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Could i get a lilttle advice

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Yes i have a 2004 KX250f havent had it long bought it used recently. When i first got it it run fine for a couple rides then it got to where it wouldnt Kick start..when i would try it would start to Backfire every so many kicks..only way to start it was to Push it...but even then that got hard to do..so i checked it out and it seemed like i needed new shims...i was running a 285 shim so we tryed to sand it down that way we could get good clearance on the Shim bucket and the cam....after all that and getting it in time we tried to start it and it started off the first kick but was having alot of noise...After a couple ride it went back to the same shape it was in...So i went and bought a New timing chain Shim bucket and also went down to a 245 shim...after we got that in we had a clearance of .002 on one of intake cam and .005 on the other part of the intake cam...After we got done tried starting it again and couldnt get it to even start..back to the Backfireing every so many kicks..even tried to pull start it that failed as well..would not fire... My question is does the clearance on the cam have alot to do with the starting issues if so How much lower on the Shims should i go...Or any other advice would be Helpful

Thanks plz reply if you have an idea

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Needs new valves, once the coating wears off the Ti valves they zero out in one ride, soon they will be paper thin, if you don't replace them you are asking for trouble. Get the seats re-cut and put new valves in, no way around it. Yes if the clearence is not correct you will have starting issues. Here is a link to the manual for the bike http://www.nbsupercycle.com/servicemanuals/04servicemanuals.htm

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Yes i have a 2004 KX250f havent had it long bought it used recently. When i first got it it run fine for a couple rides then it got to where it wouldnt Kick start..when i would try it would start to Backfire every so many kicks..only way to start it was to Push it...but even then that got hard to do..so i checked it out and it seemed like i needed new shims...i was running a 285 shim so we tryed to sand it down that way we could get good clearance on the Shim bucket and the cam....after all that and getting it in time we tried to start it and it started off the first kick but was having alot of noise...After a couple ride it went back to the same shape it was in...So i went and bought a New timing chain Shim bucket and also went down to a 245 shim...after we got that in we had a clearance of .002 on one of intake cam and .005 on the other part of the intake cam...After we got done tried starting it again and couldnt get it to even start..back to the Backfireing every so many kicks..even tried to pull start it that failed as well..would not fire... My question is does the clearance on the cam have alot to do with the starting issues if so How much lower on the Shims should i go...Or any other advice would be Helpful

Thanks plz reply if you have an idea

Dont sand the shims down!!! :banghead:🤣:busted:

Go get you a hot cams shim kit! Good luck and you need to read more on these bikes before you start wrenching on them...thats just my take on your probs. :banghead:

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Sounds to me like someones valves were starting to go so they did a quick adjustment and sold it (to you). I am not sure what the rule-of-thumb is, but I am thinking that if a valve needs to be adjusted a second time it is probably cooked. Once they are cooked you will need to have a professional recut your seats before replacing the valves (and springs). If you have an '04 I would highly recommend you get a Boyesen water pump and only use high performance coolant in it...

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After they zero out once they are gone, happened to me twice. You need to get the seats re-cut (about $50) and new valves. Also if you are looking for valves stock are about $60 a piece, but when I called my dealer last time and asked for aftermarket ones they said White Bros sold some for $32 a piece. Not sure what they are or anything but it may be a good idea to look into to save some money.

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I am in the same position as you Motoman (except I didn't just buy the bike). I am new to the 4-strokes and just wondering where could I have the seats re-cut? I think I am going to go with the Kibblewhite valves and Springs. Would this be a good set up? Any help would be appreciated.

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The minimum spec for the shim is 2.50mm (2.50mm to 3.50mm in 0.025 increments). Your down to a 2.45mm which is the range that the Yamaha's run (1.20 to 2.40mm or close to that) Any lower and the valve bucket will probably be sitting on the valve retainer and the shim will be rattling around.

The first symptom of the valve clearance being closed up if the bike will lose compression. It will be real easy to kick, hard to start which means it won't fire up, won't idle properly and will cut out while riding for no good reason.

If the clearance has closed completely then the valve is buggered. The coating has worn through and you are wearing into the softer metal below. You can re shim it but the valve will continue to wear very quickly. The only option is some head and valve work.

A lot of people get caught by buying a bike that is running great when they test it. The previous owner or shop have had the valve trouble and instead of fixing it properly which costs a lot of money they re shim it which is a temp fix.

I even looked at one the other day in a shop and the dealer said, "The motor's great, the owner just re did the shims." Warning, warning, warning. I bet that the valves are on the way out and the left intake has already gone.

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Yep, I just got caught in that situation. I bought an 04 and it ran fine, then it started running a little on the weak side and then checked my valves. The exhaust valves were fine but the left intake had zero clearance, and the right one was just out of tolerance. I adjusted them and it ran great, after about four hours on the bike I had no clearance on either intake but my exhaust valves have not changed. I then tried to re-shim the intake and had to go lower than the 2.50 and it had a Little knock. After seeing the previous reply I now now that it is likely due to the shim bouncing around in between the bucket. I obviously need head work, but do I need to redo the exhaust valves too? The exhaust valves seem fine. If you use an aftermarket spring do you need to replace the buckets due to more pressure between the cam and spring? I saw on article on here that said they spent a 1000 on head work and one of there stock buckets failed. :banghead:🤣:busted:

I think I'd rather have my two stroke back :busted::banghead:

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If the valves are fine leave them, just change out the intake valves and use stock parts. Stock is cheaper and the aftermarket stuff does not seem to be worth the extra bucks because a few people have problems with those as well.

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I took mine to the shop when it was doing that same thing and they said that the only thing that was wrong is that carb needed cleaning.

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If the valves are fine leave them, just change out the intake valves and use stock parts. Stock is cheaper and the aftermarket stuff does not seem to be worth the extra bucks because a few people have problems with those as well.

The stock stuff seems to be fine and I use it with no problems. You can buy aftermarket Ti valves that are better and will last longer but they are also a lot more expensive. You have to weigh up if the extra cost is worth it.

The drama comes with the valve seats which are too hard for the valves. You could put new valves in and they will probably last a while but I would be getting the seats addressed as well. I went for the softer seats and my clearances don't move.

Just changing valves is not addressing the problem causing the valves to wear in the first place.

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Can I get away with just buying the oem intakes and reusing the same springs. Is there a tolerance for the length of the springs so that you know when they need replaced? Do I need to recut the intake valve opening?

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