Walbro question

[400brian]

OK, so I got the tach hooked up today, so I could see where the engine is idling.
Without really getting it warmed up properly ( lack of snow ), once it would idle without the choke, it was running about 1900 rpm. Book says 2200-2600 rpm.

So here is the problem. When I first ran the rebuilt carb, one of the first things I noticed was that I had to turn the idle stop screw pretty much all the way in to get a decent idle speed ( one it would run at ). I have the mixture screw set somewhere between 3/4 and 1 turn open.

I had not turned the idle stop screw before that, and I've noticed that the WRA-31 carb I have, is set pretty much the same as the first one was originally, the throttle plate cracked open just a bit.

I'm thinking I need to pull the carb apart again to see if one, or more, of the idle ports are plugged. I thought I looked all this over good when I cleaned the thing, but that is the only thing I can think of in regard to why I need the throttle open so much to get the idle speed I need. As it stands right now, I don't think there is any way I could get 2600 rpm out of it, unless it idles a bunch faster in cold temps ( which I really doubt ).

Any other ideas, or something I am missing in my thinking here?

[ProJd69]

Brian, One thing That I Do, (Walbro carbs. are very touchy as Im sure you know But aren't as bad as people make then out to be) Once I have rebuilt the carb. I take the plates, Making sure all the gasgets,dio's and springs are installed correctly and set them asside. Then I take a twisty tie from a loaf of bread and strip the coating so all you have is the wire. Then I take the carb. body and poke through all the holes also useing carb. cleaner and an air compressor, If you don't have an air compressor then get a can of compest air for cleaning you computer from Wal,Tar,or K-. Works great cause it come with a tube that goes on the spout for getting in those small spots. Cost's about 4 buck's and well worth it.

The idle problem sounds like you have some pluged holes. All I have to do is turn My idle set screw about 1 to 2ish turns and its fine, Hell I can get mine to Idle at about 1000 R.P.M's if not lower. Its really cool cause when I first start it idle's high and after about a min. it comes right down. Just like a car/truck with electronic choke.

Hope this helps you out.





:unsure:

[400brian]

Took a look at the carb this afternoon. Found absolutely nothing, clean as a whistle, just as I had thought.

So I bolted it back on the sled with internal tooth lockwashers, hooked up the choke cable, and put the airbox on. Fired it up and ran it for a while.

Nothing changed, just don't have the crackling throttle response I would like. But, it idled at 2000 rpm nicely. It has been almost 30 years since I rode our 400s, and the memory is not to be trusted, but I'm thinking it should be a bit crisper. Could be a ignition tuning issue I suppose. I would think if it was a seal issue, I'd have to have the idle screw set pig rich.

Pretty much got to put the sled away for now, spring work is looming large.

I made some progress this winter, I think I'm close to having a sled.


I'm also getting close to having messed with every single assembly on the sled. Haven't been inside the engine, but that is about it. I might as well put seals in it on a preventative basis, rebuild the clutch as long as I have it off. I've got the correct flywheel that needs to be put on so I can have elec start, and the muffler needs to be pulled for cleanup and paint, and to make sure the flex joint is loose.

Then there is a seat cover to be installed, the skis could be painted, and the hood could use a little fiberglass repair.

That's all