I have a 1992 Vmax with 5k miles on it. It is in excellent condition, but we're having trouble with a small sputter in the number one cylinder at normal running temperature. We installed the cobra jet kit and quad exhaust a few years ago and it has always run great. Within the last month or so, we started noticing a sputter. It runs perfect when the engine is colder, but begins to sputter slightly when it warms up. We have tested all the electronics (plugs, wires, harnesses, battery, etc) and they are fine. We have cleaned and tested the carbs and jets, and they are fine. We have also tested the compression in each cylinder and it seems fine. A Yamaha tech told me it could be a valve pad sticking when it warms up, but I wanted to see if anyone had any other ideas before I spend the money to replace the valve pads. Thanks for the help.

Tripp

You're running rich. Take out the Cobra jet kit, it's not a good kit. Put your stock needles in, springs, and lower you main jets to 147.5 Mikuni.

Mark
#1098

Look more closely at that cylinders spark plug cap/boot. A slight crack will cause you grief.

maleko89 wrote:




Mark knows his shit .. Check all the carb boots. 92 chances are there cracked or they will be with all the on and off .


Chuck

I had that same problem. Once with my '89 and again with my 2001. believe me, you can go around and around with this. I've got a hell of a trouble shooter that's worked on my vmaxs for years and years. Both times the #1 cyclinder came up black (rich) and the others were beautiful brown. The first time in the '89 it ended being a mud wasp nest in the vent for the fuel tank breather. Pull the breather hose off by the fuel filler under the seat and put the air to it. listen for a pop at the lower end of that hose,then you know it was plugged. It took about 50 or so miles to clean the carbon out of that #1 cyclinder and then it ran like new. I don't know why it showed up only in the first cyclinder??? Then last year it did the same thing with my '01. When it was cold it ran good, then it would hesitate. When I checked the plugs all were a perfect brown except #1, it was black (rich). Come to find out, #1 cyc. was the coil wire I tapped into for my MSD shift light. Disconnected the shift light, 50 miles later, #1 cleaned up and it ran like a bear. Those things fixed mine, maybe it'll help you. Remember also, Your tach is tapped off #1 cyc. also. Good luck Ron