1996 RMX 250 noise

I am hearing a what seems to be a rattle noise. It seems to happen at high rpm at the end of a gear pull, but not under much load. Could it be anything to do with the power valve? Piston slap? Chain noise? It starts and runs strong, The chain seems to be adjusted OK. Any Ideas or what to check?

Thanks, Steve

Sounds like chain slap if it does it under low load. Try running at half throttle and back off a little and see if it does it. Power valve doesn't make noise and piston slap would be heard at idle. Unless REALLY loose.

I hope its only chain noise. It really sounds like an engine knock

Does it only do it at high rpm? Engine knock would happen all the time.

but it only seems to be when it is not under as much load. kind of at the higher revs at the end of a gear but not really pulling hard

They will make a wierd rattle when they are too lean so be careful. My friend has a 93 RMX and his did the same thing after installing a PWK a/x carb. We did quite a bit of jetting to get rid of it. He was also running 50:1 and we moved to 32:1. The noise is gone:ride:

A plug check would eliminate jetting.

the plug color is a nice light chocolate to tan color. If I pull the exhaust can I inspect the piston and cyl through the exhaust port? Could It be a bearing or wrist pin? The bike runs really well and the noise is kind of intermitent. I hate to tear it down and not find anything. I had an experienced 2 stroke rider ride the bike and he thought he heard something once but wasn't sure. He thought it was when he was down shifting to turn around. I took the bike out yesterday and when I was warming the bike up I could hear a little noise when reving the engine. While riding if I pulled hard in 2nd and before hitting 3rd backed of the throttle a little and held it at a constant it seemed to make the noise there. It almost sounds like spark knock in a car.

What carb and jetting do you have if you dont mind me asking. 32:1 is a great mix ratio, but you could still have a lean spot in your jetting. Your pilot could be fine, but you could have a lean spot in your needle( example). The needle was the culprit with my friends RMX

I believe it is original carb. It says pj on the side of it. The bike has no air box cover and a fmf fatty. The main is 165, I am not sure about the pilot. The air screw was at about 1 to 1 1/4 turns out. I run 32:1 mix. The bike had a 170 main when I got it but I was getting some oil at the back of the pipe. The shop told me to try the 165 and a #9 heat range on the ngk plug.

Could you tell me what size jets your buddy ended up using? Is it going to make a difference with the different carbs. If I am getting the noise at mid range do i need to increase the pilot size, or maybe change the needle clip height? Thanks for all your help.

We switched his bike over to a PWK airstriker, but the PJ is a good carb. Assuming that your top end is in good shape with no air leaks, then you will be in the ballpark with : 55 pilot, DDJ (option needle), and I would go back to a 170 main. Dont try to get rid of spooge, as a little spooge isnt bad. I would have to go back to your post to see where you live, and your elevation. I am pretty sure I know the noise you are describing, and it sounds like a lean spot. What was the temp when you have heard the noise? We run Castor 927 at 32:1, and I just pulled my RM down to find this stuff lubricates excellent. :smirk:

I see your in New York so your temp and elevation will be somewhat close to ours in Indiana. It has been cool this spring so jetting will act leaner. Remember that jetting will act richer as everything goes up( temp, humidity and elevation), and unless you live in the catskills the jetting I gave you will be close. I am not sure how the fatty will change things.:smirk:

I would check the crank, could be a worn out rod bearing..

Thanks for your help JCAT. I will try your recomendations. The temps were probably in the 60's that day. I am not sure what needle I have but what clip position should I be in? We are at about 700 ft. in elevation. The header pipe is a little beat up and looks a little bent, but I dont here any leaks. I have heard that an exhaust leak can cause a lean condition, but like I said I don't see or here any sign of leaking. I have been running maxima oil but I will have to try the castor 927. The bike runs very well, and even idles pretty good. Thanks again for your help.

I think you will be on pos.2 with a DDJ , but try to lower your clip on the needle you have. I think the stock needle is a R1472M, but I dont remember. I am amazed that it will idle, as PJs arent known to idle very well. Take one step at a time so that you can go back if needed. Start with your pilot circuit, and if your 1 -1 1/4 turns out then you are close to bumping up a size on the pilot. If the noise is coming at 1/4 to 3/4 throttle then its probably your needle. Check the size and position first. Let us know.

OK, Here is where I am at. I took the carb off tonight and I have the stock needle and it is in the 3rd grove from the top. I put the 170 main back in. The pilot is a 52. I warmed the bike up and it does idle very well with the air screw at about 3/4 of a turn out. When I backed the screw out more it would increase in speed but would get irratic. If I went in from the 3/4 turn position the engine would slow down and stall. At 3/4 it really idles quite well for a two stroke. I here a lot of guys running at 1 1/2. Does this mean I need a different pilot? If so what size should I try? Thanks, Steve

Yes go to a 55 pilot. When you turn the air screw out you are adding air or leaning the pilot circuit out. Start at 1 1/2 turns out. When you say you have the stock needle, was it the R1472M? Get your pilot circuit set first, and if your getting a PJ to idle then your right on the hairy edge of lean. If with the 55 you end up at 1 1/2 to 2 turns out then you have a half turn either way for changing temps. After this if it is still has a little noise at mid range then go to a smaller diameter needle. The 72 portion of the number would change to a 68 or 69. :smirk:

Well, I finally got to go for a ride. I have the 55 pilot, 1472 needle, 170 main. the bike ran strong, good throttle response. If I putted through the trails for extended time it would load up a little. I can still get it to make the noise. I was in second gear on the level, just kind of cruising along, If I just barley opened the throttle and held it there, I would get the noise. Maybe I am just hearing chain noise? Most of my riding is in the 0-3/4 throttle range. If I get into full throttle, it is only for a short time. My plug is now a dark brown, and for the 5 miles I rode I have no spooge dripping from pipe. Will a smaller needle make the low end a lot richer? What size should I try? Thanks, Steve


Try moving the clip up on the needle to lean it if you spark plug is too dark. Go one slot at a time and test. If it's in the top, then a leaner needle may be needed. I don't know if you read this http://www.thumpertalk.com/forum/showthread.php?t=412662 but it may help. It worked great for me. Just keep testing. It's worth getting it right.

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