Topic: CB750 K8 carb problem (dies when throttled)

[vintagemcycleguy]

Kiehin carbs on a CB750 K8. Have to keep choke on to get them to run and when they do idle, as soon as I try to give it some gas they die. Whats up, cleaned all jets. Could it be the pilot jets they are set at 2 turns out. Any help would be apreciated.  PS another symtom is sometimes the rpm's will rise real fast and then just die.

[TwoTired]

Did you yank out the pilot jets pressed into the carb bodies?  (required for proper cleaning)

Did you verify the accel pump operation?  Both check valves function, the diaphragm intact, mickey mouse ears clear, and the 4 jet nozzles squirt a full strong steam into each carb throat?

Are your carb boots sealing properly?

[KB02]

Did you yank out the pilot jets pressed into the carb bodies?  (required for proper cleaning)

Did you verify the accel pump operation?  Both check valves function, the diaphragm intact, mickey mouse ears clear, and the 4 jet nozzles squirt a full strong steam into each carb throat?

Are your carb boots sealing properly?

Yeah, what he said. 

[kerryb]

I just went through all that on my k8 carbs (first ones ever).  It took three cleaning episodes,  new pilot jets after I made the originals TOO BIG with a TINY little drill.  Many hours of reading here on the forum (Thankyou everyone!) and I lost count of the number of times they were on and off the bike trying to get the boots (both sets) to seal tight.

However...last night I reset the points and timed it with a timing gun  (also first time ever)  and it runs so sweet I can't believe it.  I just got an old tach/dwell meter from my 84 year old father-in-law, and we are both looking forward to tuning  and synching the carbs with the fancy vacuum gauges from cycle X.

It will idle with the idle adjust stop all the way out and above 80 degrees it will start and run with no choke at all.

Hang in there, keep reading and learning the names of the carb parts, and you will be rewarded!!
kerry 

[cookindaddy]

+1 on pulling the pilot jets. I didn't do it the first time (in spite of the recommendations here) and it ran just about like vintage says except I was getting backfiring also but it wouldn't stay running at idle. The hole in the pilot jets is SO TINY I couldn't believe it and of course three out of my four were plugged even after what I thought was a very thorough cleaning in the tank and blowing out with air. Pulled the pilot jets and cleaned them and it runs beautifully now.

[Inigo Montoya]

When you clean the idle jets, use a thin wire and do it by hand. A handy dandy jet cleaning tool works great. Also, clean ALL fuel passages, you may as well do it just to be sure.