Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 5:45 pmLook by the gudgeon pin..
as used on millions of racing 2 strokes since the 70's...
as used on millions of racing 2 strokes since the 70's...
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Who else drills holes in their piston?
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Posted: Tue Jan 27, 2015 5:45 pmRe: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 6:05 pmThey're for bridged exhaust port lubrication.
Re: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 6:35 pmAn old boy, brit bike mechanic. Told me yearrs ago that when he had a nip he would Clean it up then drill a 1mm hole T that point.
Holds oil in the same way as an oiler ring does on a four stroke.
Holds oil in the same way as an oiler ring does on a four stroke.
Re: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 8:32 pmIan Frankland recommends drilling such lubrication holes either side of the exhaust port on the old iron barrelled 240cc conversion.
It is a simple and virtually risk free.
It is a simple and virtually risk free.
Re: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 8:55 pmI don't know how much communication you want between the exhaust port and the crankcase though (I really don't know)? Obviously, the exhaust bridge would normally form a barrier to the exhaust pressure pushing burning fuel into the crankcase through these holes. Without the bridge/barrier it could be an issue... or perhaps not.
Adam
Adam
Re: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 8:59 pmWhen knowledge said 'either side' did he mean out side the width of the port on either side?
Re: Who else drills holes in their piston?
Posted: Tue Jan 27, 2015 9:26 pmHarry Barlow drilled two holes, one either side of my Rapido 250 piston between the piston crown and gudgeon pin. I can't remember the exact size but they were in the order of 4mm. I think this was more about improving big end lubrication though but may be wrong, it was about 4 years ago.
Re: Who else drills holes in their piston?
Posted: Wed Jan 28, 2015 8:03 pmrapido 250 phil23fair how have you found the kit? torquey ......peaky......thursty.......??? wat setup av u got am thinking of a 250 race? 
Re: Who else drills holes in their piston?
Posted: Wed Jan 28, 2015 9:32 pmrexton270s wrote:rapido 250 phil23fair how have you found the kit? torquey ......peaky......thursty.......??? wat setup av u got am thinking of a 250 race?
I'm very please with mine but it has been tuned by Harry Barlow. It is very torquey and I don't think overly thirsty for the way I ride it. I probably get about 40mpg. It can cruise quite comfortably at 65 mph plus and get there quickly. I'm guessing the top speed is probably low 80's but the speedo is not that reliable at the top end, but it will keep up with a well kitted out TS1. I'm running it with a 30mm Dellorto and Taffy copy exhaust. Li150 gearbox with 46/17 sprockets giving a final drive ratio of 4.6. I live in Devon and we have got a fair few hills around here and the 250 makes easy going of them.