Piped Viper question ?

w8tn4snow

w8tn4snow

New member
Joined
Oct 20, 2006
Messages
156
Age
50
Location
upstate ny
Ive just got my Viper running yesterday ( just piped and jetted ) , I took a few rips around the yard and notice a weird issue . When I let off the gas from a hard burp , the engine will kinda do a (BING BING BING ) thing until it revs down on its own , and while its doing this i cant get back on the gas until the RPMs come back down or it will bog ?
I know this is explaing like im like a turd but thats exactly what it does !
Im stumped , I can probably ride through this but , on a trail sometimes you just need to get onto it , off then back on , and this could be a problem .
Any ideas ?
 

sounds lean on the needles to me, have you done any plug/piston wash checks at various throttle openings?
 
I havent had a real good chance to open it up yet to WOT . i have pulled a few plugs after revving to about 8000 RPM on a stand . The plugs were a dark chocolate brown . but with no real load on it how accurate can this be ?
 
Tors

It sounds like the (tors), throttle override. Check your throttle cable adjustment.
 
Yep, I agree the TORS. Same thing happened to me after jetting down for spring riding. The throttle cable alignment had moved (lock nut came loose) at the carb rack. Good to hear your plugs are brown.

Congrats on the triple exhaust! Keep us posted on what you find.
 
Yep TORS.......been there before. But don't rule out Mr. Viper 700's idea either. That one could be costly if true. Just curious, are you running EGT's? I feel it's a good idea on the Viper. They are more touchy than a non valved 700SX motor. Who's pipes are you running?
 
Well im pretty sure its not TORS , Ive had issues with that before on another Yammi and this is different . i took it for a rip down the road to a freinds and it screamed ! 85 MPH at half throttle just burping it !.
It sat for about an hour outside at about 15 degree temp . I started up to leave and had to half choke it , it fired up and seemed kinda sputtery , on the way home i could tell it was missing at least 1 cylinder . When i got home I pulled the plugs and the mag and center cylinder plugs were clean as a whistle white around the base of the electrode . I flipped !
praying I didnt melt it down , I shined a light in the plug holes and the pistons were carbon black no holes, PHEW ! New plugs and she fired up like new ,Im pretty sure i just didnt let it warm long enough . Im pretty nervous since Ive never piped a sled before and these things are notorious for meltdown . They are Bender pipes and Ive got theyre recommended jetting in it . Also had them do the headmod . and opticool gasket . I did have 1 plit jet slightly bent when I got it , but straightened it best i could before using it . anyway still got the (BING BING ) !
 
she's LEAN!!!!!!!!, fix it now or youll be replacing #$%&* pistons!!!!!!!!!!!!!!!!
 
trottle cutting out

I had a very similar problem last year and trouble shot everything.Couldn't find the problem.It would come and go and soon as you let machine idle down it would be ok.I checked the hole wiring harness and tors couldn't find anything.It sounds like the same problem.Any way I checked the wires coming of the stator coil and found a bad wire.It wasn't producing any volts.I think there are 3 wires each carrying 4 volts.Any way we took stator off and discovered a wire broken @ the stator.This would cause a faulty connection whenever it got bumbed or snow went in side of hood.soldered it back and all was ok.when wire was shorting out(no connection)The sled was running on 7 or 8 volts which would screw everything up.Lose of power was the obvious.Just check the wires coming out the stator i think they all should have 4 volts.Good Luck
 
So if its lean then what should i do ?
Im running Benders recommended jetting , which from what ive heard is notoriously fat .
Do i need to change clip position ?
Even bigger jets ?
If i didnt get that pliot jet that was bent straight enough will it cause the plugs to foul and at the same time look to have been running lean ?

Is it possible to get a good plug reading with the sled on a stand ?
 
did you change the needles or just the pilots and mains? sounds like you need more fuel from the needles,
No you cant jet it on the stand, you take the sled out and a plug wrench with you and do 1/4-1/2 throttle chops and then pull the plugs and shine a light down inside and look at your piston wash.
 
I havent touched the needles , just the pilots and mains . I cleaned the carbs when I had them apart , so I know that isnt an issue . Will a lean condition really foul a plug ?
 
lean foul a plug, no, but your white spark plugs tell the story, if they are white they are lean. so its my guess your rich on the low end and lean in the middle section

whats the jetting reccomended from bender?
 
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They sent me 162.5 mains and .55 pilots . The center and mag plugs were white like they were new and pto plug was a nice dark brown ? the porcellain under the electrode was clean white not an ash white .
 
I have the same set up. I turned the fuel screws out 2 turns. 55 pilots and 165 mains and it was leen on the top end. I installed 170 mains and left the 55 pilots. The idle hangs a bit at 2 turn on the fuel screws but no big deal. The sled runs perfect and no DCS light. If you had a bent pilot jet and tried to straiten it, it may not be pefect. Try another pilot jet. I'm running in -10 to -15f temps at sea level and the 55 pilots work good as do the 170 mains. Be sure to check the numbers on the jets. Bender sent me 2 different sizes in the bag. Good thing i had extras. Also make sure your carb boots are installed right with no leaks. If the boots are not perfectly over carbs when you tighten the clamps they can slip off.
 
Ill swap out the bent pilot then . i also cut the airbox like they recommended in their install sheets along with gutting the baffles . Did you hapen to do this ?
 
I have mine set up with 170mj and 55pj 1 7/8 screw, stock needles. The bender spec for my area was 162.5mj and 52.5pj for known good fuel. For unknown quality fuel they recommended 165mj and 55pj. I am at sea level to 1500ft. I am trying to adjust for 0to10*f, any colder than that and I probably won't ride. I have a Peak Performance water rail head with 22cc chambers. I have stock gaskets. My top end is fresh.

I haven't been able to do any more testing on mine. Partially because of time, partially trail conditions. I want a nice flat spot to hold the thing WOT for half a mile...

My last testing I was rich at WOT and rich at idle. I was pretty good across mid range. I think I need to drop down my mains, drop down my screws and retest. I expect that leaning out the top and bottom will result in a need to richen the mid range. I plan to tune toward the rich side, not taking chances. I haven't even seen the DCS light flicker, ever, not even sure if it works... I am going to put the 167.5s in and turn my screws in(?). I will look it up again before I do it just to make sure I go the right way.

My conversation with bender about jetting didn't go as well as I thought it could. The guy I talked to thought the 22cc chambers on my peak head were way too small. Told me I would need at least a 170 main to run them. Well 22cc is stock on 2 of the 3 cylinders and I think a lot of people run the benders with that head (stock) and 165s or 162.5s.
 
Well my initial start up while i was getting the air out of the system . I revved it up to about 8500 on a stand and killed it with the switch . checked the plugs and they were a perfect dark brown . Ive just never seen a plug foul and clean itself before . I have a hard time telling myself it was so lean that it fouled a plug . i am almost sure i just didnt let it warm enough before taking off . . I am nervous now though ill tell ya ! I think im gonna take it to a feild somewhere and do some testing at different throttle levels and check plugs under more controlled conditions . . Oh did you happen to do the airbox mod jeep therapy ?. Im wondeering if thats causing me to run a little lean .
 
you cant jet a sled up on a jackstand because there is no load from the track, because its up in the air just spinning freely, so youll get false information. The way to do it is just like your talking about doing it. Take it to a field and do some checks, one at low speed, does it bog or take off cleanly?, are the plugs dripping wet if it idles?(checks the pilots), one at mid throttle(checks your needles) and then move up to wide open(mains), this is a very easy process to do and sure beats replacing pistons.
 
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