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Discussion Starter #1
Hey everyone, need a little help if you guys can manage it!

I just buttoned up everything on my 1973 CB450 cafe racer. The bike starts up and idles well but as soon as i put it into gear the bike stalls. I cant figure out if it has some sort of kill switch associated with one of the two kick stands or if there is a kill switch associated with the choke. Can anyone provide any insight???

FYI I got rid of the old lead battery and replaced it with a lithium ion battery. I put on shortened the intake and replaced the old intake with new ones and now i cant turn the choke all the way off...thats why I'm thinking it might have a kill switch associated with the choke. I really dont know what else it could be...any help would be appreciated.

Thanks!

-Mike
 

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Troublemaker
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A 73 has no safety kill switches other than the one on the handlebar. It sounds like the clutch is out of adjustment and when it goes into gear, it is enough drag at idle to kill the engine. Try turning the cable into the clutch handle as far as it will go and lock the thumb nut to it, if it still does it, check to see if you can adjust the cable shorter at the clutch itself. If that isn't the problem, it may be that the clutch plates are stuck together and will require taking it apart.
 

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Discussion Starter #3
A 73 has no safety kill switches other than the one on the handlebar. It sounds like the clutch is out of adjustment and when it goes into gear, it is enough drag at idle to kill the engine. Try turning the cable into the clutch handle as far as it will go and lock the thumb nut to it, if it still does it, check to see if you can adjust the cable shorter at the clutch itself. If that isn't the problem, it may be that the clutch plates are stuck together and will require taking it apart.
I gave adjusting the cables a try... I tried both extremes on the length of the cables. One extreme of the cable completely disengaged the clutch even though the clutch lever wasn't depressed, while the other extreme didn't seem to disengage the clutch enough.

I changed the style of handle bars (stock bars to straight drag bars) which I'm starting to think will require a shorter clutch cable. Perhaps even at the extreme its not disengaging the clutch enough to avoid a stall?? How much shorter of a clutch cable might you recommend or do you think i should pop open the clutch to snoop around first?
 

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Troublemaker
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The longer cable won't matter since both mounting points are the same, the housing will keep the cable fitting at both ends.

Does the bike jump forward when you put it in gear with the clutch handle pulled before it dies?
 

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Discussion Starter #6
The longer cable won't matter since both mounting points are the same, the housing will keep the cable fitting at both ends.

Does the bike jump forward when you put it in gear with the clutch handle pulled before it dies?
The bike doesnt jump forward at all when the clutch lever is engaged and i put it into gear...which is strange. Ive tried artificially increasing the idle speed with the throttle
 

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I'm afraid I'm out of ideas. The only thing I would do if it were me is put it on the center stand, get on it, give it some gas, and put it in gear. IF it doesn't kill, then it's because the idle is too low. If it does die, there is a problem somewhere.

I just thought, it could be a loose connection on the battery, or a weak battery. Putting it in gear may cause it to move just enough to cause a no connection.

It should have an on and off switch on the headlight too, does it die in neutral when you turn the headlight on?
 

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Discussion Starter #8
I'm afraid I'm out of ideas. The only thing I would do if it were me is put it on the center stand, get on it, give it some gas, and put it in gear. IF it doesn't kill, then it's because the idle is too low. If it does die, there is a problem somewhere.

I just thought, it could be a loose connection on the battery, or a weak battery. Putting it in gear may cause it to move just enough to cause a no connection.

It should have an on and off switch on the headlight too, does it die in neutral when you turn the headlight on?
Alright, i got it up on the center stand and got 'er running. I popped it in gear and spun the tire a little bit then moved between a couple gears. Then I got confident enough to try to rev it up near 3000/4000 rpm after rolling the bike in neutral. I was able to get it into gear and took it for a short spin!

In the process i noticed that the idle is way low, down near 500 rpm at neutral idle.

Long story short, i did what you said and it worked! Now that we identified that the idle is low, ill check the manual to adjust it.
 

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Should be a knob on the left side by the carb, it is on a cable and if you turn it clockwise, it should raise the idle.
 

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Discussion Starter #10
Should be a knob on the left side by the carb, it is on a cable and if you turn it clockwise, it should raise the idle.
Thanks for all the help today! Its been an all day project finishing out this build and we couldnt have done it without you!

There is a lot of tinkering still left to do, but she is finally running and street ready.
 

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Troublemaker
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You would have gotten it, all it takes is a little time and a service manual you can probably download online somewhere if you don't have a hard copy.

Looks good, will be a fun ride!

:71baldboy:
 

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Without adding vacuum ports, the carburetors are synchronized by feeling the exhaust pressure, and adjusting the idle set screws to make both match, then have an assistant open the throttle a bit, and adjust the cable length at one carb to make them match again. It will run lots better after this adjustment.
One other thing - what size jets did you change to? Those pod filters will make it run very lean, unless you go up to a 150 or 155 main jet. Also, the intake tube on some pods keep air from flowing into the air jets in the throat of the carbs, and also cause mixture problems.
 
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