Scooterotica

Just run in my Imola 186 (S2 Mikuni TMX30 powerjet franspeed JL4) now have 360 miles on the clock. Was running very rich low down (loads of 2 stroke ont the boards) so I dropped the needle by one about 24 miles ago...sorted
Took her out today going very well indeed ....er well until in 4th she dies pulls in th clutch no dramatics rolls to a halt. No compression at all. Got her back home...1cm hole in piston

Had noticed the week before after I had dropped the needle whilst 8 miles from home when pushed in 4th a similar feeling to today ..I thought I had just hit reserve so backed off and came home anyway.

Now I ran her 3% on SIP 100% synthetic, ran her in for at least 240 softish miles...Is it a power jet thing (as in wouldn't notice till higher revs used)or a timing thing apart from the obvious lean issue......

The carb was jetted by Allans for my stated spec..no gripes by the way..........opinions much appreciated

Snap!

peter357bikes wrote:
The carb was jetted by Allans for my stated spec..no gripes by the way...

If you specced it then there can't be any gripes, have you actually checked what they put in though? I've heard many instances where what was requested wasn't actually put in...

What was your plug telling you?

i was always led to beleive that holes in pistons were predominantly due to over advanced timing, or a overheating spark plug (wrong temperature range)??

incorrect (weak) carburation would be more likely to cause heat seizures than a hole?

Rebuilt and run now for 30 odd miles, heres the plug..




Which looks quite good to me.

If the timing was out, would it not show on the plug?

What throttle position were you when your piston went and what position was your plug chop?

a hole in a piston could be done in many ways: wrong carburettor set-up, wrong ignition timing, detonation...

Once I nearly holed my Malossi 210 piston due to a wrong squish that created an alectric arch at high revving and high temperature. Cylinder-head changed, and I was able to drive my road with no problem

soulsurfer wrote:What throttle position were you when your piston went and what position was your plug chop?

I know what your thinking Mike , was he giving it some and the PJ wasnt working, it had crossed my mind too, sounds like he,s only had any trouble since dropping the needle to lean it up lower down though. What plug were you running Peter.

An N3C couldn't really tell its condition as it got blasted by the piston material...but looked very lean at first glance.