Topic: CB750K starting/idling trouble

[celebutante]

I recently had my tank painted and replaced fuel lines and rebuilt the petcock on my '74 CB750 (stock everything- airbox, pipes, etc.). Now I'm having a lot of trouble with starting- sometimes runs down the battery entirely. Idles well only after about 20 minutes. A couple months back, I had Kurt at Valley Cycles completely go over it and, in his words, it ran "like a top" (it did run really nice).

Any ideas? Slow jets maybe? I searched threads, but couldn't figure out whether slow jets could be removed without removing the carbs. Any help is appreciated!

[CB750Winger]

  You can drain and remove float bowls with carbs on the bike. You can also remove the floats, needles and seats, and both jets. It's almost as easy to pull the carbs to work on them. Have you checked the mixture screws or maybe a carb sync nut came loose? Maybe check the points and breaker plate to make sure everything is set properly and still tight.

[Spanner 1]

Is the petcock definately clear and delivering a fast flow of fuel to the bowls ? If yours is a '74 750 then the slow jets are easy to remove with the carbs still on the bike... they just unscrew. Must be able to see thru' the very tiny jet and all the cross-holes need to be clear...I use an 'E' guitar string to verify the jet is clear...........

[celebutante]

Thanks much for the tips. Fortunately I'm a guitar player... I'll assume you mean a high E string, not a low one 

[Johnie]

Just curious...what did you use for the gold paint? Was it vintagehonda.com or did you use House of Color?

[traveler]

not that it matters, but in the future, it might be a good idea to add a bit of fuel injection/carb cleaner to the fuel periodically, and a bit of Sta-Bil if it will sit for a time.  Mix it in good, and let the engine run to get it through the carbs. 

"it's what I do"....just my .02

~Joe

[celebutante]

Johnie- the saga of my tank and cover painting is too long to bore you with, but the short version is that I took it to Bar Italia scooters in Van Nuys, CA and told Gary over there to paint it Honda candy gold. Don't how he arrived at it, but he seems to knows his vintage Honda colors pretty well. The pic in my avatar is kind of a fake... I included a pic of the real bike. Obviously the black inset and painted headlight bucket aren't correct, but I wasn't going for perfect restore (you'll note it as euro bars too). I'm not sure how close the gold is, but it's close enough for me.

traveler- sounds like an excellent idea- I suspect leaving it sit around for a week or two is what caused the problem if it is indeed a clogged jet.

[Johnie]

Johnie- the saga of my tank and cover painting is too long to bore you with, but the short version is that I took it to Bar Italia scooters in Van Nuys, CA and told Gary over there to paint it Honda candy gold. Don't how he arrived at it, but he seems to knows his vintage Honda colors pretty well. The pic in my avatar is kind of a fake... I included a pic of the real bike. Obviously the black inset and painted headlight bucket aren't correct, but I wasn't going for perfect restore (you'll note it as euro bars too). I'm not sure how close the gold is, but it's close enough for me.

traveler- sounds like an excellent idea- I suspect leaving it sit around for a week or two is what caused the problem if it is indeed a clogged jet.

Thanks for the info...that bike looks great!!!

[celebutante]

Thanks again for the help- two of my slow jets were clogged (and one of the main ones was a little grunky too). I'm guessing some junk got in from the paint job. The slow jets were so clogged that carb cleaner and guitar string wouldn't do it- I could get the string through (an .011, btw), but I still couldn't see daylight through them. Took a walk across the street to the nice tire shop and they let me use their compressor to blow them out (they had the perfect little metal attachment), and that instantly de-gooked them. Took a bit to get the bike started, but I assume that's because I drained the bowls.

BTW, removing the jets with carbs still on bike is kind of like building a ship in a bottle. Upside down. Guess who's buying a wee ratchet VERY soon?