First Start of the Year - 1 Cylinder firing

[tomassend]

I have a 2003 Yamaha Mountain Viper. Last season I fogged down the motor, stabilized the fuel and shut her down in February. It ran perfect last year, jetted for 3-5000 ft at 0-20 degrees.

Just walked out to the sled tonight, popped a few gallons in it and turned it over. It started and lagged a little, but never got going. The only cylinder that is working seems to be the mag side.

I pulled the plugs, mag side was chocolate milk brown in color, the rest were gas logged. No warning light comes on either, it just bogs along. I ran it at idle for a while and it seems like one of the cylinders is put put put putting (like it wants to go) but never does.

Steps Taken:
- Disabled the TORS
- Disconnected headlight relay on clutch side
- Put in new plugs
- Gave some throttle to work the gas out


Anyone have any ideas? I am super stumped on this one.

Thanks in advance,

DT

 

[TRIPLESWILLNEVERDIE!]

1. fresh plugs
2.switch plug wires between the cyl thats firing and the cly thats dead. Does the dead cylinder start firing? That would be a bad coil or even a bad cap. Sometimes those caps can get some corrosion going on and dont make good contact with the plug. They just screw onto the plug wire so if they look suspect unscrew them and replace. Like $4 a peice for new NGK caps a your local autoparts store.

3. Although this doesnt sound like your problem but should be checked anyway. Take your carbs off and remove and thouroughly clean out the pilot jets.They have a very small orifice and will clog easily. If they are plugged there wont be enough fuel going into the cylinder to make it fire at idle. I have seen this time and time again. Sometimes the plugs even look a little wet and you'd swear it getting enough fuel to fire but thats not the case.

Also make sure your choke circuit plungers are going all the way back to fully seated when you turn the choke off.

 

[MNBlizzard]

Clean your carbs. As stated above, I bet your pilot jets are plugged. I would also clean the powervalves too.

 

[zoombyu]

I'd say 9 out of 10 times it would be the carbs need a clean, especially if it is the first time you started for the season. If you pull off the carbs, be sure to check your reeds when there too. They can wear at corners and also get cracks. Don't think reeds would give your symptoms, but always good to check when there. My Son pulled and cleaned carbs 4 times one year looking for a mid range bog only to find it was a reed problem. As was posted above, you also need to check your power valves for cleaning periodically. Don't think power valves would be the problem at idle but they do need maintenance. We try to make it a habit of always cleaning the carbs at the beginning of the season. If your sled ran good last year, pay attention to the pilot screw settings when you take it apart so you can set the same way after your clean. It can be a pain, but Yama 2-strokes like clean carbs. Most times we have a problem with them running, it is a carb issue. Let us know what you find. Good luck.