The infamous powder bog

97 sx 700

1st time poster over here on the mountain side.

There are 4 warm air ports that are incorporated into my hood. This pulls warm air from the engine compartment along with the the factory cold air intake. 100% completely stock setup.
The question I have is....if I block off the warm air, and the carbs get all cold air, does anyone see any problems. Besides leaning it out a bit. Still have stock jetting in it anyway, so it's a bit rich anyhow.

Thanks
Dan
 

Steam

Water expands 1700 its volume as steam. In a confined area under the hood when the pipes hit snow and steam is created the underhood pressure increases greatly which pressurizes the float bowls and you go pig rich something like what the turbo sleds use to increase fuel flow on boost.( non injected ) Eliminate the pressure buildup or isolate the carbs to maintain a constant atmospheric pressure under any condition and it will be fine. I remember also the SRXs are known to go rich because of the increased underhood pressure due to speed.
 
I've ran mine sleds with those ports taped off for years. No problems.

A couple of bucks said:
1st time poster over here on the mountain side.

There are 4 warm air ports that are incorporated into my hood. This pulls warm air from the engine compartment along with the the factory cold air intake. 100% completely stock setup.
The question I have is....if I block off the warm air, and the carbs get all cold air, does anyone see any problems. Besides leaning it out a bit. Still have stock jetting in it anyway, so it's a bit rich anyhow.

Thanks
Dan
Click to expand...
 
Bog

RIVERRUNNER said:
Hi guys....I have been reading these threads since they started and the under the hood air is the key. But on a side note. I have always had this problem with my sled and have never cut the flow rites in, but this year I wrapped my pipes with exhaust wrap and put the shields back on. (The insulation was gone and pipes were wearing threw the shields)(I only wrapped under the shields) I have done nothing else to combat the bog!! I was out in the powder last weekend with snow covering the hood and NO BOG! First time I have ever been able to play in the powder without bogging!! I was pumped!!! With my sled all warmed up my pipes with shields are warm to the touch. I have a SRX 600 not a MM but if you have triple pipes and want to help you bog tremendously wrap them up you wont be sorry! ;)!


Note: jetting too can be effected when you wrap up your pipes, So check plugs and piston wash!!!!
Click to expand...



Way i understand it, wrapping your pipes will increase rust. Ceramic Coat your pipes to hold the heat in......
 
Wow, what a read this post is! I just picked up a Mountain Viper with ceramic coated SLP tripples so I was interested in the read. A couple of posts reminded me of something, but it was whoever mentioned the jetski that tripped my memory.

I've worked on many a vehicle over the years as a semi professional mechanic. On a couple of jet skiis I worked on, the flexible exhaust coupling went bad and in a tight (read small non ventilated or porly ventilated engine compartment), guess what, instant bog!

I also had a big SeaRay with an I/O for a number of years, and at one point my engine compartment blower gave out. At low speeds where there wasn't enough velocity to creat a "draft" through the engine compartment with the vents, engine would run rough/bog.

My point being: an engine compartment with a contanimated air flow (steam, exhaust fumes, ...) can have a direct affect on how an engine runs. this is true on 2 strokes, 4 strokes, and even big diesel engines. (I've personally seen 2500HP diesels run on a dyno, and when the exhaust ventillation isn't adequate, the engines loose power or bog.

A relativly small air volume (under snowmobile hood) would have a much faster reaction to any change in air pressure/density/quality, whatever you want to call it.

I don't think sealing off the entire engine compartment and drawing cold outside air is a great option as these sleds were made to get rid of the underhood heat.

Perhaps a temporary test/solution would be to somehow mount a bilge blower under the hood and exhaust it outside? Changing nothing else, this may be a definitave answer as to why the bog is oggurring?

Just my random thoughts. What do the rest fo you think?
 
Hey Dan, aka Grizzly1, welcome to the 2 smoke side!!! And expect to see that Mountain Viper of yours January in Mt Iron, MN at the TY ride there!

You'll love that Mt Viper, they are a great all around sled. Cripe, well pretty much have a fleet of them now on the Ty ride, lol!!! ;-)
 
Thanks Mike. I was always nostalgic for my MM700. It was one of my favorite sleds. I see this as even better with the power valves. I'll miss the Apex, but it was time for a change, and besides I'm sure I'll have a new sled in the next year or few.

I know you have one, but who else makes up the fleet? I only remeber the two of them last year.
 
thegrizzly1 said:
Thanks Mike. I was always nostalgic for my MM700. It was one of my favorite sleds. I see this as even better with the power valves. I'll miss the Apex, but it was time for a change, and besides I'm sure I'll have a new sled in the next year or few.

I know you have one, but who else makes up the fleet? I only remeber the two of them last year.
Click to expand...

What about Nicko's, or did you buy his? What happened to your Apex?
 
thegrizzly1 said:
Wow, what a read this post is! I just picked up a Mountain Viper with ceramic coated SLP tripples so I was interested in the read. A couple of posts reminded me of something, but it was whoever mentioned the jetski that tripped my memory.

I've worked on many a vehicle over the years as a semi professional mechanic. On a couple of jet skiis I worked on, the flexible exhaust coupling went bad and in a tight (read small non ventilated or porly ventilated engine compartment), guess what, instant bog!

I also had a big SeaRay with an I/O for a number of years, and at one point my engine compartment blower gave out. At low speeds where there wasn't enough velocity to creat a "draft" through the engine compartment with the vents, engine would run rough/bog.

My point being: an engine compartment with a contanimated air flow (steam, exhaust fumes, ...) can have a direct affect on how an engine runs. this is true on 2 strokes, 4 strokes, and even big diesel engines. (I've personally seen 2500HP diesels run on a dyno, and when the exhaust ventillation isn't adequate, the engines loose power or bog.

A relativly small air volume (under snowmobile hood) would have a much faster reaction to any change in air pressure/density/quality, whatever you want to call it.

I don't think sealing off the entire engine compartment and drawing cold outside air is a great option as these sleds were made to get rid of the underhood heat.

Perhaps a temporary test/solution would be to somehow mount a bilge blower under the hood and exhaust it outside? Changing nothing else, this may be a definitave answer as to why the bog is oggurring?

Just my random thoughts. What do the rest fo you think?
Click to expand...

From what I have read is everyone including my self is sealing the airbox to not allow the fine powder snow dust and steam to reach the airbox. airflow frow outside still flows through the motor compartment but does not have a chance to get up to the airbox if sealed correctly. Vipers tend to overheat anyway so you want to make sure that plenty of air is getting into the engine compartment.
 
i bought a 1999 srx last year that draws all of its air from under the hood. I would get bog when im riding in deep snow and when i am carving exhaust pipe outta the snow. So i find it hard to belive that a exhaust deflector will slove the problem. I guess the frusterating thing is... if so many people have had issues with this, myself included why has yamaha not addressd it themselves.
 
my mountain max700 tripple rolled chain case 153 track really likes the deep snow but the motor boggs out so imtaped up the vents on the front of the belly pan and up front no more problems i run with the air box attached and holtzman temp compensator so jetting is allways right so im going 2 say something 2 do with under hood air pressure and possible wet wiring on ignition. it would cut out on 1 cylinder
 
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