vespa nipping

[anjie1967]

54 reg px125(150) keeps heat seizing blanked auto lube ,pre mixing .simonini exhaust on

[Muttley McLadd]

Cool

[Spider]

Nowt worse than a show off!!

[Juan]

Well you should go up 2 points on the mainjet for premixing and another 2 if it was a catalised model. From memory the cat 125's ran a 96 main so you should have a 100 in it if it was cat or non-cat.

That's based on hazy recollection of PX jetting and I've not looked near one in years. Sure someone else with a better memory / more recent experiance will be along shortly.

*Edit* - Noticed it's a 150 but I can't remember 150 jetting but at a guess somewhere in the 102 -106 range should be around right.

[RICSPEED]

NOTE ....topic moved from welcome section

[Donnie]

keeps heat seizing

There's the problem, you should have been looking for help after the first seize.

However, more information would be needed ie when you say seize do you mean full lock seize or soft seize where it nips up and dies as you pull in the clutch?

Im assuming too that this engine was a 125 and you've put on a 150 top end?
If so how many miles has it done?

You say you're premixing in the tank so what % oil are you actually using?

[anjie1967]

when it was a 125cc it holed the piston , so bought 150cc barrel and piston then holed again, couldnt get ovesized piston because the barrel was ok so bought another 150cc barrel and piston ran it in for 500 miles . took it to wakefield scooters and timing was out got that sorted now its soft seizing after the 1st soft seizure it sounded run ok with no rattling 108 main jet in it. started to give more speed thats when 2nd soft seize happened is it anything to do with having simonini exhaust on ?

pre mix at 50-1 plus little bit extra
millage _ overhall 6.500km
problem started around 5,000km

chris

[C*NTSPEED]

has the autolube been blanked off properly as it could be sucking a bit of air personally id start at a 112 main and work back

[Donnie]

agreed, also have you actually done your jetting properly? ie I'd be looking at the idle jet right the way through to the main personally.

Also, you should be using 3% if your premixing on that set up and when you say ran in for 500 miles Im assuming you know you need to run in a cast iron for near 1000? oh and you're not running in on fully synthetic?

Also, when the barrel and piston were checked on fitting what was the piston to bore clearance?

[soullad]

You need to remove the top end and remove all that alloy from the barrel. Check piston / rings haven't been damaged and rings stuck in grooves. Then try and address why its seizing ... any obvious air leaks, loose exhaust / carb inlet etc? did you simply just upjet the main on a 125 carb setting? did you reuse the 125 head etc, what ignition timing you using.