Scooterotica

px200/HB stage 4, catastrophic metal down/grooved and piston rings nipped into piston, 2inch strip down piston "Exhaust side". rest of piston/crown and plug powdery brown/black spot on!!! scoot was jetted and chopped right, 18deg timing...but did notice since january the exhaust downpipe getting far to hot!!!
what do ye reckon lads before i crack engine open! airleak, seals, airleak exhaust stub/exhaust, timing

Thats not good !

had a very similar thing on Sean Macs Malossi 172 T5 a few years ago

Ran loads of miles no issues - had ring chances done as they should be, using the same oil (autolube blanked off) etc then out of the blue -it had was he thought was a soft seizure but it wouldnt restart.

When it came to me i had a good look round it and checked it out - No visible oil leaks - exhaust, base and head gaskets okay, carb on tight, g/box oil spot on, timing okay, woodruff key okay, flywheel side seal no visble leaks

When i stripped the head off and looked in the edge of the crown of the piston had started to melt taking out the ali down to the first ring - plus the crown was melting from the exhaust side to centre. Crown was dry and grey

The size of the area melting on the edge of the piston was virtually identical to the exhaust port

Top ring was siezed bottom still free - It damaged the nicosil cylinder and we replaced the kit

It was reassembled with new gaskets etc and given a thorough check over and still going strong today - and its had diesel in it since !!

I never new what caused it - bad fuel was my only thought at the time.

You`ve got that GTS now so just put a cover over it !!

Just wondering what size bore, clearance and what piston where you using ?

I`ve just done a stage 4 ish cast barrel myself - spare genuine barrel newly bored out with 4 thou clearance using a cheap thin ring 67.5mm piston which i have enlarge the ports, cleaned up and knife edged all the ports in the barrel and widened the exhaust. First cast barrel i`ve done for years - have a packing plate so might recess a spare head (but no intention to at minute)

Piston came from AF £25.00 - out of those indian ali 210 kits - thought id give it a punt - quality seems okay, rings are good - nice little top end for less than £50 (piston and bore) - another spare on the shelf !

Standard barrel n thick ring piston, Piston to barrel 4thou a mick abbey worked stage 4, beautiful in every way, burned and pulled strong, barrel needs a rebore now it's scored and melted alli above n below exhaust port...bah happy dayz! Gunna replace seals and get casings mpi'd at work to elliminate cracks n air leaks!!!! Bring on the darkside and embrace old age and peace n quite

Isn't melted ali on the exhaust port side a sure sign of pinking?

Cheers joey, no pinking at any point on the throttle on this engine, like i say i did notice exhaust down pipe getting excessively hot, but engines gunna get stripped and hopefully see something....

Gadge what pipe are you running?

JL right hander, Wot ye thinkin joe

H,POOL GADGE wrote:JL right hander, Wot ye thinkin joe

Sell it? Stainless pipes no-good for your highly-tuned gadge-speed special?
You kno who has money waiting for it fella )

DAN, SEAN, DAN, SEAN....Will ye please delete Norrie The Bodger! He's a gypsy stalker and he's trying to have me over on me JL....