066 RPM's creep up at WOT, ? about fuel filter

[mtngun]

mtngun, did you ever find out anything else with the RPM creeping?

I'm trying to remember what I've done to the saw since the last update. :msp_rolleyes:

I leak tested it again, after it sat for a week or two, and the leak rate was much, much better, about 3 inHg/hr. Apparently, the Permatex #2 just needs time to stiffen.

I didn't figure out an easy way to degree the ignition timing with the engine running, but just turning it over by hand, it seemed to be sparking near TDC, so no red flags there.

At that point I was out of ideas, so I pushed it aside for a while. :msp_sad: Seems like I've isolated every possible problem other than the carb -- and remember, the RPM's creep up with 2 different carbs.

 

[72thing]

Dan, I can't remember if it was mentioned, but what if you put some sort of mild threadlocker (Loctitie 242) or a dab of paint on the H screw that way you can see if it moves at all. A lot of potentiometers I've seen on circuit boards at work have a red "glue" on the head so its tamper resistant. Sorry if you've already covered this...trying to think of some options.

Will

 

[David (saltas)]

As an electronics tech I can say I used the wife's nail polish to stop those pots from moving after I had set them.

I also used the clear stuff to mark components before returning them to the manufacture to see what they had done:msp_sneaky:

 

[mtngun]

The o-rings on the needles are in good shape and the needles don't seem to be moving.

 

[komatsuvarna]

I thought of this thread today. I rebuilt a non running 670 Jred. New seals, piston, and rings. Popup piston and ported. It had been setting for quite a while and the carb was dried out and stiff, so I went ahead and put a kit in it. Took it apart and cleaned it and put it back together in the exact orentation that I took it apart in...checked twice. Started it up and liked to have never got the carb adjusted right, but I did get it fairly well. It ran and idled decent, but was not 100% right, and the RPMs creept up noticeable every cut. Decided to try a different carb I knew was good, but had to change the top cover for a different impulse connection. When I took the known good carb apart I noticed the top gasket's weren't in the same order as the one I just rebuilt . I went back and looked at the old ones I took out and they were different than the known good carb. So I swapped the gasket order around on the top of the carb, and bingo!! Instant fix.

Im glad I had a known good carb laying around that was the same as that one, or Id never figured it out since I was 110% sure I put it back together just like I pulled it apart...and I did, but it wasn't right. No telling how long it had been ran that way.

Its just a thought, sometimes a man can look over the simple stuff looking for something else.

 

[MTNBOY]

I am having the same problem with my 440. I have a carb kit, fuel line, and fuel filter on the way. Idles fine but when in the cut for an extended amount of time. It leans out and over revs. I was hoping the diaphragm was stiff and not letting enough fuel in. So I'm going that rout first. Hopefully we can figure something out here.

check the vent man mine did the same thing