port timing for modded saws

volks-man · Mar 15, 2010

is there a general number one shoots for on port timing on a modded saw?
lets say a torqy work saw that is a borderline gtg race saw.

i understand that not everyone will time their saw the same... but there must be a guidline?

i am especially interested in port timing on saws similar to the husqy 357/359 with and without crank stuffers. i want to know how the smaller volume crankcase cyl would be timed vs the larger volume case version.

another saw of interest is the 046 top on an 044 bottom. i can see it being a high rpm saw with the low case volume, but how do you get some torque back in it with the port timing?

input?

volks-man · Mar 15, 2010

nobody has any insight in to basic performance port timing?

suggestions where i could read up on it?

poulson01 · Mar 15, 2010

Check Snellings builds.
He's got it down.

J.W Younger · Mar 15, 2010

volks-man said:
nobody has any insight in to basic performance port timing?

suggestions where i could read up on it?

Intrested here to, not a lot on 2-strokes with can mufflers it dont seem.

billmartin · Mar 15, 2010

volks-man said:
nobody has any insight in to basic performance port timing?

suggestions where i could read up on it?

PM me for some reading that I havn't even looked at but I think it should get you started!

It was sent to me by a member here. I was asking a similar question and he sent some good stuff my way.

Bill

blsnelling · Mar 15, 2010

A ball park number, that is not for all saws would be:

Exhaust 100
Transfers 120
Intake 80

volks-man · Mar 15, 2010

billmartin said:
PM me for some reading that I havn't even looked at but I think it should get you started!

It was sent to me by a member here. I was asking a similar question and he sent some good stuff my way.

Bill

blsnelling said:
A ball park number, that is not for all saws would be:

Exhaust 100
Transfers 120
Intake 80

thanks fellas!

wigglesworth · Mar 15, 2010

volks-man said:
another saw of interest is the 046 top on an 044 bottom. i can see it being a high rpm saw with the low case volume, but how do you get some torque back in it with the port timing?

input?

I just built one. The port timings are stock, the transfers are just cleaned up and the exhaust and intake is widened. Torque is not an issue. You can stand on it with a 25" and an 8 pin and cant stop it.

volks-man · Mar 15, 2010

wigglesworth said:
I just built one. The port timings are stock, the transfers are just cleaned up and the exhaust and intake is widened. Torque is not an issue. You can stand on it with a 25" and an 8 pin and cant stop it.

are you saying it will outrun a stock 046?
i'm wondering if this is an effect of the stock 046 timing sitting on top of the small case?

blsnelling · Mar 15, 2010

It's hard to go wrong just widening the ports and leaving stock timing alone. You may leave a little on the table, but it will run good.

wigglesworth · Mar 15, 2010

volks-man said:
are you saying it will outrun a stock 046?
i'm wondering if this is an effect of the stock 046 timing sitting on top of the small case?

Yes, by a long shot.

lamar_3704 · Mar 15, 2010

I'm also interested in port timing. I've been wondering that when you remove the base gasket, should you raise the ports the thickness of the gasket to bring it back to stock timing, or does it make much of a difference???

Widening ports is quite easy and I agree, its hard to go wrong there. I want to get into this deep enough that I can really screw something up. lol

blsnelling · Mar 15, 2010

Just removing the base gasket doesn't make that much of a difference. You're only talking about maybe 2° there.

volks-man · Mar 16, 2010

blsnelling said:
It's hard to go wrong just widening the ports and leaving stock timing alone. You may leave a little on the table, but it will run good.

i wouldn't even expand the ports on the saw. i am concerned with port timing only. if the timing needs to be adjusted then i would go ahead and port for gains as well.

basically lets say i want to drop a 066 jug on an 026. with that tiny case volume, when the piston drops, there is a lot of fuel/air displaced. i would assume i would need the intake to close as soon as possible so not to spit it all back to the carb.
i also assume i want the exhaust to close as soon as possible to retain the charge before it is forced out by the high pressure of the tiny case. i can't do both at the same time without a TIG.
i am not real sure about the transfers though. just extend them all the way down the cylinder (sorta increase case volume) and make them bigger and hope for the best, i'd guess.

thoughts?

blsnelling · Mar 16, 2010

volks-man said:
basically lets say i want to drop a 066 jug on an 026.

???

volks-man · Mar 16, 2010

blsnelling said:
???

it is an exageration to illustrate the point.
should i have said 880 jug on 026?

edit:
crap, i have to go to work this morning. try and solve all my problems before i get home.

blsnelling · Mar 16, 2010

volks-man said:
it is an exageration to illustrate the point.
should i have said 880 jug on 026?

edit:
crap, i have to go to work this morning. try and solve all my problems before i get home.

I thought so :cheers:

A couple things to think about. Go too high with the transfers, and you start pushing exhaust down them and hindering flow and RPMs. Raise the exhaust too high, and you loose compression and torque. Lower the intake too far and you start loosing base compression. It's all a balancing act. And some saws like what another saw doesn't. For example, a 7900 likes more blowdown than say a 372.

gink595 · Mar 16, 2010

How are you guys attaching your degree wheel to get accurate readings?

blsnelling · Mar 16, 2010

gink595 said:
How are you guys attaching your degree wheel to get accurate readings?

I measure the flywheel diameter and resize this picture to whatever size I need. I cut it out and super glue it directly onto the flywheel. I then secure a piece of wire under a screw into one of the recoil mounting holes.

gink595 · Mar 16, 2010

I guess my question was kind of loaded becasue I've seen people mention doing that. I really think that is a very flawed way to go about it, how can that be accurate at all? if it isn't dead center how can you get accurate results. To me thats like measuring a piston with a tape measure, it will get ya somewhat close but not dead nuts.

port timing for modded saws

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