Gas In Air Box?? Tech Challenge

viperdougc

viperdougc

Member
Joined
Feb 25, 2005
Messages
151
Age
54
Location
Arnprior, ON
Ok Boys if anyone can figure this out I have an Oreo cookie and a big glass of milk for ya. There seems to be a lot of knowledge on this website maybe someone can help. You have probably seen my posts over the past 4 years about excessive fuel consumption on my viper and no one has figured this thing out including me. The viper is completely stock 10 000 miles and I just put rings and pistons in. Compression 110 Pto, 125, 125. It seems to be running quite strong and pulls like any other viper I have seen 106 mph on GPS.

Here are the symptoms:

1) lots of fuel in the air box....keeps the aluminum under the stems of the airbox nice an shiney all the time

2) I might be lucky if I get 100 miles to the tank of fuel

3) The sled seems to burn the same amount of fuel cutting thru 2 feet of snow as it does riding mid-range on a groomed trail. This I am sure of. I just cut thru 12 miles of bush trail in 2 feet of snow and it didn't burn any more fuel than on the trail. I know this makes absolutely no sense but its true.


Here is what has been done to find the problem.

1) Carbs checked and rechecked numerous times. I recently dropped down to 152.5 on the mains and droped the needle .5. No change in the symptoms

2) New reeds

3) As mentioned above rings and pistons

4) Changed Stator

5) All bearings are new

6) Switched out the CDI


Here are a couple of questions:

Could I have a bad seal and what are the ways to check the seal???

Does the TPS have that much of an effect on mid-range riding????

Is there any way that the timing could be off other than the CDI???

Is the motor sucking too much air that is causing the fuel to blow back???


Guys any help here would be appreciated....I think I have about blown my mind and I really want to figure this out!!!!
 

I have checked the exhaust in the past with no success. I could not find any blockage but how the heck can you look thru there anyway.

I was reading some posts and have another idea though. One dude had a fuel pump that was flowing too much fuel and spitting it back into the airbox...maybe thats the culprit its the only thing I haven't checked. The pulse line from the fuel pump that goes into the motor could be defective. If it is spitting fuel thru the line instead of holdinkg suction then that could be my problem. I have to get the hell out of work here and check it out.
 
you will always have spit back in a triple without a boost bottle,just nature
of the beast.

i cut a few piec's of vac line and shoved in the holes @ the bottom of the
air box(acts like a wall so the oil can't escape but air can flow) so the oily mess stay's in the air box, may need to clean out you air box
once evry few seasons..
 
floats seem to be set to speck....I was going to do a test to see if I have a needle hanging up or something....I've gone thru the carbs numerous times.....as has yamaha dealer and a few guys I know that are good with carbs.. all seems well.....I was hoping to get another carb rack from a buddy to throw in and give a try.
 
Your fuel consumption doesn't seem all that bad to me, depending upon riding conditions 100 miles on a tank seems resonable. Are you losing any performance? The incoming fuel/air charge when it slams into a closed reed cage has nowhere else to go but back the way it came, someone mentioned that a boost bottle counteracts that somewhat, I have two installed on sleds and believe I can feel seat of the pants, difference. The air boxes both are wet inside. Do the vent lines from the viper carbs dangle loosely below the carbs, or do they exit in the air box? Seems like I remember them being connected to the air box, and guys mounting triple pipes on the Viper couldn't get enough fuel into the engine with the lines in the air box.
 
well what seems to be the spec and actually measuring it can be 2 differnt things, a high float level will make the engine rich, even if its not high enough to spill out the overflow, so having it at the exact yamaha spec or slightly below may make a differance if all was done was "that looks ok to me"
 
daman said:
you will always have spit back in a triple without a boost bottle,just nature
of the beast.

i cut a few piec's of vac line and shoved in the holes @ the bottom of the
air box(acts like a wall so the oil can't escape but air can flow) so the oily mess stay's in the air box, may need to clean out you air box
once evry few seasons..
Click to expand...

I put my entire air box in the dish washer every season. I wipe out any obvious oil and gas first
 
Beth Viper Thread I think

I am going to check my float levels again!!! been there done that.... but will pay very close attention and set them to the lower end of the spec.

One thing that is weighing on the back of my mind is a thread I believe was either bethviper of mrviper 700. Someone was inquiring about how the TPS would affect top end speed in a drag. I can't remember who answered the thread but they said that the TPS had not effect on top end/performance. They had run the drag with it unhooked and hooked up and it made no difference. Thus performance didn't suffer and my Viper is pulling hard and has great top end for a stock viper...... However, what they did say was the TPS did have an effect on mid-range trail riding and fuel consumption. What are you thoughts guys.

I have a buddy with another carb rack. I'm going to give it a try after christmas and will let everone know. If the new carbs work I am almost 100% it was the TPS but when I checked it on my carbs it was reading in spec.
 
yeah my 02 viper (when stock) would only get like 10 mpg also. when I had my 99 srx 700, I could get 12-13 mpg. I would think that you should be able to get more than 10 mpg, but maybe not...I think the vipers have more of aggressive porting than an srx.
 
I see you have 10,000 miles on the sled, have you ever rebuilt the clutchs, and ever checked the buttons in the rear secondary clutch?

You are correct the TPS switch does alter the timing for mid range cruising for gas mpg and throttle response, has no effect at WOT!
 
Last edited:
Can he check the piston wash to see how rich you have been running? There are proper piston wash pictures to go by to see if you have been getting the right amount of fuel.
 
I have maintained the clutches but they have not been rebuilt. Will the sled still perform well if the clutches are worn though. I would think that the sled wouldn't perform well if the clutches were that badly worn. I have a good top speed and it seems to pull real well. Small over rev on the tack (100-200 rpms) at most but would it contribute to the bad gas consumption.

The bad TPS seems to be making sense with me because the sled seems to pull real well and is getting horrible fuel consumption in mid-range trail riding. No matter how I ride on groomed trail or cutting trail thru 2 feet of snow it gets the same milage. Thats what makes absolutly no sense to me. I will be pulling both clutches over chrismas when I actually have some time on my hands. I will keep you posted if I ever figure this out!!! I think I am getting close though
 
You must log in or register to reply here.


Back
Top