Ported Husqvarna 372xpw

[blsnelling]

If you're willing, I say go for it! I would like to see the results. I however don't see it doing anything positive without raising the transfer tunnel wall, thus lowering base compression, and creating turbulence. But what do I know.

Yeah, if the cavity doesn't open before BDC, then windowing the piston is pointless, unless you window the cylinder like Scott did. I'm not willing to sacrifice my cylinder though, lol

 

[mdavlee]

18.25 mm venturi.

Thanks. So it and the 372 xtorq carb are close to the same size.

 

[SawTroll]

Thanks. So it and the 372 xtorq carb are close to the same size.

The xt carb is 19.03, if memory serves.

 

[mdavlee]

The xt carb is 19.03, if memory serves.

It's 19.xx. I can't remember either. I could go measure one

 

[SawTroll]

It's 19.xx. I can't remember either. I could go measure one

The RWJ-4 is 19.05 nominally, just looked it up.

 

[Chainsaw Jim]

This thing is still alive and kicking. I'm wondering what it would be like if I hadn't free ported it.

 

[SawTroll]

Wow, just saw this thread, 5 pages already. But it's a good topic : porting, a different recipe than the "norm", a well respected saw... Popcorn!

I think a lot of people have doubts about methods that stray from the norm. Videos showing stock/modded would always help convince people.

Also, a 372xpw is 75cc, lots of torque, and a 24"-28" bar territory saw. If you only need a 20-24" bar get a 60cc saw. Cutting smaller wood like 18" pine will likely be more a factor of chain speed than torque. I think that could be one reason it smoked the 660. Got anything bigger to test that saw with?

Only if sold in the USA, about 2006 - 2009. Most of them are 71cc, like the other versions,

 

[Rx7man]

OK, I'll admit this isn't the prettiest work around, but the cylinder wasn't very nice to begin with and I didn't care a whole lot, it was a proof-of-concept job on my L65, Bottom fed, closed single transfer converted to a bottom and piston fed semi closed transfer design. Yes, I lost base compression with all that I removed, and it does show in the bottom end grunt of the saw, but the top end gains were very good.
I had previously ported the saw with a bit excessive timing numbers, close to 90/118/90, and it ran like CRAP... there was a ton of intake reversion, and it would bog badly at anything under 8000.. it was unworkable... I think anyone would agree that these saws have pretty lousy transfer ports, so I figured if I could improve the flow there, it may come back to at least a tunable state if the transfer port flow improved, thus emptying out the crankcase better, which would in turn lead to higher intake velocities and less reversion.
This is a stock (left) and ported (right) version of the same cylinder... but I didn't change the basic design of the transfer at all


Here is a side view of my modification, showing what I cut out


And here is the windowed piston shown at BDC with the modification



This really helped 'cover up' the excessive port timing.. it does have a narrower powerband than a saw with 'standard' numbers, but it's still a whole 'nother animal compared to the saw in stock form. Also, because of the high exhaust port, the saw only has about 140 PSI compression, but I'm happy with it now. if I had as much foresight as hindsight, I'd have taken .020" off the base while I was still able to chuck it on the lathe, but with the skirt mostly gone, I can't do that anymore with the tooling I have.

Here's the saw with a 24" bar in dry fir... I think it's OK for saw that's usually considered a slug at best


The long and the short of it, is I could have left my 'mistake' cylinder alone, tossed it in the garbage, and never learned anything... Instead I took a chance and spent a few hours and got a saw I enjoy running once again.

 

[Chainsaw Jim]

OK, I'll admit this isn't the prettiest work around, but the cylinder wasn't very nice to begin with and I didn't care a whole lot, it was a proof-of-concept job on my L65, Bottom fed, closed single transfer converted to a bottom and piston fed semi closed transfer design. Yes, I lost base compression with all that I removed, and it does show in the bottom end grunt of the saw, but the top end gains were very good.
I had previously ported the saw with a bit excessive timing numbers, close to 90/118/90, and it ran like CRAP... there was a ton of intake reversion, and it would bog badly at anything under 8000.. it was unworkable... I think anyone would agree that these saws have pretty lousy transfer ports, so I figured if I could improve the flow there, it may come back to at least a tunable state if the transfer port flow improved, thus emptying out the crankcase better, which would in turn lead to higher intake velocities and less reversion.
This is a stock (left) and ported (right) version of the same cylinder... but I didn't change the basic design of the transfer at all
View attachment 473376

Here is a side view of my modification, showing what I cut out
View attachment 473380

And here is the windowed piston shown at BDC with the modification
View attachment 473379


This really helped 'cover up' the excessive port timing.. it does have a narrower powerband than a saw with 'standard' numbers, but it's still a whole 'nother animal compared to the saw in stock form. Also, because of the high exhaust port, the saw only has about 140 PSI compression, but I'm happy with it now. if I had as much foresight as hindsight, I'd have taken .020" off the base while I was still able to chuck it on the lathe, but with the skirt mostly gone, I can't do that anymore with the tooling I have.

Here's the saw with a 24" bar in dry fir... I think it's OK for saw that's usually considered a slug at best


The long and the short of it, is I could have left my 'mistake' cylinder alone, tossed it in the garbage, and never learned anything... Instead I took a chance and spent a few hours and got a saw I enjoy running once again.

That thing rips. Good job.

 

[Rx7man]

Thanks.. for comparison, I think (can't watch the vid to be sure) that this is the vid of it when I had gone too far with the timing but before I had reworked the transfers. I don't think the chain was too sharp either, but just listening to it you can hear things aren't working together. I may put the pipe from the Manhattan project on this saw (same bolt pattern), and I think it would be really sweet then. Such is the joy of having lots of cheap (but good) saws of the same model

 

[Chainsaw Jim]

Thanks.. for comparison, I think (can't watch the vid to be sure) that this is the vid of it when I had gone too far with the timing but before I had reworked the transfers. I don't think the chain was too sharp either, but just listening to it you can hear things aren't working together. I may put the pipe from the Manhattan project on this saw (same bolt pattern), and I think it would be really sweet then. Such is the joy of having lots of cheap (but good) saws of the same model

I'd like to see what it does with the pipe on it.

 

[Rx7man]

Yeah, I have more fiddling to do with the piped '277' as well.. I really want to try it with the 7 pin (instead of 8) and 32" bar again, then see how the 65 does with the same pipe. I figured for sure I'd have blown the '277' up by now, I ran about 10 tanks through it with the pipe, WAY above factory redline, and with a crank I did so much cutting on I though it would be off-balance for sure.. I even overheated it once and it was fine once it cooled.