Bought my first bike, woohoo!

[mora]

Yeah I have been reading in the Clymer about doing all the carb set up, tools I don't have, don't know, and don't have anyone I know to borrow them from

I plan on trying to tackle it this winter when I have time, now I have to ride it just to survive, otherwise I can't afford food.

Float level checking is easy. There is a plug at the bottom of the side of the float chamber. Unscrew it and attach a transparent gas line or similar to it(you need to seal it somehow). Hold it next to the chamber and check the fuel level per the instructions in the manual.

[SD67]

I was thinking the slow return to idle could be a mixture issue too. 1.5 turns might be a bit rich. Did you check each of the mixture screws for equal length when you had the carbs apart? Did you replace the Jets?
Have you balanced the carbs yet? This could also be part of your problem. You will need a balancing set (4 vacuum gauges) and you hook them up to the vacuum ports in front of the carbs. Some models have srcews and some have blocked off vacuum take offs, you will have to check to see what you have. You hook up the balance set and adjust the throttle bodies on each carb individually until they read the same, then you adjust the master to get the correct idle speed.
I'm sorry I cannot remember if the old Hondas have an automatic tensioner or a manual one, your best bet is to refer to a manual.

[bmwgs]

Congrats on your new bike.  A Honda CB750 was the second bike I ever purchased.  Of course that was back in the 70's.  I started touring on the 750 and put close to 80,000 miles on it before I had to sell it.  Having had numerous bikes since, and still own a couple and regularly tour on them, you see the world with new eyes while riding.

My suggestion, since you stated you are not a experienced rider, is to take a safety course like the MSF.  You will learn a lot from it.  Having the battle scars from some mishaps, believe me you don't want to see my X-Rays, wear the proper gear and start slowly.

I'm not a safety guru, just someone that learned the hard way.

Fred

[Jackal1]

Since the bike has been sitting up for a while, the slow response to idle might be as simple as sticky cables. The cables can be dragging on return. I have had it happen a couple of times.
unhook the accelerator cable from the grip, make a funnel around the cable shroud, then use MML or WD-40 . Stand it in place upright and give it time for the lubricant to work it`s way though the cables.

[Gixer]

My suggestion while building up the CB, buy a cheap small bike to learn on first and take a few lessons after six months on that and your still around try out the CB and do some more advanced courses. After a year you'll be enjoying the bike a lot more.


<S>...-Gixer

[Mustaine]

As I wrote earlier, check your idle mixture screw(s). If broken you'll need to fish out the broken tip somehow. Very common with Mikuni's. Then check the fuel level in the float chamber and check for intake leaks.

I'll bet it's something like this... obviously too rich, getting lower MPG's than I should and sluggish some times (flooding my guess)

[Mustaine]

1/ When I rev up the engine, the RPM increase fast, but when I left the trottle snap back to idle the RPMs decrease very slowly. Takes about 5-8 secs to come back from 4K to 1.5K. I do see the slider cylinder rod push all the way back in, so I'm thinking the "butterflies" close.

PLEASE MP's this isn't a "punt"

Frenchy, with all the work did you get this problem solved? I am still struggling with it on my bike, and was looking for insight on to what caused it / what fixes were involved?

[SFRT - Frenchy]

Oh boy ... I don't recall what fixed it. I did adjust the valve clearance and the timing. The timing was a off mainly because of my point gap. I used a dwell meter to adjust them, and a light gun to adjust the timing. It seems I'm doing ok now, still a bit slow to decrease, but not nearly as extreme as it used to, seems definitly "acceptable".

My problem now is my idle not wanting to stay put. I have to blip the throttle ot maintain it, or it just jump 1.5K by itself. I did put new intake manifold rubber boots suspecting an air leack but it still does it. I still have to synch my carbs, I have still to pay some bills first.

If u can get your hand on a timing gun, a dwell meter and a feeler guage set, I definitly you adjust all that. It doesn't take a rocket scientist to do and it's quick. As mention earlier, adjust ur mixture screews per manual. What year of bike/type are u driving?

[SFRT - Frenchy]

NM .... 1977 KZ650  search function is a beautifull thing.

[Holden McGroin]

I found my first bike... in San Antonio... in the basement of some old ruined mission.

[SFRT - Frenchy]

 

[Mustaine]

Oh boy ... I don't recall what fixed it. I did adjust the valve clearance and the timing. The timing was a off mainly because of my point gap. I used a dwell meter to adjust them, and a light gun to adjust the timing. It seems I'm doing ok now, still a bit slow to decrease, but not nearly as extreme as it used to, seems definitly "acceptable".

My problem now is my idle not wanting to stay put. I have to blip the throttle ot maintain it, or it just jump 1.5K by itself. I did put new intake manifold rubber boots suspecting an air leack but it still does it. I still have to synch my carbs, I have still to pay some bills first.

If u can get your hand on a timing gun, a dwell meter and a feeler guage set, I definitly you adjust all that. It doesn't take a rocket scientist to do and it's quick. As mention earlier, adjust ur mixture screews per manual. What year of bike/type are u driving?

hmmm

I don'e even know what a "Dwell meter" is of where I'd find one. I did read in the Clymer book that it was the best tool to use. I did just put on new points a month and 1/2 ago, used feeler gauges to set it.

My problem has steadily gotten worse, I have no money, and need to keep riding it to save the gas money LOL. What it's doing is listed above, it will race at 4K RPM and just sit there. I can engage the clutch a bit and force it down to normal idle (1K) but it will not go down on it's own if I rev it. Lately it has also given me a ton of trouble starting. I can't help but think it is all related to the carb adjustment, and syncing. best price I can get to sync them is $350 (no one will touch them and just sync them, they will only sync carbs they have cleaned / rebuilt fully because they don't know what might be mis-set).

[Jackal1]

Have you checked to see if the cables are letting it return to idle without sticking?

[Mustaine]

Have you checked to see if the cables are letting it return to idle without sticking?

yup, the throttle arm on the carbs does return to idle, and I have replaced the throttle return cable (it was stretched). I do have about 1/4 inch too much play right now in the cable I need to adjust, but the arm does go to the correct idle position.