Viper Bog

OldIron

OldIron

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Joined
Nov 13, 2010
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377
Age
54
Location
NorCal
Ok,
This bog is getting the better of me. I have rebuilt this viper and it starts and runs great. However if put the throttle to the bar, it acts pretty normal until midrange and I get a bog. I only develop 7900 rpm and she moos like a cow! I've done a bunch of trouble shooting to include the following:

*fresh gas 91 octane
*cleaned carbs
*cleaned power valves
*power valves adjusted properly (a few times)
*power valve installed correctly (bevel on bottom, long side on top)
*swapped CDI with known good sled
*changed out power valve solenoid
(solenoid moves at startup and moves when I idle engine down to adjust them)
*headlight, tail light, gauges, and hand warmers all work normally. No flickering or dimming.

This feels like a power valve issue to me but I'm not sure. I was wondering if the rectifier/regulator or the smoothing condenser could cause this effect of a bog? Also, could either of the two relays above the CDI cause this? I also read a post that mentioned a CDI box switch? Not sure what this is.

Something I noticed was a small square end plug coming up from below the CDI. Does anyone know what this is?

I feel slightly under the gun since I have family coming out to visit in two weeks. I appreciate any help in advance.
 
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I think this is going to turn out to be a TPS issue. I read where bluemonster disconnected his TPS and he could hardly pull 8000 rpm. This is what mine is doing. I was wondering if the TPS signal has any input thru the CDI for power valve solenoid function. I was told it does by a former yamaha mechanic but not 100% positive.

Looks like I'm going to be doing some TPS testing / swapping / adjusting.
 
OldIron said:
I think this is going to turn out to be a TPS issue. I read where bluemonster disconnected his TPS and he could hardly pull 8000 rpm. This is what mine is doing. I was wondering if the TPS signal has any input thru the CDI for power valve solenoid function. I was told it does by a former yamaha mechanic but not 100% positive.

Looks like I'm going to be doing some TPS testing / swapping / adjusting.
Click to expand...

I suppose it could as 2 of the wires from the tps are spliced into the wires that go to the servo motor. electrical can be funny and back feed into other systems, hard to always pin point a definite answer. With everything else you have done this looks to be your last ave of investigation to the problem, sorry cant help more then that have not had that actual symptom happen to one I have worked on before.
 
mrviper,
You've already helped out 100s of times over. This is just one of those buggers.

I'm not sure if I would see it or not but I did run it up to 7500rpm with the track lifted and the PV solonoid did not move. So it's had the bog after each rebuild. I was expecting to see the powervalve start moving around 6500rpm but I wasn't sure if this was a valid test since there was no load on it.

Last night when I took it for a test run I felt there were a few times it hit because once or twice I saw it shoot up to 8200 and 8300. However for the most part it was only making 7900 to 8000.

I didn't have any instrument gauge warnings or flashings. It seems like it's acting like the TPS is not plugged in however it is. And the fact that I can idle it down to 800rpm and I've never had any instrument guage irrigularities while hitting the break with the handwarmers on hi, the high beams on tells me it's not the stator.

I may be wrong but my next check is this TPS. Time will tell.
 
Bob,
It pulls best off the bottom to around 6500 to 6700. Then it seems to bog and only comes up to 8000. Thanks to your post last year I've come to the TPS. So thanks for your postings on that subject. I have an extra tps but I'll run the service manual test first. Then I'm thinking about removing and replacing it with the other one and adjusting it to see what happens. I need to make the adjustment coupler tonight.
 
Make sure you have the carb vent lines in the airbox.

With the TPS:
-mark your current TPS position on the carb rack
-loosen the two attachment/adjuster screws just enough that you can move the TPS with a little effort
-with sled running rotate the TPS clockwise until the Temp light starts to flash then back it up just enough to put the light out
-if TPS position is in a different position then it was...take sled for a ride and see if condition improves

If the condition doesn't improve return TPS to original position.

Typically the TPS postion is rotated almost to the stops clockwise to get the idle voltage to Yamaha specs .

I have found that if the Wide open throttle voltage is too high my SRX will bog above 3/4 throttle.
 
Ok, S.SBob I'll give your process a try. Unfortunately, I have to trailer about an hour to try it out. I may not get a shot at it untill this weekend.

Have you noticed any relationship between the TPS and the powervalve solonoid? A friend of mine who is a past SRX / Viper mechanic says the TPS has input to the power valve solonoid thru the CDI. Not sure but I was just wondering.

And by the way, realistically I think most of my bog is probably 3/4 and up.

Thanks for the info.
 
I don't know for sure if the TPS has an effect on the power valve solenoid but it definately effects performance if it is defective or way out of adjustment.
I also discovered when I put a set of Polaris TM38s with a TPS on my SRX that because of the extra throttle shaft travel the TPS was sending a higher voltage to the CDI then the stock carbs and TPS were at full throttle. This resulted in a Bog above 3/4 throttle not unlike overly rich jetting would give you. I found that if I installed a dummy TPS fixed at @ 3.1 volts the bog was gone...I am still working on a solution to this delemma so I can have a working TPS.
On my 2002 SRX the power valves don't start to open until @ 7500RPM with the track off the ground...
 
I went out and did the TPS test. The temp was 20 deg F so I'm not sure how this correlates to what would happen on a 68 deg F day. I would say that resistance would increase with temp so it would be slightly higher.

R1 = 5.15 kohms / should be 4 to 6 ohms so this was in.
R2 = 0.88 kohms to 3.2 kohms / should be 0 to 4 kohms so this is in.

I'm hoping to make up the adjustment harness tonight. And looking at the TPS position it looked full counter-clockwise. But I did not loosen it up yet so I really have no idea where it's set. Hopefully tomorrow I'll have some more info.

btw carb vent line is plugged into the air box

Thanks all for the help. I really appreciate it.
 
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Last night I built up a voltage regulator box. And today I got to do a little testing on my sleds TPS. I measured my base voltage or "voltage A" and it was 4.94v so I came up with a "voltage B" of .672 Then I checked it at idle and it was .762v and at wot it was 2.982v. Idle is off but it doesn't seem to be a lot. But then again I haven't started to adjust it yet either. I don't really have a feel for how far off this is.

Now that I have a tester I'm thinking about marking the current TPS position then just adjusting it to .672 at idle and giving it a try this weekend. I suppose it may not be .672 next time but I would have to run the numbers again and set them based off of what I get.

I'm wondering what other checks I could pull off when I go up to the mountain. I'll most likely try swapping primary clutch with a good one if it's not the TPS sensor causing the problem. Another thought is swapping voltage regulators but I really think it's fine. No electrical issues at all. I also wonder if the smoothing condenser is worth swapping. Other that that I can replace the stator but then again... I've had no electrical problems / indicators.

Hope it's the TPS sensor. :o|
 
Tonight I marked the TPS's current position then tried to adjust the TPS until getting the warning light (like SideshowBob said) with full counter- clockwise and full clockwise on the TPS. It wouldn't come on. I was pretty patient also. I let it run in those positions for over 30s or so each way. So I adjusted the TPS with the test coupler that I built two nights ago and I set it at .672v at idle. I noticed that when I went to full throttle I got 2.886v. I thought I read somewhere that voltage should be around 4.0 at full throttle. Can anyone comment on this? I'll have to re-read some posts on that one. However, what I did notice is that the idle was a lot smoother. I also noticed that this idle setting was about 3 mm from where it was set prior to my adjustment tonight. I'm not sure if this is a big change or not but I'm going to try it on the hill Saturday. I didn't touch the idle because I knew it was last adjusted spot on for the hill.

Friday I'll be bringing up my spare carb rack so I can rob the TPS if I need to. I also plan on swapping clutches if this TPS adjustment doesn't help out. I'm pretty much running out of ideas but hopefully the TPS adjustment will do the trick.

Oh and lastly, when I did fire it up after adjustment I did see the warning light along with the check engine symbology since I forgot to plug the TPS back in. I'm sure that's been done before and will be done many times again.

Not sure if I'm looking forward to Saturday or not. I'll report the results good or bad.

:itchy:
 
Well, unfortunately it was not the TPS. However I do think I may have found the problem. I was thinking ignition / electrical problems. So after being disappointed with my short ride yesterday I decided Sunday would be Electric Sunday. Looking at my plugs (one of the attached pictures) made me wonder if I had a compression problem. So I did compression checks, seemed ok. Then I pulled carbs and coils. I started doing all the checks in the book to the coils. The # 1 cylinder has always been the problem. So since I had a brand new coil I decided to throw that one on the #1 position. They had all checked good but I figured I should do it anyways. I will say the ignition lead caps on #1 and #3 had a slightly higher resistance then the book #s. 5.5 ohms rather then 5.0. So I switched cap #1 and #2 in hopes that if the problem followed the cap I would know what's going on. I also decided to check the stator coil and pickup. They were spot on within limits.

So I finally got to the carbs. I opened #1 carb up and the attachment is what I saw. It was almost like it was Christmas in Springtime! The crazy thing is I'm afraid to try the machine thinking that the carb problem may not be it!!! lol I'm obviously now conditioned to be disappointed so maybe it's a good thing I don't earn my living by fixing viper motors. I'd be pretty lean!

I can only guess that when I went thru the carbs this year that I put that main in finger tight and forgot to tighten her down.

Hopefully, I'll be able to get up to the hill some time this week to try her out. I'm keeping my fingers crossed.
 

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I noticed that when I went to full throttle I got 2.886v. I thought I read somewhere that voltage should be around 4.0 at full throttle.

:itchy:[/QUOTE]

Somewhere around 3.0 volts is normal full throttle TPS voltage on the stock 33s although between the 3 TPS I have it does vary slightly. I have found full throttle higher voltage up closer to 4 volts on my SRX gives it a bog at full throttle not unlike overly rich jetting.

Sounds/looks like you have found your problem in your carbs...great!
 
Glad to hear you found your problem. I know for sure that that is not my problem had he carbs off again and everything is in place ???? I took it to my buddy to check it over. I'll post if he finds anything. Thanks for the info greatly appreciate it.
 
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Thanks for the followup on that TPS question Sideshow. That makes sense with what I had on my TPS adjustments then.

Yamaman, keep on plugging on your problem. It will be something small hopefully at the end of the day. By the way, if you have the carbs off I would pull the coils out and test them along with the caps. I've heard of people having a bad spark plug cap which was causing a plug to cold fire. Also I would check your stator and pickup coil. All these electrical checks amount to disconnecting the electrical connections and testing with an ohm meter. Really pretty simple checks. And the service manual does a great job of walking you thru the checks. Or if you needed some help I could walk you thru it since I've just done these myself.

Hope you find it.
 
Thanks for all the help on this bog issue I had on my viper. It turned out to be that main jet in the #1 carb. I would have gone right to the carb but I had gone thru it in the beginning of the season. Evidently, I may have gotten distracted after putting the main back in after cleaning and inspection and only hand tightened it. It was rattling around in the bowl.

I will say that I learned a lot from this episode and I know my sled better then I did before. All the machines were up and ran 100%. The family had a great time. I appreciate the help making that happen. What a great site.
 
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