Any of you work on 2 cycle motors (more specifically chain saws)?

I have a Husqvarna 350 that I'd like to port and polish as well as do a little bit of muffler work to squeeze any cheap power out of it.

The only engine work I've ever done was handing my dad tools as he worked on our cars or changing my oil and transmission fluid, but I can read and follow directions well.

If any of you know of good online or printed references that could guide me through the processes it'd be appreciated.

6/8/2006 11:49:02 PM

why dont you just spend the extra money and buy a good chain

6/9/2006 12:32:41 AM

A good chain? My chain is fine.

6/9/2006 12:37:51 AM

man i wish i could help but 2 strokes sorta baffle me i don't know how to port them so you get more airflow without letting too much air blow out at bottom dead center.

6/9/2006 2:51:49 AM

sell it and buy a stihl.

6/9/2006 7:29:30 AM

i not so sure there is much you could do for those. other than perhaps widening the jet in the carb a little, given the way the little 2-stroke carbs work i dont think you will have much luck at anything.

but i could be wrong, it just seems to me that a little carb working off the vaccum of the cylinder to pull fuel and air wouldnt be very moddable unless you could increase the amount of vacuum inside the cylinder to pull in more air/fuel...

6/9/2006 7:33:43 AM

not much you can do, and you will probably end up leaning it out too much if you do anything like that and don't change the carb, and burning it up

6/9/2006 7:47:14 AM

There are lots of guys who port and polish all the time and have measured 0.8hp changes, all with factory parts.
I'd be able to adjust the carb enough for minor air flow mods.

I'm just looking for good reference material because I want to do with without screwing with the timing.

6/9/2006 8:55:05 AM

I highly recommend putting Automatic Transmission Fluid in the carb. Ask zxappeal for more tips.

6/9/2006 5:46:40 PM

Sell it!! and buy one of these monsters

http://tinyurl.com/p9qw2



[Edited on June 10, 2006 at 4:43 PM. Reason : fixed link]

6/9/2006 9:10:44 PM

what pitch chain are you using and is it anti-kickback? we have an 034 stihl that would barely cut with the anti-kickback stuff but when we put some 72 on it, it perfomed very well.

6/10/2006 5:02:38 PM

It's 0.325 pitch, 50 gauge, 72 drivers, semi-chisel low kickback.

I'm not really interested in changing my chain right now. I'll get a full chisel down the road.

I just want to try my hand at squeezing more power out of the engine.

[Edited on June 11, 2006 at 2:00 AM. Reason : oops, this was posted by Fumbler]

6/11/2006 1:59:27 AM

Just go buy a new saw.

Really, there are three ways that you can squeeze more power out of the engine.

1. Go with a bigger carb. You probably have a Walbro on there right now, and there are Walbro carbs in a bajillion different sizes. Problem here is that they are not cheap.

2. Work your porting on the engine. Here's the Catch-22: if you raise your intake porting too much, you also serve to drop your compression ratio. I'm not really sure of the predominant porting design on Husqvarna cylinders, but most high-performance 2-strokes use a Schneurle-style porting which incorporates between 3 and 5 intake ports (with peripheral, or side, ports called transfer ports, and a boost port directly across from the exhaust port(s)). On a lot of engines, they are timed differently, so that initially, the boost port helps to scavenge the cylinder, but then the transfer ports force more air/fuel mixture into the cylinder to converge and force upward the charge from the boost port.

You can chamfer the boost port at the top somewhat. This will help fresh air/fuel mixture to move upward into the cylinder, and less will be lost in scavenging. You can do the same for the transfer ports, but I'd make sure the timing differences between transfer and boost ports remains roughly the same.

You can clean up the exhaust ports as well, possibly with a slight chamfer at the top of the ports.

You can also clean up all case passages, but resist the temptation to hog anything out. You do want to maintain good flow velocity and turbulence. It's essential to maintain mixture homogeny.

Oh, BTW...make damn good and sure you're not going to hog any ports to the point that they catch a ring and break it.

The engine has to come completely apart to do this. Seriously...go buy a good chisel chain. It's a fuckload cheaper if you place any value on your time or if you have to go and buy gaskets for the cylinder, case, and carb.

3. Adjust your ignition timing. As a rule, the ignition timing is fixed at one place, and it's a compromise. First of all, you've got to be able to start the damn thing, and really advanced timing makes this an absolute bitch to do without breaking something. And then, of course, you need enough timing to produce optimum power. The two are, for the most part, exclusive of each other. I know, with kart engines, you can either get slotted magneto mounts or you can run an offset flywheel key. But be careful, because too much timing breaks and burns pistons.

6/12/2006 2:29:25 AM