Walbo carbs...and prepping for the Ride with the Champs

[400brian]

I rebuilt the engine in my 74 X8 back in 2021. I rebuilt the Walbro WRA-31 at the same time. I had put 2000 + miles on the sled after having gotten it running in 2007. Excessive end play at the crankshaft was the reason it was rebuilt.
Since the rebuild, I have not had a good time with the sled. Despite having good success with Walbros up to that point, I just couldn't seem to get the rebuilt carb dialed in. The problem ranged from over fueling to running short of fuel at the top end.
The most recent apparent issue seemed to be over fueling. If you refer to the first photo, you can see the black goo has been spraying out of the exhaust. In my experience this indicates gross over fueling, or an engine running on one cylinder. The spark looked good, so more tinkering with the carb seemed in order.

Last night I pulled the plate stack off and adjusted the metering lever. Normally I just eyeball it, and they work. As noted though, recently that has not been working. I laid a piece of .030 thick steel across the gasket surface and wrote down where I estimated I had it set. I then pulled a spare WRA-31 I had taken off because of the same issue, adjusted the metering lever, noted and recorded that position, and put the carbs in a box for testing today.
For whatever reason, I felt the most confident about the sled's OEM carb. I bolted it on, fired up the sled, and it ran terrible. Smoking profusely, no throttle response, and would not idle. I didn't waste much time with it before deciding to try the second carb.

When I originally acquired this carb, it was a mess. Corroded, rusty, and oxidized. Guys told me not to bother with it. However, the three metering plate screws were successfully removed with some heat, so I went through it . I think I tossed one plate as too badly corroded, and the main body got a dab of JB weld to fix a sealing surface. I had tried running it a couple times over the past three years, but it didn't work any better.
So today I bolt it on and crank her over. She barked right off, and idled nicely! The throttle response was excellent, and the smoke was at normal levels. I decided a test rip was in order. We got a dusting of snow this afternoon, so the lawn looked like the test track. I would like to test it on a longer run, but there simply wasn't any place to do that.

I pulled it out of the garage and fired it up. After getting it lined up on a short straight, I punched it. Holy cow! That sucker hooked up, pulled the skis off the ground, and hauled ass! I couldn't believe it, the sled hasn't ran like this for ten years. So after ripping around the lawn for a bit to verify this wasn't a fluke, I put it back in the garage to get the goo cleaned off and everything put back together. Dang it, it is going to have to go in the trailer with the rest. Heading for the Ride with the Champs next week.

[400brian]

All three sleds I put in the trailer made smoke in the north woods!