Hi to all

I am new to the site but have been reading it for long while now and it is a great place to talk and listen to other CBR owners.I have a 1990 Cbr1000f that I have been putting back together for some time now and I am having trouble with idle staying high if I rev it up over 4,0000 rpm's.I have cleaned the carbs inside out and everything looks good and also have new boots on them, it idles ok and I can rev it up with no trouble and ride the bike has long i don't rev it hard.I suspect that it is my carbs but does anyone have any sugestions for me to try?

 

Try checking the throttle and both cables.It may be that they are not returning all the way back check to see if the cables arein their correct routingpositions. Also place some oil on the external carb connections.

 

Cables look good and clean,the throttle snaps right back smoothly and quick.Do you think it could have anything to do with needing the vales adjusted or running to rich?

 

Have you ballanced the carbs? The valves wont have anything to do the the idle as such

 

Yes the carbs have been sync'd ,that was the first thing that we did.

 

Then I would have another look at the cables again. When you stay below 4000rpm things return as normal but when you exceed that then it struggles to return to idle. It maybe that you have a kink inside the cable sleeve which may have been caused when cables were removed or replaced. Its easily done. If you remove the cables from the carbs, then hold both ends and opperate the throttle, both in and out and feel if there is a snag in the sleeve. This from what you are saying seems to be the most likely cause. As for the valves, you can check them as for routine service.

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Ok, Collector I will check the cables very closely tonight and thanks for your help.

 

Thanks guys, my problem turned out to be that my idle speed knobwas turned to far up which yes was keeping my idle alittle above the 1000 rpm arange.But this uncovers a pattern of three acceleration transition ports which shouldn't be uncover at idle.They are NOT controlled by the idle mixture screws, they are controlled by the bottom edge of the butterfly.So when you blip the throttle to check for response, the engine won't idle back down.All I had to do was to bring the idle **** back down which caused my idle to get real low but I was able to set the air mixture screws little better which gave a good idle speed, again many thanks and to you "Collector" for thegood advise on check the cables.

 

Glad that you got the problem solved, and that your bike is back on par. Carbs are tempermental things and it always seems to be the simplist of things that cause the problems. Happy riding.

 

That's classic 4 carb inline 4: Air leak between carb and head. Check the parts diagram for all the O rings both ends of the intake pipes/boots, they all need replacing. The pipes/boots are probably ok.