Hi Guys,

Got a bit of a strange noise going on with my MK2.
Its a kind of vibrating metalic rattle that you only hear at low RPM if you give the bike some throttle in too high a gear. If your gentle with the throttle the bike pulls through it cleanly, If your harsh with the throttle thats when it makes the sound?
If you can Imagine the sound of a frozen pea in a pint pot being rattled thats it.
The motor sounds sweet as a nut at tickover and everywhere else through the rev range - Its just at low RPM under load
Has anyone got any ideas or advice or do they all do that?

Cheers
Robb

Hello Robb,

I have a similar noise/rattle with my MK2!? Can only hear it when road riding in 5th & 6th gears at low RPM!?. When I first heard it,I thought it was 'piston slap', loose drive chain or the dreaded 'death rattle' that Ive read so much about. I can't seem to pin point were the 'noise'? is coming from? and like your bike, mine is fine at tick over and no problem when riding it with a few more 'REVs'!. Got a mate (car mechanic!!!! - owed bikes for year's) to take it out for a spin! who came back looking puzzled! Only explanation he came up with was that he thought it was maybe the exhaust note when at low rpm on a 'neutral throttle'! He didn't seem to think it was anything to worry about!!!??? but I'm not fully convinced!.

Lets hope someone out there has an answer? for us new CRM owners! or are we just paranoid????

Steve.

my Mk 2.2 does the same at LOW revs, ie in 3,4,5 or 6 gear, and you throttle off for a while and then throttle up without changing down. no probs with the bike though. my was this: I fitted a 50 tooth rear sprocket! problem solved no noise!!!!

My MK 3 has the same noise, it has done it for as long as I have owned it. I used to be worried but now just accept that it is a chracteristic of the motor.
I have run 45, 48 , 50 and 53 rear sprockets on mine all with 13 front and yes the higher gearing makes the noise more noticeable, this is because the engine is loaded more under accelaration.

my mkIII does it also. Sounds like the powervalve in between open and closed ?

Gentlemen,

Two stroke motors are designed to run specifically at high revs - this is when they are the happiest. The noise that you hear is your bikes way of telling you that you should be in a shorter gear.

Well thanx for the response guys

It seems as though its just one o them things and there are enough of you with the same noise for me not to worry about it.

Its just got me puzzled a bit. Ive worked on 2strokes for many years and have extracted damn good horsepower out of Yam LC & YPVS motors but have never heard a noise quite like it. The nearest I can think of is poor carburation causing pre-ignition, but Ive run it at low RPM making the noise and done a plug chop and its textbook.
Only other thing I can think of is something resonating at a certain RPM?

I agree with Bargos though that we should try to keep the rev's up a bit and Ive never noticed it offroad, but it is noticable when shortshifting through traffic.

Cheers for the replies lads
Robb

I've bought my CRM MK2 last year. At tidy, very low mileage example. Only this year it started that low/mid-range noise. Prior to this it ran clean as a whistle at any revs or throttle opening. Something has changed. I've adjust mixture,power valve (which operates well), air filter , spark plug and cleaned the carb. All had no effect! Could it me gunk in the exhaust or baffle? Can the rear baffle be removed to de-coke? Do owners with after market pipe get this problem? This noise is not right.

sorting my swingarm bearings on my mark II and noticed my chain guide rubber was goosed, ordered new from leisurtrail, he asked me weather i wanted the active radical one as this stops the chain slapping around and making a chattering noise, will let you know when i get it cos mine is making the same noise at low rpm with lowish throttle

Yep, even the AR's do it too - doesnt worry me too much although it sounds a bit of a dog at times

ive now fitted the new ar chain guide (£49 from leisuretrail) to my markII and that bloody awfull noise (loud metalic rattle at low rpm and throttle) has vanished completely, marvelous. when i asked the bloke at leisuretrail if the noise might be balance shaft wear, that we have heard so much about, he laughed knowingly ???????

this interests me... my bike has a loud metallic rattle. i took it to a mechanic to rebuild the engine and it still rattles. what is the chain guard and where do i get one in australia?

it is the guide rubber which wraps round the front of the swingarm to guide the chain in and out of the front sprocket and also protect the swingarm. its standard fitment on the active radical (so im told) and as far as im aware no one does a patern one so you could get one from your honda dealer if you have the part number, sorry dont have it.

I now anticipate its the power valve. It rocks slightly when lowered at tickover/low revs, so the metal slider clatters against the slider wall. This can be checked with front section of the exhust pipe removed, reach in to touch the bottom of the slider and attempt to rock the slider with your finger. Apart from the simple timing check I've not messed with the power valve, can this play in the slider be adjusted out?

just replaced my chain guide with a newer model one from L.T. not cheap, but an instant cure,