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Hi all, my mate holed a piston (mugello 198) coming from Cleethorpes at the top of a long (6miles) incline on the a15 just south of the Humber bridge. We've just done a leak test before stripping it and the head was leaking above the exhaust port, and a lesser leak on the exhaust manifold. Would this have contributed to the holed piston? Just looking for reasons before we rebuild. Thanks in advance

hi steve,
bad news.i did the same thing last year and my pal did the same this year coming back from scarborough, your leaks will make a holed piston more likly, but i would seriously look at your jetting, if they were the only 2 leaks you had then i guess i would have been running pretty lean before the leaks, my pal and i both have egt gauges fitted now so we can monitor exhaust gas temp and if it gets too high we can use our chokes to cool it off, a headwind can make things worse, so can hot ambient air temperature,or carrying a lot of baggage, or passenger, make sure you check fuel flow as well as low fuel flow into the carb can end up the same way, i prefer to have an engine running slightly rich and miss out on some performance, rather than set up very lean and making high power, but close to grenading itself, remember with a 2 stroke engine the biggest cooling factor is the inlet charge coming in that is nice and cold, getting the scooter on a dyno when you have it rebuilt would be money well spent,
good luck with the rebuild,
holty

Thank you for that.

I had mine dyno'd at Scooterotica and Dan set them slightly rich. We'll leak test after rebuild and see if we can get it booked in for a dyno. Timing was at 17 degrees btw. Don't know jetting until I strip it, but I can check it against how my 198 mugello is set up.

Stevepshipley wrote:Hi all, my mate holed a piston (mugello 198) coming from Cleethorpes at the top of a long (6miles) incline on the a15 just south of the Humber bridge. We've just done a leak test before stripping it and the head was leaking above the exhaust port, and a lesser leak on the exhaust manifold. Would this have contributed to the holed piston? Just looking for reasons before we rebuild. Thanks in advance

Anybody that has welded with oxy-acetyline will know the difference between the temperatures of the flame just by adding more oxygen. It’s all in the mix! The torch will turn from one that heats & melts a weld rod to a device that cuts holes through the metal to be welded.

Similarly, adding oxygen (in air) to the mix of an engine will cut holes through a piston due to the elevated temperature.

Thanks WT, I think that was a confirmation from you that the leaks were a significant factor.

Bit more info regarding my pals set up, it had been running really well until the failure. Do these look ok? 30mm delorto with a JL3 exhaust
Main 120.
Needle x7p2
Atomiser av268
Pilot 50
Slide 40

Stevepshipley wrote:Bit more info regarding my pals set up, it had been running really well until the failure. Do these look ok? 30mm delorto with a JL3 exhaust
Main 120.
Needle x7p2
Atomiser av268
Pilot 50
Slide 40

Good, 'ball-park' settings.

If anything, the Atomiser AV268 looks (to me) on the large side, which is safe.