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Discussion Starter #1 (Edited)
EDIT/UPDATE: Post #9...




I'm going to try to make this as short as possible (famous last words...).

*The problem: When I dump the clutch on the XT250 (as in hard launches or clutch wheelies), there is a semi-loud "pop" sort of noise. This only seemed to happen in first gear.

I kind of thought it might be clutch-related (something hanging up in the clutch pack...it sounded a bit like that). Now I'm pretty sure it has to do with the chain/sprockets/swing arm.

I tried tightening up the drive chain slack (one click on the adjusters) and that seemed to help a little bit. So then I tightened it one more click on the adjusters (two tighter than how it was). After doing that, I can do very aggressive launches and big clutch wheelies and there is no more clunky sound. Unfortunately, the chain slack is now only about 1.3 inches. The manual calls for about 1.6 to 1.8 inches. I don't think I want to run it that tight. My (weak) hypothesis is that the chain was getting yanked hard by the clutch-dumping, and then whip-lashing into the top of the swing arm as the shock pulsed through it.


*My solution (??): I think this could have something to do with the fact that I went down one tooth on the front sprocket...so the chain is slightly closer to the top of the swing arm. I'm thinking of trying a couple of different front sprockets to see if that will help. I have a 14 tooth on it now. Stock is 15. I may try that again and/or a 16 tooth. I'm not really sure what else to do. I don't want to just ride it around like that (especially since aggressive clutch abuse is the norm for me - hard enduro use...). I believe this is the same issue that people commonly experience with the Yamaha WR250R - wherein the chain can eventually eat through the chain guard and into the swing arm over time (a bigger front sprocket is the cure). If I want to keep the same gearing, I could go to a 16 front, and then go about 6 teeth up on the back...

I don't really expect anyone to really offer me a better solution or provide some new insight that I haven't considered... But I'm all ears if anyone does have anything to say. If you've had a similar experience, for example... I guess I'm just kind of venting a little. Thanks.
 

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Your on track. I'd add that if your rear sprocket is fairly worn noise could come from the chain slapping the teethe. With the ajuster loose does the chain slide front and year on the sprocket or is it held tight. Check the swing arm bearings and the lash of the front sprocket, both chain to the sprocket like in the rear and the sprocket to shaft. I've had everyone of those make noise over the years dumping the clutch, usually only in first do to there being more torque.
 

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Discussion Starter #3
Your on track. I'd add that if your rear sprocket is fairly worn noise could come from the chain slapping the teethe. With the ajuster loose does the chain slide front and year on the sprocket or is it held tight. Check the swing arm bearings and the lash of the front sprocket, both chain to the sprocket like in the rear and the sprocket to shaft. I've had everyone of those make noise over the years dumping the clutch, usually only in first do to there being more torque.
That's the sort of feedback I was looking for. Thanks! The chain and sprockets are almost brand new (I believe it was also doing this before I changed them). I didn't specifically look for sprocket-to-shaft freeplay, but I didn't notice any when I was messing around with the chain and sprockets and checking them out. I'll have a look and check for that in particular, though. I really don't think there is any, but just in case, I'll look.
 

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Discussion Starter #4
I guess I'll start by ordering a 16 tooth. It's only a few bucks and I won't need a new chain to see if that would fix the issue. If it does, I might just leave it that way (from the current 14 tooth); the bike won't really get up hills in second gear now, anyway, and with the taller gearing, I'll have a hair more speed in first gear, and can cruise 10 mph faster on the highway...
 

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Best of luck. I hate noises.
 

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Discussion Starter #6

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kj, just curious, did you post this on the XT 225/250 Forum?

jb
 

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Discussion Starter #8
kj, just curious, did you post this on the XT 225/250 Forum?

jb

I did not. If someone posted about the same issue there, maybe direct them to this thread or something, if you feel like it :) I am awaiting my sprocket and will report the results of my "experiment".
 

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Discussion Starter #9 (Edited)
Damn it. 16 tooth front sprocket installed - no change in symptom. Any ideas? I've searched around online a bunch and can't find a damn thing on this issue. I have ideas that I can try/things to look at, but I hate having to mess around so much on a new bike with 5k miles - it's stupid. I have frequently done 8,000 RPM clutch dumps up steep, rocky hills on the DR200 - no problems ever with that clutch, in several years and 20k miles. I just don't get why Yamaha can't make a clutch that's not a POS on these budget bikes. If Suzuki can do it fine at the same price point, what the hell is Yamaha's problem?

Anyway, rant aside, I'd like to get this fixed. Next things I will check are clutch cable and then the actual clutch assembly...I just don't get how tightening the chain tension (overtight) eliminated the symptoms... Any ideas on the matter would be welcomed.

The service manual does also say that if the chain touches the chain guide (on the bottom of the swingarm), that that "is the limit" (of the acceptable tension parameters)...the thing is, if you adjust it so it doesn't touch, or just barely touches, it seems to measure lower than the spec, but the noise does go away then...
 

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Does your bike have rubber dampers in the rear hub? Might be worn, cracked, deteriorated, etc. Loose wheel bearings or swing arm bearings/bushings?
 

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Discussion Starter #11
Does your bike have rubber dampers in the rear hub? Might be worn, cracked, deteriorated, etc. Loose wheel bearings or swing arm bearings/bushings?
No cush drive. I suppose in theory it could be wheel bearings, but it seems like it would do it in other gears and other speeds and stuff, and under just hard throttle? I had the bike set up on a stand/lift, with the rear wheel suspended off the ground, and it would do the same thing...make the popping noise when the clutch is dumped. I watched the chain as it did this, and it did appear to be slapping the top of the swingarm, as I had thought.

At this point I'm thinking of just adjusting it so that it doesn't quite touch the swingarm (since again, the manual says that is the limit of adjustment...even though that's a little tighter then the actual range that is provided for acceptable tension limits) and leaving it like that.
 

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I'd second Mr Scotts query. Also does your clutch have rubber bouncers internally? They can crack n fail under abuse like wheelies. Just remove them.
On really big bikes I have stretched links before in sections that caused wierd stuff. Oh yeah and spokes coming loose can make for some noise too.
Good luck
 

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Discussion Starter #13
Alright. I got it worked out. The 16 tooth didn't fix it, but I'm running that gearing for now anyway; I might keep it on there. The service manual provides a range of acceptable chain slack, but it also states that "if the chain can touch the chain guide [on the bottom of the swing arm], that is the limit of chain slack", meaning that the chain is too loose if the chain can touch the bottom of the swing arm. If you adjust it so that it cannot touch the swing arm at all, then it is quite a bit too tight (seemingly, and according to the range provided in the manual). I ended up adjusting so that the chain can touch the swing arm if you push on it a bit hard, but so that it is fairly taut just before it touches the swing arm. This completely eliminates the noise I was hearing, while following the manual in one way, and being at about the very bottom of the slack range in the manual, if you push the chain up and down fairly hard. The noise is gone, it isn't too awfully tight, and it works...I have to call it good :)
 
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