Scooterotica

holed the piston on my imola yesterday,,its been runnin fine for 3000+ miles never missed a beat,,been thrashed within an inch of its life on more than one occation,,no air leaks,,no jetting change,,correct amount of 2 stroke oil,,im really scratching my head on this one,, cheers steve,,

If you have checked everything (including ignition advance with a strobe) and find no problem then it has simply been running lean all the time. Alloy kits are far more forgiving with jetting, just because they didn't go pop when you were giving it "some beans" does not mean that it isn't being progressively damaged.

Like all two stroke road engines, it is best to run a little on the rich side to account for changes in ambient conditions (even if you set up on a dyno with AFR information).

...blew my mugi recently...like you been perfect full thrash for ages...i put it down to loose head nut...there was no signs of blowing...it went within about 10 miles down the motorway doing a slow 50mph two up...it was pinking slightly so i was changing throttle position thinking it was just a weak spot with jetting...very suprised for it to fail...

Maybe fuel supply issue (junk in the tank, plugged fuel filter, plugged carb screen, plugged gas tank vent)....

Just a thought.

I'm with Rich_T on this, I holed the first piston on my muggy within 400 miles Upped the jetting and fitted a new piston and all was fine for 2,ooo miles and then the 2nd one went The 3rd one has been in there for well over 4,ooo miles now but I'm still wary of sustained high speed thrashing. One of the downsides of nicasil barrels is that they don't nip up, the first you know is when the piston lets go and jams solid due to the debris. You realy need to go up on your jetting until it bogs and then come down one step, plenty of plug chops ar half to full throttle.

The other thing to concider is the wheather, if it's a warm day then it won't help given the marginal cooling on a lammy engine

the above is prob a good reason to fit a EGT guage saved my dragster when the manifold came loose i know there not the be all and end all but they can help

coaster wrote: The other thing to concider is the wheather, if it's a warm day then it won't help given the marginal cooling on a lammy engine

Eh, Bad science surely? On warm day an engine will run richer due to air density. Ambient temperature will have little effect. Unless sat in traffic. How do people in hot countries manage?

As stated above nicasil barrels give little warning and tend to let go with severe damage to piston. Barrels can usually be cleaned up.

If I was running a Mugello or Imola I would check the head comp because these can be way off. Or possibly fuel BP high octane is bad news for our engines.

Chutney Brownlove wrote:Eh, Bad science surely? On warm day an engine will run richer due to air density. Ambient temperature will have little effect. Unless sat in traffic. How do people in hot countries manage?

Hmmm, I somehow doubt they are completely self compensating, anyone with an EGT or CHT confirm if ambient temp has a bearing

Chutney Brownlove wrote: If I was running a Mugello or Imola I would check the head comp because these can be way off.

Do you have or is there an ideal figure for this?

coaster wrote:
Hmmm, I somehow doubt they are completely self compensating, anyone with an EGT or CHT confirm if ambient temp has a bearing

Possibly..my cht reading drops slightly if its p1551ing it down ( regularly)

One thing I did notice last week on the way to and from Blackpool we filled up at the same filling station both ways and my cht temperature shot up both times a good 20 degrees straight after both fill ups - it is normally fairly steady.

Maybe another fuel issue??