We have a group that rides lightenned, non-boosted, RX-1's. Last year we got into very, very, very deep snow a few times and had a WOT bogging issue. The snow was flowing right over the top of the sleds and you were full into the throttle contiuously. The sleds would be fine for about ten miutes, and then would start loosing power at wot. If you backed off the throttle a little you could get some power back and limp along. If you let the sled sit a minute it snapped back to life and you were good for ten more minutes of full power before it started bogging down again. It would get so bad a few times that the sled would bog right down and stall the engine. We tried jetting up and down to no avail. Carb heat made it worse. One of my theories was that the carbs are heating up (no airflow through hood vents) like they do with carb heat is on. Anyone know why the sleds run crappy with carb heat? I also suspected vapor lock in the fuel lines and tried re-routing the lines away from the engine, but to no avail. I have also felt that maybe the undertunnel exhaust was getting restricted, but we are often in deep snow when we don't have the issue, plus the sleds would run fine for awhile before bogging out. We have big holes up high in the hood so the engine can get air. I've considered trying to run fresh air to the airbox intake (like the two strokers do), run cooling air across the carbs, installing an electric fuel pump like the apex, even extending our exhaust outlet. Our turbo has never had the problem. It doesn't happen often but when it does it sucks. Ideas?
I need help fixing an old issue.
- Thread starter Kachess1
- Start date
I think you're on the right track with the vapor lock idea. Under slow moving, WOT, your airflow in and around the engine is reduced and even further reduced with deep snow surrounding the hood/engine. I would guess that may be causing a momentary vapor lock condition in the carbs. Also, one thing to check into is the vent lines......I know water crossings on a carb'd dirtbike are an issue with low hanging vent lines and maybe there's something to that on these sleds. Also, in deep powder the *** end will be lower than the hood (like climbing hills) and may be getting a little gravity-feed problem? Not sure, just brainstorming.
I'd say the most probable is the vapor locking, and I'd wrap the fuel lines in tin foil to reduce the radiated heat transfer. Silk covers on the vents might keep the snow from blocking as much airflow through the hood, and you might even consider adding a few additional vents (with silk covers, of course).
My $0.02
The electric fuel pump was my first thought, it just might do the trick.
M5
M5
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colorado yamaha
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I would second Budda's diagnosis ... too much heat. IME the carb heaters put too much heat in the carbs, around 160 degrees and the engine bay temps under "most conditions" never get anywhere near that temp.
You could try propping the hood open a little to help the air flow, like 1/4" to 1/2". We use to put the rubber end with the hook removed (cut off about 2" long) of a black rubber tie down and rivet it to the plastic around the steering column on the Mountain Max's and Vipers. Did the trick.
You could try propping the hood open a little to help the air flow, like 1/4" to 1/2". We use to put the rubber end with the hook removed (cut off about 2" long) of a black rubber tie down and rivet it to the plastic around the steering column on the Mountain Max's and Vipers. Did the trick.
i would look into an outerwears pre-filter for your intake. sounds like you are ingesting powder into the intake and causing the sled to bog....when you take a break the under hood heat will melt the snow that has been ingested and will allow you to get another "10 min" of riding.
