oil leaking from air box??

S

Steven DeMarco

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Feb 16, 2004
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I have an oil leak on my viper. It appears that the gas/oil is blowing back into the airbox and leaking out all over the belly pan and frame of the sled.

I dont ride the sled much. I keep it as a back up in case my apex breaks but my friends ride it from time to time. Last week i rode it and noticed that the idle seems to stick after driving it for a bit. what is happening is you drive down the trail and come to a stop. the idle sticks at aproximately 4000 rpm for about 10 seconds and then drops down to normal. now this weekend when i went to my place i see a puddle of oil under the sled. When i went to look at it i found the airbox was filling up with oil and it was leaking out the 2 support legs on the bottom of the air box that rest on the frame.

I don't know if the 2 issues are related but i thought i would mention them both just in case.
Anyone have any ideas what would cause this?

I am thinking it might be time to clean and adjust the carbs but i was looking for a specific area of the carbs to pinpoint for this issue.

The sled has 5200 miles on it
The mods to the sled are boysen rad valves and a clutch kit.

Thanks in advance for any help.
 

That oil is called spit back,it's normal,you may want to change out your reeds with new,my srx did the same thing, i changed reeds and it help alot with the oil/gas mixture spitting back in the air box.

and your idle is hanging because your too lean at idle,you need to adjust
your fuel screws,turn them out 1/2-3/4 turn, should help..
 
daman said:
That oil is called spit back,it's normal,you may want to change out your reeds with new,my srx did the same thing, i changed reeds and it help alot with the oil/gas mixture spitting back in the air box.

and your idle is hanging because your too lean at idle,you need to adjust
your fuel screws,turn them out 1/2-3/4 turn, should help..
Click to expand...


I aggree .....

To check if you are too lean @ idle: when you come to a stop and your rpms are high pull the choke out...if they drop it is too lean at idle...adjusting your fuel screws should fix that
 
daman said:
That oil is called spit back,it's normal,you may want to change out your reeds with new,my srx did the same thing, i changed reeds and it help alot with the oil/gas mixture spitting back in the air box.

and your idle is hanging because your too lean at idle,you need to adjust
your fuel screws,turn them out 1/2-3/4 turn, should help..
Click to expand...

Thanks i appreciate the input
I am running the boysen rad valves. Any idea if the rad valves are more prone to the spit back? my original reeds started chipping and cracking around 4000 miles and i replaced them with rad valves. the valves cost an arm and a leg and besides the spit back i have been happy with them.
do you think there is anything i can do to stop the spit back? install spacers or something like that? This also seems like it just started spitting back. Do you think i need to inspect the rad valves? I would think they should still be ok with only 1700 miles on them.
It is not a big problem for me just a mess. i guess worst case scenario is I still have the old valve cages, i could repair those and reinstall them. I am trying to avoid investing more money into this sled as i barely use it.
 
spit back can be almost eliminated by a boost bottle, other than that, its normal, nothing is wrong.

your high idle is more a sideffect of your pipe being really hot after a hard run. this is where the problem arises. you could back the fuel screws out to 4 turns and still not make it go away, you just cant add enough gas to it with that curcuit and if you used the pilots to add gas to it on the way down the sled would run rich normally.

the cure i have found is to simply run your idle below around 13-1400.

carbon fiber reeds wear out faster than stock, i doubt they are wore out already though.

if you want to do your carbs, if they have never been set up, they will almost allways need to have the floats set and slides sincronized. set the floats to 14mm, measured off the body of the carb to the top edge with the carb upside down and level.
the slides are adjusted by setting all the slide gaps at the carb floor to be the same. this is measured with a small drill and adjusted under the top cover on the rail.
 
I'm going to have to go with Betheviper on the high idle thing---- mine did the same thing, i turned my fuel screws out to 2 turns, then 2-1/4.... 2-1/2... and it didn't fix it, so i put bigger pilots in (47.5- the next size up), set screws at 1-7/8 turns out and it still does it. So i guess i'm gonna put the stock pilots back in and turn the idle way down -which sucks because she shakes like hell when it's that low. Kinda like the way it purrs nice and smooth at 1800 BTV -so it's from a hot pipe and not a lean condition?
 
Idle down

Betheviper got it right...worked on my viper, 1300rpm & go with oem reeds & clean, set carbs and your good to go...
 
So do any of you think the rad valves cause more spit back then standard yamaha reeds?

Up to the 4000 mile mark when i ran stock reeds i always noticed some oil in the air box but it was never an issue. now that i have changed to the rad valves there is a 6 inch diameter puddle under it every time i park it. and i am absolutely positive it is spit back and not an oil leak.

I also agree with your Idea on lowering the idle. I know this is the problem because i turned the idle up at the beginning of the season so when my friends ride it they are not sitting around pumping the gas for fear it will stall. I will back it down to where you said and see how it goes.

Thanks Guys
 
Go back to stock reeds. They truly are the best you can do on a stock engine or even a piped yamaha engine for that matter. Also much cheaper to replace and last a lot longer.
 
you have more than a spit back problem if you have that much oil. spit back will never end up on the floor. sometimes it will make the top of the tunnel dirty, even under the gas tank but never drip down on the floor.

you need to investigate further. spit back just makes a mess, not a puddle.
 
It is weird.
it only leaves a puddle after it has been run.
If you let it sit for the day after using the sled it will have a puddle under it. Slide it over to a new spot there is little to no leaking.
none of the lines are lose cracked or missing clips but the inside of the airbox is soaked with oil.
it appears to be draining through the little support legs on the botton of the air box.

I think i will spray it down with some degreaser and clean it up and start fresh to see if i can find a leak. everything is so covered at this point it is almost impossible to track this down.

Thanks for everyones help
 
If it's like the srx's there's holes in the bottom of the A/B,not sure
if there for air or let oil out,,none of my twins have these holes in the
bottom..
 
twins dont need holes, they have boost bottles that all but remove this problem. they also add power which leads to the question, why didnt they install them on all sleds.
 
what is your oiler set to?? if it is really rich on oil, it might be just spitback. should be 22mm stock up to 24 would be lean. sled should use about 1 quart every 150-200mls.
 
The holes in the bottom of the air box give the oil a place to go so that it doesn't just all puddle up in the bottom of the box after being spit back from the carbs. The twins dont need these drain holes because they have MUCH less spit back because of the boost bottle.
 
yamaholic22 said:
The holes in the bottom of the air box give the oil a place to go so that it doesn't just all puddle up in the bottom of the box after being spit back from the carbs. The twins dont need these drain holes because they have MUCH less spit back because of the boost bottle.
Click to expand...
Right.......i knew that much
 
pro116 said:
Than why did you ask
How does holes in a air box make up for a boost bottle??
Click to expand...
i knew tha holes were for that damn oil but i wasn't sure how they were
related to a B/B!!!!

didn't you see my bold in holics post????? i was answering that....
 
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