Salvaging the Walbro carbs

[cordes42]

I ran it Saturday for awhile. And somehow the bog at idle is gone but it's hard starting after sitting over night in a heated shop. The idle screw is at 1 and a quarter turn.

[400brian]

Do you have the screened pickup fitting in the tank with a check ball in it? ( they came with and without ). This prevents the fuel from running back to the tank. I find they work best if they hang straight down.

This sounds dumb, but what is your starting procedure? The Mikuni guys try to start these without touching the throttle, which doesn't work. For first start of the day; Pull choke, open throttle half way, crank till it fires...sometimes you can get the choke pushed off and keep it running.

[cordes42]

Yup that works so much better to start now. Still have fuel residue at the intake of carb. I have adjusted the lever to .015 so I'm going to keep going down. Still boggy at the low end again.

[Cdnturboz]

Brian Quick question - I rebuilt a WDA-32 to convert my 400 over from a bendix, it’s idling ok and has a slight bog when taking off, but the big issue is when I turn off the sled I get a big burst of fuel shooting back out the carb/makes a mess.

Would this be similar to the issues a above with the float arm needing adjustment? (It’s an aftermarket rebuild kit)

[400brian]

I have to say I have never seen backflow of fuel on shut down. If you run with the engine plastic and the airbox removed it is normal to see some spit back on the front of the seat after a test rip.

On the slight bog, Sometimes adjusting the idle mixture screw up or down a little can resolve the acceleration bog.

Taking the two together, my first thought is that the metering lever may be slightly high,

The only Walbro kits that seem to be available right now are the Vertex, I believe they bought out Windrosa. Over the years I have had success with SPI and Windrosa kits. But I gotta tell you, I have struggled with the Vertex. I have found it really difficult to get the metering lever correct.
For years I was setting the arm just slightly above flush with the carb body, and they worked. Now if I set them there they are starving for fuel. I never measured the things, I just set them by eye and they ran. I am going to have to start measuring them I guess, just so I can tell guys where the sweet spot is now. At the moment I'm not sure there even is one.

I was trying out a WRA-31 I had put together as a spare this winter on my 74 X8 with the 440/22. First it was way too rich, I set the arm down and it then idled great, but topped out at 40 mph. I set the arm up a bit more and it hauled ass, but now it acts like it is way too rich at idle, almost as if the arm isn't allowing the needle to close completely. The carb doesn't overflow or anything that obvious, but it doesn't want to idle well and there is a bit of a bog until it clears out and hauls. Also adjusting the idle mixture screw seems to have little to no effect I can close it tight and it keeps idling.
We had little to no snow most of the winter, so I had limited time and conditions to test in.

I have a WDA-32 on a 340/5 engine, and it has performed great, so I do not believe there is any issue with that carb on a 340.

[Cdnturboz]

I took it all apart and adjusted the arm just just above the plate - fired it back up and no more fuel blow back but after a few secs it starts starving for fuel (needed to give it some primer to keep it running. It’s spitting zero fuel (light amount on the seat kind) I think I’ll tear it apart and adjust it slightly higher to give it more fuel.

[400brian]

Lately I have been starting with the arm above the base about the thickness of the arm, and the tweak it from there.

[Cdnturboz]

I went higher than you mentioned above (read your reply after the fact) - idles and starts great (first time I’ve had it idle properly in the 6 years I’ve owned it) no fuel blowing back - but I have a bad bog at full throttle - almost floods it/stalls. Once it hits full throttle it’s fine, it’s if I’m at lower speed and give it full throttle it seems to flood.

I have to almost stop and give it some throttle to clear out then it runs fine. It’s for sure rich in the top end as there is a bit of excess fuel/oil leaking out of the exhaust at the jug after a higher rpm pull.

I have the high speed jet 7/8 out as per the manual - leaning out the high speed needle about a 1/4 turn in helped but not great. It’s super warm out today, +1C (34F) so I might try later this week when it’s colder out too.

[400brian]

I have been having the same experiences trying to find the sweet spot where it works on both ends. They didn't use to be this finicky to set. I am still hoping to find the sweet spot. I have been messing with 2 different WRA-31s, and while I certainly have made some progress, I'm not there yet. That is why I guess I am going to have to start measuring my setting, so I can tell exactly where I am, and document the effect.

[Cdnturboz]

What were the rebuild kits you weren’t having problems with? I might try and find one of those

[400brian]

Windrosa or SPI

[jep_800]

I've experienced most of what you and Brian have been discussing on both my 800 and JDX8... I've currently found that if I have the metering arm slightly above the body, it gets all the fuel it needs on both idle and between 1/2 - WOT. The slight bog here and there, I've been able to adjust away by playing with my low speed and high speed needles. Currently my 800 is damn near perfect. Idles great, throttle response is great, good top end, pulls hard, and has that wonderful throaty growl you get through the tuned pipe when you come to a stop... and it goes right back to perfect idle. I hate to even breath on it, so I don't mess it up.

The JDX8 is close, but I don't seem to have the top end that the 800 currently has.

I found that Winderosa kits were pretty good... I agree with Brian that Vertex is not as accurate. I've looked hard to find actual Winderosa and not a Vertex that advertised as that, but they're really hard to find. I did find an SPI, and I cannibalized that kit and a Vertex kit to rebuild a spare I have on the shelf. I had to inspect every gasket and diaphragm, and even did some trimming hoping to make sure everything is lined up as it should. Haven't tested that one yet.

Jason