Constant HL adjustment on strimmer

[ipbr21054]

Saturday i adjust the HL screws on the strimmer to do a job as it would rev properly.
Came to use it today but it bogs down when reving etc.
I adjust the H screw with the throttle wide open until it was sweet and used it for 1 hour

I need to use it again tomorrow on anothet job so will i need to adjust it again or should it work as is.

I seem to remember im doing this a few times now so wondering if there is an issue with different temps each day or maybe the mixture is slightly different each time.

Whats your verdict ?

 

[Burnerman]

Not an uncommon phenomena I’m afraid, but you should reach a happy medium where the machine behaves itself more or less - but at least remains useable.
Its usually a sign of one or two things.....a worn carburettor or maybe worn crankcase oil seals - which allow air ingress to a variable degree.
Both of these cause the carburation to be upset, and if you find success at high rpm you sometimes find the tickover suffers
John

 

[ipbr21054]

Ok thanks.
I take note of where the screw is before I make my adjustments and once revving fine it’s not far from where it was before I altered it.

Second question.
Let’s say I need to replace the carb.
I have another but it’s a different model number etc.
The mounting fixture is the same. The throttle fixture is the same. The fuels pipes etc really the same. So the only difference must be the internals. If I adjust the HL screws like I normally do where the problem if there is one as to why I can’t use it or can I ?

 

[Burnerman]

Id give the thing a try when you have time.....the only difference will be the internal jet sizes which may or may not suit your engine.
Maybe its been designed for a larger capacity engine but you’ll be able to adjust it the same way.
John

 

[ipbr21054]

Ok thanks.
I assumed it would be maybe jet related but thought if I adjusted the HL screws it wouldn’t make that much of an issue

I will give it ago.

 

[Burnerman]

Just for interest, the new carb throat diameter (the tube where the air gets drawn in) needs to be the same diameter as the original.....the engine produces a 'venturi' effect down the throat which sucks the fuel into the air stream. If the throat is too large, the venturi effect is reduced considerably and the engine doesn't like it.
Also check the replacement carb has a small hole on its back face that fits the original manifold and gasket (if applicable with the existing carb.)
John

 

[lostinthelight]

Often when warm tuning for the sweet spot it could be slightly on the lean side so try tweeking it slightly back off to richer . This way it there is less danger of exceeding maximum revs resulting in a lean seize of the engine .

 

[ipbr21054]

So you mean anti clockwise

 

[lostinthelight]

Yes richer, you could look at the plug at your setting and after if you back it out to get an idea of the mixture?