Hello.

First trip this spring on my PX125 with Pinasco 177 alu. And The bugger seized on me in 90 km/h! Really hard seized as well, the back wheel locked up without warning and skidded for about 20 m before I pulled the clutch.Waited for it to cool down, but still no movement.

Pushed it home an got the top off. The piston is stuck pretty far down the barrel, and there is some scorcing, but not as bad as I would imagine.

Now questions:

* Is there ANY possability to smooth out the scorches on a nicasil coated barrel with a dremel? Or is the cylinder just scrap metal now (hardly broken in) ?

* How does a hard-seize affect the crank? Does it get unbalanced? Do I have to get a new one?

*WHY does an alu-cylinder seize? I´ve upjetted to 114 main on a 20/20 carb?

* Since the Pinasco was a true dissappointment - what cylinder should I get instead to get a daily commuter?

/Johan

It is really very very difficult to seize a pinasco alu!!! Actually it is probably the most difficult cylinder to seize!!! Considering the big main jet, the cause must be something else: either the oil seal (flywheel side) does not hold so that the engine gets air from it (did you notice problems for the engine to get back to the minimum rew after accelerating?), or the autolube, if you have it, failed. In any case, there must be a notable problem which caused the seizing (may be also the cylinder head not properly screwed), the problem is not the cylinder, you must find the problem or else you are going to seize also your next cylinder. The crank may have been affected by the seizing, you have to verify that the conrod moves not excessively laterally, and that it does not move axially at all with respect to the pin.

OK, thanks Oscar. The quality and robustness was the main reason why I bougt a Pinasco Alu. Now I'm not very happy with it, hardly lasted past breaking in...... Bullet proof (not)....

No autolube and I filled it up with the proper mixing ratio just before I took it to the road. It seized on the flat of the highway. The engine was revving but not at all under heavy load.

The seize occurred very suddenly, I really didnt notice anything unusual before. (I know what a soft-seize feels like, experienced it a couple of times with the stock cylinder).

The oil seal seems unlikely, the engine started right up and idled nicely. So no Air leak. I was also very thorough during assebly, used a torque-wrench and crisscrossed the head bolts carefully....

Since break-in was performed by-the-book and I'm a gentle driver I suspect that the cylinder was faulty... Any chance that SIP will compensate? Because a seized snicasil-cylinder i scrap - right?

Any advise?

Did you check the ring gap?  Did you seat the rings correctly?  It's a nikasil kit, so I assume that it comes pre-chamfered?  Did you check the timing with a strobe?  Any kinks in the gas line?

There are so many reasons why an after-market kit can seize, and 99% of the time it comes down to user installation error.

Have not checked timing with strobe, but since I have not changed it during the installation process I´m pretty convinced it was OK. According to Pinasco´s manual the timing advance shall remain on the IT-mark, which it still is....

The piston rings had a tight fit around the location pegs (it was a NEW kit goddammit) and even after the seize one can tell that the rings have not been dislocated or caught on to ports. The circlips holding the gudgeon-pin was also still in place. Also, fuel was running freely when I dropped the engine after the seize, and there was no signs of lean mixture before the accident.

Sure, I may have made a mistake during installation - but I really cannot figure out what it might be. Especially when It had been running great during break-in and that it really wasn´t under strain when it seized.

Anyhow the cylinder kit is now scrap. Anyone who beleive there´s a chance tha SIP will compensate me?

Take photoes of the cylinder and piston so that we can try to judge the situation and hypotesize the cause of the seize.

Assuming jetting and timing were set up properly, and that the engine had been run in correctly I'd certainly be looking at something mechanical as the cause of your problem - an air leak being the favorite.

I have also experienced on problem an otherwise healthy Malossi 210 engine which had been running fine then after a petrol stop at a small garage it holed the piston...... certainly shitty fuel wrecks motors, worth a thought.

As for the barrel, as long as the alloy isn't damaged, you should be able to get it re-plated.

OK.

Now I have split the cases and performed a mini-renovation of the engine. Changed oil seals and opened up the intake hole a little. Changed cruciform and Put the stock 125cc cylinder back in, and she´s up and running again!!! No damage to gears or crank, puh..... But after 1500 k:s on the Pinasco the stock cylinder feels EXTREMELY powerless.....

Now to the seized Pinasco - is there any chance that the nikasil has survived the seizure and that the "dents and scratches" seen below only is aluminium from the piston? I've read on a snowmobile forum that the nikasil is tough and survives while the piston actually melts. And that the aluminium smeared on the barrel walls can be removed using strong hydrochlorid acid that corrodes aluminium but not the nikasil coating. Anyone who have heard of this method and if it works?

If I manage to save the cylinder- what piston shall I get to get it running again. The ones in SIP:s webshop 10720000 are for the cast iron 177 cylinder, not the aluminium one. Anyone who knows if thare interchangeable?

Took a closer look at the schorching in the barrel - and realized it can NOT be saved. The nikasil has been ripped right off the cylinder wall close to the ports on both sides. The damages are about 5mm wide and 3 mm tall. The cylinder is damaged for good, a re-plating costs more than a new kit with piston and all.....

Since I beleive that there must have been a defect on either the piston or the barrel that caused the seize - but at the same time SIP gives no warranty - is there any chance getting a discount on a new kit? Anyone who has had any success in negotiating with SIP?

a) I'm willing to wager an obscene amount of money that this was a user problem and not a defect of the cylinder.

b) no one, not even pinasco offers a warranty.  too many variables of why a cylinder fails.

c) you already admitted that you didn't strobe the timing, you didn't check the ring gap, etc.  those lead one to believe that you didn't properly set up the cylinder.  did you do plug chops, run a cht or an egt to monitor temperatures?

Save up your cash and buy a new or different kit, but don't expect SIP or Pinasco to pony up.