Walbro 673 advice
 

Hi Guys
I am in the process of carrying out my first conversion on a homelite 33cc chainsaw motor.
I am in need of a bit of advice with regards to the carb.
The carb fitted is a walbro WT673, 737, and it has anti tamperproof mixture needles ,I have managed to get access and remove them.
Am I wasting my time, carrying out mods to make adjustment to the carb easier ?
Or, would I be better off replacing the carb with something that would improve the performance, if so which one?
There are so many different walbro carbs,it's hard to know what goes where and how..!![:o]

Many Thanks.

Nob.

RE: Walbro 673 advice
 

You would be better off going with a 13mm carb. My 33cc came alive when I removed the stock 11.1mm carb and replaced it with one I bought from wacker engines. Save the carb you have for a 25cc homelite conversion in the future. Just my 2c

RE: Walbro 673 advice
 

Thanks tx dive bomber. I had a feeling that the carb wouldn't be up to much ,you have confimed those thoughts.
I will contact wacker engines see if they can sort something out.
Many Thanks
Norbert

RE: Walbro 673 advice
 

How do you know if a carb is a 11mm or a 13mm carb?

RE: Walbro 673 advice
 

On the Walbro carbs, look into the carb throat near the choke butterfly. There is a number cast into the aluminum. That number is the venturi size in 64ths of an inch.

28 = 28/64" = .437" = 11.1 mm
32 = 32/64" = .500" = 12.7 mm
34 = 34/64" = .531" = 13.5 mm

(To get decimal numbers, divide the top part of the fraction by the bottom number. To get millimeters, multiply your decimal number by 25.4)

AV8TOR

RE: Walbro 673 advice
 

The number "32" carbs work pretty well on stout 25cc engines, but a 28 is probably better and easier to tune for most people, (and most applications). The 30/33cc engines work pretty well with a 32 in general.

If you are handy, a lot of times you can wander through the junk pile at a local small engine repair shop and find carbs to rebuild for "give away" prices. With the casting numbers in mind, you can find what you want, and a rebuild kit can often be bought for around $10.00. They will often give you the carb if you buy the rebuild kit from them... Just be sure it has two mixture adjustment needles. As time goes on, those are going to get harder and harder to find. Thank your local EPA chapter for that...

AV8TOR

RE: Walbro 673 advice
 

I have several walbro's without the venturi size cast into them... maybe it's just what I ran across though... i think they're mostly the same itty bitty ones like what's on the 18cc weedeater and one I found on a 32cc poulan that was the same carb...

RE: Walbro 673 advice
 

Yes, I have seen some of the really tiny carbs without the casting number.

AV8TOR

RE: Walbro 673 advice
 

Ok I got it now. I remeber seeing that before on here. I just for got it. I have 5 or 6 carbs here and they all have 28s in them. I am going to see if I can find me bigger ones. If not the one I have will have to do. They seem to do a good job on my 33cc to 40cc that I am running now but you know you can not have to much power. lol

Thanks for the info

Paul