Carb Trouble Or Air Leak

[bigbadbob]

I am at my cabin so have basic tools.
I have an old Jonsereds 90, it has 170 lbs compression. I think it was sitting for a while before I got it.
I have put a carb kit in it(HS series pretty simple), did not take out the welch plugs but did shoot brake cleaner into every oriface, made sure it came out other places.
Put the thing back together, fires up.
But bogs very bad, so I play with the L/H screws not much changes.
After backing both screws out about 3 turns it runs very well, lots of power but of course won't idle and those setting are not correct.
So I have change the filter and checked the fuel line and vent.
Double checked the needle adjustment and set it high for possible more fuel.
No cracks in the intake that I can see.
So am I correct in thinking I have a major air leak???
Are seals still availoable for this saw??
TIA
Bob

 

[Lakeside53]

Could also be a cylinder base gasket or any other leak. Looks like you'll need a full saw tool kit at the cabin!

However.... a minor air leak will affect L, but rarely H, so either you air leak isn't symeterical (seal?) or you problem is still in the carb/fuel line etc...

 

[bigbadbob]

Thanks Lake I will poke around the cylinder gasket abit today,never thought to look at that. The carb seems to be clean inside.
May have to wait till I get home and to a vac/pressure test.
I hope it warms up here.
It was 2c this morning, surpised there wasn't frost!!!
When is it going to warm up,, I want to play outside!!!

 

[bigbadbob]

So I took some more engine covers off and no obvious leaks around cylinder base, no obvious crankcase gasket leaks.
So I took Lakes advise and went to look for other carb issues.
Thought I might as well remove the welch plugs.
Low speed one came out and nothin in there, cleaned it anyway.
Took the high speed one out and there is my problem.
There is a diffuser/screen that atomizes the fuel, it is plugged with some sort of clear plastic like stuff, the same stuff I found on the old intake gasket.
So I managed to blow brake cleaner from the carb throat and get it spotless.
Reassembled the saw, three pulls a little adjustment and we have a great runnning 90.

 

[taplinhill]

 

[SawTroll]

Ditto!

 

[secureland]

I wonder where the plastic is from?

 

[bigbadbob]

Thanks guys.
When I had the carb off there was some sort of stuff holding the intake gasket to the carb, looked like that stuff that was called 'Seal All' it was fix for leaky gas tanks etc. It was hard to get off the cast aluminum, came off in little sheets/chunks. It was obvious someone had run the saw sans fuel filter and carb screen to have made it that far into the carb. I had always thought welch plugs were a difficult item, obviously not. Was a great learning experience about fuel problems.
The saw cuts great with a 8pin and a 28 inch bar in fir, but a 7 and/or a 24 inch would be perfect. Or maybe try some skip. :greenchainsaw:

 

[madrone]

nice job, you got rep from me.
I thought looking under the mysterious welch plugs was completely forbidden and perilous (or at the least unnecessary) but now I learn differently.
Thanks for the tips.

 

[Brmorgan]

Please forgive my lack of knowledge here, but welch plugs are the little brass grub screws, right? I've always been afraid to touch 'em because I had no idea what they were for.

Also, Bob, where is your cabin at? 2 degrees is even colder than it was up here this morning. Yikes. And only 2 days till summer!

 

[andrethegiant70]

Way to go, Bob! I'd rep ya but I'm out of bullets. The 90 is a HECK OF A saw.

 

[Lakeside53]

Please forgive my lack of knowledge here, but welch plugs are the little brass grub screws, right? I've always been afraid to touch 'em because I had no idea what they were for.

!

Nope... those are jets. Welch plugs are usually aluminum covers for hidden bores/pasages,

 

[Mike Van]

A good feeling when you solve the problem! I just did 2 Welch plugs on a Walbro SDC yesterday, the smaller one has a screen under it, solved my problem too!

 

[bigbadbob]

Just got in from running a tank of fuel thru it, not a bad saw I must say.
Had to tweak 'H' a little but sure runs great for a 30 year old saw.
Next project please!!!

 

[Fish]

just for the record, which time did you remove the needle/spring/lever???

and blow out that passage?

 

[Fish]

I ask just for the betterment of the "collective"

 

[RiverRat2]

Thanks Lake
I hope it warms up here.
It was 2c this morning, surpised there wasn't frost!!!
When is it going to warm up,, I want to play outside!!!

LOL Hey Bob,,,,,

I guess thats why you have all those Artic saws
in your sig line,,,,

yeah give the fuel lines a good once over too,,,, does that saw have an impulse hose????? Im thinking carb related

 

[bigbadbob]

I tried blowing out all the passages before I did the kit, then again when I did the kit without the welch plugs being removed, then again with the plugs removed, that stuff was trapped in a chamber between the H needle and the screen/diffuser into the carb throat. I has assumed I had got all the junk out with my first couple of tries. Guess I was wrong.
No history on the saw so who knows what the PO had done, the carb had been apart many times by the look of the screws, I replaced the original brass filter that was letting stuff get past, flushed the tank a few times to.
The guys at the saw shop in Princeton (great shop) had never seen a brass filter!!!

 

[Wirenut2266]

Great job on trouble-shootin yourself

 

[bigbadbob]

Great job on trouble-shootin yourself

Thanks but Lake pointed to other possible carb problems in post #2.
That is why I dug deeper and pulled the welch plugs.
My next move was to take the saw home and pressure/vacuum test it.
The guy knows his stuff.
Saved me a bunch of work, and trouble.
This site is awesome for all the help and ideas.
I could see a person becoming very frustrated and giving up, but come here and makes it all simpler.
A lot of people would junk a saw rather than spend money at a saw shop, here we have lots of real good knowledge and experience!!!!
How many saws have been saved here???
How many trips to the shop!!!!
I think I will hang around for a while.

It's 25c here, the sun is going down across the lake, got a roast in the bbq.
kids will be here soon, a fire, a few brews, got to run a old saw today, oh had a few on the beach,, some sattelite C&W radio, life gets no better.
Except a PNW GTG!!!