Walbro hdb-18

[Thesandman]

I have one on a poulan 4000 and it has two perpendicular bars in Venturi. I want more fuel/air so I was wondering if I could remove the vertical bar to venturi throat dia?

 

[drf256]

Are you certain that the boot doesn’t match the square part of the carb bore?

I am not familiar with your model, but the Stihl 038 had a similar flat in both the Tillotson and Zama that were offered in the model. The flat extends (and is matched) from the carb bore all the way to the intake neck of the jug. Must have something to do with airflow, I am not sure why they did that, but can’t see it being on a whim.

I wouldn’t grind that out. Generally there is a passage within a bore obstruction in a carb. Happens on the WJ’s for 066. If you try to widen a WT55 to a 194 bore, you’ll a.so find yourself in a channel and ruin the carb.

 

[Thesandman]

Thanks Brother RC; Carb bolts to manifold block with .750" tube that dumps into chamber with twice the volume of tube. Carb Venturi is 12.5mm and is same that is used on 54cc saws. A HD-6 I think is 16.66mm with .749" bore. I need a carb that is similar to this without impulse tube

 

[Thesandman]

I would like to find something close to hdb-18 with 15 to 16mm venturi and .749" bore.

 

[Thesandman]

The vertical dia is about .645 vs .575 horizontal. Very small.

 

[drf256]

I am not familiar with the HDB carb one bit.

@Mastermind can this be moved to chainsaws to get more traffic?

Unsure if you can swap out shafts and make another work. As for the impulse, many can be converted to external to front facing if carb models was used on saws that used it both ways. HD carbs can be convertered for instance.

 

[Mastermind]

Done.

If you grind the venturi completely round, you will cut into the passage that brings fuel from the pump side, to the metering side.

 

[Thesandman]

Well I looked at another walbro app chart and got some different numbers. First is HDB-19-1 is listed as Poulan 4000 and 3400(55cc) carb. Venturi is 16.66(.656mm). So my previous data was wrong. Around 17.5mm to 18ish should be good. Or a 16.66 that is round should work.

 

[Thesandman]

I got a hd12 from 268 husky, can the rods be removed and reversed so linkages are on correct side? Thanks