Jonsereds 90 Woods Port

[Heffalump]

Some time ago I purchased from @sawfun a Jonsereds 80 with a Jonsereds 90 P&C. A short time later, I purchased a spare Jreds 90 P&C from @Flat47 . I'm thinking about having this spare set ported. My question is, would a specialist need the whole saw, or can this be done shipping only the piston and jug?

 

[mdavlee]

They would more than likely need the whole saw unless they've done one in that series before.

 

[Heffalump]

Agreed, after reading more about the process. In my head I was thinking straight widening of the ports. I hadn't really though about raising ports or setting squish.

I started tearing into the saw last night. It seems that this jug has already seen a grinder. I could be wrong, since I haven't yet pulled the entire jug off. I popped the muff and carb. The shape of the intake is not the same as the intake on the W-2 Mahle jug that I have on the shelf, and the aluminum surface in the intake does look like it has been "embellished."

The thing that made me stop in my tracks was that the ENTIRE top piston ring, and then some, is exposed when at BDC. I seem to recall reading that exposure of the ring in the intake was not a good idea. I know about the port edges grabbing rings, but I would think that another issue would be exhaust gas or even intake mixture being kicked back into the carb if the top ring isn't holding.

Am I just a silly newbie here?

 

[Heffalump]

Well, I'm going full potato on this one. I pulled the flywheel off tonight and found a leaking crank seal. Lots of goo down there. I tried pulling the clutch but I don't have the right style puller for the job. Gonna have to make one, I guess. The muffler has already been modded, complete with spark arrest screen.

When I bought this saw, it cut like a beast. The plan is to completely rebuild this bad boy even better than before!

 

[Heffalump]

Update:

I'm terrible at managing projects.

So I got the crank seals replaced, carb rebuilt, and everything re-assembled. I had had some operation issues before the teardown and I wanted to test it out before doing any mods. During my test out something bad happened....


I was terrified that the piston had seized, but I was able to turn the crank with my fingers. Definitely not seized.

So I popped off the jug. Here's the intake side....



And here is the exhaust side....


Here is the inside of the jug.


And here is the base gasket with a missing chunk. It was not stuck to the cyl base. It was just gone. Likely this was my problem.



So now I have some NOS rings and some Threebond 1194 on the way. I'll be deleting the sad little crepe paper base gasket.

Question: do I have to prep the inside of the jug or the piston at all before reassembly? I'm used to cars where I have to give it a cross-hatch. This cylinder looks like a mirror above the bottom 2"....

 

[Heffalump]

Aaaaaand Just because because.....

 

[mdavlee]

I'd sand the cylinder lightly by hand. Scotch bright the piston lightly and put new rings in.

 

[Heffalump]

I'd sand the cylinder lightly by hand. Scotch bright the piston lightly and put new rings in.

To be clear, you do this on a Nikasil bore as well? Are we talking like a quick 600gr or 1000gr paper? Is there a reason you don't scotchbrite the cylinder? AlOxide shouldn't be an issue if the jug is off and is thoroughly cleaned afterwards....

I'm not trying to be doubtful or argumentative, just want to learn as much as possible.

 

[mdavlee]

Just something like 600 would be fine. Since there's a few light scratches it will make sure no aluminum is stuck to the cylinder wall to eat the rings and piston up as soon as you put it back together.

 

[Heffalump]

Understood. That makes perfect sense to me.

Thanks!!