Topic: CB750 cold start issues

[dimi3cb]

I got 1977 CB750 F2. But the major issue I can not solve is cold start problems.
It takes long time, many tries and it drains the battery. It fires after several attempts, few times I had to hook up bigger battery and keep trying.
After it warms up it starts no problem, every time. Runs fine after...
What could be the issue?  I am suspecting the carbs are not original and could be the problem. I have some kind of MIKUNI on it, maybe even for a 1000, not sure.

tnx.

[brandEn]

Yup the stock carbs are Keihin PD42 carbs.

[dave500]

gday dimi,,i see yours has "pod filters"(individual type air filters)these can make your carbs run lean and might be the reason for your hard to start when cold problem,,i cant quite see your actual carbs,,if they have been changed to something other than the proper honda ones with a standard type engine you may have even more problems,,first thing to do is make sure your ignition system is spot on and set perfectly,,close enough will not do!!it must be as good as new,if you have a multimeter check the spark plug cap resistance first,,these caps unscrew from the wires,they should be 5kohms,or 5000 ohms,use new fresh spark plugs aswell,your points and condensors should also be new if you doubt the age and set correctly,only when your sure the ignition is perfect should you try adjusting the carbs,dont touch the carbs untill you are 100% sure the ignition is correct,,too many people blame the carbs for trouble that is from the ignition and make things worse.you can download the workshop manual from this site for your bike.

[raymond10078]

I think your carbs have the accelerator pumps.

For my accelerator equipped bike, I:

• Turn the petcock to ON and WAIT A MINUTE.
• Crank the throttle to full, and then release (squirts fuel into the carb throats).
• Choke full on, then crank it up.

Of course, this assumes all systems on the bike are functional or in good tune.