Ported 880 tuning problems??

[Rusty-880]

I had to put a heli coil in for the spark plug so while it was apart gave it a mild port job. After this, for it to tune with out bogging/stalling off idle L needle has to be out one full turn instead of factory 1/4 and only likes to idle without trouble off idle at 2400rpm instead of 2700rpm. With having to tune like this at idle the saw will still four stroke at 12,500-12,700rpm with H needle turned right in to stop.
I havn't played with modded saws before but this dosn't seem right to me. Any thoughts?

Also, latley, when the saw is being worked on the mill if you turn if off and refill the fuel/oil and reset the height of mill straight away, within two minutes, it will start like normal. If left any longer it must be left for at least 1/2hr before it will start again. never used to do this. I just replaced cylinder gasket and checked carb to cyl pipe this morning and it seemed ok, havn't had it on the mill yet so not sure if that has changed anything yet.

 

[mtngun]

Normal porting does not cause carb tuning problems, unless something is terribly wrong with the porting.

Why can't it idle faster than 2400 ?

Did it pass a leak test ?

What exactly did you do to the ports ?

Dunno the answer, just trying to get more info so we can figure something out. Could be something unrelated to the port work.

 

[Rusty-880]

Just widend them a little and tried to smooth any big bumps. It will idle higher than 2400 but it will stall off idle when you hit the throttle open, appears to me it has to be excessively rich so as not to bog. Havn't done leak test, should look into how to do it. Even at other settings to give approx 2400rpm idle the L must be out at least 1 turn or will bog/stall

 

[timberwolf]

Sounds like an air leak if you need to add lots of LS fuel to keep idle down. Then because the LS contributes about 25% of the full speed fuel it is over contributing giving you a fuel curve rich on the lower to mid range and a boggy saw.

I would go over the intake boot and base gasket to check for leaks.

When you say you widened the ports I am assuming the piston skirts are still fully sealing the ports closed?

 

[Rusty-880]

I was away from internet access till now. Talked to Stihl dealer while I was at my folks place and think I have it sorted. When I had the carb apart it turns out I didn't clip the diaphram into the needle lever. I'm away at the moment doing a few building jobs so will hopefully fix it and have it back to normal next week.
I was originally thinking it was an air leak.
Thanks for the suggestions.

 

[mtngun]

When I had the carb apart it turns out I didn't clip the diaphram into the needle lever.

That would do it.

Thanks for letting us know. Hope that solves the problem.