Walbro wt-194 vs wt-590

[Greg Poole]

Good morning,
I have an unmodified MS260 Pro with the 44.7mm cylinder. I'm considering doing a muffler mod, base gasket delete and timing advance.
This saw has the WT-590 carburetor with adjustable high and low needles. I can't find any information regarding if this carb can handle these modifications.

Would anyone happen to know how the WT-590 compares to the WT-194 in throttle bore, venturi bore and tunability with the above mods?
Thank you,
Greg

 

[bwalker]

194 has a bigger bore and is the carb you want for the 260.

 

[Greg Poole]

I found a WT-194 in a box of spare parts.
On the WT-590 and the WT-194:
-the throttle bores both measure at 15.85mm
-the venturi bores both measure 13.49mm
-they both have hi & lo needles

Does anyone have specific experience/knowledge with the WT-590 carburetors that can compare them to the WT-194 carburetors?
Could the WT-590 be an updated WT-194 that has the compensator end cover and larger bosses to mount the limiter caps into?
Thanks,
Greg

 

[ballisticdoughnut]

you’ll be fine with the carb that’s on the saw now.

 

[bwalker]

you’ll be fine with the carb that’s on the saw now.

I believe the problem with the 590 is it has a weird bypass style HS jet. As such it won't flow as much fuel as the 194. The 194 also I believe has a slightly bigger bore diameter. This is going by memory as I haven't messed with a 260 in many years and always out 194's on them as mine all came with fixed jet carbs.

 

[ballisticdoughnut]

I believe the problem with the 590 is it has a weird bypass style HS jet. As such it won't flow as much fuel as the 194. The 194 also I believe has a slightly bigger bore diameter. This is going by memory as I haven't messed with a 260 in many years and always out 194's on them as mine all came with fixed jet carbs.

Yeah I was thinking the 590 may be a semi-fixed jet? I can’t remember been a while since I was inside one of those carbs, or a 194 for that matter. I purchased a few genuine walbro carbs for my 026 Pro a while back, WT-194 and WT-426. 426 had the snorkel so that’s what’s on the saw now. I can open up the high speed on that carb to the point the saw will die if given any throttle. I suppose that would be one way OP could find out if his WT-590 is up to the task. Would certainly rule out a potential lean condition at WOT.

 

[bwalker]

Yeah I was thinking the 590 may be a semi-fixed jet? I can’t remember been a while since I was inside one of those carbs, or a 194 for that matter. I purchased a few genuine walbro carbs for my 026 Pro a while back, WT-194 and WT-426. 426 had the snorkel so that’s what’s on the saw now. I can open up the high speed on that carb to the point the saw will die if given any throttle. I suppose that would be one way OP could find out if his WT-590 is up to the task. Would certainly rule out a potential lean condition at WOT.

And I am not sure on that. As I said it's been along time.
FWIW the snorkel for the Intellacarb bolts right up to the WT194.

 

[Greg Poole]

I believe the problem with the 590 is it has a weird bypass style HS jet. As such it won't flow as much fuel as the 194. The 194 also I believe has a slightly bigger bore diameter. This is going by memory as I haven't messed with a 260 in many years and always out 194's on them as mine all came with fixed jet carbs.

I believe you nailed it!
The WT-590 does have a fixed jet, in the fuel inlet end, as well as a Hi adjustment needle.

At least, I have a WT-194 here.
Thank you Gentlemen