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

[Rich Fife]

Love'n it!!!

 

[upstateamish]

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

Ha! exactly what I was thinking

So this morning I pulled out the old 7900 crankshaft that's cracked on one lobe.

Seup up an approach I thought might work and was able to press it apart with only minimal 'I hope this doesn't go really wrong' thoughts that occur whenever I use the 20 ton press.

But I was Successful so experience achieved!

The large pin had a bit of spall I think was because the crank lobe had cracked into the pin area, we'll see how the new crank presses apart when that arrives. If nothing else, the crank lobes make good paperweights now...

 

[Jake Dykstra]

This is awesome. Making the best chainsaw ever into a big whopper.
I'm gathering parts to do the same with a 57mm bore. If I can get it to run as good as my 390xp bb but a couple lbs lighter it will be a monster!

 

[MG porting]

Pretty dang cool.

 

[upstateamish]

Ok, figured out some youtube stuff. I don't have any of the fancy things everyone uses to make nice videos so you just get my phone in the hand videos that i've taken for now

1st runs:

Added the echo exhaust deflector

 

[Jake Dykstra]

Sounds like it needs a timing advance.

 

[Woodwackr]

Dang, that a lot of vibrations. Gonna have to check bolts every hour
Might want to figure out a way to secure that carb.

 

[upstateamish]

Sounds like it needs a timing advance.

maybe? probably... I'm still new to the saw tuning / adjustment side of things and have much to learn. I'll add learn more about timing advance to my reading list

Dang, that a lot of vibrations. Gonna have to check bolts every hour
Might want to figure out a way to secure that carb.

Yeah, it does vibrate quite a lot . Short term, I've been liberally lubing up things with blue locktite and so far the carb hasn't fallen out ... yet... but I have had a couple bar nuts loosen up which made things exciting

But it's a weight thing. Even with the amount I turned off the piston, the weight came in a bit more than I was hoping & the wrist pin that came with the piston is one of the AM thick walled ones. What can I say, I got excited to see if it would run and charged ahead.

Here's couple pics showing the size difference between the 56mm (hadn't turned it down yet) and the 48mm piston



After I got it turned down to 55mm (I had zeroed out w/the paper towel on the scale, but the plastic bags probably added some weight) so we'll say roughly 22+/- gram difference between the two

I'll have to work on trying to source a lighter weight OEM sthil wrist pin for it to swap out when I go back in but... even with that change it's still a lot of weight to throw around on the end of the rod.

But this project has been fun and for me so far and the journey is always more interesting than the destination.

the first attempt works but also highlights a couple things that may be changed in round two.

 

[Woodwackr]

maybe? probably... I'm still new to the saw tuning / adjustment side of things and have much to learn. I'll add learn more about timing advance to my reading list

Yeah, it does vibrate quite a lot . Short term, I've been liberally lubing up things with blue locktite and so far the carb hasn't fallen out ... yet... but I have had a couple bar nuts loosen up which made things exciting

But it's a weight thing. Even with the amount I turned off the piston, the weight came in a bit more than I was hoping & the wrist pin that came with the piston is one of the AM thick walled ones. What can I say, I got excited to see if it would run and charged ahead.

Here's couple pics showing the size difference between the 56mm (hadn't turned it down yet) and the 48mm piston

View attachment 447402

After I got it turned down to 55mm (I had zeroed out w/the paper towel on the scale, but the plastic bags probably added some weight) so we'll say roughly 22+/- gram difference between the two
View attachment 447403View attachment 447404
I'll have to work on trying to source a lighter weight OEM sthil wrist pin for it to swap out when I go back in but... even with that change it's still a lot of weight to throw around on the end of the rod.

But this project has been fun and for me so far and the journey is always more interesting than the destination.

the first attempt works but also highlights a couple things that may be changed in round two.

Can you turn the inside of the pin down something like the 500i’s?
Did you balance the ‘new’ crank, at speed?

 

[Ketchup]

Lots of vibration isn’t good. Because you kept some cylinder extension your bore should be aligned but it’s a common problem when stretching bolt holes.
500i pin may just fit. Maybe 462 is the same? There’s usually 8 or 10 grams of casting that can be ground out of the piston belly too.

 

[Ketchup]

I’m with @Jake Dykstra. I want a 57mm version.

@upstateamish, would you mind sharing a few numbers? How much base did you take off and where did your squish land?

Also, did you need to trim the skirts on the 661 piston? My piston skirts bottom out in the case with the 57mm slug.

 

[upstateamish]

Disclaimer: Remember this is what I considered the "1st prototype" to see if it I could put things together based on what videos and breadcrumbs I found in threads out there. (and it may help someone else build something like it) at the very least it will help identify the changes needed (e.g. figure out / try and fix vibration) But getting things to fit and get it running is a good first step.

Can you turn the inside of the pin down something like the 500i’s?
Did you balance the ‘new’ crank, at speed?

I mean, anything is possible but my skills may not be there yet. I haven't tried turning down pins (but we'll see)

I didn't split the case so the crank is 'factory' fresh

Lots of vibration isn’t good. Because you kept some cylinder extension your bore should be aligned but it’s a common problem when stretching bolt holes.
500i pin may just fit. Maybe 462 is the same? There’s usually 8 or 10 grams of casting that can be ground out of the piston belly too.

Agreed and that makes sense on elongating / stretching bolt holes. I used the stock 365 base gasket but I bet seating things down it could have become slightly misaligned, inducing some of the vibration. My plan was on the 2nd round to fill in the holes in the cylinder with aluminum pins and re-drill instead of elongating bolt holes. Assuming that might be part of the cause for vibration, insuring that bolt holes are accurate will be key.

I have a 462 pin I was hoping to try but unfortunately it was much shorter than the 661 length wise

I’m with @Jake Dykstra. I want a 57mm version.

@upstateamish, would you mind sharing a few numbers? How much base did you take off and where did your squish land?

Also, did you need to trim the skirts on the 661 piston? My piston skirts bottom out in the case with the 57mm slug.

I ... thought I had taken more pictures (with measurements) but apparently failed. So, I want to say it just fit the bottom end... I did have to make changes to make it fit the top end (but I don't have a good method to cut squishbands at the moment) when I go back in I can get more info for you (sorry!)

Squish: I ended up re-using the stock 365 gasket, the squish ended up with 0.025" at the edge

Pics of the piston before I turned down the top to fit the cylinder. (Note: I realize that this could probably be a better popup... on the list for when I go back in and make adjustments)




with the popup


right before assembly with the gasket

 

[upstateamish]

took some measurements off the other 661 piston I had planned to use on the next project (although the 390 big bore 57mm direction is tempting. If I can successfully get the crank rod swapped, that may be prototype #2.

anyway, here's some measurements on the piston that came out of it vrs the 661. which is why I think if any piston skirt needed to be removed it was minimal.

365 vrs 661 height:
365:


661:


Wrist pin to top of piston measurements: wasn't sure if where the pin was located on the piston (well the difference between the two) might help explain some of the vibration.
365:

661:

 

[Ketchup]

Okay, that makes sense. With the pin boss that much lower there’s no skirt interference. Where did the intake land before epoxy?

 

[upstateamish]

Okay, that makes sense. With the pin boss that much lower there’s no skirt interference. Where did the intake land before epoxy?

before epoxy it was reading 90 so I didn't even attempt running it

 

[upstateamish]

I was curious if I could attempt tig welding the intake ... of course then I wasn't sure if the plating would lift

 

[Ketchup]

Definitely seems challenging to weld inside the spigot. Epoxy works fine.

I wonder if this build could be done with a 385 jug and a 660 piston.