Holed piston ?

[poose]

Wondering if any of you guys have any ideas on my scoot as I holed a piston yesterday. Scoot been running fine up until few weeks ago blew main oil seal so replaced it, put new rings on and had to put short fin flywheel on as old one was kaput. The top end is a SIL 200 and has been ok for over 4000 miles, the rings improved the compression no end, but yesterday having only done about 200 miles since rebuild it had a sieze going up hill two up but restarted ok, then a few miles later did the same thing but this time piston had gone. As far as I know the timing is ok, gonna test it when its up and running, I had not noticed any pinking either any ideas ?

[Avantone]

I'd imagine it is either an air leak on the inlet side or over-advanced timing following the rebuild.

[J1MS]

I agree with Tony... With the addition that the shorter finned flywheel might not have shifted as much air, so cooling might not have been as good as it was before, which might make any other of these factors even worse...

[Mel K]

I holed mine on a ts1 doing about 50mph, I had slowed down from 65 after a sieze but carried on, it didn't feel right and I should've checked a few things before setting off again. On inspection the carb was loose and the cylinder head bolt that the cowling bolts to was loose, an air leak was the agreed cause, prior to that it was running ok, flying in fact.I've been reliably informed that my compression was way too high also as I'd had some pinking issues

[poose]

Timing was spot on, changed flywheel cover to short fin one, lowered head compression and then as I was putting carb back on noticed split in air hose ! Probably the cause of it.

[tavspeed]

I holed mine on a ts1 doing about 50mph, I had slowed down from 65 after a sieze but carried on, it didn't feel right and I should've checked a few things before setting off again. On inspection the carb was loose and the cylinder head bolt that the cowling bolts to was loose, an air leak was the agreed cause, prior to that it was running ok, flying in fact.I've been reliably informed that my compression was way too high also as I'd had some pinking issues

hi all,had the same problem yesterday,tramming along the dual carriage way on the york to scarbarough road,engine lost power,got clutch in quick and pulled over, engine restarted ok,went another couple of miles at 40 ish,then engine stopped dead,carb had fallen off,so think it had been letting air in previously to cause the sieze.this is the 3rd time carb has come off,with a new rubber !.running tmx 35 on a rapido 250.is solid mounting the carb a definite no no,i read somehere that the increased vibration transmitted to the carb causes the fuel to froth at high revs leaning off the mixture,apart from being a pain in the arse having to refit the carb every 40 miles it is dangerous.any ideas, thoughts anyone.

[shocky]

instead of the carb rubber use a radiator hose from a car i used a second hand landrover top hose of unknown origine that i found at work cut about 50mm off it and used that as there fibre reinforced the seldom split and mine never came off also i was able to get the carb closer to the barrel with this as well as there no internal rib as there is in the mollosi type rubbers i have some left if you want it or camlam sell it as do other dealers there is neatly cut ,a small metal tag fitted to the carb and the frame somewere taking the weight might be an idea as well

[tavspeed]

speaking to one of my mates earlier,and he reckons you can get double width jubilee clips from chiselspeed,he reckons these are a lot better than the standard type,as these can start to force the carb out of the rubber,especially if overtightened,will get some and try them,cheers all.

[jimmers]

I holed mine on a ts1 doing about 50mph, I had slowed down from 65 after a sieze but carried on, it didn't feel right and I should've checked a few things before setting off again. On inspection the carb was loose and the cylinder head bolt that the cowling bolts to was loose, an air leak was the agreed cause, prior to that it was running ok, flying in fact.I've been reliably informed that my compression was way too high also as I'd had some pinking issues

hi all,had the same problem yesterday,tramming along the dual carriage way on the york to scarbarough road,engine lost power,got clutch in quick and pulled over, engine restarted ok,went another couple of miles at 40 ish,then engine stopped dead,carb had fallen off,so think it had been letting air in previously to cause the sieze.this is the 3rd time carb has come off,with a new rubber !.running tmx 35 on a rapido 250.is solid mounting the carb a definite no no,i read somehere that the increased vibration transmitted to the carb causes the fuel to froth at high revs leaning off the mixture,apart from being a pain in the arse having to refit the carb every 40 miles it is dangerous.any ideas, thoughts anyone.

well for starters are you using the correct size rubber with the locating rib around the inside of the rubber thats matches the carb??
these are obtained cheaply and easily enough, which in turn means you do not need to overtighten the jubilee clip as the rubber is located to the carb, rather than just pushed up a piece of pipe and the jubliee strangled to death

solid mount is fine, i ran my mugello for many thousands of miles with zero problems from that at all

personally a very regular check on these small items takes only a few minutes and saves a whole lot of trouble

[soosh]

I holed mine on a ts1 doing about 50mph, I had slowed down from 65 after a sieze but carried on, it didn't feel right and I should've checked a few things before setting off again. On inspection the carb was loose and the cylinder head bolt that the cowling bolts to was loose, an air leak was the agreed cause, prior to that it was running ok, flying in fact.I've been reliably informed that my compression was way too high also as I'd had some pinking issues

hi all,had the same problem yesterday,tramming along the dual carriage way on the york to scarbarough road,engine lost power,got clutch in quick and pulled over, engine restarted ok,went another couple of miles at 40 ish,then engine stopped dead,carb had fallen off,so think it had been letting air in previously to cause the sieze.this is the 3rd time carb has come off,with a new rubber !.running tmx 35 on a rapido 250.is solid mounting the carb a definite no no,i read somehere that the increased vibration transmitted to the carb causes the fuel to froth at high revs leaning off the mixture,apart from being a pain in the arse having to refit the carb every 40 miles it is dangerous.any ideas, thoughts anyone.

I used to run solid mounted Dellorto PHBH,as long as you adjust the float height to allow a higher level of fuel in the bowl,it will be fine.Used it for many 1000`s of miles and all was fine.