Stihl HL-92K carb settings.

[Trots55]

Hi all. I had a new carb fitted on my 3-4 year old HL-92K and it’s not running well at all. The screw settings are all over the place now and I don’t know the factory settings in order to start over again. Can anyone give me them? Thanks

[Muddy42]

I put high and low screws out by 1 and a quarter turns on everything, then fine tune. If I've done that and can't get the tuning to respond and settle down, something else is wrong, probably an air leak. Is the carb genuine, what was the reason for replacement or symptoms beforehand?

[Trots55]

The motor would start to die after about 5-8 seconds of full throttle. If you let it return to idle for a few seconds you could repeat the process and rev it flat out for 5-8 seconds before it would die again, and on and on. 
 

the shop said bad diaphragm and replaced that, then said it didn’t help so replaced the carb. It actually still didn’t run well and I suggested if the pipe in the fuel had gone soft so was sucking tight with the draw of the fuel and restricting fuelling. When I went back in later they said sorted: it was due to no grease in head which I thought was crap. I think they replaced the pipe but were too embarrassed to say the carb had been fine!

 

After a month it started playing up again but I didn’t trust the shop to have another look. 

 

Sorry, long answer. 

[spudulike]

Try changing the fuel filter, I have had this happen and it sorted it. Other than that, if it is fading on high revs and the filter has been changed, undo the H screw 1/4 turn, try again and if needed, try another 1/4 turn. That should sort it.

I am assuming your gauze strainer is OK and that your fuel hasn't got water in it as these can also have a similar effect.

[Muddy42]

No "grease in the head" - that should tell you they don't have a clue!

 

As above if its chocking during high revs I always think of this as something restricting the 'throughput' put of the system - basically fuel needs to get in to the engine and exhaust out - so check the fuel filter, fuel tank air vent (which stops air getting into the tank to replace the fuel) or blocked spark arrester.  I sometimes try removing the fuel filter or leaving the fuel cap half screwed on to let air in (with a clean tank) to help with the diagnosis.

 

You can 'tune away' minor issues to a certain extent but if your settings need to be way off default something else is going on, like a major or inconsistent air leak (which requires a pressure and vacuum test).