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Montesa 315R 2003 Engine Knock. Ideas? (Video)


331sam331
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Betarich, That is the worst I have ever heard. Quite obviously a victim of the silly trend in thinking

that a 2 stroke runs so much better without oil.

Have a nice day.

Larry

Hi larry

to be honest im not 100% sure what had caused it, when i stripped it it had had water in the crank case at some point, but the idiot i bought the bike from had tried to cover it all up by filling the crank case with old engine oil, and filed the barrel and piston smoth where it had siezed and basically tried shafting me. believe it or not that sounded sweet when i went to view the bike it just smoked a bit. it wasnt until i rode it for the first time it burnt all the old oil off and sounded like it was going to throw a rod any monute.

shes all healthy now though had a complete rebuild with new everything.

well worth the hassle best trials bike ive owned.

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Right, just been on the phone to Sandifords who sell the piston kit, and looks like the only option is an "A" piston and putting any larger piston in the barell is a big no no.

Glad I rang because I was going to buy a "B" piston.

Will keep this updated and hopefully an after video next week with a nice quiet engine!

Did you get sorted mate?

I've just got mine back together and its sounds like new! The letter is stamped on the out side of the barrel on the intake side

On putting it back together there wasn't any problems apart from putting the head on backwards haha but well impressed with the power gain!

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Did you get sorted mate?

I've just got mine back together and its sounds like new! The letter is stamped on the out side of the barrel on the intake side

On putting it back together there wasn't any problems apart from putting the head on backwards haha but well impressed with the power gain!

Yea the piston kit came today, just in time for fitting it tomorrow!

The barrel letter was A. I had no trouble finding that. There was just a bit of confusion, as a lot of threads on forums were saying that you could put the B piston in, which is slightly larger, to compensate for the wear in the bore. After ringing up though they said that it is really not advisable, I imagine due to the chance of smashing rings and seizing :wacko:

I'll update again tomorrow, hopefully with pictures and a nice video!

Glad yours went together OK and is sounding smooth :thumbup:

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So I got everything back together relatively smoothly, and she fired up on the second kick!

I'll be honest I am a little disappointed that there is still something there. The little end clacking has gone, but I think there is still some piston slap. I feel a bit miffed that I could have maybe gotten away with putting the B piston in, but hey, it's got serious compression and as long as I can have some fun that is all that really matters :guinness:

Have a listen and see what you think :thumbup:

BEFORE NEW PISTON

AFTER

Please excuse the purple, the chip/sensor in my phone is knackered.

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So I am starting to thing it might be bottom end rumble or bearings or something. My other theory is the fuel octane but not sure as it is running super unleaded at around 98 octane. Maybe worth a shot with octane booster?

In your case it may of been worth getting the barrel checked over, as from the video the knocking is pretty loud! Much better than before though really depends on how long your looking to keep the bike and how much you want to put into it!

My bike ran well after the top end was done! loads of power until the coil decided to pack up and god knows what else so now that's been replaced its back fighting fit! Got to say its amazing the difference!

keep us posted on what happens!

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In your case it may of been worth getting the barrel checked over, as from the video the knocking is pretty loud! Much better than before though really depends on how long your looking to keep the bike and how much you want to put into it!

My bike ran well after the top end was done! loads of power until the coil decided to pack up and god knows what else so now that's been replaced its back fighting fit! Got to say its amazing the difference!

keep us posted on what happens!

Yes I think you are right. It is definitely something I will keep in mind for the future as I like the bike a lot. I took it out to properly run it in over the weekend, and it pulls like and absolute train, definitely no problem in the power department. :hyper:

One thing that has completely gone is the horrendous tapping at higher revs (little end I imagine). The only thing that remains is the idle and slightly off idle knocking.

Yikes, I really hope my coil doesn't go anytime soon, just looked at the price :o

Pull the flywheel cover off. Give the flywheel a good tug. Is there any movement up and down.

Yea, might have a gander. I should really have a look inside there anyway just to check it over.

Cheers guys, much appreciated :guinness:

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