The infamous powder bog

mod-it

mod-it

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Nov 15, 2006
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Location
Lewiston, ID
Ok, I know this has been beat to death and there are tons of threads on this. I've read all of them twice. I still haven't seen anything definite that cures the problem. Here are my thoughts:

Can't be the exhaust being plugged.
It still does it even when the sled is laid over on its left side. Heck, I can side hill on the right side all day long and it doesn't bog. Get snow on the hood...immediate bog.

It can't be clutching.
I ride all the time in powder, it never does it until snow gets kicked up onto the hood. As long as I am packing the skis it runs great. Hit a drift, or slow down so that the skis throw snow on the hood...bog.

The first thing I thought was that snow was blocking the vents, which caused under hood temps to go sky high. I thought the really hot air going into the box was creating a super rich condition, just like when riding in really warm spring weather. Put in slp flowrites, problem not any better.

I then thought that blocking all under hood air would definitely cure the problem. It had to be the snow mist going through the hood screen, hitting the pipe, turning to steam, and then getting sucked into the air box. I'm going to try blocking the under hood air this year. Then I read that A K MntViper has already blocked his, put on an air box pre-filter, and still has the bog. :o|

So then, as crazy as it may sound to some, I thought it must be the snow hitting the pipe and cooling it in that one spot. I read an article in Snowtech about this being very possible. The article wasn't about the triple piped Yamaha's problem, but the info applies nevertheless. This makes some sense, as the single pipe Vipers don't have this problem. Maybe the shroud over the single pipe prevents the pipe from being cooled? But I also read that kimoaj tried blocking off all his hood vents, still had the bog.???????????? :o| Now I'm wondering if it might be BOTH. Steam into the air box, AND the pipe getting cooled???

So, has anyone tried blocking their under hood air AND putting some prefilter material on their hood vents?

I don't care if every single ride I go on this year gets ruined. This sled is going to be able to perform in light floof powder, even if I have to get NASA involved, lol.
 
I had your bog on my stock Mountain Viper, I blocked ALL under hood air from the air box, made sure the ram air vents where blocked off and then I installed four M.P. air vents with powder screens behind the windshield on either side of the tach. I also did not use any carb heat unless real cold. My bog was pretty much gone all the time.

Good luck
 
had the same problem with my msrx ran strong all day long.....until you hit powder then the bogging started....finally came across changing the plug boots......problem fixed.....also i run my heated carbs off 99% of the time....worked great after that
 
Thanks for the replies!

I haven't ever thought of the carb heaters. I run with mine on ALL the time. Very interesting that both of you make reference to this.

LoneViper: I haven't ever heard/read that the stock Vipers had this problem. My ram air vents came blocked from the factory since it is a Mnt Viper, like yours, did you do any additional work on them like pre filters or something? I already have slp flowrites, so I will just try turning off the carb heaters and blocking under hood air. Thanks.

chevyracer68: Did you change to different style of caps, or just put in new oem caps? I'm definitely going to turn off my carb heaters. Thanks.
*edit* I saw you mention in another post that you used Napa caps. Will you please share what kind/style they were? Thanks!
 
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My stock Viper bogged from day one in heavy snow, I monkeyed around with the ram air vents and quickley discovered that wasn't the thing to do. I always thought it was hot humid air from under the hood and the only thing I conld see to do was block off all air and draw from outside.

Another guy had a stock Viper and he wouldn't do anything to fix, he was always bogging.

Fresh air and no carb heat.
 
I have ceramic coated pipes and air vents by speedo. I do allow the air to draw from under the hood also. I have a friend set up exactly like me and he bogs when doing a deep powder right hand turn only, not left. The only dif. is his slp triple pipes are painted not coated. :dunno:
 
02 Viper 144 x 16 X 2" paddle
CPR pipes, with head mod
Yamaha exhaust deflector
8ek no rivets stk spring
43' helix silver spring 90' (plus) twist I think
21 top 41 bottom gearing 70L
8 tooth drivers
holtman Atacc installed
jets 162.5 162.5 165
pilots 47.5 47.5 47.5
needles 3th groove washer top & bottom
fuel screws 1.75 1.75 1.75
all stock carb parts
2 flo-rites, ram air filters, air box prefilter, 1-1/2" hole drilled in each ram air duct to dump air right into the air box
all under air inlet to air box are duct taped off, to suck only outside cool air, from ram air and flo-rites
and still tuning LOL
LET ME KNOW WHAT CURES THE BOG!
 
Who knows if I'm on the right track, but I am down to two or so things that might be causing the bog from what I have read.

My first guess, based on all the reading I have done here, is that a pipe is being cooled by snow when it comes through the hood vent and lands on the pipe. My SLP pipes are also painted, not dipped, but I have the bog anytime snow comes up onto the hood, not just carving to the right. Based on what A K mntviper said, could the excellant protection of the pipes provided by ceramic coating be not letting the snow cool the pipe as much as painted ones do? This should be an easy fix, simply put pre-filter material over all the hood vents so that no snow can get under the hood. Has anyone tried blocking all the hood vents with pre-filter material? My sled will clean out, even with the vents still blocked by snow, after a little bit. It seems to be the initial blast of snow hitting the hood vents that causes the problem.

My second guess is based on what Chevyracer68 has posted, which is that snow mist/steam is shorting out the plugs. He put different plug caps on his sled from Napa. I would be interested in finding out what kind exactly. Are they the hard plastic ones that have the little rubber boots that fit tightly around the spark plug? This would make sense, because they create a good seal and prevent mist/steam from getting up into the top of the cap. It seems funny to me that there are so many people that have done some minor things to their sled and have cured it, yet others like SNAKEBIT still have the problem. I can't seem to find a common mod that cures this. Maybe it is so elusive because it is a combination of several things?

SNAKEBIT, I would have expected what you have done would cure the bog. One question, do you run with your carb heaters on? If you do, try turning them off. Another thing I would suggest is to try putting on spark plug caps that seal really well, like what I said above. Lastly, try putting pre-filter material over your hood vents. If your sled still has the bog after all this, I give up!
 
I always thought it was DEEP snow smothering the exhaust exit and altering much required flow/ back pressure?.. Seems that when snow is DEEP enough to come over top of the hood and windshield, it's also deep enough to smother the exaust exit...

Always thought it was back pressure variations??... maybe I've been on the wrong track??
 
Just a thougth on this plug boot theory.
Got caught up in the Spiltfire craze when they first came out back in the 90's, and got to using them on our Exciters. Started having a bog and sometimes a slight miss. Found out it was the Splitfire plugs.
If you notice on the Splitfires the porclein on the plug is smooth. On a normal NGK plug the porclein is ribbed. This was allowing moisture to enter the boot and was the cause of the problem. Switched back to the NGK and all good.
Not sure that this is causing the Viper problem but who knows???
Also was a post here last year or so and someone was convienced it was the small vent on the right side of the belly pan which was allowing snow to enter onto the silencer.
I have the stock pipe, bender can, peak head, no flow vents, and can say I haven't experienced a bog significate to do a lot of searching.
However I have been thinking of installing some to help with under hood temps, not so much for fresh to carbs.
I think the under hood temps are more of a concern, have seen some guys litteraly melt hoods when running in continues powder.
After a few minutes of running with snow over the hood I allows stop and brush it off to let things cool down.
Just my experience.
 
I have a 98 MM 700 and when the exhaust was stock it never bogged. Put on a Bender can and it never bogged. Put on Bender triples last year and it started to bog, but only when sidehilling to the right. I figured it was the pipe outlets jamming with snow so I installed a bigger exhaust deflector. I haven't had any trouble since (yet).
 
I have NEVER run with the carb heaters on!
going to try new boots and maybe use some electrical gell?
I have very fine screens on my hood, but not the pre-filter material
holes in belly pan under bumper etc. taped closed
 
I've heard the exhaust deflector theory several times, here's why I'm pretty sure this isn't the problem. I would agree on a sled that doesn't have one on it, but my mnt, viper came with one.

When I was riding last year in McCall, it was excellent "fluffy" powder conditions. When off the trail, my sled ran flawlessly until snow came up onto the hood. I run with my limiter straps as loose as they can go. As long as I was wide open and packing the skis, it ran good. As soon as the skis hit a drift or I let them touch back onto the snow, they threw snow onto the hood. Immediate bog when this occurred. It always has happened (for me anyway) when I see light powder hit the front hood screens. In heavier snow, I can have snow come up onto the hood and no problems. It is always the super light, "fluffy" snow that I have trouble with, the kind that has super small particles that can "mist" through the smallest of openings.

I appreciate all the comments. It will be another month or so before I ride, so I can't try any hands on experimenting until then. Even at that, it has to be one of those super powder days before I have the bog. In all honesty I only seem to get about two or three rides a season that are like this. Those days are the absolute best riding conditions, very annoying to watch all my buddies riding their ski-doos and polaris's around submerged in the snow while I dig myself out because I got stuck when my sled fell on its face.
 
i think its the snow getting under the hood and rapidly cooling the pipes. IMO , if it was the exhaust deflector thing that everybody is talking about, the other brand sleds that you ride with , on the same day, same snow --they two would be having the same symptoms! i think the pre-filter mod over the vents will work.
 
not a mountian guy but with the spark plug boots when we were racing snow x we would put a small ziptie around the boot so that it held tight on the pocilen we did this to keep the boot from coming loose on hard landings but may help to seal up the boot to the plug to just a thought
 
First check you getting, make sure your not to rich. What worked on mine is taking some foam sealer from Home Depot. THe stuff that is around 3/4 inch thich by 3/8 inch wide, that is sticky on one side. Run that all the way around the top of your air box where the hood meets it. Solved my problem. Also tape off uder hood vents to airbox, the vent that sucks the under hood air, and get some flo-rites in the dash.
 
MM700
After doing that, you are now pulling in nothing but cold or cooler outside air.
Did you increase the jet size or make any carb adjustments.
The main jet size (according to the factor) for my elevation is 148. However I am presently running 145 with no problem.
If a guy does what you did, do you think a person should go back to the factory specs.
Colder air is making for a leaner condition.
 
Snomoguy, I ran my Mtn Viper ( stock) with 143.8 and all the outside air I could get with no problems. We are 7500' to 9000' I did hold back some on the real cold mornings. I would only use carb heat on the coldest days. The sled would bog a little if moisture would form on the air box foam.
 
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