HELP! 650 TWIN CARB low rpm

[123indyrt]

Ok, I'm lost. I did the carbs, needles n seats, set pop off at to 30 each.. no change. It appears that the rear cylinder is running rich n bogging it down @ wot. Perfect start up and part throttle. As soon as I get over 4500, it starts acting up. Wot, just over 5k. I'm so lost.. I'd appreciate and help.

 

[Cablebandit]

make sure the fuel/water separators are screwed on properly and not letting in air...i chased that prob for 3 days

 

[123indyrt]

I took it off and we tightened it again. A few times ago. Again, it's only foweling the number 2 cylinder. I can swap the plugs to each other cylinder and it will do again. The weird part is it runs perfectly below 4500

 

[Dr Honda]

Were the parts you put in the carb OEM/Mikuni... or were they aftermarket?

If they were aftermarket... that's probably where the issue is.

With that said... what EXACTLY is the problem? A rich condition will feel like a studded. If it's just a loss of power... then that's generally a lean condition.

 

[123indyrt]

Looking at pictures of spark plug readings on the internet it's wet fouled in one cylinder the other is perfect. It's the rear cylinder. I can put new plugs in it and as soon as I go wide open throttle, it goes to almost 7 k then drops back down to about 5 OEM Parts. High speed screw is at zero

 

[Cablebandit]

hmmmm so you determined that the compression is relatively the same between those cylinders I assume. Did you try the easy old "cut 1/4" off the spark plug wire and screw the boot back on"?

 

[123indyrt]

No. Oddly enough, when this first started, i believe I could hear it misfiring

 

[123indyrt]

And yes on compression 145 both

 

[123indyrt]

Runs great up to 1/2 throttle. Had it out yesterday

 

[ORION '95 Speedster]

Hold it wide open for 5 minutes, while cruising across a lake. Shut her down and quickly access the engines. Use a thermal heat gun to check the temps on the heads near the spark plugs. You should do this on a regular basis, even when everything is acting normally. It will tell you if any of the 4 cylinders is running abnormally cool, or abnormally hot. Engine are all about temperature. 70% of the energy created by and engine is wasted as heat. So measuring the heat to the nearest degree can tell you how the engine is performing more easily and more accurately than MPH, or RPM.

Cylinder temp:
Under 100 degrees: Not firing
Over 100 degrees: Firing

One cylinder with a much higher temp than the other cylinders indicates that the cylinder is running lean and is going to fail if the lean condition is not remedied.
One cylinder over 100 degrees, but less than the other cylinders indicates that the cylinder is "missing" or possibly very rich.