288 carb won't stay adjusted?

[Cowboy Tom]

I put a new piston in my 288 and am starting to get it broken in on a thinning project. The problem that caused it to go lean, loose muffler bolt, has been fixed.

Now my problem is that the carb won't seem to stay in adjustment. I've gone back to the initial settings 3 times but every time I get it going good it seems to want to die when I come down from WOT, especially after it gets good and warmed up. It has a new carb kit and has also had a leak test done. What am I overlooking??

CT

 

[atvdave]

What kind of leak test? just the top end?

It kinda sounds like a air leak to me, but I'm new to the saw engine thing. One other thing I had go wrong with one of my 2 stroke ATV's I couldn't keep adjusted was I found I had a bad crank seal. I put a new one on and it ran fine..

 

[grandpatractor]

One way to verify if its a bad crank seal would be to squirt something like amsoil MP or somethng similar down in behind the flywheel while its runninig.
I use one of them long red tubes. Just a quick test without doing a full leakdown test.
If the rpms go up and down she's leaking.:monkey:

 

[Paul001]

One way to verify if its a bad crank seal would be to squirt something like amsoil MP or somethng similar down in behind the flywheel while its runninig.
I use one of them long red tubes. Just a quick test without doing a full leakdown test.
If the rpms go up and down she's leaking.:monkey:

Use some WD-40 and start spraying around all the seals. You mentioned a pressure test but didn't say who did it nor if they did a vacc test.

Crank seals can hold pressure and then leak under a vacuum.

Outside of that, impulse hose...then on to the carb.

 

[Brad101]

Also check the throttle butterfly shaft. It could have wear and be loose in the carb body and will cause the saw to run irratic at low rpm's. If it is loose be sure and change the shaft and butterfly. I have seen this quite a bit on 281/288's.

 

[crane]

I put a new piston in my 288 and am starting to get it broken in on a thinning project. The problem that caused it to go lean, loose muffler bolt, has been fixed.

Now my problem is that the carb won't seem to stay in adjustment. I've gone back to the initial settings 3 times but every time I get it going good it seems to want to die when I come down from WOT, especially after it gets good and warmed up. It has a new carb kit and has also had a leak test done. What am I overlooking??

CT

Here's a link to pressure/vac testing http://www.arboristsite.com/showthread.php?t=42768&highlight=poor+mans By Four Paws

Step by step. It's an easy way to diagnose any leaks. Maybe something went wrong between now and the last check.

 

[Cowboy Tom]

I had the leak down test done in a shop a couple of weeks ago (less than 1/2 hour run time since) and have shot ether on both crank seals, intake manifold, muffler and cylinder gasket. No change in RPM's. I will take a look at the throttle and choke shafts today. Any other comments and ideas would be appreciated.

CT

 

[Dan_IN_MN]

How much compression does it have?

I put a new piston in my 288 and am starting to get it broken in on a thinning project. The problem that caused it to go lean, loose muffler bolt, has been fixed.

Now my problem is that the carb won't seem to stay in adjustment. I've gone back to the initial settings 3 times but every time I get it going good it seems to want to die when I come down from WOT, especially after it gets good and warmed up. It has a new carb kit and has also had a leak test done. What am I overlooking??

CT

How much compression does it have? I found that I was frequently adjusting my 49sp Jonesred when the ring was stuck in the ring groove. I'm not sure why that was the case but I cut with it yesterday and didn't touch the carb. The saw would have a rolling idle, die at times and then race.

Just some of my thoughts.

Dan

 

[Mad Professor]

A little leak in a fuel line?

Sometimes you need to bend the line to see where it's cracked

 

[Jacob J.]

Also check the throttle butterfly shaft. It could have wear and be loose in the carb body and will cause the saw to run irratic at low rpm's. If it is loose be sure and change the shaft and butterfly. I have seen this quite a bit on 281/288's.

+1.

A little leak in a fuel line?

+2- The fuel lines on those saws have a habit of cracking where they enter airbox area.

A loose muffler bolt does not cause a saw to run lean. I've seen a variety of saws run on landings with loose mufflers for months- to the point where they banged up the outside of the exhaust flange so much that you could no longer actually mount a muffler on them.

 

[Taylornic]

Does the 288 have the enrichment valve? If so, and it is gummed up it will have similar problems.