CBR125,ER6f NINJA 650, ZZR600 Current: VFR750

[moonzoomer]

If it was a horse you would shoot it

[andyscooter]

its a 30 year old bike

it needs a bit of tlc
____________________
gilera runner vxr200 (chavped)
if its spelt wrong its my fat fingers and daft auto correct on my tablet

[WD Forte]

Almost as old as my 79 CX and as mentioned
the older they are the more tlc they may need.
Often that may mean putting right 30 years of abuse, bodges and neglect.

Once its sorted though it should be as reliable as any other bike
( mine is)
providing its fixed by someone whos skill matches their enthusiasm.
not some numpty

Forums can be very useful to get tips and tricks but if you can find someone locally
who has some real skill and experience and willing to give you pointers,
you may find you learn more. and you get the bike you want.

'hannadarling' suggests you're of the feminine persuasion ?
and while a lot of these chaps are probably jolly decent sorts
who play with a straight bat,
some may be utter bounders and cads for all we know so a certain degree of caution is advised

If you state your location ( town/area not address!)
you may get someones name put forward who can be trusted
to give good advice and assistance and the only danger will be an outrageous consumption of tea and biscuits
____________________
bikers smell of wee

[Fisty]

[hannadarling]

Teflon-Mike, thanks so much for the deep detail of writing, which has now given me insight of what my next steps will be.

I'll try to keep this in order of what you've written aha

First things first, I forgot to mention I've had to replace the starter motor so the bushes should be in great condition still.

I have replaced the spark plugs also after I rebuilt the engine and have just checked them and they look good still. (Ive also got spares for when they need replacing)

I've sealed the tank (with no short cuts aha) When I found the pivot screw stuck, I didn't know whether to replace the screw or seal the tank but then thought the tank will just fill the carb with crud again so Sealing the tank has done the job. I've cleaned the carb again with more attention to the pivot screw and seating and the pivot screw is now freely working so that's sorted.

I'm going to be honest and say I'm not sure what you mean by grinding or lapping the valves, but I can tell that the tappets have been adjusted to the Haynes manual (manufactures) specifications so it should be correct.

I have followed every procedure for the engine from the manual, well the specifications and torqueing settings anyway, the rest was just common sense to me aha But it was a guide incase I got alittle stuck.

The exhaust is in pretty good condition, no dents or corrosion or unwanted holes, Ive noticed there are two holes on both exhausts at the bottom in the same place.
I believe these are "breather holes", they are definitely supposed to be there anyway aha

Ah, now to the clutch.
I know the adjustment on the clutch cable on the handle bar lever is correct, also down to the engine case is correct.

It rode 3 days ago now (just before I got the puncture), and the engine "purred", all the gears were working fine, selection of the gears worked smoothly, there was literally no problem what so ever until I got home and there was alittle bit of oil from the bottem of the engine.
Fixed the puncture yesterday, accidently snapped the bolt of the gearcase side (at the bottom), started it up and now this?

Could it possible just be that bolt perhaps? And lost that pressure for the gear selection?

Anyway, the oil is the right grade, I replaced it about 4 months ago and topped up alittle yestaday before I started it up. Would The rest of the oil sat in there be classed as clean and new if Ive only ridden yesterday and the day it had got the puncture in the last 3-6 months? That means the oil has only been pumped round the engine twice(in the last 3-6 months).
Would the oil in that length of time go gloopy as no heat has gotten to it and its just been sat there? aha Its a good point you asked about the oil.

I will check the cam and pressure pin to make sure nothing is worn and get back to you on that one.

Definitely going to investigate The crankcase, Ive got to see if the broken bit of threaded bolt is through just the engine side or through the engine and the case, either way I'm going to have to drill it out to fit another bolt in and plus I need to get in there for the clutch plates! That's going to be fun..

Yer, someone told me it could be the ratchet spring, I just wont know till I get it off tomorrow.

The rest I'm sure is not a problem. Though it will be in the back of my mind just incase I do everything above and there is no improvement.

I believe it's worth it, this is my first bike, and I have learnt so much in the last year by fixing it.
Though I'm confident I can fix every problem that comes up, I wish the bike would let me atleast let me have a good week riding it before a problem comes up..
Though I do enjoy fixing the bugger, 8 months is really pushing it with my motivation!

I'll never sell it though! I've put all my determination and money on it to fix the bloody thing I'd never get my money back and I don't want it scraped! aha

Well thank you for the information, I'm very appreciated and glad I can talk to someone that actually knows what I'm talking about aha

I'll be intouch and looking forward for any further replies before or after mine!
Anything I've missed just ask or say
Thanks!

Hanna

[hannadarling]

[Islander]

My OH learned to ride on one of those in the 80s. I thought she was hopeless until I tried it for myself - they handle like shite. Oh and they're sluggish

Good luck with the rebuild though.

[dydey90]

[hannadarling]

[Teflon-Mike]

[inconsequential rant]
I'm in a grump. I have had too little sleep. And on going to have a look at Benley bottom end sat on my work bench, to reply, this morning, 'some-one' has parked a two-wheeled tractor in front of it. Get past that, I got tangled in wires, apparently leading to a battery charger, apparently connected to the tractor. I then got shouted at for going near MY work bench, when I went to shift bits of chuffing tractor wontenly abandoned on top of MY carefully laid out 'job'!

GIRLS! I know that this is the modern post feminist society of equality; but PLEASE, a mans shed is his last bastion! We have let you in... does NOT mean its YOURS!
[/inconsequential rant]

[hannadarling]

Ah, I hope you didnt go through all that trouble just to look for that bolt/screw I was on about because I was typing the wrong component name as I was half asleep replying As you'll find out when you read on, I typed this bit in last..

[lukamon]

[Islander]

[hannadarling]

[Islander]

[hannadarling]

[Teflon-Mike]

[hannadarling]

phhh I checked the clutch plates, teeth on the cogs, detachable bits, even the casing and theres nothing wrong!

Put it all back together, even spent money on the new gasket.

Started her up, checked the gears and guess what?

Still the same.

I'm starting to give up, I can really feel it..

Is there any other idea anyone has to mind before I take a hammer to it?

Only thing I can do to decrease the problem is replacing the gear lever to stop the sticking, but the rest I'm really stuck at..

Appreciate any comment at this point, silly or not.
Thanks

Hanna

[Teflon-Mike]

Well, if its not in the clutch or ratchet, then it has to be in the gearbox, between the crank-case halves, doesn't it?
Selector fork bent, broke or slipping on rod; or engagement dogs on the gears worn away.
Thems your options really.
Question is what do you want to do about it?
Its a dead duck as it stands... you have little to loose pulling covers back off, pulling head and barrels off, and splitting the cases to have a look.
Unless everything in the primary drive side ISN'T 'fine' like you think.
But you can tripple check that as you take it apart again.
____________________
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?'

[bypass2]

what about pushrod seat or pushrod. belville washer fitted right. when fiting the clutch cable to the clutch arm is the clutch arm damaged

[hannadarling]

Ok, today I've gone through a moment of just finding a cheap bike to ride because I cant get my head around the gear problem..

But right now this second have thought why am I going to spend more money getting another bike when it will be cheaper to just suck it up and either strip down my engine again to find the fault and fix or replace it or take my cm to a garage to save the misery..

Lets forget the garage at this moment in time, I'm trying to save as much money as I can.
In total I have spent around £800 for the bike, gaskets and all parts I have replaced, I had a moment of selling the bike to get my money back and start over, but right now Im thinking f*ck it, I CAN do this!

So, my plan is to go through the Manual again, note down all the questions you guys have asked and start from there.

When I did the engine strip down last year, the furthest I could go down to was to the Pistons, I could not for the life of me pull apart the crank case halves, so I will have to take it to a garage from there.

I'm going to reuse the main middle gaskets again unless they are damaged, I am planning on making the side casing gaskets with cereal boxes because I am trying to do this cheap aha

Where the clutch plates are housed, there was no worn, chipped or snapped teeth from the cogs, the arm on the outside and inside (on the side casing) is not bent or damaged in any way, all of the little detachable bits are there and correctly inserted, I'm terrible with component names which doesnt help considering I'm a qualified motor mechanic aha, well I have my moments and todays one of them aha but everything else is how it should be so it probably is the gear box.

I had a ride on the bike to a garage yesterday to see if I could get a gear lever and and see if the guy had any suggestions but he didnt have one nor any suggestions towards the gears? The only useful thing that was said was from one of his customers, who said to use an angle grinder to cut 1mm off where the lever "sandwiches" and get a better bolt and nut to squash the partings closer and tighter or to take off the little cover to see if its restricting the lever in any way, so I'll give that a go.

In the mean time Ive learnt how to ride the bike with the funny gears, atleast all the gears engage still so I can still go a decent speed.

Well wish me luck with the strip down again, time to get my hands dirty

These bikes are not ideal for first bike keepers! Unless your a fast learner and want a HIGH maintenance and very temperamental bike!