Not a holed piston
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Special X
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- Joined: Wed Jan 07, 2009 9:38 am
- Main scooter: Lambretta 125 special 230cc
- Location: Wakefield
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Bad luck Muttley . . . life's a bitch!
Sounds like you had the kit nice and loose and now it's a rebore and another few K till you get the new set up as good. I've seen this happen twice on Wellerchaps Mugello. Luckily, on both occasions the piston had started to melt and deform on the crown and was spotted when we took it apart to change the rings. Replaced the piston both times and all was ok. The mixture was spot on but was upjetted after the first problem and still did it again. Wellerchap did tend to hold WOT for vast distances like you.
I think part of the problem you've had is due to the very high quality of the piston in the GT kit, a cheapo piston may just have holed and let you off with a cheaper repair bill.
I'm now running cast iron (Harry Barlow 230) due to the cost of repairs when a nicasil kit lets go, but I do tend to have my left hand on the clutch when caning it. I still reckon a cast iron kit running on the clearance that "grown ups" reccomend will seize up if you cane it. I run 3.8 thou clearance on a 70mm barrel and have no trouble, bit noisier than one with the "correct" clearance but you can't have everything can you.
Sounds like you had the kit nice and loose and now it's a rebore and another few K till you get the new set up as good. I've seen this happen twice on Wellerchaps Mugello. Luckily, on both occasions the piston had started to melt and deform on the crown and was spotted when we took it apart to change the rings. Replaced the piston both times and all was ok. The mixture was spot on but was upjetted after the first problem and still did it again. Wellerchap did tend to hold WOT for vast distances like you.
I think part of the problem you've had is due to the very high quality of the piston in the GT kit, a cheapo piston may just have holed and let you off with a cheaper repair bill.
I'm now running cast iron (Harry Barlow 230) due to the cost of repairs when a nicasil kit lets go, but I do tend to have my left hand on the clutch when caning it. I still reckon a cast iron kit running on the clearance that "grown ups" reccomend will seize up if you cane it. I run 3.8 thou clearance on a 70mm barrel and have no trouble, bit noisier than one with the "correct" clearance but you can't have everything can you.
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Rich_T
- Dealer
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- Joined: Fri May 29, 2009 8:07 pm
- Main scooter: Li Special
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I'd be careful with that crank, it would definately be worth checking out the rod to make sure it's straight. After a huge crash like that I'd be worried it might have got a bit knocked out of shape. If it was out of shape the re-build wouldn't last long, certainly not on your average daily use.
At 7k rpm you're no where near the top end of piston speed so it must be down to a weakening of the piston crown. This would be a combination of ambient conditions and jetting. When you re-build move up a couple of points on the atomiser and a few points on the main jet. Running a bit richer will greatly help the reliability.
At 7k rpm you're no where near the top end of piston speed so it must be down to a weakening of the piston crown. This would be a combination of ambient conditions and jetting. When you re-build move up a couple of points on the atomiser and a few points on the main jet. Running a bit richer will greatly help the reliability.
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byron
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- Main scooter: Li Special; scarred,but sound
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another reason to have DC...Muttley McLadd wrote:... The scariest bit was having no lights. (six in the morning - pitch black)
nice trophy
a mate has a GT kit, thrashes that mercilessy, and it always delivers