husqvarna 254 doesn't start when hot

[1d10t]

Hello

 

Having issues starting 254 after cutting in this hot weather (30°c atm). It starts and runs great when first started, then when it gets hot it will not restart until cooling (even if letting it idle a bit before shutoff).

Low jet is set to highest rpm and then quarter turn ccw, high jet is set to 13500 (13800 is supposedly best but I set it a bit richer). I did tune it at about 25°C, but if anything hotter weather should make it richer, no?

Tank vent is new, fuel filter is replaced, coil is new, spark is newish.

Is this a problem with tuning or is there a trick to do it in hot weather? Chain is sharp.

 

[openspaceman]

17 minutes ago, 1d10t said:

Hello

 

Having issues starting 254 after cutting in this hot weather (30°c atm). It starts and runs great when first started, then when it gets hot it will not restart until cooling (even if letting it idle a bit before shutoff).

Low jet is set to highest rpm and then quarter turn ccw, high jet is set to 13500 (13800 is supposedly best but I set it a bit richer). I did tune it at about 25°C, but if anything hotter weather should make it richer, no?

Tank vent is new, fuel filter is replaced, coil is new, spark is newish.

Is this a problem with tuning or is there a trick to do it in hot weather? Chain is sharp.

 

Husqvarnas of that era were prone to vaporising the fuel in the carb which made hot starting a problem. modern saws with purge bulbs can mitigate this by circulating cooler fuel through the carb.

[1d10t]

I just saw that the winter mode is set by OPENING the little shutter in top cover on 254. is that correct? Because I had it open. 

[Muddy42]

Personally I don't think its tuning.  I wouldn't have thought the high jet had anything to do with starting, that's just for peak revs and your approach to low jet tuning seems fine.

 

Its just vapour lock or fuel getting hot and bunging up the carb.

 

I don't have any magic soluiton.  Keep fuel in a cool place or out of the shade. Open the fuel cap and pour out any remaining fuel before starting. Put saw in the shade for a few mins.  Take a break and sharpen your saw.  

[openspaceman]

25 minutes ago, 1d10t said:

I just saw that the winter mode is set by OPENING the little shutter in top cover on 254. is that correct? Because I had it open. 

that puts engine heat into the carburettor compartment which is the last thing you need

[Stubby]

Could just be lowish compression . Fine when cool , then heats up clearences open up  a touch to the point it wont support combustion . 

[1d10t]

compression is good, weirldy even after running on winter mode couple times. has to be vapor lock. 

[spudulike]

My normal reaction would be tank vent, coil failure, coil gap too large and low compression. You have covered most of these bar the coil to flywheel gap. 

Try storing the saw in the shade after use as if the parts you have used are OEM and fitted correctly and the compression is good, the issue is most likely the heat expanding the fuel in the tank, forcing it past the carb needle valve so worth checking the diaphragm, needle valve and spring assembly.