Heat seized today.. (pic of the piston added)

[bryno]

Did a 70 mile run up the M1, engine siezed up at about 70..

Came to a stop, it kicked over but very low compression. Tried again after 10 mins, still same, pushed it 3 miles to services, kicked it over and it started up

Presume it must have heat seized, not sure why I had low compression though? rode the 70 miles home without problem.

Guy I met at the services mentioned that the auto lube can't keep up with oil delivery at high revs, maybe I need to disconnect the lube and try pre mix?

Oddly enough it siezed about 5 mins after a Lambretta I'd just caught up also siezed, lots of smoke from his though, pretty terminal, had to call the AA to get his home, poor bloke had ridden all the way from Devon to Leicester and was on his way to Scarbro'

[Spence]

When we got Lu's T5, lots of people said to us we should disconnect the autolube and do pre-mix anyway, because by the time they get that age the autolube starts to give up the ghost. Might be a wise decision, and not a huge chore really.

[dto79px]

hmmm heat seized - best strip barrel down and check for damage

with your 172 kit and race pipe i take it you up jetted main jet

my p125x with 180 kit has a massive 110 main jet

the oil pump is not ajustable and is set up for standard bore and jetting .
at full throttle the oil pump will not give out sufficient oil for your set up ,

if oil pump is working ok ie level go's down approx 100ml for 5 litres of petrol used

then go for semi premix -ie leave pump connected and add oil at 200/1- 25ml to 5 litres of fuel

or disconnect oil pump ,drain tank and block oil tube on carb and run full premix at 50/1 - 100ml for 5 litres of fuel

and your need the nice little white jug all old vespa owners have ;D

ps with your kit you should be using fully synthetic oil

[mrsm]

Oh no bad luck Bryno. Glad you both got home OK.

Mrs M

[bryno]

Yep, fully synthetic, running a 115 main jet, had done a couple of full throttle cuts to check the plug colour, if anything the plug has always been a bit dark..

Just stripped it down and the piston is shot, a section has broken off the crown .

Oddly enough it was still pulling strong to 70mph, no loss in power I just noticed it was vibrating a bit more than usual at lower revs so thought I'd have a look at it.

So I've put the 125 back on for now, the 172 barrel looks ok, so need to decide if i want to try it again with a new piston, oh well

[dto79px]

Nice piston , with luck all the bits have gone down exhaust and out of harms way

looks like lack of oil seize to me , best add a bit of extra oil as advised in other post

[bryno]

Yep, I'm sure the bits made a swift exit out the exhaust!

Spoke to PM Tuning about the problem, they are not convinced it's from lack of oil, see no problems with running the autolube, other suggestion was poor fuel or timing was out, personally I think lack of oil seems the most likely..

Anyway, it's back as a 125 for now, still not sure what I'm going to do, options are to leave it as a 125, get a new Malossi kit or look out for a P200 motor which is my preferred option..

Damm slow now it's back to stock, I'm soon going to get bored of that ;D

[t]

Piston looks lovely!
I wouldn't rush to blame the autolube as I would expecet more damage if that was the case. I've only ever had one autolube fail and that was due to cheap oil from a garage blocking up the gears (It didn't mix well with the other oil I had been using).
It could have been poor fuel or even a momentary blockage of the main jet. Did you have a full tank? It's not as much of a problem with a stock carb but low fuel will reduce the fuel flow.

You could try looking on this page for some more help:
www.smellofdeath.com/lloydy/piston_diag_guide.htm
I used to run kits at 3% but now just use 2% of rock oil synthesis 2 with no problems. If you do run premix remember to up the main jet.

[bryno]

I do get often get fuel starvation under 1/4 tank, but wasn't experiencing it before it siezed, it was running strong up to the point of siezure, always use Optimax, though could have been a bad batch, but again it was running well to the point..

Don't believe there is anything wrong with the autolube as such, but i'm told when you are running highe revs than stock, it can't handle the oil flow on open throttle, looking at the cable linkage, you can see that the autolube is at full flow a few mm before the throttle is fully open.. bit of pre mix seems the sensible option