Cylinder installation

[blsnelling]

YES, you want to lube the bore and the piston. It's very critical that the piston have sufficient lubrication. There's more concern with it than the rings, especially during the first few heat cycles of a new piston. I personally like to get the cylinder warmed up a few times and let it cool before putting it in wood.

 

[oldbigred]

That brings up another question...I know there has been some discussion on here about it before, but I never found a clear-cut answer that suited me. What is the best proceedure to break in a newly rebuilt engine?

 

[huskydave]

Don't worry about breaking it in. Just use the saw. I like to load it good for the first few tanks and setup the carb a bit rich until it is broken in 10-15 tanks. Never rev it full throddle with no load for long.

 

[blsnelling]

Many just say to run it normally, just don't rev out of the wood. I personally like a few heat cylces, getting it hotter each time. That's not required though. Put your 50:1 premix in it and go cut wood. It'll last for years. If you want to be obsessive like me, warm it up good a couple times, letting it fully cool in between.

I used to run a highly modified Yamaha Banshee. It has a water-cooled 350cc twin cylinder 2-stroke engine. Breakin was critical on this thing. A fan was placed in front of the radiator and it was idled for 15 minutes, then a cool down. This was done again. Then it was riden with 50% load for 15 minutes and a cool down. This process was done again, increasing load by an additional 10% each time until 100% was reached. This is the process prescribed by one of the premier engine builders, Duncan Racing International. He did my boring and port work. The idea was to gradually get the piston hotter each time, ie bigger, letting it breakin to the cylinder bore. It was NOT for the rings. Many a machine is not broke in like this, but I'd rather err on the side of caution and have a long lasting engine. BTW, the Banshee does not have a lined cylinder, so breakin ma be more critical.

 

[oldbigred]

blsnelling:
how do you heat your saw up during heat cycling, just idle? then let it idle longer each time or do you increase rpms each time for the same amount of time? I am kinda like you...very particular about engines.

btw: i too am a Yamaha fan, banshee's were some of the best (347 cc twin 2-strokes) I currently ride a slightly modified Warrior (348 cc single four stroke)

 

[rxe]

I've just rebuilt a saw, new jug and piston - so basically a "new" engine. I rebuilt the carb as well, so all settings are lost. To tune it, I need to rev it to the limit - which pains me from an engineering perspective.

What I have done instead is start it, let it idle for a few minutes after setting the idle, then tuned it to blubber at 7000 rpm, and gone and cut wood. It is an 070, so the choke flap kicks in about then - but you are meant to disable the choke and tune it to 11,000 rpm to get the right setting. Once I have run two tanks through it, I will tune it properly to 11K.

 

[blsnelling]

I'm not near so scientific about breaking in a saw engine. I'll give them a couple heat cyles by just warming them up at idle, blipping the throttle to clear them out and get rid of all that excess assembly oil. I'll then tune the high side of the carb, which will get it good and warm. After that, I'll take it out and cut wood with it. I just won't bury a 36" bar in hardwood to start out with. I know what you mean about running anew engine at WOT to set the carb. Everyone says not to got WOT no load on a new P&C, yet that's how you set the carb. Chainsaws are the only engines I've run WOT no load in all my life. It seems crazy everytime I do it. You get used to it after a while Don't take my practices to be fact. That's just how I've chosen to do it based on my prior experiences. I'm sure most take the saw from the shop straight to the wood and are fine.

 

[blsnelling]

I've just rebuilt a saw, new jug and piston - so basically a "new" engine. I rebuilt the carb as well, so all settings are lost. To tune it, I need to rev it to the limit - which pains me from an engineering perspective.

What I have done instead is start it, let it idle for a few minutes after setting the idle, then tuned it to blubber at 7000 rpm, and gone and cut wood. It is an 070, so the choke flap kicks in about then - but you are meant to disable the choke and tune it to 11,000 rpm to get the right setting. Once I have run two tanks through it, I will tune it properly to 11K.

I wouldn't want to run near the rich, even on breakin. Maybe a little, but not near that much. I'd be worried about all that excess oil forming carbon on the piston crown. I personally use my standard premix and set the carbs where they're tuned correctly. I'm not talking the ragged edge here, but I don't purposely set it rich.

 

[Lakeside53]

I've just rebuilt a saw, new jug and piston - so basically a "new" engine. I rebuilt the carb as well, so all settings are lost. To tune it, I need to rev it to the limit - which pains me from an engineering perspective.

What I have done instead is start it, let it idle for a few minutes after setting the idle, then tuned it to blubber at 7000 rpm, and gone and cut wood. It is an 070, so the choke flap kicks in about then - but you are meant to disable the choke and tune it to 11,000 rpm to get the right setting. Once I have run two tanks through it, I will tune it properly to 11K.

Just tune it correctly from the first use. In the factory the brand new saws are run at WOT to adjust the mixture and perform epa tests... then it's shiped to the dealer and they check it by doing the same again.

After rebuilding an old saw with a rehone bore and new rings, I set the carb about right, the leave it running at about 3-4k (a fast idle) for 15 minutes or so to bed the rings (assumption - my hone isn't as good as the factory) - the rpm will pick up 500 or so in this process, then a fine tune and hand it off to the customer.