bobb Posted January 29 Report Share Posted January 29 Hello My 301rr has a knocking noise on low revs. Not sure what it could be but a good mechanic told me it sounds like a worn piston. Bike is a 2020 and it has been used most weekends. Bike has no vibrations and runs great, it doesnt smoke. Anybody had to change their piston on the 301? Could their be other issues with the bike? Main bearings, big end? Or is this not something that goes wrong quickly? Kind regards bob Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted January 29 Report Share Posted January 29 (edited) Before going all in on that I would double check the timing chain tensioner. I know that you can get a noise that sounds a bit like piston slap from the chain. Would be the least invasive check and if the issue would be one of the lower cost options. Well worth a look in my opinion. Also, unless you put piles of hours on your bike or are not doing oil changes it is more likely something simple like the tensioner than a piston issue considering the year of even the oldest 301's in comparison to how long most Montesa's last in my opinion. good luck. Edited January 29 by jonnyc21 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 29 Report Share Posted January 29 Does the knock lessen when the engine is hot ? If it remains the same I would be looking elsewhere. Quote Link to comment Share on other sites More sharing options...
lemur Posted January 29 Report Share Posted January 29 Too new to expect serious problems, I would check the plug gap or replace the plug, check the air filter for cleanliness and the correct saturation of filter oil, basically anything that would cause fuel to incompletely ignite in the combustion chamber such as the ignition timing. Quote Link to comment Share on other sites More sharing options...
jrsunt Posted January 31 Report Share Posted January 31 As mentioned before, I very much doubt it will need a piston or cam chain unless oil changes have been seriously neglected, they are properly built. The cam chain tensioner is self adjusting and shouldn’t be out of spec at that age, but well worth a look. Checking valve clearances would be an easy one too. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted January 31 Report Share Posted January 31 3 hours ago, jrsunt said: As mentioned before, I very much doubt it will need a piston or cam chain unless oil changes have been seriously neglected, they are properly built. The cam chain tensioner is self adjusting and shouldn’t be out of spec at that age, but well worth a look. Checking valve clearances would be an easy one too. I only suggest the cam chain tensioner because I have heard of a few of them having issues where they would bind up and not keep the needed pressure and so get some chain slap. Where not a common issue one of the ones I know about was on a newer 260 (couple years old) so figured considering how easy it is to check that part it was worth a look. The one I indicated here was replaced by a manual tensioner and the sound went away and the owner likes it better, however if swapped with a manual version it would need to have the tension checked from time to time. What ever the case I hope it turns out something simple to fix it like changing fuel, the tensioner, or spark plug etc. 1 Quote Link to comment Share on other sites More sharing options...
lemur Posted February 6 Report Share Posted February 6 Check that your oil delivery hole is not plugged, possibly even since new, somebody just now reported that issue on a 4-ride, & that would certainly account for an engine knock. Quote Link to comment Share on other sites More sharing options...
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