1986 TRX 250 Starter Bypass Gear Problems

[Gwbarm]

The one on the right is the one that was in it. Even the teeth have a different arcitecture.

[Mech]

Ho yeah, they are quite a bit different. So the other gear in there must be different too or it would be chewed up.

You'll suss it. If it's not a market difference(thinking starter motors) then it must be some after market I reckon. Those chunky teeth don't really look like what a honda would have..  haha..  maybe. Or a honda mod.. There's probably a "old new stock" dealer somewhere with a set. We have one here called Anaconda.. They have a lot off old stuff.

[Gwbarm]

Iv just got to locate the other gear original honda gear its also unavailable. Strange that it would be so different.

[Mech]

Yeah it's either super-ceded or an aftermarket, designed to overcome some weakness I'd guess.

[Gwbarm]

I was asked one time why have all your problems have to be so complicated, well my answer, if it wasnt for bad luck i wouldnt have any at all. 

This is a perfect example clearly a straight forward fix, instead i find gears that dont match anything i can find and completely does not match anything sold to fix the problem, but when i find that larger gear that is unavailable i should be good. Then i have to find why its shearing the gears and i suspect its the one way bearing on the clutch side not doing its job.

[Mech]

haha. Yeah I'm always telling people that nothings ever simple.

The thing is, that we all need some satisfaction in our lives, and there's no satisfaction in just doing the simple things. We need to do the hard stuff. It's good for us.

[Gwbarm]

Actually found an OEM one way bearing for the clutch side still available the alternator side is not .

[Mech]

Those sprag clutches are really robust and hardly ever give a problem other than getting dirt/grit/metal dust in them, of which it only takes a very minute amount to make them slip, but if they get washed and washed in thin cleaner, like fuel or white spirits, they come clean and work fine again. I've washed heaps in bikes, both clutch and starter, and in auto trans which always have several of them, and they've always passed inspection and gone back in perfectly fine and done their job. I've never replaced a sprag in a bike or auto, and I've handled dozens and dozens of them. Car starters have them but they are sealed and can't be washed, and they get dry and rust too, so different story there, those we replace.

I've talked people in forums into cleaning them, and after they reckoned they washed them good, I convinced them to wash them more and more, with lots of shaking about in clean fuel, and eventually their sprag clutches have come right.

People replace them unnecessarily.

[Gwbarm]

I was going to replace the clutch side because the kick starter is also not working thought they might be related plus these starter gears dont seem to last very long before they are stripped out also thought that might be related causing that problem

[Mech]

Yeah well you're onto it and I'm not there..  haha.

You can test the drive sprag by putting the bike in a forward gear and try pushing it. If the sprag is working, and the gearbox shaft/clutch basket, (which turns with the kickstart), turns faster than the crankshaft(which in this case is stationary), then the sprag should lock and turn the crank. If the gearbox shaft or the kickstart turn the clutch basket faster than the crank is turning, then the sprag locks. That's what gives engine braking at low engine revs when the centrifugal clutch has disengaged. The common symptom of a faulty sprag on a quad is they run away down hill once they have slowed to just above idle speed.

[Gwbarm]

Thanks! I havent ridden the thing in years i will have to ask my brother to check and see if it passes the test. I know the kick starter hasnt worked in years and i was going to fix that for him and thought while i was in there just go ahead and replace that bearing but if not needed would be a waste.

[Mech]

I always aim to change everything that is needed, and nothing that isn't.

There's always something better we can do with the money..

[Gwbarm]

👍

[Gwbarm]

Well finally getting back around to the TRX 250. I found a gear set on ebay . Gears look good hopefully this will solve my problem. Soon as they arrive i will get them installed and smoke test it.

 

 

[Mech]

Fingers crossed...

[Gwbarm]

Finally got back to the 86 Honda TRX 250. Got the starter and the correct gears installed. Everything work great. But it still has this clunking noise when starting, once started everythings good, except it would only run on half choke, hadnt been run in a year and wouldnt start so my brother left gas in the carb, i powered some of my Berryman in the tank and in 15 minutes turned the choke off ran great. I hadnt riden this thing in years and i noticed a few thing when going up a hill if you let off the throttle it will roll back down the hill unless you apply the brakes. Also if it in in gear you can push it backward but not forward and i have no engine braking. So im not done yet, it was supposed to be an easy fix, i think the starter clutch is not working.

[Mech]

Rolling down a hill backwards sounds normal, and being able to push it backwards in gear but not forwards sounds normal, but that "normal" implies the sprag clutch in the centrifugal, for engine braking, should be working, so it's strange the engine braking isn't working because it sounds like it is when you can push it backwards but not forwards. If you put it in reverse you should be able to push it forwards but not backwards if the sprag is working.

The starter sprag must be locking up if the starter can turn the engine, and if it was jammed solid and not slipping once the engine started, then you'd know about that by now, the poor old starter motor would have been doing about six times the revs it was designed for, and it would have almost certainly have blown up..  haha.. or made some terrible noise/vibration/smell.

 

[Gwbarm]

Thaks Mech! It has been years since i have ridden this one and i think the ones that im used to riding are heavier and lower geared and also 4 wheel drive so i may not have noticed the rolling backwards . The noise that i hear during cranking and especially after you let off the starter button thats when its most prominant,i thought might stop once i replaced the al the gears. So something else is causing it.

[Mech]

Oh ok. I have heard a noise like you are describing, a growl/whizzing sound between when you let the button off and before the starter stops turning.. That is quite likely from the sprag, but I've known bikes to do it for years without any troubles..  Your the man on the spot and best qualified to make the call but I think I'd just monitor that and ride it more hoping it either stops or the bike starts starting easier and so the noise gets to be less of an issue. If it persisted load or got worse, then I'd pull it apart and inspect it.

It's possibly caused by the engine reving at start up. I think a lot of bikes make the sound, but we mostly don't notice if the bike starts first press and at an idle. If we use the throttle and it starts with a rev they make the noise longer and we notice.  Maybe. 

[Gwbarm]

Good call ! Those were my thoughts as well, it has been doing this for years but its never caused a problem its just annoying. I am very suspicious of the starter clutch(sprag) biggest concern is if that is what is causing the starter and bypass gears to shear off every few years i need to replace it. I think the one on the clutch side is working with no issues, but i do have to pull that side off to repair the kick starter. 

[Mech]

Yeah I can't think of any way the sprag could damage the gears though, not without over revving the starter motor. I think the gear problem was the starter only working on half the gear width.

There are sprags in car starters and they sometimes make a bit of noise on the over-run but be fine. And they have sprags in auto trans and they get filled with clutch plate and metal sometimes, but clean out and pass inspection to be used again.. They are super reliable things.

[Gwbarm]

The old honda is working great with the new honda gears. It does still make the clunking sound on starting and this is with new gears and new starter. 

[Mech]

You could check the air gap on the trigger coil..A big air gap means the magnet has to get closer to the pulse coil as it's rotating, before it makes enough voltage to fire the cdi. A small air gap advances the ignition timing. At slow(cranking) revs the magnet has to get really close to the pulse coil as it's rotating before it fires the cdi, and that's supposed to make it very retarded at cranking speeds. A big air gap might reduce the knocking when the starter's operating. 

Later model bikes have a signal from the starter into the cdi unit to retard the timing at starter operation, but older cdi didn't have that and relied on the air gap and pulse coil position to set and advance the ignition timing. That bike will be one of the old system I'd think.It'll probably respond to the air gap being changed. Later designs don't respond much by altering the air gap.

[Gwbarm]

Well the little 87 Honda TRX 250 has failed again. Its only been about 3 months and its not used everyday Havent got to it to see what happened yet, brother said it got real noisy when pushing the start button  and  now wont start. Curious to see what has happened i replaced all the gears with original honda gears except for the starter couldnt find an original honda starter in good shape, but i did use a reputable aftermarket Caltric. My suspect is it has sheared the starter gears and metal chunks have gotten into the stator, but could be something else. I think im going to take him my Big Bear to use bring this one home so i can really go through it and see whats going on.

[Mech]

Man that's annoying..  It must be something causing it..  You are onto things so I'm sure you'll suss it eventually..

Could the ignition timing be too far advanced, or, if it's meant to have a start signal going to the cdi to help easy starting, could that start signal be missing/not getting through ? Surely it can't be a mechanical fault, or you would have fixed that by now..