Author Topic: 74 cb750 running issues (Read 3270 times)

tanman855 · « **on:** October 09, 2011, 08:57:48 pm »

This bike has been sitting for about 10 years, I cleaned the carbs, replaced fuel lines, changed oil, changed plugs. It runs awsome at idle, fires on all four and revs good. But When I take it out, I only get full power some of the time. If im riding wide open it bogs down so I opened the choke then shut it and it takes off then. So does that mean it is running lean? I think this might be the problem because it is running straight out of the headers and no air filter whatsoever. I recently purchased the pod filters and a set a of jets that come with them.It's in the mail and I'm hoping this fixes the problem of it bogging down around mid-high range.

bluesmoke69 · « **Reply #1 on:** October 09, 2011, 09:13:34 pm »

Need to inspect the plug color. Are you on reserve instead of on, and how full is your gas tank. One more thing check routing of fuel line.

tanman855 · « **Reply #2 on:** October 09, 2011, 09:17:00 pm »

The plugs are dark but lighter on the end of the ground electrode. And it is on reserve, there is fuel in the lines (they are clear).

bluesmoke69 · « **Reply #3 on:** October 09, 2011, 09:33:18 pm »

I don't recall the place that I read it, but it said something about low fuel levels making the 750 not run right. Especially on reserve. hope this helps. Search the forums.

tanman855 · « **Reply #4 on:** October 09, 2011, 09:46:08 pm »

Ill top it off tomorrow and see if it helps, thanks.

Zim · « **Reply #5 on:** October 09, 2011, 10:00:45 pm »

Having no air filter and an open header is definitely not helping your cause. Make sure your carbs are synced as well.

Retro Rocket · « **Reply #6 on:** October 09, 2011, 10:14:09 pm »

Quote from: Zim on October 09, 2011, 10:00:45 pm

Having no air filter and an open header is definitely not helping your cause. Make sure your carbs are synced as well.

+1, i explained this in reply to your other post...

Not enough back pressure without the rest of the pipes and no stacks, it will never run right like that....Jetting would also be all over the place.
Do as Scottly suggested and put all the stock parts back on, tune it then and see how you go, then your questions will be a little easier to answer.....And, welcome to the forum mate.....

NewOldSchool · « **Reply #7 on:** October 09, 2011, 11:32:06 pm »

Pod filters are one of the worse things you can do to your motor. It will be difficult to get it to run great with pods, stick with the stock air box and go from there.

tanman855 · « **Reply #8 on:** October 10, 2011, 03:36:30 pm »

K put the pipes back on and the air box, it runs better and revs up to 6 very well. But I still have the same problem, as soon as I get under power it bogs down around 5k rpm and is taking its time getting to 5k. And when im bogging down at 5k I flip the choke on then off and it takes off like crazy.

Gordon · « **Reply #9 on:** October 10, 2011, 04:07:16 pm »

This may be a dumb question, but is the air filter in the air box?

Retro Rocket · « **Reply #10 on:** October 10, 2011, 04:18:25 pm »

Pulling the choke on richen's up the fuel air ratio. I would be looking at jets , if it is idling well then main jets could be either blocked or to small. If the air filter isn't in the airbox, you could experience the lean condition you describe as well.... Are you running fuel filters.?

tanman855 · « **Reply #11 on:** October 10, 2011, 04:35:04 pm »

it aslo leaks a lot of gas out of the overflow tubes

Retro Rocket · « **Reply #12 on:** October 10, 2011, 04:37:54 pm »

Quote from: tanman855 on October 10, 2011, 04:35:04 pm

it aslo leaks a lot of gas out of the overflow tubes

Sounds like your carbs need a good going over....

Johnny5 · « **Reply #13 on:** October 10, 2011, 04:45:25 pm »

Quote from: Retro Rocket on October 10, 2011, 04:37:54 pm

Quote from: tanman855 on October 10, 2011, 04:35:04 pm
it aslo leaks a lot of gas out of the overflow tubes

Sounds like your carbs need a good going over....

Agreed. Double check your floats for sure.

tanman855 · « **Reply #14 on:** October 10, 2011, 05:49:21 pm »

I discoverd it is having a fuel drawing issue, but im not sure where I should be running the fuel line to the far side.

tanman855 · « **Reply #15 on:** October 10, 2011, 06:13:59 pm »

YAHOO! re-routed the fuel lines and the bogging down is almost gone, still a little hesitant but a lot better! I think I'm going to go up a jet size only problem is I'm not sure what size I have. is there supposed to be a number printed on them?

alfego · « **Reply #16 on:** October 10, 2011, 07:42:54 pm »

How many turns out do you have your air screws set? Try bottoming them and turning them a 1/2 turn out. That will richen it, and it should run much better up to 5K rpm.
Alfego

tanman855 · « **Reply #17 on:** October 11, 2011, 02:56:47 pm »

Those screws were the ticket!

Retro Rocket · « **Reply #18 on:** October 11, 2011, 07:43:30 pm »

Quote from: tanman855 on October 11, 2011, 02:56:47 pm

Those screws were the ticket!

Nice.....

bjatwood · « **Reply #19 on:** October 12, 2011, 08:35:03 am »

I had to adjust my screws a bit yesterday also. Was running kind of lean I believe. With the colder weather, I'm thinking it was leaning out a bit with the dense air.

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Author Topic: 74 cb750 running issues (Read 3270 times)