A forum for owners of Yamaha TTR250 trail and enduro bikes!

TTRfan · Super Guru

Sprag clutch

leigh · Senior Member

Ok makes sense, if they jam on there they probably clunk when they release on startup?

I'll replace to alleviate further damage. Thanks for your help. I had a look at the "how to", fantastic help again Brian.

Cheers.

leigh · Senior Member

I'm about to change the Sprag and reading the excellent "how to" on here.

Do you need a special tool to hold the flywheel to get the flywheel bolt off? Looks like you might, although I'll be using an impact wrench/gun - may not need to hold the flywheel?

Once that's off (I've bought the flywheel puller) is it literally just screw that in and keep going till the flywheel comes off?

Ta

-- Edited by leigh on Monday 11th of July 2016 05:55:51 AM

TTRfan · Super Guru

You won't need a flywheel holder if you have an impact wrench.

Yes - tighten until the flywheel's grip on the taper breaks.

When doing it "by hand" I sometimes tighten up the puller and help by giving the end of the puller a sharp tap with a hammer which usually pops it.

Brian

leigh · Senior Member

Great, thankyou Brian.

Easy.

leigh · Senior Member

annnnnd sorry one more.

I'm guessing to do the flywheel nut back up you have the motor in gear and or rear brake on to do it up? (without a flywheel holder)

TTRfan · Super Guru

Place a suitable sized Allen key into a flywheel balance hole and brace against the bikes frame.

Otherwise I am sure your system will work.

I have an old plumbers spanner that has been ground to fit the flywheel "flats" which makes life a lot easier. These spanners are often in amongst the other old rusty tools at car boot sales and recycling centres.

leigh · Senior Member

Sorted the Sprag last night, pretty easy job in the end (thanks to the instructions on here) and even easier with the 18v Impact gun. Got 2 out of 3 of the bolts from the starter cover, drilled the head off the third one. Strange that they seem so soft.

Otherwise all good, took me a while to find the spare sprag I bought from BM Steve, I managed to hide it in the shed. Works perfectly thanks Steve. I then noticed the decompressor plug was leaking oil, no problem bought one of those from Brian ages ago just in case. Could not find it for the life of me. Wasted a good hour or more searching for it......bought another one this morning from Steve!! Doh.

TTRfan · Super Guru

LOL - the new plug you bought from me will turn up as soon as you have fitted the one from Steve wink

At least that's how it works for me disbelief

leigh · Senior Member

I bet your right!

John L · Member

I'm thinking of fitting a kick starter to my TTR after the starter clutch failed the other day and leaving the electric start disconnected. Can anyone tell me if the failed sprag has to be removed first before the bike is used again. Had this happen on an old T3 Triumph Speedtriple some years back but still used the bike with no issues until it was fixed. The TTR has not run since it failed I might add just in case.

ttr steve · Super Guru

Hi John

You say failed, could you give a bit more detail please.

Steve

John L · Member

Hi Steve. Yes. It has been making a loud bang after switching off for some time and was a job I had marked up to do in the near future, knowing this would eventually happen. When the starter is engaged, it now spins freely without turning the engine over. And it has sounded rough when it was started up in the past. I'm pulling it this Sunday so will have more information as to what has actually happened when I get a look inside. This was a daily user and I'm missing it.

John.

Tarbone · Veteran Member

Hi John,

I can't answer your question unfortunately
However, I just did the sprag clutch on my bike this past week and it's a super easy job!

I too want to retrofit my bike with a kick starter but I'm having a tough time locating all the goodies needed from eBay.

My only pointer that I can provide. Get yourself two decently long M6 bolts to use as pushers to help remove the one way bearing from the hub of the gear!

-Matthew

ttboof · Super Guru

I've only used my kick start a couple of times but have found it a bit awkward and turns the motor over a bit slow so cold starts and awkward hill starts are a pain

Or maybe the electric leg has made me a bit soft

ttr steve · Super Guru

Hi John

Have you found the problem?

Think it is more likely that the pinion is stripped on the starter motor.

mossproof · Super Guru

You may be right Steve, but I found my starter gear would spin both ways without engaging on my project motor. Took the flywheel off and all the "teeth" fell out of the sprag! (Hence my order from the shop yesterday!)

On the kickstarter issue, I've never been able to start it from cold with the kicker. Been close a couple of times but had to resort to a push. When warm it's no problem (usually happens if I leave the ignition on with the lights on for too long) I don't see a problem leaving the sprag in place as long as it hasn't fallen apart, but removing it will lighten the flywheel (faster revving).

Kickstarter parts are harder to find than rocking horse s**t! (And probably more expensive than a new sprag clutch even if you do find them)

Ride safe,

Simon.

John L · Member

After some delay, I managed to get a look inside today. Not good. Upon removing the generator cover, I went to remove the centre bolt and found that it was loose. When removed, the flywheel came straight off. The woodruff will need replacing but my biggest concern now is whether any damage has been done. How on earth has this come loose. I believe they are torqued up to 60Nm. Someone else has been in sometime in the past as I found traces of blue Hylomar near where the wires go into the casing. Could the banging from the sprag clutch shocked it loose. I have not opened up the spray clutch yet.

John L · Member

Sprag not spray. Phone auto spell fail.

John L · Member

As you can see, the woodruff key has sheared leaving half of it in the channel. The other half fell out when I removed the flywheel.

The starter clutch had jammed slightly to the Idler/starter gear boss but was easy to loosen off. It was then possible to separate the Sprag from the large gear. There appears to be no damage to the boss.

Do you think the small idler gear is ok to use again

It's still a mystery how that flywheel bolt came undone.

TTRfan · Super Guru

On first glance it looks as though there is some wear or damage to the small idler gear in which case don't be tempted to re-use it.

What is the starter pinion looking like - is there matching wear or damage?

Brian

JOHNYBOY · Super Guru

flywheel bolt can only come loose because not tightened properley no other reason

John L · Member

Hi Brian. I expected the starter pinion to be damaged as stated earlier by Steve but it appears to be undamaged with all the teeth showing little or no wear. I will be ordering a replacement small idler gear shortly.
As stated by Johnyboy, someone has been in their and not done the job properly.

ttr steve · Super Guru

Looks like you got away lightly smile

All parts are on their way to you.

Steve

John L · Member

Thanks Steve. Some parts arrived today. Waiting for the small idler gear then it's back in the workshop with endless tea.

lostoutbush · Newbie

Hi All, I have picked up a 1999 TTR250 and it has a sprag that is starting to get noisy. My question is can I simply remove the idler gear and use the bike as a kicker only? will this cause any damage? This bike will only be used on occasion and not really wanting to spend money if it can be avoided.

Cheers

TTRfan · Super Guru

Welcome to the forum! I hope you enjoy your TTR wink

If you remove the starter gear then you should cause no problems.

Brian

lostoutbush · Newbie

I have now taken out the idler so that the bike can only be started via the kick start, now the clunk is gone but it is still pretty rattly whilst running. Not sure if it could be the sprag?

I'm not real sure on the background of the bike but got the old storey of it having a top end freshen up.... I may just have to take it to someone to have a look.

And thanks for the welcome, I have been lurking around for a long while and have found plenty of useful info on here.

mmwain · Veteran Member

I don't think this will be a complete fix. The sprag clutch will still be in there with it's broken parts and still going round with the flywheel and will presumably still make the clunk of doom when the engine stops and still wreck the flywheel and other parts if it totally fails, although that might be less likely now it's not being driven by the starter. Maybe a better option would be to remove the sprag? Removing the pinion seems about the same as just not pressing the starter button to me, but a lot more difficult!

mossproof · Super Guru

I think it's the kick-back through the pinion gears that does a lot of the damage, so removing the gears at least prevents the housing from cracking.

mmwain · Veteran Member

I'm not particularly clued up on the damage that's normally associated with this as despite having run mine for about 18 months wondering what the strange clunk was I still saved mine in time! However, from other posts it does seem that you can get damage to the boss inside the sprag clutch. What nobody will know is for sure how removing the pinion might affect things. My best guess is that with no drive going into the sprag it will just stay in freewheel mode forever and give no problems, but there could be something we're not considering that could result in a seized on big gear spinning for ever more or lots of little bits of very hard metal floating around inside the casing so having got that far why not go a bit further and just remove the whole thing? And having got that far why not just spend the money and restore one of the TTRs very best features! It's ability to start on the very touch of the button when stuck in a hole or even after just stopping for a chat is something I would never give up - you're gone before they've even swung their kicker out! The sprag itself is vastly over complex and has no place on a dirt bike but when it's working the overall starting capability of the TTR is almost unrivalled (apart perhaps from some really modern fuel injected bikes that I have no experience of that maybe start that well and continue to do so after being on their side!) and to me that's one of the main reasons why it's such a good trail bike. Handy for my commute in town as well as I know I can filter to the front at the lights, engine off to save the planet, hit the button on amber and still be away just as the green comes on!

So I've changed my mind. Don't take either part out except to replace the sprag. You only live once, why spend it kicking when you could be riding?