2005 CR250 (2 stroke) - Engine Rattle


Could anyone shed any light on engine rattles for a Honda CR250 (2 stroke)2005 model?

Before I purchased the bike it had a new top-end fitted and the bottom-end checked and has had about 3 hours use since. It has excellent compression but when the bike is idleing there are some strange noises/rattles from the engine.

I have heard that the later CR's are notorious for strange engine noises is this the case or could it be something else...........

Any feedback would be appreciated as it is driving me mad!!!!!!



Thanks for comments, it sounds like it could be pretty normal then........

It was not for me at least. The rattling stopped when I fixed the Power Valve.

Did you clean it or replace any parts as mine has a new power valve on it - apparently.

Unfortunately I cannot hear the noises on the attached links as I cannot access them for some reason so I can't compare....

Did you clean it or replace any parts as mine has a new power valve on it - apparently.

Unfortunately I cannot hear the noises on the attached links as I cannot access them for some reason so I can't compare....

The servo motor and cables were trashed and needed replacement.

If you want to know if it works on yours, just remove the cover on the left side and start the engine. The butterfly should spin open counter clockwise as you rev up and back the other way when you rev down. :thumbsup:

P.S. I'll try and fix the file.

Any feedback would be appreciated as it is driving me mad!!!!!!

It might just be your clutch rattling around - there is play between the friction plates and basket, and when disengaged sometimes makes quite the racket. If your bike is in gear and moving slowly under load (running close to idle), does it make the same noises? If not, it's just the clutch clattering around and it's normal.

My GasGas clutch sounds like shaking a coffee-can full of bolts when it's sitting at idle.


I have an 03 cr250r and it rattles a little bit. I have ridden with others and they rattle too. It's just the way these bikes are. Now if the noise gets noticibly louder and louder then I would start worring about it. Just ride it and pay attention to how it sounds when you ride. And compare the sound every ride and get the know how the engine sounds. Thats what I had to do. The noise was driving me mad too!!

Put your mind at ease and quickly remove the left side ign cover, try moving the flywheel up and down to check for bearing play, if you have never been in the motor yet, at your next ring change check the top and bottom end bearing play if any, also axial play on the rod. The pv is most likely your culprit, there is a thread on adjusting it properly as the honda manual is very lacking on this one, as I recall its 12mm from the nut to the housing but do a search it in the archives somewhere. If the noise changes with clutch you may need the basket bearing.

Many thanks for info, I have checked the flywheel on the hand side and fortunately there is no movement. The top-end has been rebuilt approximately three hours ago so that should be ok but you may be correct on th clutch basket bearing, this has been mentioned by someone else. In

addition I may also have a problem with the crankshaft seal on the clutch side as speckles of black oil are coming out of the tailpipe. I would assume that this would cause the engine to be both erratic and noisy......?


addition I may also have a problem with the crankshaft seal on the clutch side as speckles of black oil are coming out of the tailpipe. I would assume that this would cause the engine to be both erratic and noisy......?

Rich jetting will also cause that.

Did you check if the PV was working?

Some speckles are not a sign of a problem at all , its proof you have adequate lubrication. If you are oozing and dripping lots of oil then you have to look further. Have you checked your jetting, plug condition, wet and oily doesnt always mean a bad crank seal, you may just be way rich on the jetting. Whats your oil type and mix ratio? How do you ride, hard on the gas, or more laid back? Does the bike smoke excessively even after a few good laps? Like they have mentioned , go the jetting route, then you can test for crank seal. There is a thread here on a homemade $15 pressure leak down tester you can make from a gas gauge from a home improvement store a pvc union and an automotive freeze plug for the exhaust port, and some soap solution, to verify crank seal integrity, and check for case leaks etc, handy little tool. I doubt your to that point though, most bikes have rich stock jetting.

The pv appears to be working fine, apparently the previous owner used to compete in Hare and Hounds and ran the bike slightly rich. I have a friend who is coming round next weekend to sort the jetting out as I am not confident enough to fiddle with it. I run the bike at 40:1 with Putoline MX5 oil and unleaded at 95 octane rating, I did put too much oil in previously but I have sinced drained the tank and the float bowl but the outcome was still the same.....Does the wrong mixture cause the engine to rattle because of the air/fuel ratio?

Good advice by everyone who has responded......I have just had my bike re-jetted and it goes like stink with no rattles and no spewing of oil. Keep up the good work!

p.s the bike is stalling when put into gear and/or creaping forward. I have adjusted the clutch cable to it's maximum and have been told that it is not the plates but the spacer/washer, does this sound familiar?


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