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Jerk/jolt with throttle engagement and when I let off of throttle

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Hello all,

 

I have what seems to be a lot of play in my drive-train while riding. When I let off the throttle to coast the bike seems to disengage from from being under power to coasting with a small jerk. Then when I apply the throttle again there's a more pronounced jerk as the engine engages the drive-train again. My YZ250F doesn't have this at all. I've searched all over and can't quite find a similar post or just don't know what key words to use. 

 

Admission; I'm newer to dirt bikes and have only ridden these bikes twice. This is a 2004 crf250r that could have been maintained better. I've been working hard to get my bikes dialed in; this is the next problem I'm tackling. 

The sprockets and chain are NOT worn much at all... they look quite good. I don't see much difference in my chain play relative to my YZ which is very smooth, but I will measure and adjust. 

 

Any ideas other than adjusting my chain? (I will adjust it and post results soon)

Doesn't seem to me that it would be my clutch... am I wrong? This has nothing to do with shifting. How about throttle settings? Can the throttle be adjusted to pick up this slack in a gentile manner? 

 

Thanks all! 

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You may be able to smooth that transition with some jetting changes, possibly leaner slow jet, or fuel screw adjustments. And the chain should only have about 1" up and down play in the middle of the two sprockets. But a little abrupt lash is somewhat normal on these bike, remember they are race bikes, not really designed for comfort.

 

If you jet differantly and it becomes dificult to start, probably not a good trade off!

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Thanks bucket list. I know a bit of lash is expected but I feel like I could be on a dirt road with this and bite it if I try to slowly accelerate out of a turn... it's just too aggressive and would cause my tire to lose traction if you ask me. I'd feel comfortable applying some gas out of a turn on my YZ no problem. Because of the difference between the two I'm pretty sure it's too much of a jolt. 

 

That 1" of play figure; is that with me sitting on the bike or on the stand? I'm about to download and print off the manual to see what it says about all this chain adjustment mumbo jumbo. 

 

Thanks again. 

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Alright, I just printed out the service manuals for my bikes and referenced the chain slack for the Honda... the 2004 crf250r is permitted 1 to 1 3/8 inch of slack at the mid way point of the chain above the sway arm when the bike is on a stand. Mine has over 3.5 inches!!! I'm really hoping this is the culprit and will adjust it right away, but unfortunately it's pouring outside so I'll have to wait till tomorrow to test it out. 

 

Also; It has a 53 tooth sprocket on the rear. You think it would help to drop this to 51 or 52 teeth instead? Seems 53 is a bit aggressive for trail riding unless you're doing really technical terrain. 

 

Will follow up soon. 

 

Cheers

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I think you just stumbled apon your problem, and ya, a 50 or 51 would smooth things out a bit, certainly help you from having to shift quite so much. As long as you don't do many tight trails, which these bikes weren't really designed for anyway.

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Indeed, I adjusted the slack to just over 1 inch and the jolt largely went away! I then put it at exactly 1 inch and there's no jolt at all now! Hopefully this will help the next person in my shoes. 

 

Thanks all! 

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I don't think 1" is enough play in the chain if your setting it with the bike on the stand and the rear wheel off the ground.

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I don't think 1" is enough play in the chain if your setting it with the bike on the stand and the rear wheel off the ground.

Well it is the tight end of the Honda spec.

 

When I had my shock out I put all shafts in line (theoreticly the tightest point in the suspension travel) the chain seamed very tight when set 1" on the stand so I tend to run mine 11/4" to 11/2" so I know what your thinking, but Honda wouldn't lead us astray, would they?

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Well it is the tight end of the Honda spec.

When I had my shock out I put all shafts in line (theoreticly the tightest point in the suspension travel) the chain seamed very tight when set 1" on the stand so I tend to run mine 11/4" to 11/2" so I know what your thinking, but Honda wouldn't lead us astray, would they?

I don't think Honda specifies only 1" of chain slack anywhere in documentation. It's always more than that...

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I just read through the manual and honda doesn't really give a specific number for slack in the chain..

I would say a little over 1inch would be good though. My streetbike recommends 1in.

Also check the axle blocks and make sure they are even if your axle is a little crooked it could cause some of this along with other things like accelerated wear on everything on the back of the bike.

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Hot damn, it does say that in the owner's manuals. I stand corrected. I guess in my mind I know that 1" isn't enough, and I am certain more than 1" is specified on the swingarm decal.

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I don't understand the physics behind the argument "1 inch isn't enough"... The measurement is taken while the suspension is fully extended which is the tightest point for the chain; it can't extend farther thus there will be a minimum of 1 inch of slack in the chain at any given time. Why all the fuss? 

As I mentioned earlier; with 1 3/8 inch I could still feel a slight jolt when engaging the throttle whereas it's nearly non existent at one inch. To me that's slack that doesn't need to be there in my drive-train. I've heard a number of people say "it's a dirt bike, it's supposed to have play" but I'm thinking too many people are just making that assumption based on misinformation on the chain tolerances. 

Edited by davidgsmit

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I don't understand the physics behind the argument "1 inch isn't enough"... The measurement is taken while the suspension is fully extended which is the tightest point for the chain; it can't extend farther thus there will be a minimum of 1 inch of slack in the chain at any given time. Why all the fuss? 

As I mentioned earlier; with 1 3/8 inch I could still feel a slight jolt when engaging the throttle whereas it's nearly non existent at one inch. To me that's slack that doesn't need to be there in my drive-train. I've heard a number of people say "it's a dirt bike, it's supposed to have play" but I'm thinking too many people are just making that assumption based on misinformation on the chain tolerances. 

 

Well you know those frame rollers just above an below the swingarm, they take up much of the slack of the chain at the extreme ends of the travel. The tightest point should be when  the two sprocket shafts and the swingarm pivot are lined up. With out those frame rollers there would be huge slack at full extension and full compression.

 

But why i don't like 1" of slack as Honda says you can use, is that if you ride in sand or mud the chain can get even tighter yet, with all the build up on the sprocket. I've had it so you couldn't push the bike the chain was so packed with sand or mud.

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I see, good info... I'll probably stick to an inch as i'm in dry colorado on mostly rocky trails. I see your point though!

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