Hi guys,
as reported in a previous thread showing pic of my newly aquired cbr1000fp,i was having problems when the rev's got up to 6,000rpm,it would start cutting out and stuttering.
I have bought another set of coils and leads but still the same problem so today i took the carbs off and cleaned them out with carb cleaner and a high pressure air line,some crap in there so cleaned all jets and fuel lines,then when i went to put the carbs back on i noticed a set of alloy restrictor plates across the rubber inlet manifolds,whipped them out,had to reset the mixture screws to run leaner at idle,thought i had found the problem so out on the road to test....
....pulls alot harder up to 7,000rpm but then starts stuttering again,will pull through it and rev harder than before but its still there!!
The bike is an import so belive it was restricted for the market it was from(france,germany,switzerland have 100bhp limits or less) but after removing the inlet restrictors does anyone know if the ECU has a restriction in it?
A bit confused as to where to go next with this problem,
kind regards,GN

 

Good you found the restrictors (ba5tard fun police!!). Maybe the main jets are different in the restricted models. Was the 7k at full throttle? Did you re-balance the carbs too? I'd say taking the plates out would have thrown them out of balance. When you get to the stuttering stage, if you don't accelerate through will it keep stuttering? If so I'd try throwing in some brand new plugs, running it for a minute or so stuttering then kill it and check the plugs. At least then you'll get an idea if it's rich or lean and if all plugs are even. It can't be anything too major so keep at it mate.

 

Yep, just like Dave said. I would see if you can find any info on the jets. They may well be different, too. And a sync I'm sure is in order.

Nope. Don't see how it could. All mechanical, no maps, etc.

 

No restrictor in the ECU - all in the carbs. I can't tell you about the jets, mine had been rejetted to Dynojets when I bought it.

 

Easy/fastest way to go, might be to grab a used set of "regular" carb's somewhere ! instead of having to dick around with jetting it etc.

 

You may well be buying an even bigger pile of d-gshyte buying used carbs, unless you know where they come from.
The replacement of jets is really not difficult - there are a number of how to's on the forum on how to clean carbs and fit new jets. I'd remove the restrictors and run it as is until you feel how she goes - the std jets from the factory are slightly rich anyway so shouldn't be a problem.

 

Quote:

You may well be buying an even bigger pile of d-gshyte buying used carbs, unless you know where they come from.

Obviously !

 

An update on the rev problem....it's fixed!!
Ordered a Dynojet jet kit as TTS were selling one at £65 instead of the usual £115 so thought i would give it a go at fixing my problem.So yesterday morning took the carbs out and found out by the carb code that it was a German model that were restricted to 100 bhp,checked the jet sizes and that confirmed it,in went the Dynojet kit but the slow jet is still #40 and needs to be a #42 so ordered 4,a tip was given to me from a Honda mechanic,when installing the slides make sure the diaphrams are pushed up from the carb mouth using your fingers so it is a dome shape when you screw the top on,not as had been done before with the slides fully down in the carb mouth.
Bolted back up and went for a quick spin to see if it made a difference........wow,what a difference,it's now the bike i always thought it should be and then some!The dynojet and K&N filter make a difference but it is very quick and smooth with instant pick up and a mega rush to the redline,i was whooping into my helmet such was the difference from beforeI think it was the diaphrams which were the guilty party not being able to open fully with the way i had installed them.
When the slow jets come i will put them in when i have had some carbon cans made to look the same as standard but be alot lighter as i will have to change the main jet size aswell.
I am surprised nobody makes twin carbon cans for the cbr,it seems its just the one long can on the right side which in my view spoils the lines of the bike.I am getting a local craftsman to cut 2 round carbon cans to the same size as the standard ones with link pipes and stainless end caps,should breathe,sound and go alot better,the standard cans are very heavy.
Off to enjoy the new found top of the rev range,
kind regards,GN

 

I've been following this because I am anticipating the same carb headaches. Great to hear you got her running right!!!!!

 

I had forgotten how tricky it was to keep the bead on the edge of the diaphram in the groove on the carb. If it doesn't seat correctly you will have an air leak. Glad you got the technique.