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

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?

Have a listen to the second vid if you get chance dude, I wanna see what you think compared to yours! haha

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 Have a listen and see what you think BEFORE NEW PISTON AFTER Please excuse the purple, the chip/sensor in my phone is knackered.

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 I'll update again tomorrow, hopefully with pictures and a nice video! Glad yours went together OK and is sounding smooth

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!

Thanks, I really can't afford a barrel as well though. Plus it looks like mine has been pretty well looked after and I don't see any wear on the barrel. I have had a look around on other forums and they are saying that the difference between A B and C pistons is very small. My thinking is that any wear on the barrel will be compensated by a very slightly larger piston. On the other hand, I don't want to go ahead and cause any damage. I may just end up getting an A piston and given that the main source of the noise was little end wear I hope it will cure the noise. Cheers for the reply

Bump.

So I whipped the head and barrel off today. All looks very good. Definitely play in the little end and the piston noticeably rocked in the barrel (at TDC). Now there is no letter on the piston for A, B or C but the barrel says A so should I put a B piston in? The piston lining has a very very slight lip at thebbottom and top. I would like to put the B piston in if it will improve sound and longevity. Here is a picture of the piston ring gap. Obviously I am worried if I go up a size in the piston I could break a ring and wreck everything... Here is a picture of the piston. And the barrel Thanks guys!

Looks good, tidy bike as well. A lot cleaner than mine! Quite a bit of room to work with as well which is good to know. Do I spy a Beta Techno in the background? Cheers, good luck with the refit

Awesome, nice one. Have you got any pics? Just interesting to see it in bits!

Will do. Probably won't be for a while as I just splashed out £200 on new boots/gloves/helmet haha

Alright cool, I'll see how I get on cheers.

Yea I would like to fix it. I'll do the full piston kit I think. Is there anything else that is worth replacing while the head is off. Also, is it a hard/big job? I haven't been around bikes much, only cars. I also know that 2 strokes are a different beast. Thanks Right OK, thanks for pointing me in the right direction on parts. I'll have to keep running it as is for the moment though as the piggy bank is getting low No not at all.

Yea, could be. It does sound like a lower tone in person. Here is another vid:

Hey guys, bought a 2003 bike a few weeks ago (LOVE IT) and other than the knock it pulls like an absolute train!! Anyway, here is the video of the knock. Some friends have suggested the small end bearing. My dad has just rebuilt his Beta Techno and it sounds like a sewing machine compared to mine now!! Any ideas? Also, I live in the UK and I can't find a small end bearing/con rod kit anywhere. Does anyone know where would be best to look? I don't mind paying overseas shipping if it is this that's the problem. Cheers

Great, gives me more confidence. I am not sure but the MOT form says "Front wheel has slightly distorted bead rim" Thanks for the tips, I will examine it more closely on the weekend. I have heard that Montesa spokes can be a tad fragile especially on the rear wheel, so I will keep that in mind. Cheers

Oh good, I was under the impression that they were like a dodgy budget tyre. I also noticed that the front wheel has a slight but very noticeable buckle in it, which is something I don't want especially at speed. Do you know how easy it is to remove a buckle? Will I need to send it off to a shop? I have a small hand pump yes. Haha yep, plenty of that stuff as I live out in the sticks and the roads are pretty badly maintained

Nice bike, not scary/smokey enough though

Alright great. Yea I notice how soft they are just from touching them compared to say a car tyre. Ah, I see. Well I guess I'll just have to take it easy and find a speed that is comfortable, cars can always go round me haha. The front is Michelin and the rear is an IRC tyre. Both are fairly new with the mould marks still there. Thanks for the suggestion Thanks to everyone for there help, really appreciate it

I see what you mean now yea. That square wheels explanation was bang on. Thanks for the tips!

Right OK. I think I will go for that option as I don't want to fork out a load of money on sprockets/chains. So when you say smoother, do you mean less snappy when pulling off? (total novice here...) Cheers for the reply. What would be dangerous about it? Thanks for the reply. Don't tempt me! Does anyone know what kind of tyre pressure would be best for the road?

Sounds good, I'll have to play around with some different set ups. Cheers for the suggestion.

How about if I had a spare set of sprockets I could change over? Bearing in mind I plan to commute pretty rarely. Would I also have to change the chain with such a difference in sprocket sizes? Would I be OK running different jets and say a 50:1 fuel mix? (standard is 80:1).

Yea, probably less than that actually. It is also a well know cycle route so I don't have to do 60mph. I would get away with between 40-50mph most likely. I am not really sure 60mph on a trials bike will be too comfortable. Probably pretty exciting though haha...