Husqvarna k760

[Tothemax]

Hey guys. I posted this in another area but I am not getting any hits so I figured I would try here.
I have 2 husqvarna k760's with brand new piston and cylinder kits on them. One runs like a raped ape. It throttles up from idle to high rpms with no issues. The other one seems to have a lag from low to high rpms. It will hit a wall for a few seconds and then hits the high rpms.

What would cause this? Carb looks great. The fuel filter is new, new air filter, new Oregon plug, etc.

The only difference between the two saws is a serial number break. Both saws required different cylinder kits. The difference looked to be in the intake. I had to measure the intakes on both and there was a difference there.

 

[Vintage Engine Repairs]

Open the L screw (anticlockwise) 1/8 - 1/4 of a turn to give the low side more fuel.

Edit: you may need to turn the idle screw in a little to maintain rpm as the first adjustment will lower them. Use the idle screw to bring it back to where it was.

 

[Tothemax]

I should add, I messed with the carb screws for over an hour and I could not fix it.

 

[Vintage Engine Repairs]

You may have a restriction in the progressive idle drillings. If the carb is oem you should be able to clean it out. If it is an aftermarket carburetor, your chances of success in fixing issues like this are fairly low and inconsistent at best - they often run poorly.

Edit to update:

The questions we really need to know are

1). Why do they have new top ends?
2). Are all the parts oem? If not are they standard or big bore kits
3). Have you pressure and vac tested your work?
4). Where did you buy these from?
5). Do you know why they were up for sale?
6). What’s your experience with small engine repair?
7). Have you confirmed the filter, fuel line, impulse line, carb and manifold are good?
8). What’s the history of both of the machines?

To verify if it’s a carb issue, swap them over as you know the carb on the other saw is good. It’s
handy having two machines

 

[Tothemax]

You may have a restriction in the progressive idle drillings. If the carb is oem you should be able to clean it out. If it is an aftermarket carburetor, your chances of success in fixing issues like this are fairly low and inconsistent at best - they often run poorly.

Edit to update:

The questions we really need to know are

1). Why do they have new top ends? -Improperly mixed fuel caused scoring
2). Are all the parts oem? If not are they standard or big bore kits - Aftermarket p&c.
3). Have you pressure and vac tested your work? - no
4). Where did you buy these from? - saws were brought in by a customer
5). Do you know why they were up for sale? - ?
6). What’s your experience with small engine repair? - 20+ years
7). Have you confirmed the filter, fuel line, impulse line, carb and manifold are good? - Yes
8). What’s the history of both of the machines? - Unk.

To verify if it’s a carb issue, swap them over as you know the carb on the other saw is good. It’s
handy having two machines

Answered. I set the ignition coil timing and put a NGK plug in it and it cleaned up 95% of the stall.