My 03 FSE450 has a new interesting problem, seems the sprag clutch isn't making enough grip to spin the motor thru the compression stoke. I have pulled it apart and it has no cracks or broken parts. The valves are in spec and the auto decomp is working. It spins at about 25 psi compression.
Can a sprag clutch wear out?
- Thread starter racepaul
- Start date
iancp5
New member
Never heard of that. Have you watched it with the casing off to check it is the sprag not a gear damaged or misaligned?
You can buy sprags from some engineering suppliers at about a 1/3 of the price from GasGas.
GasGasDreamer
Platinum Level Site Supporter
it is possible that the sprague can wear out. what i think usually happens is the decomp wears out so you dont get the right amount of lift but more important than the amount of lift is the timing of the lift. just my experience from non-gasgas four strokes
I?ve had that same problem for some time now when it?s cold weather. Well today it completely stopped spinning the engine, only the startmotor spins when i press the start button.
It was guite a problem because my kickstarter doesn?t work and I was about 5 kilometers away from home. I got the bike running by pushing it but it was a lot of work because of icy roads.
Does anybody know if some other bikes parts fits in? It?s hard to get GG parts here in Finland(And the original parts are also over priced). I happen to know that DR-Zs ignition clutch doesn?t fit... It might be fittable with some work but I?d rather buy straight fit part...
It was guite a problem because my kickstarter doesn?t work and I was about 5 kilometers away from home. I got the bike running by pushing it but it was a lot of work because of icy roads.
Does anybody know if some other bikes parts fits in? It?s hard to get GG parts here in Finland(And the original parts are also over priced). I happen to know that DR-Zs ignition clutch doesn?t fit... It might be fittable with some work but I?d rather buy straight fit part...
Cold weather could cause the grease to get hard and prevent the sprag from working properly. Did it work right once it was warmed up?
Yes, after warming up it worked fine. But now it doesn?t work at all, no matter of temperature. I?m pretty sure that I need new starter clutch. I rebuilded the engine last summer and it was pretty worn looking already then.
I have used sprague clutches on packaging machines for years. They do eventually wear out. The sprags develop a small flat spot that keeps them from rocking into lockup. It takes a long time for this to happen.
There is normally a spring around the perimeter of the sprags that holds them under tension. This tension provides the grip so they respond quickly. You can get a bit more life out of them by shortening the spring but it's tricky to get right.
Thick, cold oil will make it harder for them to lock up. If you ride in cold weather, thinner oil will help. Usually there is some sort of slip clutch in the starter system that loses friction as time goes by. The slip clutch is often what gives trouble well before the sprag clutch. Some slip clutches can be taken apart and shimmed for higher torque.
There is normally a spring around the perimeter of the sprags that holds them under tension. This tension provides the grip so they respond quickly. You can get a bit more life out of them by shortening the spring but it's tricky to get right.
Thick, cold oil will make it harder for them to lock up. If you ride in cold weather, thinner oil will help. Usually there is some sort of slip clutch in the starter system that loses friction as time goes by. The slip clutch is often what gives trouble well before the sprag clutch. Some slip clutches can be taken apart and shimmed for higher torque.
A sprag clutch is primarily an over-running device. It allows one element to be stationary while the other rotates around it. The sprag clutch is needed to let the drive gears spin at motor speed when the engine is running (while the starter gear is stationary). Thus the over-running function.
Note that cam shape of the individual sprags allows lockup when the starter motor is driving the gearing. Sprag clutches are also known as one-way clutches.
A bendix style starter arrangement has the gearing move into engagement while cranking, then it moves back to release when the operator stops using the starter button.
Note that cam shape of the individual sprags allows lockup when the starter motor is driving the gearing. Sprag clutches are also known as one-way clutches.
A bendix style starter arrangement has the gearing move into engagement while cranking, then it moves back to release when the operator stops using the starter button.
Mine went on my FSE400 , the engine was just spinning over.
My solution was to get rid of the bike as i was sick to death of trying to find spares and them costing a bloody fortune.
As much as i loved the bike im glad its gone. Still have Gasser trials bike so not a complete turncoat 
My solution was to get rid of the bike as i was sick to death of trying to find spares and them costing a bloody fortune.
As much as i loved the bike im glad its gone. Still have Gasser trials bike so not a complete turncoat I just ordered a flywheel puller so I can take my starter mechanism a part. Had to got my flywheel taken out by shop last summer when I rebuild my engine.
I found out that Stieber makes all kinds off sprags and they are alot cheaper than OEM part. I am going to take my Gassers sprag to local bearing dealer and replace it with stieber clutch, if there is a same size and torque available.
I will post how it goes and tell the part number if I find a replacement that works.
I found out that Stieber makes all kinds off sprags and they are alot cheaper than OEM part. I am going to take my Gassers sprag to local bearing dealer and replace it with stieber clutch, if there is a same size and torque available.
I will post how it goes and tell the part number if I find a replacement that works.
No luck with stieber freewheel. Now my gassers parts are at metalshop and friend of mine who works there is going to fit DRZ sprag to my gasser parts. I'll get parts back next week and will post how it goes and what had to be done...
I refuse to pay the gasgas origal sprag price (over 300? and a months wait) and from now on I can just get Suzuki sprag if it wears out again.
I refuse to pay the gasgas origal sprag price (over 300? and a months wait) and from now on I can just get Suzuki sprag if it wears out again.
This is the answer in most cases. I went through all of this last year. I suspected the torque limiter from the start but I was told by mechanics that it would be the sprag. After spending money on parts and tools I wasn't happy the first time I hit the starter after doing the job only to hear the starter freewheeling again.
There is a simple test to determine whether you have a sprag problem or a torque limiter problem. Remove the torque limiter and draw a line on it like in the photo below. Put it back in and press the starter button until you hear the freewheeling sound. Pull it out and i'll bet the marks don't line up any more.
If you find that you're torque limiter is slipping you can disassemble it and add a washer to increase the pressure on the gears. You can see the washer I added to mine here. It's a bit tricky to line up the 3 large gears when you put it back together. Don't bother trying to line them up when you press them back together. If you put the small gear in a vice you can turn the upper and lower gears individually with a big pair of multi grips until they line up with the centre gear.
I used a bearing puller like this one to do the job.
That means yours is ok. They are not supposed to slip when you hit the starter. I think some of the parts that were designed for the drz400 engine have trouble coping with the 450 and 515 motors.
iancp5
New member
Ah I see. I now hope mine has one as a couple of years ago it sheared all the little screws/bolts that hold the starter clutch to the flywheel through backfires and I replaced them with the highest tensile I could find! I must say when it backfires it doesn't sound like anything is slipping. I shall have to look closer next time its apart.
No luck fitting the DRZ sprag 
Friend of a friend had done similiar part fitting on a different bike and it didn't last more than couple of starts. Now I'm back to square one and waiting for local bearing salesman to find suitable sprag for me... I still refuse to pay over 300 ? for such a simple part.
Can I put my bike back together without sprag and starter gears, or will it cause me more trouble? I'm hoping to get my kickstart working tomorrow and would like to try if I could get it started with that(I've never managed to kickstart it when engine is cold )
Friend of a friend had done similiar part fitting on a different bike and it didn't last more than couple of starts. Now I'm back to square one and waiting for local bearing salesman to find suitable sprag for me... I still refuse to pay over 300 ? for such a simple part.Can I put my bike back together without sprag and starter gears, or will it cause me more trouble? I'm hoping to get my kickstart working tomorrow and would like to try if I could get it started with that(I've never managed to kickstart it when engine is cold
)Embalmer, unless your sprag is severely worn I would put money on the torque limiter being the problem. As a reference point, HERE is a ducati sprag that was unable to start the engine. You will notice that the spring that holds the sprag together is completely destroyed. You can also see that there is severe wear on the inner race(the sleeve on the drive sprocket). If yours isn't as bad as that one then I will guarantee that the torque limiter is the culprit.
Don't do what I did and put it together with all new parts only to find that there was nothing wrong with your original sprag.
Unfortunately you will have to put it all back together to test the torque limiter.
Don't do what I did and put it together with all new parts only to find that there was nothing wrong with your original sprag.
Unfortunately you will have to put it all back together to test the torque limiter.
stainlesscycle
Site Sponsor
No luck fitting the DRZ sprag
sprag bearings do go bad. it is quite obvious when they do - pieces will start falling out
is there a number on the bearing? sprag bearings are expensive no matter how you look at it - but i've replaced 2 on other bikes (a nordic track! and a duc pantah) - i'm 100% sure there is an interchange for it - probably torrigton. there is no way it is gasgas specific.
Well, I'm pretty sure that the sprag is my problem
And EC400 sprag is different than Ducati or DRZ sprag. It doesn't have that spring descriped on that ducati threat but instead it has a small spring on each "tooth"(you can see one of them in the middle of the "cage").Here's a picture to show why I'm so sure that sprag is causing my problem
:
It was in that shape when I opened it up, only couple of tooth were still on their place. And before anyone wonders why it's in such a bad shape, it has a lot to do last summers engine brakedown.
Similar threads
