Have had a starting problem on my 1993 CBR 1000. Will take about 30 seconds to start when cold. Have noticed that if I sit on bike, put choke on and tilt bike over to the right that bike will start up normally and within a few seconds. Wondering if anyone has experienced this. Was going to synch carbs but the Haynes manual I purchased is not clear so I'm waiting on a Honda manual. I'm debating doing so if the carbs have other issues. Thanks.

 

the only reason you will need to sync your carbs is if when you rev. the bike up and it doesn't come back down other than that you don't need your carbs synced

 

Mine takes two stabs of the starter to start, even after cleaning the carbs. The carbs (on a 1990) have to come apart from each other to clean the choke plungers, but I didn't want to do that. With the vacuum chamber covers off, you can spray carb cleaner down the bleed into the choke chamber while holding the choke open. I'll have to try tilting the bike to the right before starting next time.

Carb synching shouldn't affect starting since the choke system bypasses the main circuits. But if the Haynes manual about carb synching isn't clear, forget about the Honda manual. Here's what it will say: "For detailed instructions, refer to section 2 of the Common Service manual." The Honda service manual will show you where the vacuum taps are and where the adjusting screws are. That's it.

 

Yea I'm having the same problem, when its cold in the mornings I have to crank it about 5 - 6 tries with full choke before it will even keep running at very low rpm. Had the carbs apart and they are all clean and have sync'd the carbs all at 7. Plugs are perfectly tanned. Timing is right on the 'F' mark every time.

When the motor is warm works great full RPM range, quick throttle response, idles at 1k, lifts the front wheel by cracking throttle just this hard time starting when cold problem.

Anyone have any suggestions

88RedBlack

 

88RedBlack

Yeah, I have an 87 that had the same problem. Even though the plugs looked good, I put a new set in and it's been fine ever since.
Your lower temperatures might make the problem worse, since I've noticed that cold mornings were more troublesome than warmer ones.

 

I did my carbs a while back on my 96 you have to take the fairing off and move the tank to make it easier book says lift it up but i found it better to move it
then locate the connections underneath the carbs,
you need an adapter for no 4,
no's 2&3 are on the carbs
no1 should have the vac connection on it to the tank ( this runs from the intake not the carb)

a second pair of hands don't go a miss

hope this helps

 

Thanks zeebee

I just finished readjusting all valves they were set at .004 when they should be around .006 and then I got the energy to take all the carbs apart and rebuilt them completely. Got it all back together sync'd the carb's to 7.4

It runs really good but one thing I did notice is that I might have had a bad needle & or seat and that the fuel might have been missing from one carbs if left overnight. So what I am going to try next is before starting it when cold I will manually run the fuel pump pressurize the fuel system and then try starting it. I will keep you posted.

Just a quick question does anyone know if the fuel pump should pump as soon as the key is turned to the run position?? Mine does not, it only starts to pump when cranking or running.

Just out of curiousity if anyone wants to try one thing. Is to first thing in the morning after leaving the bike sit overnight manually override the fuel pump before starting to see if the pump will run to presurrize the fuel system, or if the fuel system is still presurized.

Good way to tell if the carbs needle & seat are holding pressure or if the fuel pump is allowing back drain.

Be interesting to hear results.

88RedBlack

 

According to the wiring diagram the fuel pump relay runs off a junction in the wire that goes from the spark unit to one of the coils. So I would say its correct that it only turns on when cranking or running.

 

Results are in.

Tried 2 days in a row and found that the fuel pump did not have to top up (presurrize) the fuel system, it remained presurrized over night. (good thing ) It started right away now when it was cold. I think I found the problem. After taking the carbs apart I noticed that some of the pilot mixture screws were set incorrectly (very lean) and so after rebuilding them I read the manual and it stated to start at a setting of open 2 full turns (1 of mine was set at 1 turn, another at 1.5 possibly & the other 2 at 1.25 turns I think that was the starting problem). The darn thing is that you can't get at the 2 middle pilot screws while they are on the bike (without reinventing a special tool to get at them). It now also has much better throttle response from idle. I am so happy now and can't wait for warmer weather.

Will post pictures after I get it polished up.


88 Red & Black Hurricane