2002 Viper Intermittent Miss

After reading this thread a couple of things stand out. You said you have not gone thru the carbs. Its usually one of the first items to consider because of the ethanol most of us struggle with. It really does sounds like clutching....... simply because you were working on both clutches recently. Ninety twist. Holy smokes is that a long track thing? Most of us run 70 twist. If you've never changed the springs get both and make sure the twist is properly set up. Maybe try a test at 70 and see if that gets you closer.
 
UPDATED THINGS I HAVE DONE:
Checked the primary wiring ... they all test OK
Reset the secondary clutch to 70, and checked the adjustment.
When I went for a ride and it started to bog, I slammed on the brakes, to see where the belt was sitting in the secondary, .. it was only and inch or so from the top.
Removed the airbox to check for potential blockages.
Likewise the exhaust. Nothing found.
No clutch springs available around here, so going to order them online.
Will tear into the fuel system if it warms up a bit .. little chilly to be working bare handed.
Thanks for any ideas
Keep them coming
 
UPDATE 2
Figured I would try to get the revs up, so drilled out the top rivets on the primary weights.
Test drive, and the revs were better .. hitting around 8000 before bogging.
So .. I thought maybe reed valves were suspect .. so got into removing the carbs
Reeds looked brand new.
Figured since I had the carbs off, may as well strip them down, and make sure they were good to go.
Well lo and behold, one of the carbs' main jets had loosened off and was just hanging in the ring.
Eureka me thinks. When the carbs were on the low speed circuit, they would run fine, but when the high speed circuit kicked in, it would flood the cylinder since there was no jet to meter the amount of fuel .. with the jet bouncing around, maybe occasionally blocking the orifice to kick the affected cylinder back into firing.
Finished cleaning all the carbs, put them back together, and test drive.
At first I had a S#$T eating grin, because I thought I finally had it figured out. Then despair.
After numerous test drives .. this is what I have come up with.
It seems to be heat related.
I would leave my driveway, go down the road to the test field .. and it would pull hard on the first pass. 8000+ rpm and sounding great.
Then on the second pass, when it seems things have warmed up, it would go back into bog mode. Same as before .. great at 1/4 throttle, but once I opened it up, it would pull then bog. From a standstill, if I hammer it, it would pull hard to 8000+ rpm, then after about 5 seconds, go into bog mode.
When I brought it back into the yard to look at things .. plugs, belt, clutches etc .. while it cooled down a bit, then back to the test run ... same results. First pass .. great .. then the next passes, bog city.
Gonna do some googling ..
What are your thoughts.
 
Its good to hear your making progress. Something to try. As simple as this sounds change all three plugs no matter what they look like. resistor plugs can break down with heat.

I had a Honda power washer that would run perfect until warmed up. Once warmed it would stop running after two minutes. once cooled run perfect again two minutes. Over and over same result thinking i had fixed something two minutes later dead. I replaced fuel pump, took carb all apart. Looked at everything I could work on.
I then googled my problem and someone online suggested change the plug. Ran perfect.
---mac---
 
After reading this thread the first thing that comes to mind to me is that your carb vent lines may have been removed from the airbox.

The Vipers were the only triple Yamahas that vented the carbs to the airbox and the reason they have much larger main jets then say the SRXs.

If the vent lines are not connected to the airbox and just hanging down the sled will begin running richer as the sled goes faster and under hood pressure increases.
 
Skycoupe1 said:
If that is the case .. I havent taken the carbs out yet, .. wouldnt it be running lean, and risking burning up a piston?
What caused your bowls to run dry? Pump? Needle float valve?
Click to expand...

When you run out of gas it only goes lean for a short time. Not usually enough time to cause detonation or too much heat. It speeds up a little and then stalls. Sitting still, you can usually get to fire a few times after that. Bouncing around it is out period.
 
At this point I will try anything ..
They are brand new plugs in there now, but its worth it to drop 3 more in to see if that is the issue.

I am wondering if it is clutching .. Maybe when the clutches and belt warm up, they start to bind.
The only thing I haven't done is replace the belt .. I have 2 new belts coming, as the ones I have are fairly well used.

Blizzard here today, so will post when I venture back out.
Thanks
 
sideshowBob said:
After reading this thread the first thing that comes to mind to me is that your carb vent lines may have been removed from the airbox.

The Vipers were the only triple Yamahas that vented the carbs to the airbox and the reason they have much larger main jets then say the SRXs.

If the vent lines are not connected to the airbox and just hanging down the sled will begin running richer as the sled goes faster and under hood pressure increases.
Click to expand...

I can confirm that the vent line into the airbox is connected . . and when I was working on the carbs, fuel ran out of the vent line when I inverted them . . I will recheck to make sure one is not broken or disconnected.
 
Ding said:
When you run out of gas it only goes lean for a short time. Not usually enough time to cause detonation or too much heat. It speeds up a little and then stalls. Sitting still, you can usually get to fire a few times after that. Bouncing around it is out period.
Click to expand...

Ok .. I see what you are saying in regards to the bowl going dry.
Not sure what you mean in your last sentence.

What caused your bowls to run dry? Pump? Float valve?
I had the carbs apart and could find no issues.
 
Bouncing around (sled moving at speed) the bowls go completely dry.

Fuel supply blocked off to the carbs for various reasons - causing the bowls to run dry.
 
Ding said:
Bouncing around (sled moving at speed) the bowls go completely dry.

Fuel supply blocked off to the carbs for various reasons - causing the bowls to run dry.
Click to expand...

I see what you mean.

I am leaning toward electrical, because when it is cool, relatively speaking, it runs great.
Once it warms up, it starts the bog thing.
Am leaning towards stator or less likely one of the coils.
Once again this is solely based on the fact that it runs great right out of the barn, but after a 15 or 20 second full throttle burn, in which it runs great, it then starts the bog thing. If it was fuel supply, I would think that it would be blocked off at any given time, not after a run and a warm up.
It might be a rub through somewhere, but seems to be related to engine temperature.
Thanks
 
Mac said:
Attached is a picture of the very fine screen that clogs.

Click to expand...

Wow ... eye opener ... will get back into them and see if that is the issue
I assume that a Viper carb has the same screen?
Thank you
 
Holy smokes. $39. each. That's robbery.
The attached pic is from Viper 2002 33VM carb.
 
Hey Mac
If you ever make it north of the border, I owe you a case of good ol Canadian beer.
It looks like that was the problem.
Finished putting them back together late tonight and had to take if for a boot to see if it was successful.
10 minute ride and not a hiccup. Heres hoping.
Will know for sure tomorrow.

All of the screens had some degree of contamination .. looked like hard water scale flakes.
One in particular was the culprit. In the channel where the screen sits was a large clump of hard brown sediment that almost entirely encompassed the screen. That combined with the flakes made it so there was very little exposed screen for fuel to flow through.

The only problem I had was pulling them out. They have been in there for almost 20 years, so they were a b#$@h to get out. I ended up squishing 2 of them a bit. Had to bore them out with a drill bit to let the needle travel smoothly.

Will post tomorrow if there is an issue, otherwise this is solved .. .
Thank you to all who posted solutions!!!!
 
Good to see you solved your problem. You stayed with it. Many guys quite when they run out of ideas.

Rooster - yeah i see the ebay auction $10 dollar each. Ive always just cleaned mine.
 
Thanks for the kind words, but the saga continues
I figure by now you guys are just reading this for a good giggle.

So I went to take it out for a rip today, after last nights quick boot, to see if I had actually solved the issue.
When I went to pull it over it was unusually stiff. A friend had hydro locked his MXZ before, and hand grenaded one of the pistons, so I know symptoms.
I pulled the plugs, and as I suspected, copious amounts of fuel game gushing out of the plug holes as I pulled it over.
100 pulls later, yes I counted, with the throttle wide open, and a killer sore shoulder, there was nothing coming out of the plug holes.
Put the plugs in and it fired right up as usual.
I let it sit and idle for 10 minutes or so, because I didn't want to risk scorching the crank bearings by hammering the throttle, after they were washed with all the fuel.
Once it was well warmed up and blowing typical 2 stroke blue smoke, I took it for a rip.
Ran like it did 19 years ago. Lots of power and the typical Yammy triple smoothness.
I was thinking that when I got back, I would be back into the carbs and probably have to replace the needle/seat assemblies.
Then.
Screeeeeeech!!!
Started with just a squeak squeak squeak .. then quickly progressed to a constant screech.
Seemed to be coming from the stator side, perhaps the chain case.
Strange thing is only while I am applying power.
When I let off the throttle, silence.
So I am now back into the carbs, and have to try to find a bearing that let go.
The joys of riding a 2 decade old machine.
Will keep you posted.
 
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