Scooterotica

im posting this on behalf of my friend!!
Any help/advice apreciated

Long story but here it is:

Series 2 with TS1 225, Mikuni TMX35 and modified clubman:

After a top-end rebuild due to hole in piston, Scooter ran perfectly all day then suddenly it developed this symptom:

It will start fine and tick over on stand. It will ride fine on very low throttle openings (ie on pilot jet) so will ease up to 30mph given time...but if i open throttle more than this, it simply makes loud induction roar and doesnt go faster - it doesnt go slower either, just makes WAAAAAHHH noise.

On the stand, if i open throttle I can see fuel spraying out of needle (so fuel being delivered) but loads of spit back and it just doesn't rev - like the engine cant cope with the fuel.

I pulled reeds (boyson stage 2) and all seemed fine, nothing stuck.

I had the timing strobed and solid 19 degrees through rev range the day before this happened.

Engine has ran well with no dramas for a year and a half, but a few weeks ago i was riding along and bike started losing power like was going on reserve. Pulled over, wouldnt restart for ages, gave serious backfires and would occassionally strat then low rev fourstroking (pucketa - pucketa - pucketa) for 10 secs or so then die - refused to pick up. It did this a couple of times during the week but when it did start it would run perfectly - nasty intermittent problem.

I stripped carb, replaced fuel hose and fuel tap, new rubber mount, pulled flywheel - nothing loose and all seemed fine. (bugger - hate that!)

Anyway - it started and felt fine but then rode 5 miles and totally without warning it went bang.

Stripped top-end - neat hole in centre of piston, ally chunks and ally dust eveywhere!

I would have included the history in post above but no room!

Hope that helps give a clue as to what is going on now!

Thanks for posting that Grubbie...Yes it's my bike with the problem, here's some background that might help..

Engine has ran well with no dramas for a year and a half, but a few weeks ago i was riding along and bike started losing power like was going on reserve. Pulled over, wouldnt restart for ages, gave serious backfires and would occassionally strat then low rev fourstroking (pucketa - pucketa - pucketa) for 10 secs or so then die - refused to pick up. It did this a couple of times during the week but when it did start it would run perfectly - nasty intermittent problem.

I stripped carb, replaced fuel hose and fuel tap, new rubber mount, pulled flywheel - nothing loose and all seemed fine. (bugger - hate that!)

Anyway - it started and felt fine but then rode 5 miles and totally without warning it went bang.

Stripped top-end - neat hole in centre of piston, ally chunks and ally dust eveywhere!

I would have included the history in post above but no room!

Hope that helps give a clue as to what is going on now!

Andy

Had similar symptoms once.

long story, but cause was a knackered and stretched choke cable, that was permanently having choke full on.

Just check out your choke.

Good luck

also if you are getting alot of spitback from carb you may want to check your reeds they may have feathered i have had this happen before

Sometimes the obvious isnt so obvious...

There I was thinking - stator dodgy, oil seals,leaky gasket, blah blah blah...

Started stripping the motor last night and just happened to look in the end of my exhaust pipe and saw a massive chunk of what looked like exhaust sealant hardened into a solid hard chunk, vitually blocking the tailpipe.

Just tried her out at lunchtime and all absolutely fine!

Makes sense now - to tick over and rev a little would manage to expell gases through tiny gaps around said chunk, as soon as i rev, it cant cope and ran lean with all exhaust gases building up and forcing their way back into cylinder!

So glad it wasnt anything expensive. At the same time spinning around trying to kick myself in the arse that she's been off the road for two weeks, blown a piston, all cos of something so basic!

Heyho!