Topic: RPM comes down slow

[friedfish80]

76 CB750F with 78K motor

Work done in past 100 miles: checked timing, set valves, set cam chain tention, oil changed, set idle air screws.

Running pods that have been clear coated to reduce air intake and straight piped threw 4-1.

Ordered my morgan carb tune today. When I rev the bike around 3K and above it takes some time for the RPM to drop back to idle. Also sometimes it comes down to around 2K and idles there. I got a strong feeling I that i just need a sync to get it all dialed in.

Am i at least on the right track?
Am i forgetting anything?

[BlackMax]

could be the cable.   I've had a sticky cable before.   However, I usually equate a resistance to idle down to a mixture that may be too lean. 

[Inigo Montoya]

Try spraying carb cleaner around the airbox and carb rubbers to see if the rpm changes. If it does, air leak.

[friedfish80]

could be the cable.   I've had a sticky cable before.   However, I usually equate a resistance to idle down to a mixture that may be too lean. 

New cables last year.

[Laminar]

could be the cable.   I've had a sticky cable before.   However, I usually equate a resistance to idle down to a mixture that may be too lean. 

New cables last year.

If you physically twist the throttle grip further "off," do the RPMs go down? My Nighthawk had good cables, but they weren't adjusted perfectly, so at times the cables would hold the throttle open just a tiny bit.

[friedfish80]

Ok I know that my cables aren't fully adjusted properly. But no twisting back to off dosent help.

Also when I'm ridding and at speed I pull in the clutch it will rev up about 200 RPM if not more.   

[mystic_1]

pods that have been clear coated to reduce air intake

CV carbs?  If so then too much air intake restriction can cause this.  Remove pods, problem remains?

mystic_1

[friedfish80]

pods that have been clear coated to reduce air intake

CV carbs?  If so then too much air intake restriction can cause this.  Remove pods, problem remains?

mystic_1

had the same issue when they werent clear coated.

[friedfish80]

Try spraying carb cleaner around the airbox and carb rubbers to see if the rpm changes. If it does, air leak.

tried that and dident noticed any change in the rpm

[friedfish80]

Ok got the morgan carb tune and went and got them sync this morning. bike runs alot better. But as i rev it still comeing down slow. I know that the throttle cables are loose. I cant seem to get the cables tight.

Any help??
Please?

[jumpjg]

Might want to check the operation of your ignition advance mechanism. If the springs are sacked out and/or there is friction in the mechanism, it could stay advanced and hold your idle high.

[UnCrash]

I know on my 76K that after the bike is warmed up the RPM's come down slow if I haven't pushed my choke completely off.

[friedfish80]

I know on my 76K that after the bike is warmed up the RPM's come down slow if I haven't pushed my choke completely off.

barely ever use the choke. bike starts on one kick cold everytime.

[Head]

Which carbs do you have???,(1) I would suspect the mix is lean, (2) Is one of the slides a little bit sticky in the carb throat,(3) Do you have an accel' pump,Is it weeping a tiny bit  of gas,    Some things I have encountered over the years,   Head

[friedfish80]

keihin carbs.

Perhaps a lean condition. Now that i got this all set "corectly" it will not fire on its own without starting fluid when cold.

[Head]

Recheck the slow jets to make sure they are clear?   Head

[friedfish80]

yea was thinking the same thing too. Thats the one thing i havent done yet is rip off the carbs and checked them.

[UnCrash]

barely ever use the choke. bike starts on one kick cold everytime.

Even when it's cold out?

That is quite unusual.

[friedfish80]

barely ever use the choke. bike starts on one kick cold everytime.

Even when it's cold out?

That is quite unusual.

well bought the bike middle of the summer last year. First bike and never started the bike under 50. untill now

[friedfish80]

ok ripped off the carbs and replaced the bowls with clean ones i had. The old ones had some varnish on the bottom of them. Replaced the slow and the main jets. The slow jet on carb #1 was completely plugged. i just got them back on and ill run the lines and redo the cables tomorrow after work. hopefully it will fix my issue.



This is the rag on my was on my toolbox what i used to soak up the carb cleaner. It was clean when i started.

[cherry bomb]

ive been having the same issue with my 77F...originally the #2,3 were totally blocked so #1,4 were doing all the work cleaned them good and it still had the problem so I gave them a good bench sync and changed the mains and set the idle screws to the recommended "stock" position...I have pods and straight pipes too so I went with 115's on the main...it seems to work well if I have the throttle stop set really really low...but the second I adjust the throttle stop the RPM comes right on up and holds about 2k I just adjust the throttle stop back down and down she comes...I need to get a good gauge sync on 'er just to busy right now...sounds to me like you are on the right track to get it taken care of...just eliminate things one at a time.

[ev0lution7]

condition of hanging RPM:

advanced timming

mixture off

idle screw off

those are just about it if you have checked your cables those are the 3 things that will make the rpm hang...

[friedfish80]

timeing checks out. All idle screws are out 1 full turn. How would I know about the mixture?
Also I never cleaned the idle  screws. Should I pull them out and shoot some carb clean down there?

[friedfish80]

Got the carbs plumed up and cables on. I dont know what told me to check it out. But got opened up the R handlebar control and took a look at the cables. Turns out that the PUSH cable was broken. Thankfully a buddy of mine had given be a bunch of parts when he locked up the motor on his chopper. Ran the new cable and WOW what a diffrence. Bike starts cold on 1 kick without the choke and wants to idle now. As opposed to haveing to keep it reved till it warms up. Bike runs strong and the RPM acts the way it should.

Thanks for all the help to everyone.

Now i got to fix the leaky carb bowl on carb #3. I guess it never ends.