Walbro 152 carb adjustment 2 stroke - pmh
As fitted to a McCulloch Strimmer

This is one of those clever carbs that pumps it self and can be operated at all angles. It also regularly gums it self up so that every year I spend more time rebuilding it than using the strimmer. (Despite the fact that I try to wash it out at the end of each season). It has always been difficult to start, but Instant Start does what it says on the tin.

Can any body supply info (or better still a manual) for what the 3 adjusting screws are supposed to do and how to set them up correctly please. If I was in the UK I would try the Haynes garden manual but I doubt whether it has this carb in it.

An internet search has proved fruitless, although the American manuals for hedge trimmers with 21 pages looked promising until I found that it contained 19 pages of 'Safety information' like, .......if operator label is defaced return the unit to your dealer for rectification....

Mods since this is IC engine and technical I hope you will tolerate posting here (or move to I have a question...

pmh (was peter)

Me ? I'm happy where it is, it is a techie questiona and carb experts are more likely to pick it up here - PU
walbro 152 carb adjustment 2 stroke - Peter D
I think I have the same momel I will look this evening and if appropriate I'll scan the manual and send. Regards Peter
walbro 152 carb adjustment 2 stroke - Peter D
Your profile does not contain an email address. Sent it to me via my profile address. Regards Peter
walbro 152 carb adjustment 2 stroke - Kuang
There are a few diagrams in Walbro's own page under the aftermarket section. No setup instructions, but it might be a start!


That section doesn't mention the 152 as a McCulloch part though, although you can find it if you dig a bit deeper into the parts catalogue:

walbro 152 carb adjustment 2 stroke - Cliff Pope
I don't know this particular strimmer, but I had a chainsaw with that kind of carburettor. The 3 screws were idling speed (a simple throttle-stop), low speed mixture, and top end mixture. You adjusted the first two in combination to get a nice even idle by adjusting the mixture to get the fastest idle, then adjusted the stop downwards to the point where the centrifugal action did not quite cut in. Then adjust the speed mixture screw to give the most power for the weakest mixture. Snap the throttle open - if it hesitates, enrichen it a bit. If it gurgles and chokes, weaken it.
walbro 152 carb adjustment 2 stroke - pmh
Peter D

Thank you very much, I have Emailed to your profile address with my Email that I regularly access when away.


Thank you for those links. Google failed to find it for me. What is interesting is that the documention I have shows some McC parts diagrams for the WA152 and WA146 BUT the drawings are different from those on Walboro site (eg no priming facility and showing a different projection!). The McC diagrams contain no part names only McC part nos.

pmh (was peter)
walbro 152 carb adjustment 2 stroke - Roly93
I have a McCulloch strimmer very similar to this and have been using it for some fairly tough work for about 9 years now with no real problems.

If the strimmer is hard to start and keeps stopping etc, assuming the carb is setup correctly (I'll come on to this), I would say that the most likely culprit is a tiny split in the fuel pump diaphragm that you ca'nt see with the naked eye. I have experienced this with some 2 stroke outboard motors in the past.

Now, on the carb, you have the 3 screws, one screw will probably be the throttle-stop screw where you can adjust the idle speed purely by mechanically altering the throttle opening.

The other 2 screws whish usually look the same are the idle aire correction and the fast-running mixture/air correction adjustments.

Usually as a default both of these screws should be 1 turn anti-clockwise from the closed position. So what I suggest you try is to set the idle screw for a fast idle and the 2 other screws at the default setting. Get it started and when hot tune the low speed screw for a reasonably smooth idle, and then tweak the fast running screw so that the engine accelarates without-dying out. This may take a bit of fiddling buit isnt too difficult.

Hope this helps....
walbro 152 carb adjustment 2 stroke - Mondaywoe
If /when you get it running properly be sure to let it run dry at the end of the season then fill up with fresh fuel at the beginning of the next. A garden machinery chap told me that unleaded can 'go off' in about 3 months!

My (4 stroke) mower refused point blank to start this year. Emptying the tank and filling up with fresh unleaded did the trick.

I'm assuming this would also be true of 2 strokes, although oddly enough my strimmer started no bother and it was full of the same batch of fuel.

walbro 152 carb adjustment 2 stroke - John S

Sounds like you may not have the instruction manual. The manual doesn't help on the carb adjustement, but I'm pretty sure you have been given the right information on that. My McC Strimmer tended to run rich at high speed, and had a poor idle. Some judicious trial and error of the adjustment screws cured it, and it seemed to be each one affected a different part of the operating cycle. It's never been a great starter, but it's better now I've tweaked the idle mixture a little. They do have an odd start procedure (forgive me if you do have the manual!) Set the throttle part open with that little clip on the trigger. Prime carb. Set full choke and pull the starter a time or two till it just coughs and fires once. Set to half choke and it should start and run with a few pulls. These things are seemingly not designed to start and run on full choke - full choke seems to be just a priming position. I have to say in the 8 years I've owned it I believe the total maintenance apart from carb adjustement is to clean and gap the plug a time or two. Never bother to drain the old petrol or anything!


John S
walbro 152 carb adjustment 2 stroke - Peter D
I have sent you the manual as a couple of jpeg file 50 to 70 K. Yes unleaded fuel ages over the winter and is fairly useless in 2 and 4 stroke application in the spring always mis up some fresh fuel for the new season. Clenn and lube the air filter and if it says 20 to 1 then use 20 to 1. 15 to 1 can foul your engine and give you real problems starting. Regards Peter
walbro 152 carb adjustment 2 stroke - pmh
Thankyou for all your answers and PeterD for the manual.

I have now set it up properly and it runs better than it ever has done.

I will have to wait for the temperature to drop to see if cold starting has improved, but tickover is now smooth and picks up without hesitation.

pmh (was peter)
walbro 152 carb adjustment 2 stroke - Leoone
Any chance you could send me the manual jpg's please! I have similar problems with strimmer.
walbro 152 carb adjustment 2 stroke - pmh
Unfortunately this date coincides with a period when I was changing PCs and some mails appear to have gone into a black hole!
I suspect I have a copy in France but my current planned return there is delayed by a pair of crutches and a plaster cast!

PeterD is still around as a contributor, hopefully he will pick up this message and send you an original copy.


pmh (was peter)

walbro 152 carb adjustment 2 stroke - Peter D
And your email address is. ??? Regards Peter
walbro 152 carb adjustment 2 stroke - Peter D
And still no email address. Regards Peter
walbro 152 carb adjustment 2 stroke - 2hvdcman
Peter; I also am having a problem with this same carburetor. Could you possibly send me the manual?? email is: surfing69@earthlink.net Thanx in advance for any help.. Chuck

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