Stihl hl94 cutting out

[hamdogg]

One of my hl94s has started a cutting out problem!

 

starts and ticks over absolutely fine but when it is revved it cuts out after maybe 5-10 secs - will start straight back up flyer but will do the same again!

 

it’s had a new spark, fuel filter and carb 

 

any suggestions? 

[swinny]

Crack the fuel cap open when running on a level area.... see if that works.... 

[Stubby]

5 minutes ago, hamdogg said:

One of my hl94s has started a cutting out problem!

 

starts and ticks over absolutely fine but when it is revved it cuts out after maybe 5-10 secs - will start straight back up flyer but will do the same again!

 

it’s had a new spark, fuel filter and carb 

 

any suggestions? 

Sounds fuel related , like the high speed circuit is blocked . Maybe the little gauze filter in the carb is blocked ?  Spud will know . @spudulike

[spudulike]

I have done a few of these and the thing that baffles me is that the fuel filter and the carb are both of them.

It is most likely not enough fuel at high speed so.....have you set the carb up? ....either of them as I don't think your old carb probably had much wrong with it.

There are two adjustments on the carb, the obvious one is the L (low speed control) the one on the top in the middle of the barrel adjusts the height of the high speed needle on the slide valve or barrel valve.

Either may bring your 94 back in to life but worth trying the low speed first as it is easier - 1/4 turn counterclockwise and if that doesn't improve it, give the one on the top of the carb the same tweak and it should work.

You will need the Stihl hexagonal adjuster driver to do the adjustments.

I just hope you didn't pay someone to not fix it!!

 

[hamdogg]

5 hours ago, spudulike said:

I have done a few of these and the thing that baffles me is that the fuel filter and the carb are both of them.

It is most likely not enough fuel at high speed so.....have you set the carb up? ....either of them as I don't think your old carb probably had much wrong with it.

There are two adjustments on the carb, the obvious one is the L (low speed control) the one on the top in the middle of the barrel adjusts the height of the high speed needle on the slide valve or barrel valve.

Either may bring your 94 back in to life but worth trying the low speed first as it is easier - 1/4 turn counterclockwise and if that doesn't improve it, give the one on the top of the carb the same tweak and it should work.

You will need the Stihl hexagonal adjuster driver to do the adjustments.

I just hope you didn't pay someone to not fix it!!

 

Thanks for this! Yeah I sent it to a shop and it came back no different so I had a gamble at a new carb! 
I will try this and fingers crossed it fixes it 👍🏻

[pleasant]

Worth checking the fuel pick up hose as well. Had a machine in last week. Same symptoms and turned out the fuel pipe was deteriorating and allowing air in which leaned it off under high rpms and it cut out. Would restart and on idle fine but do same again when trying to accelerate. New hose cured it.

 

If its not fuel then look at the module...these can break down under load and heat over time. Again, had machines that would start fine but cut out under load and the modules do occasionally do this an fail. As youve changed the plug we can assume its not that.

Edited December 9, 2022 by pleasant

[hamdogg]

On 08/12/2022 at 23:43, hamdogg said:

Thanks for this! Yeah I sent it to a shop and it came back no different so I had a gamble at a new carb! 
I will try this and fingers crossed it fixes it 👍🏻

 
Are these the carb adjusters for low and high speed adjustment 

 

4mm socket 

[spudulike]

The one on the top is basically raising and dropping the needle on the slider valve assembly so it is adjusting the idle adjustment. The other one is the High speed adjustment and is for mid to high speed running.

 

If your HL94 is not revving out correctly, changing the fuel filter is the best first thing to do...plus cleaning the air filter and if this doesn't cure it (it often does), try adjusting the H speed screw (anticlockwise). I would also strongly suggest checking the carb internal gauze strainer as it often gets clagged up with fine chip.