Holzfforma G660 / Ported Cylinder for Milling

[Paul Fithian]

Received a new G660 powerhead yesterday to use with a 36" Alaskan mill I'm setting up. Started right up, great throttle response. Ran perfect through several stop/start cycles, no leaks, all good. Serial number shows it was built November 2022.


Checked timing in stock form, got these numbers:
- Exhaust: 95
- Transfer: 117
- Intake: 82

Plan is to install a Cross cylinder kit and OEM piston bearing, should arrive next week. Some pictures of the as built saw, overall looks pretty good. NGK plug, all fasteners were tight with blue Loctite





Crankcase washout with mineral spirits showed no sign of metal.

Any other advice for this build?

 

[Funky sawman]

I wasnt too fond of the cross piston. I used the oem piston in my cross jug, but a meteor piston would also be an excellent choice.. I'm a commercial cutter so my opinion might be bias

 

[Maintenance Chief]

Use a Husqvarna 372xp decomp, your shoulder will thank you.

 

[Funky sawman]

I ported the outside of my cross cylinder. Ground down all the casting lines and flash between the cooling fins. This style porting is what I perfer, it makes my job easier to clean the fins out once a week. No joke!!!!!!!!!!!!!

 

[drf256]

There are knockoff NGK plugs too, so I’d swap it out.

Counterfeit spark plugs: The ignition villains that could ruin your engine!

NGK SPARK PLUG advises on how to beat the counterfeiters. Fake spark plugs can do serious damage to cars and businesses.

www.ngkntk.com

Youll need an OEM decomp valve. The China ones are known to retain the stem solely from the top cap. Once the top cap falls off, the stem can fall down into the cylinder and cause catastrophic damage.

 

[Paul Fithian]

Thanks fellas, really appreciate your help so I can do this right. Here's what this saw will be chewing on, red and white oak from my yard.


List of items for this build and running as an Alaskan mill / 36" bar:
- Real NGK spark plug
- Stihl or Husqvarna decomp valve
- Cross 54 mm P/C kit - Check ports, especially exhaust chamfer. Modify as needed to prevent ring snag
- Stihl OEM 9512 003 3281 piston pin bearing
- 40:1 XD-100 or Sabre // 25:1 any other type of oil
- Auxilliary oiler at nose end of bar
- Muffler mod per below:

 

[drf256]

I’d run 25-28:1 with any oil, including XD. It’s cheap insurance. Milling is very hard on an engine. It’s max load/max output for the entire process, very different than bucking big logs.

I’d remove that entire inner muffler baffle and add another deflector to the flywheel side of the can. You‘ll want the exhaust to go up and away from you while milling. It’s a lot of work, and exhaust blowing in your face can make it even more annoying.

I didn’t realize how hard milling was on a saw until I did it myself.

 

[Paul Fithian]

I’d remove that entire inner muffler baffle and add another deflector to the flywheel side of the can

Got it regarding the baffle.

Any example of the deflecter suggested?

 

[Paul Fithian]

Measured 0.011” squish with the as built P/C without base gasket.


Timing numbers in first post were with as built 0.022” gasket.

With a 0.010” base gasket, squish should be 0.020” and reveal some decent timing numbers?

 

[srcarr52]

Measured 0.011” squish with the as built P/C without base gasket.
View attachment 365604

Timing numbers in first post were with as built 0.022” gasket.

With a 0.010” base gasket, squish should be 0.020” and reveal some decent timing numbers?

0.010" is about 0.75deg on opening numbers, 1.5deg on durations.

 

[drf256]

Got it regarding the baffle.

Any example of the deflecter suggested?

I can send you one.

 

[srcarr52]

Got it regarding the baffle.

Any example of the deflecter suggested?

I'd use one of Joes' (red97) deflectors.

Muffler deflector LARGE cut to fit

Large size cut to fit. 20 gauge mild steel. Approx deflector size 1.5x1.5x.75" Good size for most 70cc+ saws

worksaws.com

 

[Paul Fithian]

I’ll take it Doc, thanks!

 

[Paul Fithian]

Received the Cross P/C kit today, not sure I like what I see. Needs additional work before I would build a saw with it.

Installation with no base gasket showed interference, contrary to what others have reported with this kit. Squish measured 0.019" with a 0.022" gasket, here's how timing numbers compare to the Holzfforma as built P/C:

For sure the exhaust needs beveling and clean up, it is very flat on both top and bottom, with jagged edges


The floor looks like it was patched with gray epoxy


Piston looks good, weighs less than the Holzfforma piston


Not sure if I would use the piston pin circlips this came with, they included 4


Next step willl be to put the saw back together with the Holzfforma P/C using a 0.010" gasket and a Stihl piston bearing.

 

[srcarr52]

I’d run the cross. I always run a gasket if I can.

 

[smokey7]

I like everything about the cross kit except the exhaust port. Good numbers light piston. I must say i am impressed with your farmertec cylinder. That sob sure looked better than any of the ones i have seen.

 

[Paul Fithian]

I must say i am impressed with your farmertec cylinder. That sob sure looked better than any of the ones i have seen.

I thought it looked pretty good as well, and timing with the 0.010" base gasket looks OK.

Maybe I'll do some mild work on the Holzfforma cylinder it was made with to widen the ports a bit?

Some more pictures. For sure the exhaust port shape on the Holzfforma cylinder looks a lot better than the Cross jug.

 

[Agent Smith]

Hey paul. Here's some pics of the duke's reserve top end I mentioned. Greg @farminkarman recently did a build with one and maybe he can chime in and give his input of what he thought. I thought the transfers were pretty nice for aftermarket as well as the rest of the ports. Here's the numbers I came up with using an oem base gasket...95/122/80 with .022 squish

 

[Agent Smith]

 

[Agent Smith]

Here's a link and if you decide to get one, message me as I have a 10% off coupon you can have

THE DUKE'S RESERVE NIKASIL PISTON AND CYLINDER KIT FITS STIHL 066 MS660

Great port timing numbers right out of the box and consistent from cylinder to cylinder. Nikasil plated, great quality aftermarket cylinder for MS660. As good as it gets for aftermarket MS660 cylinders.

www.sawsalvage.co