03 Viper High Idle and Backfiring

Grimmy

Grimmy

New member
Joined
Jan 22, 2008
Messages
64
Location
N. Muskegon, Michigan
I've been having issues this year unlike I've had before and it's killing me.

I previously was having the dreaded no display, low lights, etc...issue. I had replaced the wiring harness and that did nothing. I recently picked up a used stator and replaced that. Ta-da....problem solved. (Thanks to TY for the forum help with that issue)

The problems I've been dealing with beyond that are a high idle and some backfiring which I've never had. At the beginning of season as I went to top fluids off I noticed that my coolant tank was empty. No puddles on the floor...no leaks that I could see.....I've since filled it up and haven't seen a noticeable drop in level. The cap may not be the tightest but didnt think it would evap over a summer like that. After first initial ride which was fine I was pulling my kids around in their sled and it started acting up at low rpm's. We stopped that, they went in and I took it for a ride down the road. Once off idle it was awesome as normal. It sat for a few days and then I started it up to ride some more. The idle had been staying high at start up and slowly climbing to enagagement at which point it would back off and hang around 3000 rpm. I could get it to come down with the choke but it would go back up in rpm after I turned the choke off, or else it would die. Tried to adjust my idle adjustment over and over but it would just be erradic. Thought the pilots were plugged again even though I had already pulled the carbs and cleaned them thoroughly. Other thought was that i screwed up on my fuel screw adjustments. My plugs looked good according to the pic I sent my dad (deleted that already or else I'd post it) and the color was a choco brown. I was concerned they were a little rich but again, my dad said they looked good to him. When I was out riding the last time with a friend it was idling ok (after very warm.... was still a pain to keep the idle right when cold) ....but after a while of riding we stopped and were idling on the trail. Listening as I always am to the machine I could hear something was off. It would be just fine and then it would cycle with a really low tone (like a low decibel tuba for lack of better ways to explain it) then it would be fine for a few more cycles and repeat. He looked under at the bottom of the can and pointed.....when watching it, as it made the odd sound it would shoot a flame out of the can. WTF ya know... Once off idle...it was screaming like a raped cat and never had an issue. The ride was awesome. Got home, checked plugs...still choco brown. The whole time since start up (new plugs were put in once carbs were cleaned) theres been oil around the base of the threads nearest the electrode and the porcelain around the center electrode was getting a tiny bit darker each time checked them but the ground electrode never changed its nice brown color. I pulled the carbs again and reset my fuel screws. Put it all back together and tried to get it started. Took forever...it finally did but died so I stuck a new set of plugs in to start fresh. It started with the choke on full but any time i put it to half or choke off it would die. I could leave the choke on fully and it would stay running but would stay at 3000 - 4000 rpm. Pulled the plugs.... and the ground electrode was white. I didn't do anything in regards to starting attempts after that. I went into pulling the carbs.....again. When i got into the airbox there was a light film of oil around the perimeter of the box, which had been there each time I opened the airbox up, but this time there was a dime size puddle of bright green in the bottom of the airbox as well. There's only one thing I know that could be so I haven't bothered putting it back together yet and the blizzard just finished so now im pouting lol. I'm thinking a have to replace the head gasket, which I already have....I bought an opti-cool head gasket a few years ago to put on just in case I modified the sled later and never put it in. On that note... opinions on putting that gasket on a stock sled? How many layers is the stock one? Compression diff? performance will degrade? -- if so how much...etc.etc

Mainly after my short novel, I am wondering what my issues are caused from. The carbs are clean as a whistle.....I also just cleaned off my power valves best I could.
 
couple questions:
1.) when you cleaned the carbs, did you remove the pilot jets, and are able to see light thru them when you hold them up to a light

2.) while the pilot jets are out, do or did you squirt some carb clean or brake clean up into where the pilot jet threads in and it comes out the throat in the idle orfice hole in the FRONT side of the carb?

3.) when you adjust your throttle cable is there slack in the cable, like alot of slack,,1/8" minimum? sometimes if the cable is too tight its right on the edge of the tors switch and it can sound dull at idle.

on to your headgasket: the opticool gasket is fine to install on a stock viper, its a tad thicker then stock and will reduce the compression slightly. Not something your gonna go, wow.. its slow now.

if your headgasket was bad usually it will push the antifreeze out of the overflow or pressurize the system quckly after starting it, you can squeeze the top hose after running it for 15 minutes and see. They also will tend to suck in the green juice, this makes the plugs wet and shiny, and will wash off all the carbon on the piston to appear like new shiny aluminum color. I usually only see headgasket problems when someone overheats the sleds.

add: take a mirror on a stock and a flash light, sticj it under the water pump cover at front bottom of engine and observe the weep hole in the case, does it have a drip of grren juice on it?
 
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Carb cleaner came out all over when I sprayed carb cleaner thru every orifice. I never got a look at the pistons but the plugs looked wet but I dont know if they should be wet or dry. As of now the carbs r not in there and even when they were it wouldn't stay running for over a minute without leaving the choke fully On so I wouldn't be able to c if that were true. What would be the deal with that backfiring with flames coming out? Would backfiring cause a leaky head gasket on the viper?
 
since they are off,clean the carbs again.............go to tech section and look up carb cleaning 101 with pics, pay paticular attention to the pilot jet orfice and spraying carb cleaner up thru there, it should only come out the orfice, not all over...

the backfiring is because its lean, not a headgasket.
 
I'll spray on it thru there again......the. 101 with pics is in fact the one I follow to a t. :-). I printed that off long ago and that's what I go by. That flame thing out the can concerns me to. Have u ever seen or heard of that? And the idle hang......I've never had all these probs before. The viper has been bulletproof for me till now.
 
lets go thru the pilot circuit agin and make sure you can see light thru the jet, the spray comes out the orfice in the front of the carb and then get them back on and start it up with lots of slack in the throttle cable, lets see what it does, then we can test other things(like places for airleaks,etc.) if theres still a issue.
 
Ok....I finally got home with enough time to go through the carbs again since they r off......sprayed carb cleaner thru the pilot circuit and it came out thru the brass orifice in the front of the carbs as I thought it did this last time that I cleaned them. I dont mind going thru it all again tho, I just want it to be right. Carb cleaner was spraying back at e from he pilot jet opening also but I assume that's due to the aiz.of the hole being smaller than the carb cleaner hose. Will have it back together in a few.minutes and will update att.
 
Got everthing back together, once everything stabilized I had to adjust the idle and its now idling around 1800 but I swear it sounds a lil funny. It also still has an odd whomp to it every so often that I described in the beginning as the low tuba sound. Its not as pronounced as it was to begin with but its still there. Not sure if it means one of the fuel screws is diff than the rest or what. Remote fuel screws.would be so nice. That will be done this summer. I took some video of it running but am not sure if I can add that to the post or not yet. In the video u can see the affect of the whomp sound....it doesn't have The flame it had previously but now is a puff that comes out of the exhaust. It has great throttle response off the idle but wants to hang around 3200 for a second then slowly works its way down. I know it used to be quick up off the idle and came right back down when the throttle was let off. That alone tells me something isn't right.

It
 
My viper does the exact same thing at idle that you are describing along with the backfire and flame out of the exhaust and I have yet to find the problem. It runs perfect out on the trail so I don't worry about it. It also turns over longer than what it should on cold start ups but starts great when warmed up. I get some strange looks from my riding buddies when they hear it idle but no one seems to know what it is. I too am loosing a small amount of coolant after each trip. Hopefully we can get an answer to our common problem.
 
I get what you're saying...I thought the same thing when I was out there...once off idle it was an animal so I did t care at first. At the same time I am somewhat of a perfectionist and can't stand it running diff than I know it should. I feel like if I had just taken it into the local Yamaha tech it would be good to go so its ticking me off. There has been a definite change since going thru my carbs again and again so I'm thinking it has something to do with the settings of my fuel screws......like ones off from the others just a tad. I'm also wondering if it coud have anything to do with the power valves. I cleaned them up and they are a heck of a lot better than they were but I know they r not spotless. So glad I'm not the only one with the issue tho.
 
I was in the same position as you and did end up taking it to a Yamaha tech. He told me my fuel screws were off. However, it still does it, just not as bad. He said he had never seen it before. I would never be able to sell it the way it is because to hear it, you would swear something was wrong. It is obviously something wrong in the idling circuitry. Have you checked your compression? Mine is low @ only 105 psi....not sure if that has anything to do with it or not but it still pulls really good.
 
It really sounds like you are getting an inconsistent air or fuel supply (likely both). Could be a number of things contributing (too many to list). I would broaden your diagnosis to include all contributing components and don't rule out the electric side as well. However, back to the carbs - make sure you understand and follow each fuel circuit through including the air jets. Basically to get fuel out of the bowls at idle, the air flow allowed via the air jet is what let's the fuel come into the carb throat from the pilot jet. Until the vacuum increases in the carb throat (engine rpms enter lower midrange) fuel is not drawn thru the main and around the needle. This circuit needs clear passages from the air horn to where it meets the pilot jet tower, and then into the passages that go to the venturi. To operate correctly all must be open. Also the pilot screws need to have the o-ring, spring and washer in place so that they don't vary the mixture. As long as fuel is consistent, and the only way for air to get to the reed valves (don't forget to check them) is thru the carb (and not from leaking boots) and the slide remains unmoving, you should have a much more consistent idle then you are describing. I really wonder if you don't have multiple minor issues that are combining to be very confusing.
 
so, its better now that you cleaned the carbs again and its idling at the right rpm....then there was definitely something in the carbs somewhere.

where are you setting the fuel screws at on the bottom of the carbs?

if it wont come back down after you rev it up your on the lean side. usually on a viper i will set them to 1 7/8 out from lightly seated. set the idle speed at 1500rpm.

the powervalves are not going to do this, this is a carb problem in my opinion.
 
Mrviper700......prior to u saying to go thru the pilot circuit again since they were still off the sled I had gone thru them very well and made sure cleaner was coming out of the front when sprayed thru the pilot jet orifice as well as making sure I had seen light through each jet. However, I have no prob going thru things again to ensure it is correct as I have learned thru the years that peace of mind is invaluable. Yes, it runs great...just still idles slightly off with that puff coming through the exhaust. I'm trying to get them set to 1 7/8 turns it from lightly seated as that's what the book calls for on the stock viper. I figure one of the screws isn't right but dont know how to tell which one. Is there a tool available to balance them when setting those screws. I know......hence the point of remote fuel screws. Not too familiar with what occurs under lean or rich conditions....when the fuel pump has some freeze to it.....etc etc. Manual says the idle should be at 1800. +/- 100 rpm.......why does do j recommend it to be at 1500 as its always run great before at the normal setting?
 
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so now that its not idling at 3000rpm and shooting flames out tells me there was likely somthin there but moving on....

1.)is the throttle cable loose??, meaning at least 1/8-1/4" slack in it?

2.)set the fuel screws to 1 7/8 turns out from lightly seated.

3.) next the choke cable, are the the plungers returning all the way in when choke lever is down?
there should be some slack in the choke cable as well, double check. Then, take a small penlight screw driver and push on the end of each plunger while its idling, see if it changes its tone.

also you asked why i say 1500rpm, because the viper has a leaner set up then a srx does and if you slightly lower the idle speed and run the screws out, they return to idle speed quicker and dont have the idle hang problem as much as when the idle speed is higher.
 
I made sure that there is slack in both throttle and choke cables. I agree about the carbs.....had to be something there. What type of lube could I spray on the shaft for the choke across tha carbs? Should it be hosed down with carb cleaner first?
 
Grimmy said:
I made sure that there is slack in both throttle and choke cables. I agree about the carbs.....had to be something there. What type of lube could I spray on the shaft for the choke across tha carbs? Should it be hosed down with carb cleaner first?
Click to expand...

I use kroil spray on all kinds of linkages and stuff works well but so would just wd40 or silicone spray. spray the cam arm over where the linkage connects to the cable too.

did you have a chance to start it up and push on the plungers to see if it sounds any differnt?
 
I took the carbs back off and reset the fuel screws. I set them just a hair closer to 2 turns than 1-7/8 so I knew I wasn't on the lean side. Got it back together and once it was running again, it idles at 1800......if I try to get it down to 1500 it will keep on crawling down in rpms and die. As its idling, it slowly creeps up in rpm and then slowly come back down on its own. After a lil bit it will do it again. If I put it to half choke the rpms climb. Full choke and it kills it. After resetting the fuel screws it doesn't do the backfiring anymore....but I'm right back to the crap I've been dealing with.

Could it be something to do with the fuel pump? I see the fix on here for the frozen pump....what r the indications that the sled shows when that's the issue?

I checked the choke ..... The cable has plenty of slack, it looks like the slides r all working together and returning properly. I used silicone spray to lube as written about previously.
 
The for that info. I am so sick of pulling and cleaning the carbs. I dont doubt mrviper700 at all but I feel like there's something else going on as well. How does one test the tps?
 
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