Hi!

​​​I have an cbr 1000f 94 which is hard to start when cold. Have to crank the starter for several minutes before she even tries to fire up. I have to add som trottle when starting. Can't use chocke because it's starting to smell alot of unburned petrol. Once i get her going she runs fine and there are no problems at all. Starts right away when warm.
I have cleaned the carbs, changed sparkplugs, battery is good. Any suggestions?

Regards Rolf

 

Does it try to fire when you are having the issue?

When you cleaned the carbs, how did you do it?

 

It doesn't fire until i have crancked for several minutes. Theres no sign of life until then.

I dismantled everything on the carbs and cleaned them. Took out all the jets and nedles. Except the adjusment screwes. Checked everything and it all looked good.

 

Three things are required for fire, spark, fuel and oxygen.

What happens if your spray starting fluid or some other combustible into the carb throats while trying to start it cold? If it tries to fire, then you can assume it is fuel related. If that it is the case, I would say the issue is in the choke circuit. These bikes generally need choke to start when cold, even in warm/hot weather.

If it doesn't try to fire then, I would start by ensuring that you have spark when you have the condition. Remove the plugs one at a time and check that the plugs are firing. I'm assuming they are but it's the easiest thing to eliminate. Also, even though you have a new battery, check the voltage while you are cranking the engine.

 

It might be a good idea to check the vacuum operated fuel ****. Fuel will only flow from the fuel tank to your carbs if there is vacuum from the intake manifold to the fuel ****. There is a little neoprene pipe running from the fuel **** to the carb intake manifold.
Before you start up next time, pull that pipe from the carb and give it a good suck (or 10!). See if that makes a difference to the cold starting. If the vacuum pipe is damaged, you'll struggle to start the engine. Maybe even pull the fuel line from the **** to the carbs and see if fuel flows when you suck on the vacuum pipe.

In my experience, overuse of the starter (for whatever reason) can lead to wear (and then failure) of the starter (alternator shaft) clutch device. You want to avoid that. It's a whole new world of pain!

Good luck with your investigations. When they're running well, these are great (old) bikes.

Cheers

 

Check the petcock as above, if it's not that, then your idle jets are blocked.
You need to check them using a fine stainless steel wire - you should be able to see clearly through them center.

 

Thanks for all the replies! I have a list of things i am going to check now. Will update when/if i figure out the problem