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Post by friday1 on Aug 29, 2018 11:13:31 GMT -5
I have a 2002 SR50 Aprilia Replica and want to go to 70cc by boring my old barrel and putting in a new piston, wrist pin, rings, etc. I will do some light porting, chamfering while it is off. Did some calculating and found 47.5mm bore with stock stroke of39.3mm will yield 69.6cc displacement. Any suggestions where to get just the piston kit? Is there enough meat in the stock barrel at 40mm to bore it to 47.5mm? Research says the motor is an Aprilia/Moroni. Thanks in advance
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Post by pinkscoot on Aug 29, 2018 11:45:42 GMT -5
Just go ahead and get the whole kit, you'll be happier and save time. Check out Scooterpartsco, he has parts for the SR50 Morini.
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Post by oldgeek on Aug 29, 2018 12:08:38 GMT -5
Boring a cylinder from 50cc to 70cc will not work very well. Your exhaust duration will change, considerably. Best to just go for a complete 70cc kit.
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Post by harleyracer59 on Aug 29, 2018 12:42:56 GMT -5
im with OG. besides the fact that it'll majorly screw up your port timing, a big bore piston, rings gaskets, clips, and a wristpin bearing is gonna cost you 70-120$ then to bore the cylinder is 100-250$. you could probably get a real fancy bbk for that kind of coin. parts for scooters, treatland, are places to look for you kit or the parts. here in socal there's a place called LA Sleeve. city of santa fe springs. they're known far and wide, been around for many many years and will give free quotes. they're very knowledgeable too. and they'll straight tell you if they aren't the cheapest route. honesty goes a long way with me. good luck with your build either way
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Post by Lucass2T on Aug 29, 2018 15:13:49 GMT -5
If you put your goal and budget here the guys can give a lot of options and alternatives. Boring and honing like you said is left for last resort situations where there are no big bore kits available or obtainable. I've litteraly never heard anybody going that way in moped/scooter scene thats flooded with all sorts of aftermarket parts.
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70cc
Aug 29, 2018 19:00:01 GMT -5
Post by friday1 on Aug 29, 2018 19:00:01 GMT -5
Thanks guys. Great info. LA Sleeve may be a good place to go now but I have seen an 80cc Honda barrel they cobbled so bad the sleeve was installed crooked on a go kart motor. Guy had a major problem getting them to correct it. It was evident the sleeve was crooked just by looking at it no measuring devices needed to tell.
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70cc
Aug 29, 2018 19:18:46 GMT -5
Post by harleyracer59 on Aug 29, 2018 19:18:46 GMT -5
Thanks guys. Great info. LA Sleeve may be a good place to go now but I have seen an 80cc Honda barrel they cobbled so bad the sleeve was installed crooked on a go kart motor. Guy had a major problem getting them to correct it. It was evident the sleeve was crooked just by looking at it no measuring devices needed to tell. that really sucks. ive personally been using them for years on every thing from dirt bikes to bsa triumph flat head Harleys. knock on wood me and the others I know haven't had any problems. how long ago was this that happened. ill diffidently keep any eye out and pass the word along. im a couple miles away from there so if you do go their route and need anything checked on, let me know. maybe they put a little more care into local jobs cause if they fuck up, they'll have to deal with an actual person and not just a phone call? still not right though.
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70cc
Sept 1, 2018 5:42:14 GMT -5
Post by friday1 on Sept 1, 2018 5:42:14 GMT -5
This was back in 1999 maybe. We raced enduro (Laydown) go karts. We had a class that ran 80cc motocross motors and you could put a 100cc kit in the motor or like I ran a Kaw 80 and they made a 100 cc kit from OEM. This let us run with 125cc karts in the same class and we got a 40 lb (kart and driver on board) weight break. My friend used a Honda motor and there was no OEM 100 cc kit so he went with the LA Sleeve mod.
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