[Lingo75]

Hello chaps,

my 99 mont has developed a worrying noise from the engine, only way i can describe it is 'a bit rattly' or 'a bit like an old tractor!' no difference in performance just a lack of the nice purring i used to have. Should i take the crank case covers off and see if the flywheel is loose - any other ideas? is it all gonna go pear shaped if i leave it?? (i dont want to do that i want it sounding nice again!)

many thanks

Dan

This post has been edited by Lingo75: 26 April 2010 - 12:36 PM

[tt5th]

Did it start suddenly or has it just got gradually worse?

Does it happen in a particular part of the rev range?

Leaving it will be a bad thing in the long run.

Checking the flywheel is easy enough, it could be the top end which is easy enough to take off and have a look.

Worst case it could be the bottom end, best case it could be a leak in your exhaust somewhere or something else equally simple.

Sometimes you can find the spot where its knocking by putting the metal end of a screwdriver against various parts of the engine and putting the rubber end on your ear. Works like a cowboy stethoscope!

[Lingo75]

Thanks for the reply!

Well it started this weekend, never noticed it before.
Funny you should say about the exhaust as i had had the front pipe off to spray it this weekend and i think it was after i replaced it that i noticed the noise, could that be it??

[B40RT]

Lingo75, on Apr 26 2010, 02:48 PM, said:

Thanks for the reply!

Well it started this weekend, never noticed it before.
Funny you should say about the exhaust as i had had the front pipe off to spray it this weekend and i think it was after i replaced it that i noticed the noise, could that be it??

Always start with the last thing you did to the bike, when trying to isolate a problem !

[Lingo75]

ha.

Yeah i get that, but i due to my lack of the knowse i don't know why refitting the exhaust could cause a knocking/rattle.

Is it because it is not sealed/air tight?? and what does that do to make the noise??

sorry for all the questions. But i guess that's one of the reasons for a forum??!!

[B40RT]

If its touching the frame / engine at any point (where it should'nt) you could well get a rattle.

[Lingo75]

Aha, gotcha muchos gracias!

I dont think it is though (will check) the noise deffo sounds like it is coming 'from within' which is a worry!!!

in answer to initial questions

Did it start suddenly or has it just got gradually worse?
Well i noticed it on Saturday and have never heard it before so i'd say gradually. It hasn't got worse (rode a trial with it like it on Sunday)

Does it happen in a particular part of the rev range?
Nope just always there in the background, no change in performance

Thanks in advance to anyone who replies. I really really appreciate it.

Ta

Dan

[tt5th]

Definately double check the exhaust if that's something you've had off. Make sure it's all sealed nicely and the gasket didn't fall out/off when you removed it. I only mentioned it as on one of my other bikes I could have sworn it was tapping and it just turned out to be a loose exhaust manifold bolt so it wasn't sealing properly.

Rattling in the top end usually changes with revs. Normally worse when the engine is settling back down after a high rev.

Check all the simple things first though, 315's are usually bombproof.

[Lingo75]

Thanks all.

Should there be a 'proper' gasket where the front pipe goes in the engine. As i seem to remember it just looked a bit liek clear silicone or sort of off colour rubber. I reckon i need to put a new kind of seal on there - what should i use??

[Lingo75]

Hmmmm may have answered my own question... I reckon i should put a new one on

http://www.apexmotosports.com/montesa%20pa...20book/f-12.htm

http://www.jimsandiford.co.uk/exhaust-seal...r1-680-68-p.asp


what say you experts??

[tt5th]

I don't know what the experts say but i say yes, that's what you need.

Sounds like you've disturbed someones bodged repair, not certain but worth a try for fiver.

[Lingo75]

or even £2.60 at ww.johnoldfield.co.uk

thanks for help everyone - hopefully this will be it!