I've been having a lot of problems with my keihin flatslide carbs on my fzr400rrsp.


Last week I took the carbs off removed all the jets and cleaned them with carb cleaner. Not knowing what settings to use I set the floatbowl heights at 20mm and air screws 1 1/2 turns out. (Suggested settings from an article on google)

Put the carbs back on and they pissed out of the floatbowls. So removed the carbs again and presumed the O ring gaskets were shot and weren't providing a seal.

Got a new set today, ( 60 fooking quid for 4 gaskets!!!) put them on the carbs checked all the jets and bowl heights and fitted them.

Fuel is now pissing out of the overflow pipes. Hmm! Removed the carbs again checked the float heights and removed the float needles they seemed fine and clean, sprayed them with carb spray anyway. Put the carbs back on and still they are pouring out of the overflow pipes!

That this point I stopped and went for a run to calm down.

Somebody must be running fcr's and be able to give me some sort of clues on how to get these working/set approximately. There just seems to be very limited info on the net, and no info at all on the Standard fcr's that are on the 3tj6/7

Take it to this guy

http://www.raceengineering.info/

He's in Great Dunmow not so far, but he'll be able to sort them out where as you or I can chase it round for ever and still be none the wiser.

Cheers Boris I will give him a ring tomorrow, see how quickly he can do them. This 3tj7 really doesn't want to be used, its fought me all the way.

I'm going to buy some cv carbs to put on it in the meantime so I can finally get it running and register it.

A big problem with FCRs is that Keihin do not sell mid body seals. So they go rotten and your expensive carbs turn into paperweights. The mid body is screwed and glued with a thin line of epoxy to the main part of the body. Once removed you will find four 4 thin nitrile seals and 2 o-rings. In your case you would find some crumbs. I have a bag of these crumbs and assorted rotten pieces that Matt Harper at Harper's Ultrasonic in the UK sent to me along with the FCR that they came from. At the moment it is just scrap metal. See the image attached.
I am working with Matt to solve this problem. It won't be done overnight, but we will get it all finished. Then, not only will you not have to pay a king's ransom for nitrile garbage, but you will be able to restore your carbs to their former glory. I try to be polite and "professional" and all that, but to be blunt Nitrile is cheap crap.
cheers
Blair

^^ cheers I'm finding out that Flatslides are a total pain in the arse.

Although mine appear to be ok at the main body and not leaking from there. They are just filling up and pouring out of the overflow.

Did they overflow before you adjusted the float height?
Carbs usually only flood because the float needle is not closing off the fuel supply. They cannot leak from the mid-body because it is sealed with epoxy.

My point about the mid-body seals is that you can expect that yours are either rotten now or will be in the near future. Nitrile does not have a twenty year service life. The pieces that you see in the previous image do not include the emulsion tube seal because there was nothing left of it to show.

I am no expert on Keihin FCRs. It is all new to me, and I found it very hard to believe that the "racing" carbs from Keihin are not rebuildable and never have been. That seems to be the case though. You can buy mid-body kits for the MX carbs (image attached) but not the road/race versions.

It may be worth talking to Matt at http://www.harpers-ultrasonic.com/ He has a lot of experience with OEM flatslides.
Worth a phone call in any case.
cheers
Blair

Sounds to me like the float heights are out somewhere, I run flatslides on all of my bikes n have no problems.

Don't suppose you have run a standard ish set up have you so I can get some base settings.

I'm going to take them off and check the o ring seats see if they have perished.

Lets face it you and that bike just aren't meant to be together. I'll swap it for my project bike, it's in the not so hard to find red and white colours .... I'm robbing myself but I just don't want you to suffer

Evilchicken0 wrote:Lets face it you and that bike just aren't meant to be together. I'll swap it for my project bike, it's in the not so hard to find red and white colours .... I'm robbing myself but I just don't want you to suffer

Very generous of you!

I was telling Tony yesterday that I'm at the point that I won't ever be able to sell it as it owes me so much money and time.

Still I'm making progress with it albeit bloody slowly!