372/385-390 hybrid. Is it possible? Been done?

[JohnnyBlade]

Maybe port a 390xp and slap a 372xp sticker on it? Would have to look closely to tell the difference at a gtg. Most average suckers (stihl guys) wouldn’t know the difference. Work smarter not harder. Lol

Best answer

 

[XP_Slinger]

The 390 piston uses a 13mm pin. 372 12mm I think. Aside from the stroke issue... there are other issues

There's a lot to work out for sure. Would probably make most sense to use the 390 crank too but it's a pile of work I think. Lots of different little things to consider.


If i end up with some lathe time I'll see what I can come up with.

You missed where I said I was going to try a 272 piston...which has a 12mm wrist pin.

 

[Mattyo]

Sorry man. My bad

I dunno if it's worth the machine work to go from bottom fed transfers to side fed like the 281.

The whole project is significant. ..no question.

 

[HYPERSAWS]

Maybe port a 390xp and slap a 372xp sticker on it? Would have to look closely to tell the difference at a gtg. Most average suckers (stihl guys) wouldn’t know the difference. Work smarter not harder. Lol

What's the fun in that...lol

 

[kingOFgEEEks]

Maybe port a 390xp and slap a 372xp sticker on it? Would have to look closely to tell the difference at a gtg. Most average suckers (stihl guys) wouldn’t know the difference. Work smarter not harder. Lol

I was thinking get a low top 390, and put a 365 special sticker on it. Even more incognito.

 

[XP_Slinger]

Sorry man. My bad

I dunno if it's worth the machine work to go from bottom fed transfers to side fed like the 281.

The whole project is significant. ..no question.

No need for apologies Matt. I muddied the waters a bit by bringing up the 281 when this thread is about using the 390 jug n slug. Crossed my mind as a possibility because the 52mm slug wouldn’t over stress the 6202 bearings in the 372 which would be a big plus.

I think it might run better than one would think going back to an old school closed port cylinder because of the tight crank case. But it is a TON of work to satisfy that curiosity. I can’t see it running much if any better than a standard XPW 51.4mm top end. Unless I can find a suitable stroker crank I’m still looking into that

 

[huskyboy]

I have somewhat more faith in metal caged 6202’s on early oe 372’s than plastic caged proprietary 6203’s that we see in so many saws nowadays in all the brands. Notice how all of them have limited ignition coils? It’s for a reason. Plastic caged 6202’s that came in Xtorq are a even worse idea with the even more heavy xt piston. I could be wrong but this is just my opinion.

 

[Mattyo]

The aftermarket already makes a 52mm head for 372. The only 54mm piston that I know of that has a 12mm pin is the am 460 bb pistons. I looked into this too....it's a ton of work.

 

[XP_Slinger]

I have somewhat more faith in metal caged 6202’s on early oe 372’s than plastic caged proprietary 6203’s that we see in so many saws nowadays in all the brands. Notice how all of them have limited ignition coils? It’s for a reason. Plastic caged 6202’s that came in Xtorq are a even worse idea with the even more heavy xt piston. I could be wrong but this is just my opinion.

I hear you on the plastic cage bearings. I swapped mine out for metal cage not long ago. Not sure on the reasoning for limited coils because if you remember, even the 346 got a blue coil. I’d wager it had something to do with emissions regs but let’s not go there lol

The aftermarket already makes a 52mm head for 372. The only 54mm piston that I know of that has a 12mm pin is the am 460 bb pistons. I looked into this too....it's a ton of work.

Dimensionally the 461 piston is a much better fit. Taller compression height puts you within .080 of the squish band before any machine work. 460 compression height is too short just like the 272 piston, .256 from squish, too much space to try and make up with base cut and case milling.

Back to the thread topic, the big downer for me with the 390 top end is it is basically a ticking time bomb unless you get bigger bearings to fit the case. Was interested in hearing about those different bearings y’all were talking about. Wish I had a 390 crank and other parts sitting around to figure it out. All my parts are in running saws and that’s where they’ll stay lol

 

[Mattyo]

I just gotta figure out how to get that bigger bearing on the pto side.

I'm too busy with work to have playtime like that though. Ugh.

 

[Quzick]

My english is not the best but...

i was allways planing to do it first, and then talk about it. And im not very kind of sharing this kind of info...

So, after a year of tinkering, experimenting, mine is working for a 10 months now, more than 20 fuel-tanks trough (started as Jonsered 2171 and it is in Husky color's now)...
im using a ************* piston and Husqvarna 385xp Cylinder. Piston-ring pins are slightly better spaced then the ST*HL's option. Not the best alignment still - ring-pins very close to the upper transfers edges... but, as there is no replacement for displacement, .... and i was stubborn to finish this project... and now after this build, i can say, it can be done.

U need to do spacer's inside the **** piston/on the crankshafts rod.
Lathe work, height of the piston... cut the roof and base. my piston is roughly 47mm tall...
Lathe work on the cylinders bottom, cut the skirt to 57mm...
Mill thinner the top cooling-fin (half as thin as it was), and re-shape it, so the modded top cover will fit,
Plug the cylinder mounting bolt holes, drill new ones. (i made a plywood templates for this in cnc-mill)
Slight dremel clearence work in the cranckcase for pistons movement,
top cover cutting, cut some inner walls away, and customise the filter cover so the spark plug stays hidden.

im using also cutted Walbro RWJ-4b (massaged throttle plate, no mid splitter, planing to try a 395XP carburettor),385/390xp intakeboot, 372xp x-torq filter mount, unlimited coil, and upper port "massaged" muffler.
and the abomination works....

 

[Stevetheboatguy]

My english is not the best but...

i was allways planing to do it first, and then talk about it. And im not very kind of sharing this kind of info...

So, after a year of tinkering, experimenting, mine is working for a 10 months now, more than 20 fuel-tanks trough (started as Jonsered 2171 and it is in Husky color's now)...
im using a E*HO 900EVL piston and Husqvarna 385xp Cylinder. Piston-ring pins are slightly better spaced then the ST*HL's option. Not the best alignment still - ring-pins very close to the upper transfers edges... but, as there is no replacement for displacement, .... and i was stubborn to finish this project... and now after this build, i can say, it can be done.

U need to do spacer's inside the EC*O piston/on the crankshafts rod.
Lathe work, height of the piston... cut the roof and base. my piston is roughly 47mm tall...
Lathe work on the cylinders bottom, cut the skirt to 57mm...
Mill thinner the top cooling-fin (half as thin as it was), and re-shape it, so the modded top cover will fit,
Plug the cylinder mounting bolt holes, drill new ones. (i made a plywood templates for this in cnc-mill)
Slight dremel clearence work in the cranckcase for pistons movement,
top cover cutting, cut some inner walls away, and customise the filter cover so the spark plug stays hidden.

im using also cutted Walbro RWJ-4b (massaged throttle plate, no mid splitter, planing to try a 395XP carburettor),385/390xp intakeboot, 372xp x-torq filter mount, unlimited coil, and upper port "massaged" muffler.
and the abomination works....

Damn good sounding machine Sir. Well done!


Steven

 

[Cooper264]

My english is not the best but...

i was allways planing to do it first, and then talk about it. And im not very kind of sharing this kind of info...

So, after a year of tinkering, experimenting, mine is working for a 10 months now, more than 20 fuel-tanks trough (started as Jonsered 2171 and it is in Husky color's now)...
im using a E*HO 900EVL piston and Husqvarna 385xp Cylinder. Piston-ring pins are slightly better spaced then the ST*HL's option. Not the best alignment still - ring-pins very close to the upper transfers edges... but, as there is no replacement for displacement, .... and i was stubborn to finish this project... and now after this build, i can say, it can be done.

U need to do spacer's inside the EC*O piston/on the crankshafts rod.
Lathe work, height of the piston... cut the roof and base. my piston is roughly 47mm tall...
Lathe work on the cylinders bottom, cut the skirt to 57mm...
Mill thinner the top cooling-fin (half as thin as it was), and re-shape it, so the modded top cover will fit,
Plug the cylinder mounting bolt holes, drill new ones. (i made a plywood templates for this in cnc-mill)
Slight dremel clearence work in the cranckcase for pistons movement,
top cover cutting, cut some inner walls away, and customise the filter cover so the spark plug stays hidden.

im using also cutted Walbro RWJ-4b (massaged throttle plate, no mid splitter, planing to try a 395XP carburettor),385/390xp intakeboot, 372xp x-torq filter mount, unlimited coil, and upper port "massaged" muffler.
and the abomination works....

I must say. Thats one bad ass build with plenty of info to back it. Posts like these are why I joined this forum

 

[P.M.P.]

I want one

 

[Definitive Dave]

We are starting work to bring 385xp and 390xp CCC Racing pistons with the proper 12mm pin and pin tower spacing to fit a 372xp crank without further modifications
Light Weight, single 1mm NPR Japanese Chrome Faced ring centered on the intake. Correct skirt length and width for the hybrid. Correct windows and pop up.
We will do them in conjunction with performance pistons for the 385 and 390 standard configurations as well if there is interest in those.
Thanks to @Quzick for bringing us this idea and basic design.
Dave

 

[Absolution]

We are starting work to bring 385xp and 390xp CCC Racing pistons with the proper 12mm pin and pin tower spacing to fit a 372xp crank without further modifications
Light Weight, single 1mm NPR Japanese Chrome Faced ring centered on the intake. Correct skirt length and width for the hybrid. Correct windows and pop up.
We will do them in conjunction with performance pistons for the 385 and 390 standard configurations as well if there is interest in those.
Thanks to @Quzick for bringing us this idea and basic design.
Dave

Ohhhh yeahhhhh, man that's great man be awesome.

 

[P.M.P.]

We are starting work to bring 385xp and 390xp CCC Racing pistons with the proper 12mm pin and pin tower spacing to fit a 372xp crank without further modifications
Light Weight, single 1mm NPR Japanese Chrome Faced ring centered on the intake. Correct skirt length and width for the hybrid. Correct windows and pop up.
We will do them in conjunction with performance pistons for the 385 and 390 standard configurations as well if there is interest in those.
Thanks to @Quzick for bringing us this idea and basic design.
Dave

DAVE RULES