4 years and still can't figure it out

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yammitrip1

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Joined
Oct 19, 2013
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215
Age
32
Location
rome
okay guys, thought it was the aaen pipes but its not. i can not for the life of me figure out what is going on with my sx viper 700. so i am helping you can help me out.

Four years ago, i started having issues with a mid range cut on one cylinder. thought it was the carbs so i cleaned them, and just clutched around the issue and rode the rest of the season as it was not that bad. next year i was having issues and this was when i installed my first set of pipes. they were benders pipes and they made the problem horrible! it was like i couldn't get the pipes to "lite". So last year i bought the AAEN pipes because i thought the horrible horrible mileage was from the bender pipes which was around 2mpg. 60 miles to a tank, then at the end of last year i couldn't never get the sled tuned right, it would still bog, almost impossible to ride the sled in the deep snow, thought the cold snow was hitting the pipes cooling them off and again i couldn't get the pipes to lite again. REMEMBER though, all my issues are mid range, wot the sled would pull and pull and pull but again as soon as i backed of the throttle and chopped it the sled would cut off cylinder again and i would have to fight the throttle to get it back up on the pipe again. throttle on and off , on and off , on and off until it got past that little blip and get on the pipe. Well again i thought it was just a pipe issue again, so i spent the money on some SLP pipes, the best of all pipes that have been proven to not give any "grief" this year and i got everything absolutely perfect!!!!! Jetting is pto to mag 160,162.5 ,162.5 and needles 3.5 across with pilots 47.5 across at 1-3/4 turn.

Things i have changed to date since this problem has occurred, i have changed the stator because that died out on me at the end of last year (lights dimmed), changed the coil on the pto cylinder with no change, changed and run br9es plugs, rebuilt the top end not because of low compression but because the engine has 6000 miles on it and i wanted to freshen it up, new gaskets, run opticool head gasket. I have about had it with this thing and i am very mechanically inclined and tried everything i could think of.

i have had 3 different sets of carbs on it, so i think it has nothing to do with the tors, and again this problem happens with single pipe or triple pipes. doesn't matter. i am pretty sure i have narrowed the issue down to electrical because of the fact that the pro cylinder is wet when this issues happens.

Best way i can explain the issue for others to understand, (i know i know don't do this but its just a example). Fire up your cold sled, go in the field and try to go wot, it pulls peak rpm and then you chop the throttle and go wot again and it kind of stumbles/cuts out/sounds like its not runnning right, blip throttle a few time and its then coming alive.

let me know what you think, i am seriously going to check this week if the crank is out of phase and also try a different cdi box as well.
 

literally this morning i thought of the same darn thing, i changed out the pto coil which included a new spark plug cap and no difference after a rip in the field.
 
Hey Yamitrip, I have struggled with a similar issue with my Vmax4 drag sled. Sometimes the simplest things get overlooked but I can appreciate your frustration. One of my issues was the spark plug gap. I was running the plugs with the factory gap settting of .030-.035". It always seemed very rich in the mid range where it would spit and sputter terribly. I re-jetted many times, without considerable change.

A Yamaha engine expert suggested to me that the plug gap was too wide. He recommended tightening the gap to .018" My engine is a race engine, running 10,200RPM. I would suggest to try tightening the plug gap to .020-.025". There is no loss if it doesn't work.

Hope this helps. Good luck.
 
I'll try the spark plug gab, along with then bypassing the tors. The secondary set up is a pioneer custom 48-35 with a red spring wrapped to 80, I have 22-39 gearing as I use the viper as a back country sled and some times set it up for 500-1000ft drag races. I'll try this week and report back.

I can tell you this much so far with test, even idling I can hear PTO pipe kind of pop at certain times like it's getting a bit of a burn but a late or a faint one, also at heat up cycle the PTO pipe is cooler to the touch from the others as well
 
100 % sure these are viper pipes and not red head 700 sx. gap your plugs at .020. you ever give these pipes are real good check for a obstruction. i bought a set of power inc pipes for my srx out that way that were packed solid with a mouse nest. i also like suggested check your wiring harness. 3:16x (yammie tony)
 
OK, I re-read your post a few times now. To be clear, when the motor stumbles, is it always the PTO cylinder that loads up? When you say you "chop" the throttle, does that mean you closed the throttle completely? I know you said you have tried a few different carb racks but it sounds like the carb/throttle switch fails when you "chop" the throttle and puts the motor into "limp" mode. Try a continuity test on those two switches? Just trying to help..weird one for sure!
 
I would be suspect to the switch in the throttle housing on handlebars, does it activate if you take your hand and pinch the center pin on throttle lever while depressing the gas?
 
Just a shot in the dark my buddy bought an 02 viper last year and we put SLP pipes on it and it ran terrible!! we took them carbs off probably 10 times making adjustments and changing jets followed SLP's instructions to a T and probably about $30 in spark plugs never went right and I was the one who talked him into buying these we tried bypassing with the TOR switch and it turned out we took them carbs off every time and never took the reeds out turned out it had broken reeds! and you have to pull the carb boots off to inspect them properly!! have you ever checked yours? we overlooked them every time hope this helps!
 
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Reeds have been replaced, I can't explain this to you as I just tried swapping the cdi for a different along with putting three new plugs in it gap at .020. still is doing it. I am wondering if it indeed is not a electrical issue. Fuel maybe, I was ripping through the field and let off, go to wak throttle and stumbles a bit. Flip the choke quick while holding it wide and it kinda came back and eventually cleaned out. I did do a test when it was cutting out, I held the throttle and it would pull about 7000-7500 rpm. Wot it's at 9 k
 
Other then this intermittent issue, SLP pipes make a significant power difference of aaen pipes. Holy heck they are impressive
 
I am getting close guys!!!! This is what I have done today, I ran it again and I figured out it is the mag cylinder, not pto. Now with my testing after getting sled up to temp and pipes hot it runs good for a total of 5 mins or so them starts giving me problems again. As soon as it cuts out I can't get it to go again now like "clear it out". So I stop after a wot run and mag dies, pull plugs and compare. Mag is soaked, center and pto are looking beautiful. But I did this three or four times!!! What I noticed is that the sled consistently runs good for 3-5 mins after I pull plugs and mess around almost like a heat soak is making the problem. I swapped spark plug caps from mag To pto to see if it would follow but it didn't.

Where would you guys go next? I already changed the stator last year with a known good used one from a reputable seller on here and I do have another one as well. Should I try and change it along with maybe the mag coil as well???? God I can't wait till this crap is over with! I ride Yamaha because they are supposed to be reliable!!!!
 
Hi Yammitrip1 sometimes it's good to go to the basics. If you're sure it's the mag cylinder, compression is good, you have fuel and air, crank is properly phased, spark timing is okay, the only thing that fits is electrical. I've been lead to believe cdi's either work or they don't, so I doubt it's that. You mentioned you swapped coils and plug caps so unlikely it's that. One other thing that fits is a possible lose connection or a patially broken wire to the primary of the mag cylinder coil. According to the wiring diagram each coil has 2 wires, one to the cdi and the other to engine earth. I would try wiggling the wires from cdi to coil and from coil to engine earth, while the engine is running. It's a long shot but worth trying. You might have to undo some tie wraps.

Sent from my SGH-I337M using Tapatalk
 
Okay, let's talk reeds a quick bit here , when I said I replaced the reeds meaning I replace the pedals, now when I pulled my air box today to get to the coils. I seen alot of fluid in the air box, so I pulled the mag reed. Are the reeds suppose to be totally resting against the cage? Is it possible I put the reed pedals up side down? There is probably a 1/16 " gap on both pedals at the tip. Does this sound normal to anyone?
 
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