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

bosi · Veteran Member

Aftermarket/substitute sprag clutch

masterbill · Veteran Member

Hello,

In the link you gave you have to search for "sprag clutch Yamaha TTR"

That is only the inner - from what I've read on here you will need the other parts to make a good job.

Also It's in the USA and when you put shipping and Import duty on it - it all adds up .

bosi · Veteran Member

Hi masterbill,
Thanks for reply.

Now I see that these links do not work for some reason. Maybe this works? www.aliexpress.com/item/Motorcycle-ttr250-clutch-ttr250-start-clutch-ttr250-separator/1894894646.html

Yes, it's only the inner, but I hope both bosses are fine. Am I right?
I will know the state of bosses for sure tomorrow.

About shipping and import duties: The item I want is free shipping, and these Chinese shops know how to describe the package, so no import duties are calculated at destination country.

BTW: Any case someone knows if WR450 sprag clutch fits TTR? I saw an auction of sprag clutch on ebay or amazon, where both WR450 and TTR (and some other bikes) were listed as compatible.

-- Edited by bosi on Tuesday 20th of October 2015 10:02:17 PM

TTRfan · Super Guru

Hi Bosi

Thank you for posting up the link. A very interesting and innovative product! If both bosses are OK then, theoretically, replacing just the inner race would be a good option.

If no other member has tried this product then you could be the first! If you decide to go ahead then please let us know if the part fits and works OK.

The Yamaha part number for the sprag is prefixed 4GY which usually indicates it only fits the TTR250.

Brian

bosi · Veteran Member

Hi TTRfan,

Thanks for encouraging me.

About the Yamaha OEM number: yes, it's prefixed with 4GY. But it comes as complete sprag clutch assembly, and therefore the whole part may differ from other models. BTW, in Polish Yamaha it costs well over 200 quid.

To make things more interesting, I saw several 4GY-prefixed parts in for example in XG250 (Yamaha Tricker) parts catalogs. Basically, our 4GY model (mine actually has 4GY VIN, as it's '93) was the first application of the brand new at that time 4GY "platform". This "platform", stripped down (SOHC, 20hp, etc) is still being sold as, for example, Yamaha XTZ250, in South America and possibly other markets.

I am going to visit a local sprag clutches specialist to hear what he says.

BTW, the Chinese product, as you see, is totally different design from the original part. It has only 16 rollers, but they look far bigger, wider and stronger than the 20 original ones in TTR. If its quality is good or at least acceptable, it theoretically can last much longer than OEM part.
Also, I think the design is similar to more modern designs found eg. in WR450.

I will certainly give it a try.

-- Edited by bosi on Wednesday 21st of October 2015 10:34:21 AM

bosi · Veteran Member

So I checked the bosses and they do not look very well :(
But I ordered the clutch from China, and I will try to find a machining shop that will try to repair the bosses. Who knows.

bosi · Veteran Member

The bosses should be perfectly smooth, or should have small teeth for the rollers? I think they should be smooth, so just asking to be sure.

TTRfan · Super Guru

They should be smooth!

bosi · Veteran Member

So my father found a machine shop and the bosses will be ready by the end of this week.
A guy at the shop immediately asked if the clutch is from Yamaha, so they are not doing it for the first time.

So the bosses were machined to 59.14mm (outside) and 41.94 (inside), depending on the damage. A total of 0.20mm per two sides, so 0.10mm per side was taken away.

Now I am waiting for the rollers from China to arrive.

-- Edited by bosi on Wednesday 28th of October 2015 09:30:20 PM

bosi · Veteran Member

The rollers arrived. They look really good. Unfortunately the clutch does not work: it has too much slack, because of machining. It was not a good idea.
Now I am looking for the bosses.

TTRfan · Super Guru

Hi Bosi

Sorry to hear of the problems

I have a used gear and sprag with good bosses. £16 plus shipping if that's any good to you?

What appears as a mark in the photo of the gear boss is actually a reflection of the cut out wink

bosi · Veteran Member

It looks far better than mine after disassembly. I think I will be interested. PMed you.

TTRfan · Super Guru

Any progress Andrzej?

bosi · Veteran Member

The package did not arrive yet :( I wonder what's going on.

TTRfan · Super Guru

Just looked at our posting receipts and the parts were posted on 16th November so should have been delivered by now confuse

Maybe check with your local post office in case they couldn't deliver if no-one at home?

Brian

bosi · Veteran Member

Hi Brian,

The parts just arrived :) Thanks!

It looks very promising: when I put China rollers into it, it seems to work as intended (in my hands for now).

BTW: looks like their dimensions are not metric nor imperial: when I measured them using my old russian Vernier calipers, they are about 58.8 and 42.4 mm. So my previous assumptions about machining were totally wrong.

BTW2: After trying to read Greywolf forum (my Russian is far from perfect), I figured out that someone there is already using China rollers for 10000 km no problem.

bosi · Veteran Member

I put the China rollers and Brian's sprag and gear into the bike last weekend. Did not try to start her yet, as I had to wait for the glue on flywheel/sprag screws to dry.

For future reference: good sprag internal diameter is 58.93-58.94, measured using a professional tool.

bosi · Veteran Member

During the holidays I had some time to finish up and try the bike. It runs very well!!! Thanks to everyone who helped, particularly here - Brian!!!

admbnm · Veteran Member

hi andrzej,
could you give an update on the chinese sprag,is it still ok and problem free,all the best.martin

bosi · Veteran Member

Hi Martin,

I was not riding sice I tested after repair - no time, bike far from home.
At that time it was working perfect, I did not notice any bad signs. Started like 5 times that day.

So for now I am crossing my fingers.

Cheers,
Andrzej

TTRfan · Super Guru

Hi Andrzej

Have you been able to give it a good work out yet and, if so, is it still working OK?

Brian

Sprok · Member

Curious about this sprag as well. Specifically, I'm wondering if it's better than the Yamaha part. I mean we know the OEM part isn't that great so why put that back in if there is something better. :)

Question is whether or not this one is better.

-- Edited by Sprok on Tuesday 7th of June 2016 12:41:53 PM

ttr steve · Super Guru

After-market Chinese sprag clutch

JOHNYBOY · Super Guru

hi steve i would have thought they are made of chocolate same as their bolts etc not as good case hardening only my thoughts may be wrong never tried one same as you i would love to know how long they last

ttr steve · Super Guru

Yeah know what you mean Johnny, tried it with the aftermarket starters and they were made of cheese cry

Maybe the sprags are different

devon_rich · Senior Member

Steve. Ive been running an AHL one off amazon since June 2016. It still works! What more can i say....

JOHNYBOY · Super Guru

steve you need more people giving you good results before you put them in stock devon rich it could be a one off & not a dig at your post mate you may have a good one good on ya pal good information that what steve is looking for but needs more of us to try them only my thoughts for y pal

Kiwioshka · Member

Just how risky is this aliexpress sprag clutch if it does fail prematurely, would it be gradual and with the same warning signs as with OEM part?

devon_rich · Senior Member

JOHNYBOY wrote:
steve you need more people giving you good results before you put them in stock devon rich it could be a one off & not a dig at your post mate you may have a good one good on ya pal good information that what steve is looking for but needs more of us to try them only my thoughts for y pal

No dig assumed. Agree that all parts in the shop should be top quality, correct and risk free. As a tight bastard, but willing to take a risk I decided to try one. That is my experience, which I've shared, it' up to you if you act on it.

devon_rich · Senior Member

Quick update, I think the sprag is now wearing, no clonking but sometimes doesnt seem to engage and kind of slips.

Will take apart this week for a better look, its an assumption at the mo

ttr steve · Super Guru

Thanks for letting us know Rich, please keep us updated.

Kiwioshka · Member

Today I noticed a knocking sound on startup (besides a similar sound when engine shuts-down), its just after the engine bursts into life - is that another sign my sprag needs urgent replacement?
I removed the airbox snorkel as it was running too lean for 1500m elevation mountain summit ride I did, that has made it backfire slightly on overrun, and once backfired on startup hard enough to shake the dust off the carb on start-up - wonder if that sound is related to the carb instead?? ...need to rejet the ttr now as well.

-- Edited by Kiwioshka on Monday 25th of December 2017 09:49:27 AM

TTRfan · Super Guru

A worn sprag or Gear 3 boss can cause slipping on start up, similarly a worn sprag will seize onto the boss if it kicks back on shut down and that might produce a noise on start up - but not sure what it would sound like confuse

If you get a nasty mechanical bang on shut down that makes you wince then it's almost certainly time for a new sprag.

Does your TTR start cleanly with the choke on?

Brian

honda15i · Senior Member

Mine Chinese sprag clutch for US $37.91 died two weeks ago.
purchase details
Order time & date: 22:39 Jun. 01 2017

I bought that crap on aliexpress. Search with title "Modified High quality Overrunning clutch beads Fit For Yamaha TTR250 TT-R250 One Way Starter Clutch Sprag Bearing".
We offer the 1-month free replacement. LoL just one month for High quality item? :) OEM was lasting 20 years!
Now, I see the price is reduced to ~20€

I haven't looked what damaged is done, hopefully the idler gears are not damaged again. Will update later with pictures.

Another high quality alternative for double price and item looks very similar to OEM I found here:
www.aliexpress.com/item/High-quality-Overrunning-Clutch-Beads-Fit-For-Suzuki-DR-250-1995-DR350-1990-1999-One-Way/32812187355.html

I have DR 350 too, So I could takeout the sprag clatch and measure see if it fits to TTR.

-- Edited by honda15i on Friday 29th of December 2017 12:33:25 PM

-- Edited by honda15i on Friday 29th of December 2017 12:33:58 PM

skyrider · Senior Member

that's the trouble seems cheap at the time but long term very expensive confuse

devon_rich · Senior Member

So an update. Got round to stripping the sprag. A couple of hours wasted looking for the puller that I left in a safe place. This is what came out:

Looks lie the roller parts have lost any hardening and are very worn, and part of the casing has gone a tad wrong, backed up by the magnetic drain plug being very clever and magnetic....

In short I do not recommend the AHL unit from Amazon....

-- Edited by devon_rich on Sunday 7th of January 2018 03:56:24 PM

katana · Senior Member

The only reason I can see for the sprag to fail as it does on the TTR is due to insufficient lubrication. What say the experts on the motor?

ttr steve · Super Guru

Thanks for the update Rich.

It is the quality of the metal that is the issue, I had the same problems with the pinions on the starter motors from China. Made from rubbish.

devon_rich · Senior Member

It's a shame because it worked, was quiet, fitted well. Then broke......

ttboof · Super Guru

katana wrote:
The only reason I can see for the sprag to fail as it does on the TTR is due to insufficient lubrication. What say the experts on the motor?

i think regular fresh oil is the key to longevity of the original sprag ,the old saying oil is cheap i change mine in line with the type of riding and abuse so no set change distance /time but probably more often than required (can be a couple of rides or a few months ) , would be interesting to see the history of ones that fail from the forum stories it looks like it tends to be bikes with a bit of age and unknown history maybe the service history has been lacking . (just an observation)

in the case of the Chinese ones it looks like rubbish metal , often wonder why they do it the cost of setting up to sell sub standard parts shouldn't be profitable ?

honda15i · Senior Member

finally i found time to look into the damage.

Alternator wires are dead and six bolts holding chinese sprag are broken!

sprag it self is does not look saized or damaged.

luckly i have spare startor and new yamaha sprag

JOHNYBOY · Super Guru

chineese chocolate mess

TTRfan · Super Guru

Bad luck Arthur! cry

It would have taken a lot of force to shear all six sprag retaining bolts at once. I am surprised the Woodruff key didn't go first.

Any idea how it might have happened?

Was there a bang????

Brian

honda15i · Senior Member

I was driving in the deep forest. When i started the bike I heard loud ticking noise from the sprag. I head a feeling that the death is coming. Couple times more i refired the engine and then while driving it happened I heard load noise at that point i believe the bolts were removed. I shut the engine immediately. Then it did not start anymore.

TTRfan · Super Guru

It's odd that it happened whilst driving rather than on start up confuse

I really can't think how it broke. I can only think the sprag suddenly engaged but, if so, I would have thought it would have mashed the starter gears rather than shear the bolts. Very strange....

Brian

honda15i · Senior Member

chinesse sprag visually looks good. I drained the oil and found one metal small peace. I believe this came from damaged starter gear (I damaged it last summer).

TTR is up and running again.

https://www.youtube.com/watch?v=S0BoIdVzSjs

New starter sprag clutch sound sweet.

honda15i · Senior Member

To let you know. My friends TTR stopped charging. Later on he could not fire up the motor. The starter was spinning freely.
What we found after opening the left case cover - broken bolts holding generator. Generator is damaged by broken bolts.
We found the chinese sprag clutch that was seized. What a mess.

ttr steve · Super Guru

Thats 2 people from here who's chinese sprags have gone bust cry cry

mmwain · Veteran Member

Didn't see this before my recent sprag change, vaguely considered Chinese as have had loads of good experiences with their stuff but decided not to as this is such a complex design requiring extremely high precision and material quality. Feeling glad I did now, although not understanding why Yamaha went for such an amazingly complex design when there is a perfectly simple, tried, tested, cheap solution to this problem! The machining of the individual sprags is unbelievably complex, it looks like something that should be on a space shuttle rather than a dirt bike!