What's wrong with my Viper?

Heimdall

Heimdall

New member
Joined
Oct 1, 2004
Messages
97
Location
Sweden
My Viper rides like crap. 3 days ago, i was out riding with a friend. We had ride for about 30km when we stopped for a little break. The sled had worked good all day. But when we were heading home, it started to run strange. From 4000 to about 6/7000rpm it felt almost like you were riding with the choke. Maybe it's called bogging? Stopped and checked my plugs. They were all black. Fired it up again, and it started as easy as always and had a good idle. The sparks were pretty good on all three. But i didn't dare to ride it home so we had to get a trailer for it.
Went out the next day to see if i could find out what had happened. It started easy again, and idled good. But the same problem occured when i took it for a testride. I sat down and search this forum for several hours, and it seemed like it could have been the T.O.R.S. But it worked fine when i tested it. I also unplugged it but it still ran like crap. I then emptied my oiltank. I had 2 different brands of oil in it, thought maybe it could have something to do with that. But no, still doesn't run good. After i emptied the oiltank, i also got a self-diagnosis warning flash. And when i checked the tech pages on this site, it seems like it is the TPS messing around. I made sure that it was plugged in correctly. My tachometer now walks from ~1000-2500 rpm when it idles. Plugs are still black and the sparks are now weak. The plugs were changed for about 600km ago. It runs very bad. Anyone have any idea what's wrong before i get a new set of plugs? Have easily changed over 10 plugs on this machine, and i have only ride it for about 1500km.
 
Your choke might be sticking on , i had my viper stick on , were the slider goe's though the carb's my must have been froze.
 
I got your answer...i think haha

Any modifications to your sled? If so it might be a jetting problem, for example I bought pipes and a clutch kit and a silencer form Hartman Inc in Idaho. He also sent me jets to go with the pipes, but they were no good because they were for an air that is more dry and where I live the air is more wet, since we live on the edge of the sea. I had to test my sled for a day to see if the stock jets would be leaning gas or giving too much gas to the plugs, but in teh end it turned out ok. I have been loosing alot of plugs lately so I'm going to get it checked out. If you dont have any pipes on your sled well maybe your jets are sending too much gas to the plugs.
 
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Nope, the sled is stock other than another helix and spring in the secondary. When i checked the plugs last weekend they had perfect brown color. I talked to a mechanic today, and hopefully we are going to measure the volts on the TPS tomorrow. Anyone know how the sled reacts when the TPS doesn't work?
 
Almost sounds like a broken reed valve. I assume your going to pull the carbs off and check them out, have them take a look at the reed valves as well.
 
check your vent line to the airbox and make sure it is plugged in. if that is ok check your vent lines and make sure they are all connected
 
Anytime your Viper starts acting weird check the wiring harness where it passes under the engine, seems everybody at some point is having issues with chafed wiring contacting ground or shorting to another wire. Good luck.
 
Have you checked your compression? My sled when I blew a piston felt like it had a fouled plug at about 6-7000 rpm, checked comp. and had 10 psi on one cylinder... it ran fine after you passed the 7000 rpm range.

Then again... maybe i'm reading your post wrong and it sounds like something completely different... check compression anyway.
 
If ya need the voltage for the TPS (at idle) let me know, I have a copy of it in my shop. I broke the TPS and called Yamaha Tech for the voltage.
 
nodoo_s said:
check your vent line to the airbox and make sure it is plugged in. if that is ok check your vent lines and make sure they are all connected
Click to expand...


I second this, they don't run without the vent lines hooked up right.
 
kinger: I will pull the carbs if it's nothing wrong with the TPS. But i think that if it's a reed valve, it should work fine on the other cylinders.

nodoo_s: I think they were plugged in right. But it's never wrong to check it again!

yamahay: That sounds interesting. Will definitly take a look at it! Thanks.

change_up: No i have not done any compression test. Last time i blew a piston i could really feel that it was only working on 2 cylinders.

John_W: You've got PM!
 
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