MS271 starts on Choke...won't pop before running

[irhunter]

Let me know if you need the new style.

Thanks. I think I have a new style on a 291-in-a-box I have kicking around. But, I will figure out what the problem is with this one first.

As I have zero history... don't know how long the saw has been running on choke.

 

[HarleyT]

Look closely at the pics I put up. The white part is what works the choke, the choke rides on top of the white block and does what it tells it to.

 

[HarleyT]

At the point your at, the carb just pulls straight off, the fuel line is held to the saw, so it stays in place.
{If it is like mine}.

 

[irhunter]

Pull it off, and take some pics at the same angle that I put up. It looks like instead of the choke riding on top of the throttle shaft lobe, it is jammed beside it.

Will do.

My carb does not have the white plastic thing. It's steel on my carb.

But, standby. I might have it worked out.

 

[HarleyT]

Will do.

My carb does not have the white plastic thing. It's steel on my carb.

But, standby. I might have it worked out.

Yes, it looks like instead of riding on the top, it is jammed beside it.

 

[irhunter]

OK. I loosened the screw which holds the choke plate to the shaft. Re-centered the choke plate in the bore and re-tightened the screw.

That fixes the problem of me being unable to actually close the choke with the choke rod disconnected. The plate was located too much toward the 7 o'clock direction in the bore and was jamming.

Now...there is a combo of too much slop in the plastic-controller-switch-thing and/or too-short choke control rod. When I have my thumb on the lever...I get full choke. When I take my thumb off, it ever so slightly opens the choke just enough to allow the saw to run on choke.

Or, that is my current theory.

There seems to be plenty of opportunity for slop in that controller-switch-thing.

 

[HarleyT]

Perhaps the plastic nubs on you control lever mechanism are rounded off, maybe due to your throttle shaft/plate issue.

 

[irhunter]

OK. The first pic is of the 271 with the problem spring. This seems like a well used saw...maybe an older saw. The spring is allowing slop in the choke assembly resulting in a 90%-closed choke.

The 291 pic is from a pretty new, very low hour, MS291. I suspect that is how the spring should be bent.

The last pic is my attempt to re-bend the 271 spring. I admit, not a lot of cam meat in contact with the spring. But, i my one attempt to start...the saw started correctly for the first time, ever (i.e., popped on choke and did not start until lever was moved to hi idle).

I will let the saw get cold and restart a few times, and will report back.

 

[HarleyT]

Here is a decent pic of the mechanism for comparison.

 

[irhunter]

 

[irhunter]

OK. Thanks a ton for the help.
My saw is fine now. Pops as it should.

To recap:

(1) The choke plate was binding as it was off-center on the shaft. Corrected by loosening screw, centering plate, tighten screw.
(2) The flat spring in the switch assembly was not holding the cam-thing firmly enough to prevent the cam from rotating a bit when my thumb came off the lever. Corrected, for now, by bending the spring.

I suspect, the saw might need a new spring sometime soon. And, I suspect the spring is not available separately from the switch assembly.

 

[Bob Hedgecutter]

So after all that- we get back to......
Might be as easy as a spring bend, might be a broken bit of plastic, might be a worn detent on the rod.
Plus Harley's excellent photographs.

Hopefully you also retuned back to what it should be before you tried tuning the problem away and the carb is close to correct settings on mixture screws.