Cylinders

[cosmo440]

1980 Liquifire 440. Late last year took out a piston on the Mag side, didn't damage the cylinder though. Engine had about 100+ miles on it. Did some measuring on the cylinders and the Mag cylinder on the side to side(45 deg. from intake/exhaust ports) is right at the wear tolerance, actually about .0001 over wear tolerance. I got 2.6782, manual states wear limit at 2.6811. I guess this is why if failed. The PTO is still in spec. The rings looked like it caught the exhaust port on the power stroke on the way down, as the rings are bent up. These are chrome cylinders, bought NOS unused on ebay. Crank has been rebuilt, bearing on PTO side was damaged and replaced. Have new pistons and full gasket kit. Have a 80 parts sled, engine not seized, hopefully jugs are in good shape. Another winter of repairs.

[That Girl Racing]

That is not why it failed. Don't know exactly why, but that is not it.

[cosmo440]

I guess the next question is: would you still use it?

[That Girl Racing]

Absolutely.

[That Girl Racing]

Who measured the bore? Takes very good equipment to measure to four places.

[AirborneX4Special]

My 82 LF crashed over the weekend, same sort of damage it appears. Scoring on the exhaust side of the mag piston is evident thus far but likely more to come as I get it torn down. Looks like gasket failure as there was coolant puddled between the jugs on top of the crankcase. My niece was riding it at the time of demise, she said it backfired before shutting down.

Snow is melted but at least I can wrench and wrenching is all - weather fun.

[cosmo440]

I measured the bore with a tri-post bore mike, accurate to .0002. I build turbos at my job, so I know how to use them. Because the bore mike measures at 3 points, I turned it to measure at 6 points in the bore, at the top(below the ridge), middle and at the ports. The cylinder has no score marks on it, just worn a bit on the mag side.

[cosmo440]

Here is the cylinder.

[That Girl Racing]

Cylinder looks good. You have the right stuff.

[cosmo440]

This is the third time I will be rebuilding this engine. The first time was ok, head leaking, took it to Centre Point Performance in Leduc because the guy there was a JD guru, long story short, I got screwed by them. Second time great, lasted 2 years. No problems until this. Starting to get gun shy now.

[That Girl Racing]

Many things will cause a piston to go. Usually detonation does it, brought on by a lean mixture. Stock heads and timing? Same cylinder both times? Fuel quality is a big issue.

[cosmo440]

Possible lean mixture, did a plug check and if anything I am running rich, plugs were more black/dark brown. Stock heads, stock timing(at least stator lined up with mark in block). Centre Point had the timing mark about 4-5mm above the mark in the block the first time. The engine was blown and apart when I originally got the machine. It actually had lined cylinders in it the first time, long story there. It ran ok and then Centre Point messed with it. I rebuilt it again, this time I got NOS cylinders and new pistons, and it worked great for 2 years. Don't think it is bad fuel as I always get from major name, use premium and a bit of octane boost. The day it blew I was running for about 2-3 hours with no problem, had lunch and started going again for about another 40 min, stopped to look around and then it wouldn't start. The only thing I noticed is that about 5 min. before I shut it off it just felt sluggish, still ran, no missing or popping, just like it was tired. Towed it back to the shop, tried starting it for about 20 min., finally got it going, road around the yard and then it just died and would not start again, did a compression test and got 120 or so on the PTO, and 30 on the Mag.

[AirborneX4Special]

I've found it nearly impossible to "read" plugs with any sort of accuracy. Tending to the side of rich is hard on them but much easier on the engine. The most durable two stroke snowmobile engine I've ever owned is the original Yamaha 485 they put in the Phazer. The rest always seem to go down over varied lengths of time but that thing seemed to run forever with modest care. The rest of the sled was top heavy and rather boring.

[acesillini06]

I've had the worst luck with my 83 L/F. Since 2007 only put 130 miles on it with 4 blown motors and with 3 different engine builders. Now I can say with CONFIDENCE all the money spent is worth it to finally get it running the way it was made to. nos cylinders, kawi pistions, and nitrated kawi rings, JD gasket, factory timing and jetting, nos throttle cables, and choke cables. Im running non-ethanol 90 octane gas from our BP supplier and Klotz. It starts on one or two pulls everytime i go out!!!

[AirborneX4Special]

I always run the highest octane non - ethanol fuel I can find. Ethanol is simply not as efficient an energy producer per unit of volume as straight gasoline and let's be real, it would not exist without the subsidy schemes. If you are worried about water in fuel, use ISO Heat on the trail.