Hybrid clonesaw 365 with a 390 topend - aka the "86'r from youtube"

[upstateamish]

Based off the "86r" idea that i've seen on youtube and other links in this forum (e.g. https://opeforum.com/threads/372-385-390-hybrid-is-it-possible-been-done.17302/) Between that thread & the videos which have caught my eye I was curious if I had the skills to try and make it work.

For the moment there's no machinework on the bottom end to get things to fit.

The finest cheapest 365 clone saw I could find... it arrived with a hard nose bar, chain and bearing the name of "Hnsavrqua" looks legit

Addtional aftermarket parts:
- 55mm Husqvarna 390 cylinder with base trimmed & turned to fit the bottom end. Intake JB-welded to get timing correct (no base gasket)
- ms 661 piston
-- turned down 55mm bit of a pop up and and clearanced to fit the rod.
-- rings ground to fit the 55mm cylinder
- 390 intake boot (home made clamp, new one arrived not in place yet)
- 395 Carburetor with 372 X-torq choke lever on choke rod
- x-troq choke for 372/365
- x-troq lowtop air filter horn (hollowed out)
- x-troq top cover (to fit over the larger cylinder, had to trim a bit, also had to trim the chainbrake to clear the cover)
- Opened up the exhaust with an Echo CS-620P exhaust deflector
- OEM dogs from a full wrap kit I had left over from another project


Initial timing numbers landed (Top end isn't ported yet)
- Exhaust: 98.6
- Intake: 80.8
- Transfers: 122.2

Squish (with a base gasket)
- 0.025"

As arrived:
first glance, didn't look terrible for the sub-200 dollars shipped to my door (search for "24In Gas Chainsaws 65CC " on amazon, even cheaper off aliexpress...)



I didn't try to start it and just started tearing it down. Most parts looked ok, but a couple... well, they're not 'great' I would say quality of parts shipped reflects the price



Topend that shipped with it


Continued in the next post

 

[upstateamish]

Needed to clearance the piston to fit the rod


it fits (tight)


390 Top end... does not



Since I'm gonna need to epoxy the topend anyway, I trimmed the skirts down down to where it does (how thin is too thin? I guess we'll find out) You also need to elongate the bolt holes (or in the next build, fill/redrill) & open up the lower transfers to meet the bottom end stuff.



I've never JB welded an intake, we'll see how it holds up

 

[upstateamish]

turned the piston down, added a bit of a popup (my skills are a touch lacking)


I realize I had not ordered a clamp for the air boot so I made one up out of some stainless tig welding wire


top end together to test fit the components


Glued down with a gasket & 1184 (cylinder also needed to have the bolt holes elongated in a varity of spots to match things up)


Muffler fits and bolts up without any issue

 

[upstateamish]

Ring grinder (to get to the right diameter) I also used a sanding wheel to take off about 20 thousandths so things would fit and play nice


X-torq top cover clears everything (needs some minimal clearancing to fit) you can see the sharpie mark on the chainbrake where I trimmed it out with a cutoff wheel


added some metal ducttape on the cover in case things get a bit toasty

 

[EFSM]

Welcome! This looks like an interesting Frankenstein.

 

[upstateamish]

1st start and heat cycled without any issues (I expected it to hang a ring due said ring grinding above but pleasantly surprised)
As I noted, I haven't done any porting so the uneven exhaust port was like that from factory, I'll take care of that when I go back in to do port work.



At this point I had run 5 or so tanks through, one or two heat cycling and idle, and about a truckload of limbwood and the saw seems to be responsive, stays running and idles well (I'll have to figure out how to upload videos )

But I decided to add additional muffler openings for heat escape and found an echo exhaust deflector off of the duke that fit the bill






And it started back up and runs well. Now I need to get it back out into the wood to see how it performs with the bigger exhaust opening

 

[Woodwackr]

Another Frankinsaw, love it!

 

[Powerstroke Cowboy]

Very nice! I'm interested to see how the skirt holds up.

I think odd builds like this are the coolest!

 

[Woodwackr]

Very nice! I'm interested to see how the skirt holds up.

I think odd builds like this are the coolest!

Yea, I probably would have clearanced the case, or, done half and half.

 

[upstateamish]

yeah... I was on the fence on the skirts. But if things bomb out round 2 of will involve clearancing of the case.

I'm also thinking about ways to allow a 390 55mm piston be used (and would open up a few other piston options)

Which means either a hybrid 372 crank with a 390 rod (or figure out how to get a 390/395 crank to work)

In the "we do it nice because we do it twice" approach, I ordered another one of the 365 saws and parts to do another swap. I also have an aftermarket 395 crank on order.

But more research still needs to be done there, I ordered the crank with the intention of swapping the rod over to the 372 crank, but maybe it'd be better/easier to do a crank swap (I'm not sure of the difficulty level comparison's between the two)

 

[Ketchup]

There’s a 57mm option, just sayin’. Great build!

IIRC, I found a slender pin bearing that will allow the larger pin to fit the smaller rod. I can get you details if you’re interested. Putting the 390 (37mm stroke) crank into the 365 case is possible but makes the case very thin. 395 (38mm stroke) really pushes beyond the limit. Swapping rods is an option, but requires precision press capability and wants careful welding afterward. Putting the 37mm crank in might be easier than a rod swap.

36mmx57mm=91.8cc
Kinda far over square, but so is 500i.

 

[Powerstroke Cowboy]

What if the case was clearanced as much as safely possible, then the rest took off the counterweights on the crankshaft?

 

[upstateamish]

There’s a 57mm option, just sayin’. Great build!

IIRC, I found a slender pin bearing that will allow the larger pin to fit the smaller rod. I can get you details if you’re interested.

Oh nice! I'm def interested if you have that info thanks!

Putting the 390 (37mm stroke) crank into the 365 case is possible but makes the case very thin. 395 (38mm stroke) really pushes beyond the limit. Swapping rods is an option, but requires precision press capability and wants careful welding afterward. Putting the 37mm crank in might be easier than a rod swap.

with all the things I have going on I think you've talked me out of trying to do a crank rod swap myself (at least at the moment) I'll have to keep an eye out for a 390 crank to mess with.

36mmx57mm=91.8cc
Kinda far over square, but so is 500i.

Oh yeah, 500i's are fun!

 

[Ketchup]

What if the case was clearanced as much as safely possible, then the rest took off the counterweights on the crankshaft?

Probably can be done, the big end might get thin. Remember the crank is different though. 390 is same in design but longer. 395 is a different animal. All possible with enough machining, I’m sure.

 

[Ketchup]

My mistake. I went out and measured. These bearings are 16mmOD. They fit 7900/681. 372 is 15mm small end. You could probably bore it to 16mm, but it would be thin. But if you wanted to put a 57mm on a 681 crank they work. LOL.

Edit: 681 crank small end is 16mmID, 19.4mmOD. 372 is 15mmID, 20.5mmOD. So boring should leave plenty.

 

[upstateamish]

My mistake. I went out and measured. These bearings are 16mmOD. They fit 7900/681. 372 is 15mm small end. You could probably bore it to 16mm, but it would be thin. But if you wanted to put a 57mm on a 681 crank they work. LOL.

Edit: 681 crank small end is 16mmID, 19.4mmOD. 372 is 15mmID, 20.5mmOD. So boring should leave plenty.

Copy that, thanks for taking time to measure!

Looks like the next build will some more research before I start (and push my skills) always a good thing!

 

[Ketchup]

Copy that, thanks for taking time to measure!

Looks like the next build will some more research before I start (and push my skills) always a good thing!

Here’s your solution:

I made a crude first attempt myself. You’ll need good carbide.

 

[Woodwackr]

yeah... I was on the fence on the skirts. But if things bomb out round 2 of will involve clearancing of the case.

I'm also thinking about ways to allow a 390 55mm piston be used (and would open up a few other piston options)

Which means either a hybrid 372 crank with a 390 rod (or figure out how to get a 390/395 crank to work)

In the "we do it nice because we do it twice" approach, I ordered another one of the 365 saws and parts to do another swap. I also have an aftermarket 395 crank on order.

But more research still needs to be done there, I ordered the crank with the intention of swapping the rod over to the 372 crank, but maybe it'd be better/easier to do a crank swap (I'm not sure of the difficulty level comparison's between the two)

I have a 2100 crank with bad bearing you can have
And, a 288 in the same condition

 

[upstateamish]

Here’s your solution:

I made a crude first attempt myself. You’ll need good carbide.
View attachment 447198View attachment 447199View attachment 447200

Now that's a pretty awesome option, I'll have to get some carbide holders and bits and try that out.

I have a 2100 crank with bad bearing you can have
And, a 288 in the same condition

Nice! I appreciate the offer but let me test breaking apart a crankshaft I have from a 7900. (one of the lobes is cracked) so, not really the right length but should give me an idea of how hard it is to press apart crankshafts and mess around with swapping rods around.

found some old threads to dig through
- https://opeforum.com/threads/crankshaft-big-end-bearing-rebuild.26864/
- https://opeforum.com/threads/connecting-rod-big-end-bearing-replacement.28569/

 

[Woodwackr]

Now that's a pretty awesome option, I'll have to get some carbide holders and bits and try that out.



Nice! I appreciate the offer but let me test breaking apart a crankshaft I have from a 7900. (one of the lobes is cracked) so, not really the right length but should give me an idea of how hard it is to press apart crankshafts and mess around with swapping rods around.

found some old threads to dig through
- https://opeforum.com/threads/crankshaft-big-end-bearing-rebuild.26864/
- https://opeforum.com/threads/connecting-rod-big-end-bearing-replacement.28569/

Now that's a pretty awesome option, I'll have to get some carbide holders and bits and try that out.



Nice! I appreciate the offer but let me test breaking apart a crankshaft I have from a 7900. (one of the lobes is cracked) so, not really the right length but should give me an idea of how hard it is to press apart crankshafts and mess around with swapping rods around.

found some old threads to dig through
- https://opeforum.com/threads/crankshaft-big-end-bearing-rebuild.26864/
- https://opeforum.com/threads/connecting-rod-big-end-bearing-replacement.28569/

Proline sells the center section so how hard could it be?