Jred carb question

[bama]

Alright, I just split the saw and put in a new(used) crank and main bearings. The saw was being a little tempermental at low speed before that so here is my problem.

The gas tank check vent check valve plugged up on me and put lots of pressure into the gas tank. The pressure was so bad that it flooded out the saw at low speed and I was definitely fogging for mosquitos. Once it started acting up, I went to my other saw. However, when I try to set up the carb as per masdens1.com instructions, I am having very inconsistent results.

I get it set perfectly and cut a few pieces, then it either loads up and dies or it accelerates quite a bit. I stop and retune the saw and after a few cuts, it does the same. I have replaced most everything on this saw. New crank seals, rebuilt carb, new piston and cylinder. I have noticed some wear on the actual carb around the throttle rod on the chain side. I got a new throttle rod from George Blake so the wear must be in the carb.

Could the pressure from the gas tank have messed up something in the carb or could this play in the throttle rod be causing intermittent leaning of the mix? This saw is no longer a hobby; it is an OBSESSION!

 

[bama]

I forgot to say that it is a 621.

 

[MacDaddy]

Check for air leaks and rebuild the carb also change the vent on the tank

 

[Kneejerk Bombas]

Inconsistant running, I think air leak.

 

[Chris J.]

After you use the saw and it acts up, are the carb adjustment screws still set where you set them before you ran the saw?

 

[bama]

Yes, the carb adjustments remain the same. I know it is really rich, but the low speed is about 2 turns out, now. When it dies, I go to a little over a turn out and it runs fine until it accelerates. Then back to two turns out. I did get the check valve cleared out and working.

 

[SawTroll]

Just a thought - I am no expert on these things.......
Have you tried to take the fuel cap off and put it on again when the saw has loaded up and died?
If it runs fine again for a while after that, the tank went is probably the problem (or part of the problem).

 

[bama]

I have tried that SawTroll and there is no difference in running since I cleaned out the vent. I am leaning towards just getting a different carb from George Blake. I don't think that throttle rod should be that sloppy. Air must be leaking in there, but not always. So that could explain why I can tune it and have to retune it only minutes later. There just isn't much left on the saw that I haven't replaced.

 

[SawTroll]

Good luck, bama!
The 621 is a very nice saw as long as you don't have to carry it a lot. I mainly use mine for cutting logs into firewood length.
That saw cuts amacingly well for a 56cc saw from 1970.
It was in production from 1970 to the early -80ies.

 

[bama]

I agree. It is easier to handle than the 920 that I have. I keep a 24" bar on that and use it mostly for felling and bucking the bigger stuff and use a 16" bar on the 621 for the smaller bucking and limbing. After using the 920 exclusively for seven years, it feels good to have a somewhat smaller saw that doesn't weigh so much(compared to the 920). I found that I have much more endurance using both saws in combination than just the big one.

 

[SawTroll]

Bama, 16" bar is what I use on the 621 too - combined with a 3/8x8 rim sprocket and Oregon 73LP/Husky H42/Jred S42.
I think 3/8x8 was standard on these saws, and it works really well.....