Topic: Question for fellow Colorado riders (or any who can help)

[Obsidus]

I'll be talking to Uriah and Keith at 30 Black about this at some point, but I wanted to as ya'll as well.

I'm running Keihin carbs on my 78K. What are you air screws turned to?

Main jet and pilot jet sizes?


I noticed today, after not starting my baby for a week, that 1 and 2 were not firing correctly on idle. I may have turned the idle down too low, but I have to ask. When I pull the throttle to 1/8th, I can feel 1 and 2 get warm from the pipes. After that, 1 warms right up but 2 doesn't seem to fire correctly until throttle is applied. And a quick whip cuts the motor out for a split second at 1/4 throttle, then comes back up. When I crack the whip it kills the motor immediately, while a slow pull to full throttle does just fine. Clogged pilot jet? Low idle setting? Flooded bowls??

My timing is perfectly fine as far as I can tell.

[bollingball]

Does your accelerator pump work? Have you set the gap on the pump shaft? Is your fast idle cam set up? Is your bike stock? Or maybe I should ask if you have done any thing to the carbs and if so what? Is this a 750?

Ken

[Obsidus]

Yes, it is a 750. I'm not altogether sure that these carbs even have an accelerator pump.

Fast idle cam?

[754]

 Look under the carbs by the bowls..if bowls are held on by screws they are 77 or 78 carbs, and will have the accell pump(one bowl will be different). If your carbs have clips holding bowls on they are 76 or earlier.

[Obsidus]

Look under the carbs by the bowls..if bowls are held on by screws they are 77 or 78 carbs, and will have the accell pump(one bowl will be different). If your carbs have clips holding bowls on they are 76 or earlier.

Aaahhhh. Definitely clips. So no, I do not have an accel pump. But my motor is a 78'.

[Jerry Rxman Griffin aka MuthaF'er]

78 750K - That engine is basically my 75 750F engine but with 5^o different cam timing. So with that in mind my carbs came factory with 40 slows, 105 mains, and the needles in the middle clip position. If we want to get more specific we can compare the carb model numbers. I'm thinkin that the carbs differ only in  the needle/needle jets. Now, I was at 300+ elevation (probably close to a Japan elevation and not Colorado) when I bought it new and it ran like a scalded ass monkey. It also had the factory airbox. Whatever the screws are turned to set them all the same for comparison for beginners.

Let's make sure it's not electrical first! before you go jacking around with more complicated things like carbs. Thats a very distinct possibility and the easiest thing to verify. Being that its 1 & 2 and not 1 & 4 or 2 & 3 I think we can rule out points, condensers, and coils. Sooo, switch plug wires. Just try switching one cylinder at a time. Say 4 onto 1 since they both fire at the same time and see what happens. Then try this experiment with 2 & 3. This can point to problems with the plug wire and/or the cap. If I was to assume you are running stock style plug caps I'd then want you to check the caps for deterioration in the internal resistance. If the caps have deteriorated then you won't get as much sparks across the cap and hence the plug. Using an ohm meter check the resistance. Caps do go south and can be your culprit. Compare the readings. Most caps are 5000 or 10000 ohms depending on what you have on there. If the resistance/ohm reading is a fair amount more then you have an issue. You can also try to trim the plug wires back at the cap and reinstall to correct a bad connection. This will check your electricals. Do this then report back BEFORE you worry about the carbs! I'm open to PM's or emails also which will get my attention quicker.