What could be wrong??!!??

[bama]

I have been going around and around with getting this saw to work. It is a Jonsered 621. I have put in a carb kit and blown everything it out with air. I have replaced all gaskets and new crank seals. Put a different crank in because one bearing was a little loose. Different cylinder and piston, and different coil.

My problem is that I can't seem to richen out the high jet to make it four stroke. I have the Masden's article on how to tune a 2-cycle, so that is how I tune all my 2-cycle's and it works great. After all this work, I don't want to take out the piston and cylinder because I am lean. The adjustment does work, but it doesn't sound like it reaches the point of four stroking like my other saws do. If I tilt the saw so the clutch side is towards the ground, sometimes it will speed up the idle and if I move it so the recoil is towards the ground, sometimes it will die.

Since the seals are new, I figured that shouldn't be the problem. Is there anything else that can cause a lean condition that I should look at. Cylinder base gasket is new and tight. Should I look at re-doing crank seals? Have I missed anything? Any help you guys can give me would be great.

 

[Gypo Logger]

Check out the tank vent to see if it's pluged and causing a vacuum. Loosening the gas cap while it's running will prove if it's plugged or not. I've also seen where sawdust has accululated between the carb and the the plastic isolator it is mounted to on the intake, plugging the hole that allows fuel into the intake.
Hope this helps,
John

 

[doc874]

Jonsered 621

I don't profess to being an expert in any saw and this may sound kinda silly but, where in the fuel tank is your filter I'm thinking that maybe it's sitting toward the clutch side which would make sense when you tilt the saw that way then the filter would be fully covered by fuel and when you tilt to pulley side a part of the fuel filter would not be fully covered by fuel thus causing the saw to not be getting the proper amount of fuel if any and stall. ( Just a thought )

 

[bama]

The vent tube is venting, Gypo Logger. I can hear it and see a bubble move in the vent line. I forgot to mention, doc874, that I have the fuel tank full, to make sure that what you mentioned wouldn't happen. It is terribly frustrating. The spark plug doesn't look white so it doesn't look like it is lean. If I richen the high jet considerably, the saw should perform more and more poorly(less power) in the cut and the plug should get dark(shouldn't it??). It doesn't seem to lose power when I run it extremely rich.

 

[lostone]

Is there any side play in the crank? (will it move from the clutch side to the coil side and back if it is pushed straight that way?)

 

[doc874]

Jonsered Problem

Is it possible that when you rebuilt the carb you could have switched the H & L ajustment screws around ( if it has two screws? ) Try switching them yourself and adjust out 1 & 1/2 turns from lightly seated.

 

[bama]

I checked and there is no sideplay in the crank, lostone and I am sure that I put the high and low screws back in their correct location when I rebuilt, doc874. Keep the suggestions coming!

 

[Mange]

If you lean it forward and it changes rpm, i will suspect a air leak.
If you have both the needles set one out, and it does this, I think you have a gasket leak between carb and cylinder.
A pressour test will tell for sure.

It could be something went wrong when rebuilding the carb. Did you test it before remont?

 

[bama]

If you lean it forward and it changes rpm, i will suspect a air leak.
If you have both the needles set one out, and it does this, I think you have a gasket leak between carb and cylinder.
A pressour test will tell for sure.

It could be something went wrong when rebuilding the carb. Did you test it before remont?

What did you mean with the needles? I didn't quite understand what you meant. I did not test the carb after rebuild. I am calling around trying to find someone who can pressure test the saw for me. The dealer in town outsources most of his work. It may take awhile to get it checked. Too bad I can't do it myself. Thanks, Mange.

 

[Chris J.]

Just a thought, did you replace the fuel filter?

Bama, I don't mean to derail your thread, but I have to ask...Mange, how do you test a carb before putting it back on the saw? Maybe I'm dense, but I don't understand.

 

[bama]

Just a thought, did you replace the fuel filter?

I haven't changed the filter, but I cleaned it and blew it out with compressed air(backwards). I also hooked up a long, clear fuel hose and sucked some fuel and there was very little resistance, so I figured it was ok.

 

[Mange]

Just a thought, did you replace the fuel filter?

Bama, I don't mean to derail your thread, but I have to ask...Mange, how do you test a carb before putting it back on the saw? Maybe I'm dense, but I don't understand.

You pressure test it too see if membrane is intact correctly placed etc. and imulse system is OK. This has saved me some troubble a few times.
I will not even try explaining this in eng....

 

[Mange]

What did you mean with the needles? I didn't quite understand what you meant. I did not test the carb after rebuild. I am calling around trying to find someone who can pressure test the saw for me. The dealer in town outsources most of his work. It may take awhile to get it checked. Too bad I can't do it myself. Thanks, Mange.

Hi and lo jet needles.

I am sorry, but I am off the mark anyway so you can disregard all of this!