2002 Viper Intermittent Miss

S

Skycoupe1

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Greetings all
I put a long track on my stock 2002 Viper years ago, and had no issues until this year.
I usually ride on unimproved terrain, in shallow snow.
When I punch it, it launches well, then seems to bog around 7000 rpm and 80 kmh, then occasionally spring into life and try to throw me off the back of the sled, then go back to bogging.
I took it up onto the road, with an inch of snow, and it accelerated ok, but at about 7300 rpm and 120kmh, I could detect an intermittent miss.
It felt, and more importantly sounded, like one cylinder was intermittently turning on and off .. for a few seconds each time.
Any thoughts?
Ride and stay safe out there
 
That I didn't do .. would that cause an intermittent miss tho? .. I will go check them .. do you know the impedance value I am looking for? Thank you
 
UPDATE: When I first checked the coils and plug wires, all three checked serviceable.
When I went to check the caps, as per Maim's suggestion, the center plug wire now tested intermittent. Showed good resistance on one try, then open the next.
Thoughts on this??
Thanks
 
Your saying the wire has intermittent continuity,then I'd say the wire on that coil has a break somewhere along the length of it.These wires are epoxied into the coil itself and while not an easy job that epoxy can be dug out and the wire swapped.
 
Thank you .. went and bought three new caps, and all test good now.
Still have the same issue .. intermittent bogging .. when it bogs, I stop the machine, and pull the plug wires one at a time, and all are working.
I am stumped .. am thinking that the cap may have been a red herring.
Am looking at power valves now, as the bogging only happens when under power .. its the on and off that s stumping me.
Am searching for how to test the power valve motor on a non-er viper.
Have them out, they seem to slide quite easily and are relatively uncarbonized, but will get them spiffy before I put them back in.
Still open to suggestions.
 
From a standstill, at idle, then to full throttle, does the motor pull to approx. 85-8600 RPM and then drop down to 7000? Does the motor have this intermittent bogging regardless of throttle position / load?
 
northern srx said:
From a standstill, at idle, then to full throttle, does the motor pull to approx. 85-8600 RPM and then drop down to 7000? Does the motor have this intermittent bogging regardless of throttle position / load?
Click to expand...

So I cleaned up the valves, and reinstalled them.
Just for S&G, I adjusted them as per the instructions on another thread, although they required no adjustment at the end of the day.
Took her for a boot, and pretty much the same symptoms.
So to completely eliminate them from the equation, I disconnected them electrically, and wound them to the full open position with a pair of pliers.
Took her for another boot, and same intermittent bogging.
To answer your question, yes, it only bogs when it gets into the mid and high power settings.
At 1/4 throttle, it hums along happy as a clam.
When it starts picking up speed, it suddenly starts bogging, intermittently.
If I hammer it from a standstill, it pulls great to about 7500 rpm, then immediately starts the bog dance again.
Thinking it might be clutching next??
 
Here is what I have done so far

New plugs and gas
New plug caps
Cleaned and adjusted power valves
Ran machine with power valves set in open position
Replaced both bushings in primary clutch
Resurfaced weights in primary clutch
Wound secondary spring to 90

Don't think its carburation because when it bogs, when I pull the enrichener, there is no change.

Open to any and all ideas
 
fourbarrel mentioned a possible open in the primary (little) wire. I suggest testing the primary circuit of the coils (disconnected from the sled electrically) while wiggling the wire around. This is the small primary wire going to the coil of course not the big wire going to the plug. Viper coils should read 0.36 - 0.48 ohms at 68 F.

The Viper system fires each coil independently unlike earlier model ignitions. Thus each coil is wired independently.

If you can't find the issue with the coils, I would start testing the stator.

I know you are convinced it is electrical, but it almost sounds like a clutching issue. Watching your rpm's before, during and after the bog can give you an idea on this.

If you still can't find the root cause, I would just go through everything. Sometimes multiple little issues create funny almost un-diagnosable results. I have had success dropping what I think I know about the issue and coming at it from a different angle.
 
For the electrical side of things... take sled out (where it's safe) cruise along in the rpm range where all is well, hit kill switch, coast to a stop, remove and inspect plugs. Repeat process (at increased throttle opening while sled is bogging) to see if you can identify an individual cylinder miss-fire or all 3. Possible wire harness rub through. Remove harness, inspect and re-tape. After that, as above ^^^, start looking at clutching. When you were working on the primary did it move freely from fully open to closed?
 
Maim said:
how old is primary spring? they get weak over time.

when was fuel filter last done?
Click to expand...

The spring is original .. 9500 kms .. will look into getting a new one.

Filter has never been done .. but as above, dont think it is a fuel issue, as when it bogs, and I hit the enrichener, there is no change.

Thank you
 
northern srx said:
For the electrical side of things... take sled out (where it's safe) cruise along in the rpm range where all is well, hit kill switch, coast to a stop, remove and inspect plugs. Repeat process (at increased throttle opening while sled is bogging) to see if you can identify an individual cylinder miss-fire or all 3. Possible wire harness rub through. Remove harness, inspect and re-tape. After that, as above ^^^, start looking at clutching. When you were working on the primary did it move freely from fully open to closed?
Click to expand...

I have done exactly that .. all the plugs look fine and we could not identify which or if one of the cylinders was the culprit.
Will definitely be taking the harness out this summer if I dont get this figured out.
Gonna look at the primary windings, but am leaning toward clutching . .they are stock with some new parts, but will give them a good cleaning and see if I can find an issue.
Thank you
 
Ding said:
fourbarrel mentioned a possible open in the primary (little) wire. I suggest testing the primary circuit of the coils (disconnected from the sled electrically) while wiggling the wire around. This is the small primary wire going to the coil of course not the big wire going to the plug. Viper coils should read 0.36 - 0.48 ohms at 68 F.

The Viper system fires each coil independently unlike earlier model ignitions. Thus each coil is wired independently.

If you can't find the issue with the coils, I would start testing the stator.

I know you are convinced it is electrical, but it almost sounds like a clutching issue. Watching your rpm's before, during and after the bog can give you an idea on this.

If you still can't find the root cause, I would just go through everything. Sometimes multiple little issues create funny almost un-diagnosable results. I have had success dropping what I think I know about the issue and coming at it from a different angle.
Click to expand...

I will get into the primary windings just to confirm that they aren't the culprit, then its onto the clutching.
I agree with you that it seems to be a shifting issue .. hopefully I can figure it out.
After a good cleaning and inspection, I am thinking of removing the top rivet on the weights to try to get the rpms up, and relax the side load on the primary sheave.
That will be if I cannot find anything else.
Thank you
 
One thing to note on the fuel supply issue is that if the supply is restrained - the bowls empty and sometimes there is nothing for the starter (enrichener) valve to pick up. Sitting still there is usually some fuel picked up by that circuit after running the bowls dry, but moving sometimes it must bounce out of there. Baffled me at first until I tested it a bunch of times. Upshot, if bowls are dry then flipping the Starter lever might not do anything.
 
northern srx said:
From a standstill, at idle, then to full throttle, does the motor pull to approx. 85-8600 RPM and then drop down to 7000? Does the motor have this intermittent bogging regardless of throttle position / load?
Click to expand...

Was reviewing the replies today and see I didnt answer your question directly.
When I launch from idle, it pulls hard but only til about 7000 rpm, then does the bog thing.
Bog now seems more constant than intermittent.
 
Ding said:
One thing to note on the fuel supply issue is that if the supply is restrained - the bowls empty and sometimes there is nothing for the starter (enrichener) valve to pick up. Sitting still there is usually some fuel picked up by that circuit after running the bowls dry, but moving sometimes it must bounce out of there. Baffled me at first until I tested it a bunch of times. Upshot, if bowls are dry then flipping the Starter lever might not do anything.
Click to expand...

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?
 
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