Saw won't idle

[Peacock]

Ok, I've been intermittently fighting this problem for quite a while with my 280. Occasionally the saw would just die. Restart would be hard. I could rectify it with some light L jet opening. After doing this, the saw would have a slight hesitation coming off idle, especially when fully warmed up.

Now, after I've ported the saw(it rips!!!) it is worse. I have the L jet 3 turns out and it will barely idle. Give it throttle and it dies instantly. I've tried everything I can think of. Took the carb apart and it was clean as could be, except for a very small piece of Dirko, presumably from initial assembly. Reassembled, same problem with no change.

The saw, when off idle runs perfectly. Instant throttle response everywhere except idle.

Seal leak?

 

[Scooterbum]

Your using Dirko when rebuilding your carb ?

 

[Peacock]

Your using Dirko when rebuilding your carb ?

No. It was in the fuel inlet. No idea how it got there.

 

[huskydave]

Did you turn up the idle speed screw? I would check out the impulse line for cracks. I would also check coil screws sometimes they vibrate loose and the coil will hit the flywheel at idle and kill the saw I have had that happen a few times loctite is the answer. Check fuel filter fuel lines and go from there. I would rebuild the carb and clean it very well there may be a piece of grit in there or a stiff diaphram.

 

[Peacock]

Did you turn up the idle speed screw? I would check out the impulse line for cracks. I would also check coil screws sometimes they vibrate loose and the coil will hit the flywheel at idle and kill the saw I have had that happen a few times loctite is the answer. Check fuel filter fuel lines and go from there. I would rebuild the carb and clean it very well there may be a piece of grit in there or a stiff diaphram.

The only way it will idle hot is with the idle screw in REAL far. Give it throttle and it dies instantly. The saw is WAAAYYYY too new to need a carb rebuild. I'd think. It starts and runs perfectly when cold, and when using choke. Plug was not wet when I just checked it and no fuel in crankcase.

I just had the coil off, but set the gap per the manual.

I did just find that I had an exhaust leak around the muffler gasket. Repaired that. Will retry in the morning.

 

[Lakeside53]

Pressure and vac test it... Sounds like you're compensating for a small air leak.

 

[Peacock]

Pressure and vac test it... Sounds like you're compensating for a small air leak.

Ok, is it okay to use a 'smoke machine' to find the leak? We use them to leak check automotive EVAP systems. Basically no pressure and can find a leak down to .010"hg.

 

[Lakeside53]

maybe, but if it's a seal it may only fail under vac.

 

[Peacock]

Books shows .4 bar vacuum. How many inches is that?

So, will that cause it die instantly when I open the throttle?

 

[Lakeside53]

0.4x14.7=??? (at sea level)

It's pulling marginal gas though the carb by the vac against the closed throttle plate. Open it and the carb runs out of gas.

Are you sure you reconnectd the impulse line?

 

[Peacock]

Stupid math. I have all the info in my head, just no way to access it.

I get what you're saying.

Just checked the hose, pain to get to. Just runs to the carb gasket. Maybe 2" long.