CRF 2003 engine death rattle.

CRF 2003 engine death rattle.

I have just finished a days racing, at intermediate level. The engine has developed a death rattle, causing me to obtain my first DNF of the season. I have not pulled it apart yet, and was wondering if there was any point contacting Honda.

The bike is brand new! Done about 3 hours hard racing. Only. But about 20 hours playing (Gentle). It’s had 3 oil filters and 6 changes.
The bike still pulls well, we dropped the oil which looks fine.

I rarely hit the limiter, and generally run low in the rev range.
The death rattle (harsh vibration) happens at about 7,000 to 8,000 RPM (guess), and is particularly evident as the revs decrease after blipping the throttle (no load).

Any ideas? I have heard about intake valves problems, but only in the states. See link.
http://www.off-road.com/dirtbike/projects/crf450/kibblewhite/

Anybody have anything similar happen?
Apparently “people” have had the conrod small end ovalise on the YZF, does this happen to the CRF? I would not expect anything to make this type of racket whilst the motor is so fresh.

Should I pester Honda? Before I inspect the engine?

Please please help, I’m worried.

Thanks
Dan

Thanks for you help guy’s.

The rattle happens when the bike is NOT moving, so can’t be the chain.
Other CRF are “noisy” I agree, but this is worse, hence “Death Rattle”
Just pulled off the Clutch case, every thing looks OK. The washer behind clutch cover, look as though the nut could have come loose, the nut however is tight! Cant do it up or undo it!

The clutch basket is moving about 0.5-1 mill, is this normal?

Ignition side, all looks good.

Under the cam cover, all looks fine as well. The automatic decompressor is the only thing with any wear marks on it. The bearing for this is a little stiff.

At the RPM’s that its making a noise this is definitely not in use.

The rattle must be coming from deeper in the beast.

I recon it could be the piston, small end, for a main….

Thanks again,

Dan

Already done.....
There is a nice chain slider mod from AMP research called the power link.

OK stripped the bike engine. If you have not had the chance to take a peek in there yet I recommend it! This engine is beautifully designed. Even the cam is hollow and has holes below the lobes to save weight. Even looks like the cam balanced. Amazing.

The inlet valves were out a little. Gaps were 0.1mm. that’s a bit under speck at 0.16 +-0.03. I set them back to 0.18, by popping the shims on a surface grinder. I have new ones on the way incase I have lost me hardening (should be OK for 1-2 hours?).

Thanks for the advice on setting the valves Eric!

I also put in a new piston while I was at it.

The rattle has almost gone! It just sonds like a normal CRF now!

I hope that it does not come back.

Just for interest the engine had done 15-20 hours, the piston was well within tolerance, and the ring gap was 0.27mm, well within the 0.48? tolerance.

There was NO wear on anything. I can only put the noise down to the combination of a little bit of Piston wear and the inlet vales being a little tight. Harmonic issue?

Thanks for all of you help.

NB the chain still rattles, but I prefer that to my previous engine rattle!