670 project (pics)

[pioneerguy600]

If you can post your carb model no`s then I can tell you the venturi size. Many of the carbs used on these saws have a difference of 1/16" in the venturi sizes.
The HS 230A is the better carb if you have one, it has a 11/16" venturi compared to the standard 5/8" of most of the other carbs.
Pioneerguy600

 

[jockeydeuce]

If you can post your carb model no`s then I can tell you the venturi size. Many of the carbs used on these saws have a difference of 1/16" in the venturi sizes.
The HS 230A is the better carb if you have one, it has a 11/16" venturi compared to the standard 5/8" of most of the other carbs.
Pioneerguy600

That's the carb steve will have very shortly!!!

 

[hamish]

Very nice project, can wait to see it all finished.

 

[Cantdog]

If you can post your carb model no`s then I can tell you the venturi size. Many of the carbs used on these saws have a difference of 1/16" in the venturi sizes.
The HS 230A is the better carb if you have one, it has a 11/16" venturi compared to the standard 5/8" of most of the other carbs.
Pioneerguy600

I think the 224,230,250 and 260 are all the larger size venturi. With the 224 and 260 the only ones that will bolt right up to the Husky cyl without redirecting the the impulse. (either by tapping into the internal impulse like I did or by boring the carb body to pick up the Husky type internal impulse.) The 230 and 250 are the for the external Jonsered impulse with the 250 being a recirc type carb. But check out these carb umbers if you will Jerry, and see what the specs. are. Thanks.

 

[Steveo_supremo]

Nice project!! I'm here if ya need some taken off that cylinder base. What's the bore size?

Thanks Wil, bore is 52mm. I haven't yet decided if I'm going to machine the base or just make a thinner base gasket. I only need to "lose" about .009"

Cantdog,
That info basically confirms for Me that the HS 230A (670) carb has the same venturi bore as the HS 260 (272) carb.
Thanks

 

[Cantdog]

Thanks Wil, bore is 52mm. I haven't yet decided if I'm going to machine the base or just make a thinner base gasket. I only need to "lose" about .009"

Cantdog,
That info basically confirms for Me that the HS 230A (670) carb has the same venturi bore as the HS 260 (272) carb.
Thanks

Well I think you're right but would still like to see what Jerry comes up with for numbers. I'm running a 250A (Jonsered style) on my 268XP and am thinking that perhaps the only difference between the 230 and 250A is that the 250A is a recirc type carb.

 

[pioneerguy600]

I think the 224,230,250 and 260 are all the larger size venturi. With the 224 and 260 the only ones that will bolt right up to the Husky cyl without redirecting the the impulse. (either by tapping into the internal impulse like I did or by boring the carb body to pick up the Husky type internal impulse.) The 230 and 250 are the for the external Jonsered impulse with the 250 being a recirc type carb. But check out these carb umbers if you will Jerry, and see what the specs. are. Thanks.

They are all 11/16" venturi stock, could be bored out to around 3/4" if needed.
Pioneerguy600

 

[Steveo_supremo]

How would a guy go about boring a carb? I have a couple junkers I could practice on.

 

[pioneerguy600]

Mount it on a backing plate and internal mahine/bore it on a lathe. An endmill will also accomplish this chore but I prefer a lathe.
Pioneerguy600

 

[Cantdog]

Thanks Jerry good stuff to know.

 

[parrisw]

Thanks Wil, bore is 52mm. I haven't yet decided if I'm going to machine the base or just make a thinner base gasket. I only need to "lose" about .009"

Sure. Just let me know.

 

[Steveo_supremo]

I kinda let this thread die, but I have been working on the saw. I made a base gasket out of some brass shim stock from the hobby shop. Squish came out right at .020" with this gasket. It is .005" thick.

Next I measured the port timing before doing any grinding. Stock numbers (with thin base gasket) were:

Exhaust: 105° ATDC or 150° duration
Intake: 71° BTDC or 142° duration
Transfers: 126° ATDC, 108° duration
Blowdown: 21°

more to come.

 

[Steveo_supremo]

Here's some pics of the port work. This is my first port job so go easy on Me with the comments.

Intake:

Transfers before:

After:

Exhaust

I guess I didn't get any pics of the intake and exhaust before porting. They were both widened to within 2mm from the skirt edges. Exhaust was raised and intake lowered.

Timing after porting was:
Exhaust: 102° ATDC, 156° duration
Intake: 78° BTDC, 156° duration
I didn't raise the transfers so blowdown ended up at 24°

Sprayed the base gasket with some permatex gasket sealer and installed the cylinder for good. Ran a pressure/vac test on it.

Next, I drilled the 670 carb for the internal impulse so it will work with the 272 cylinder/intake manifold.

Sent 'er for a dip in the ultrasonic cleaner.

I put the carb together, then I cleaned up the tank and installed a new fuel line and filter and 2 new front a/v mounts. No pics of that, though.

All that's left now is to open up the muffler and some asssembly. More on that in a day or 2.

 

[jockeydeuce]

Hey Steve!

I was going to send you a PM and see how the project was coming.....Glad to see you adding to this build!!!

 

[Steveo_supremo]

Hey Steve!

I was going to send you a PM and see how the project was coming.....Glad to see you adding to this build!!!

Thanks, I'm going out to work on it some more right now. :chainsawguy:

 

[parrisw]

Nice work. Looking good.

 

[little possum]

Looks good to me as well!

Good job not going to far into the intake port and going through the impulse- ask me how I know :msp_sad: lol

 

[Steveo_supremo]

Finished!

Coming right along.

Cut the deflector off the muffler and took the baffle out.

Made up a couple of these and welded them into the muffler so I can screw my new deflector on. I don't like self-tappers.

Made up a new deflector out of some 1/16" steel plate.

Then I painted and baked the muffler and deflector and mounted 'em up.

I also polished the dogs and added a Stihl roller chain catcher.

 

[Steveo_supremo]

And here's the finished product

All it needs now is a full wrap. Anybody got one?

 

[little possum]

Looks awesome!