Stihl km90 suddenly won’t fire

[HDAV]

So a couple of years ago I bought a km90 power head (already had a km56) and it’s been great until last week and now won’t start it coughed once after numerous attempts to start? Valve adjustment ? Seemed more electrical ? I didn’t have time to look at it as needed to crack on cutting so did it with km56. It had been in fairly regular use over last few months had fuel plug looked ok seemed to have compression turned over smooth 

Edited July 11, 2021 by HDAV

[AngrySquirrel]

@spudulike

Did you checker the Clacker valve also the Giggling pins?😅

Edited July 11, 2021 by AngrySquirrel

[Stubby]

8 hours ago, AngrySquirrel said:

@spudulike

Did you checker the Clacker valve also the Giggling pins?😅

And the flux capacitor ...

[HDAV]

5 hours ago, Stubby said:

And the flux capacitor ...

Nope checked that and it’s fine 

[HDAV]

So too update the old man took it in to be looked at this morning it ran briefly then died after tweaking the carb but would die each time, suggested carb at fault.  Has left it with them 😒

[AngrySquirrel]

1 hour ago, HDAV said:

So too update the old man took it in to be looked at this morning it ran briefly then died after tweaking the carb but would die each time, suggested carb at fault.  Has left it with them 😒

Old dried fuel or cack inside could have been E5'd

[HDAV]

Thing is he has been using it more than the 56 both fuelled from same can of mixture stihl green super oil and unleaded the 56 running like a champ 90 dead as a, well dead thing, hence me thinking ignition or electrical but the man in the stihl dealer he say no 🤷‍♂️

Edited July 12, 2021 by HDAV

[adw]

I can almost hear the ring of the cash till.

[HDAV]

20 minutes ago, adw said:

I can almost hear the ring of the cash till.

Hmmmmm hence I asked here

[spudulike]

The valves usually benefit from a re gap every now and then. Usual sign it needs doing is that the engine feels to have loads of compression as the bad valve adjustment knocks out the automatic decompressor and you can feel it on the starter. A bit of backfiring can also happen!

Once the tappets are done, the engine feels like the compression is very low but starting will be easier.

If the tappets are bad they can be a pain to start. Holding the throttle fully open on these power heads can make starting easier if it is being reluctant.

Other than that, carb accelerator pump if the motor bogs straight off throttle.