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Cold Start

nnikitas16

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Have a ’74 cb750. Just replaced the battery this week and having trouble with the cold start. I’ve tried switching fuel over to reserve, opening the clutch, but nothing. Kicks over but after about 5 seconds dies on me. Wondering for tips/advice before I take it into the shop. Thanks.
 
Use the choke...you cant just take it off right away, slowly open the choke as it warms up a bit. You have to hold the throttle open just a bit till it warms up unless you use the idle stop screw and use it to play with the idle speed till it warms up. This isnt fuel injection, this is old school, nothing automatically controls the idle speed so you have to do that manually. Also not much info given so have you done complete tuneup and all engine maintenance items? fresh gas? Engine have good compression?
 
used the choke...pulled it up that's when the engine kicked over...so what you're saying is I have to keep the throttle open or manually adjust the idle stop screw until it holds on its own? Then slowly take the choke off as it warms up? When I tried to start it this morning, if I let off the throttle even a little bit it died on me. Just looking for clarity, appreciate the help!
 
Once it fires youll have to take the choke off just a little bit but yes you have to hold the throttle open a bit when it is cold. Nothing more then 1500rpm max just enough so it will stay running. Cold engines are not efficient at burning the fuel mix till they get some heat in it. Plus you have cold thicker oil which causes a lot of fluid friction which uses a lot of power. You just gotta play with the throttle and choke to keep it running. If tune up and engine are good it should still run smooth and not take much throttle to keep it running, shouldnt take more then a couple of minutes till it will run on its own with no choke and not throttle.
 
X2. It ain't no car with a computer changing all that by the second and what they do. You have to do it yourself. You'll learn pretty quick the close to exact amount to start it and keep it running, often the choke must be thrown back on for a fractional second as it tries to die but not all the way. At some point you will catch on to how much choke to open up once it fires initially. Choke should be able to go completely off in say 45 seconds-one minute and then only throttle held open to keep it running. Early on you are doing both, it's a biker skill from a long way back.

I myself use a cruise control as a throttle lock to hold it while warming up. then only paying attention to choke then.
 
X3 ;) Like the others said, you must keep it running manually until it warms up, that's normal.

If you want to walk away from it while it's warming up, reach under the carbs with your left hand while sitting on the bike and you'll find the idle stop has a knob on it designed for just this purpose ;)
 
You may as well stand over it, if right like most and you lock the throttle early on in the warmup they almost always at some point have the idle suddenly jump WAY up to maybe 3000 rpm when suddenly the engine decides it is warm.
 
yeah I never leave it unattended. It doesnt take long to warm up so normally I just stay with it and ride after a couple of minutes anyway.
 
One thing that i have found that helps mine is before i try to start it for the first time pull the choke and open the throttle a few times. I also adjust the idle up and as the engine wams and the idle rises i adjust the idle speed back down.
 
Opening the throttle a few times does nothing on the old round top carbs...no accel pump. On the PD carbs yes it helps to give it 1 or 2 twists but the OP has a 74 so no accel pump.:thumbsup:
 
X2............................you beat me to it....................lol.

Opening throttle does absolutely nothing unless you have an accelerator pump on carbs.
 
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