g395 + hyway hackorama

[buckin-wood]

Got a chinvarna 395 and had some problems with the farmetec top end. So I've moved onto a hyway 395 jug with popup piston and started making aluminum chips. As I'm "touching up" the hyway cylinder I realize I have no idea what I'm doing and looking for advise

I found a few posts by folks that have worked oem 395 cylinders and simply copied their recipe... 102/122/82. I'm finishing up the transfers, and have the intake and exhaust mostly done... I think. Hoping folks have some input on a couple questions I'm thinking about before going any further.

-should the sides of the exhaust port flare out/taper more as they approach the muffler flange? any magic ratio of inlet to outlet?

-on the intake side of the lower transfers I took out a large bulge. Now I'm wondering if that casting was intentional to either produce a specific flow pattern or to reduce volume/cross sectional area of the lower transfer

-on the uppers I'm working with the scarr contra handpiece. I've got some touchup to do, but hoping i'm going in the right direction....

 

[srcarr52]

-should the sides of the exhaust port flare out/taper more as they approach the muffler flange? any magic ratio of inlet to outlet?

-on the intake side of the lower transfers I took out a large bulge. Now I'm wondering if that casting was intentional to either produce a specific flow pattern or to reduce volume/cross sectional area of the lower transfer

-on the uppers I'm working with the scarr contra handpiece. I've got some touchup to do, but hoping i'm going in the right direction....

I'd personally leave the intake a littler shorter, around 80 but it seems you already have it done.

On the exhaust port I normally make the outside walls straight from the bore to the muffler if the muffler flange has the space. The gasses are still expanding as they are exiting so we don't want to create any restrictions by having a converging port.

The circular bulge on the outer wall of the transfer port upper is a casting core detent and should be removed. It's just some remnant of their casting core that you see a lot in AM cylinders.

Glad the handpiece is working well for you. You could square up your upper corners a bit when touching up but they are looking good.

 

[buckin-wood]

I'd personally leave the intake a littler shorter, around 80 but it seems you already have it done.

On the exhaust port I normally make the outside walls straight from the bore to the muffler if the muffler flange has the space. The gasses are still expanding as they are exiting so we don't want to create any restrictions by having a converging port.

The circular bulge on the outer wall of the transfer port upper is a casting core detent and should be removed. It's just some remnant of their casting core that you see a lot in AM cylinders.

Glad the handpiece is working well for you. You could square up your upper corners a bit when touching up but they are looking good.

Awesome, thanks for the info! Got through a 660 mmws jug and a 7900 and now onto this 395 with your handpiece. Good stuff!

I'll keep an eye out for a sale on another hyway jug to play with some different numbers. With the pop up and no base gasket squish comes to .0195, piston weighs 106g, and overall the cylinder casting looked pretty good to me... at least compared to the farmertec.


I guess I can only insert 5 images per post, the factory bulge didn't make it into my first post. If its helpful for others here's what it looked like originally

 

[srcarr52]

Awesome, thanks for the info! Got through a 660 mmws jug and a 7900 and now onto this 395 with your handpiece. Good stuff!

I'll keep an eye out for a sale on another hyway jug to play with some different numbers. With the pop up and no base gasket squish comes to .0195, piston weighs 106g, and overall the cylinder casting looked pretty good to me... at least compared to the farmertec.


I guess I can only insert 5 images per post, the factory bulge didn't make it into my first post. If its helpful for others here's what it looked like originally

View attachment 347409

I didn't think the FT/Holzfforma G395 cylinder looked bad. Port timing numbers where ok. I can't take as much out of the squish as I do with a stock jug or the intake timing starts getting longer than I like. This piston was of coarse junk!

 

[Nutball]

Why can't the intake just be filled up to the desired number, or can the roof not be raised enough to compensate for the change in area?

I have the Hyway 395 cylinders in the for sale section if you are looking for extras, Mr. buckin-wood

 

[farminkarman]

I didn't think the FT/Holzfforma G395 cylinder looked bad. Port timing numbers where ok. I can't take as much out of the squish as I do with a stock jug or the intake timing starts getting longer than I like. This piston was of coarse junk!

Sounds kinda like their 288 jugs....the one I did was already at 80 on the intake with no band cut and squish at 0.020".

 

[Nutball]

They really got the exhaust wrong on the 395: 108 if I remember correctly.

 

[srcarr52]

Why can't the intake just be filled up to the desired number, or can the roof not be raised enough to compensate for the change in area?

I have the Hyway 395 cylinders in the for sale section if you are looking for extras.

Because I don't want to use epoxy in the intake. And 0.005-0.010" less out of the squish isn't going to break the build.

 

[Nutball]

I get that.

I will say I've never had epoxy fail yet, and I have it in the upper transfers of a ms250 and 660. I was using the 250 to torture test the epoxy cutting a bunch of firewood, but the starters kept breaking on the badly designed kit saw, so now the engine just needs to go in a good chassis.

 

[buckin-wood]

On the FT cylinder there were far more casting boogers and the plating went well into the ports. Maybe because it's chrome vs nikasil on the hyway? The combustion chamber on the FT has a nub right in the center. Also for me, since I don't have a lathe, the hyway combustion chamber seems better with no squish band step.

edit: after closer examination the FT jug doesn't actually have a step in the combustion chamber, it's just plating

Here's a new untouched FT cylinder which actually looks better than the one I took off my saw.



here's a shot of the hyway:

 

[Nutball]

I prefer grinding on the softer chrome. Hyway still gets plating in their ports. I start with diamond to get through the plating.

Duke's cylinder looks good, I wonder what it times to and how big the transfer tubes are.
https://www.sawsalvage.co/products/...na-395-395xp-56mm?_pos=3&_sid=d05f77a6f&_ss=r

 

[buckin-wood]

Finally got some time to tinker. I pulled the exhaust straight back as I could. Looks like I'm going to be cutting an exhaust gasket and working the muffler flange. squared up the uppers a bit... feeling like I'm pretty close now.

 

[buckin-wood]

The day started out good, guess its time to upgrade my gauge. It ran well, was tuning easily, made some wood chips, all was glorious...





and then it all went to poop... stalled out and wouldn't restart. rip





Guess I'll clean up the flywheel and crank, lap it in, hope for the best. One of these days I'll get more than a couple tanks through this thing. It was running really well for a little bit anyway.

 

[Nutball]

Maybe add some blue loctite to the taper.

 

[buckin-wood]

Everything cleaned up fine. I can put some loctite on as well. I assume I didn't have enough torque on the nut when I put it back together. I couldn't find a spec online for a 395, but found the 394 calls for 40nm.

Curious what an oem washer and nut look like, the FT washer measures 14.5mm OD, 8.25mm ID, .48mm thick, and feels like a piece of spring steel. OEM washer looks to be 16mm? Don't suppose slightly less clamping surface area would make a huge difference.

 

[buckin-wood]

threw some dikem on the crank and gave the flywheel a few turns. Maybe I need to keep lapping, or you think the loctite will help enough with the low spots




here's the washer

 

[qurotro]

oil pump washer?

 

[afleetcommand]

Not a fan of grinding the AM cylinders as the plating is specious at best, once u break into the edge & it begins to flake that cylinder is now compromised. OEM top ends would make a better starting place, even a used one.

 

[Nutball]

Or a chrome plated cylinder. They don't flake.

 

[smokey7]

To anybody trying to get a flywheel to stop breaking the key. Lap the two together as best you can then make them both clean and dry of anything. Put nothing on the taper and assemble and properly torque. Ive had stuff sid down too far and the nut couldnt torque the assembly properly due to the shoulder of the taper stuck up too high.