KEIHIN Carburetor Work - it's endless!

Smithers · Post by **Smithers** » Sun Dec 05, 2010 8:26 pm

I'm going to be a carb pro by the time this bike is running in top shape again. I never thought it would be this much work to recondition these Keihin CR carbs. And I have another issue that I thought was kind of odd. This brass nipple is leaking fuel from it when I pull the throttle quickly to activate the accelerator pumps. It was really leaking down on the engine so I put a long clear fuel hose on it to route the fuel to the side of the bike while I worked on it.

Smithers · Post by **Smithers** » Sun Dec 05, 2010 8:35 pm

Here are some more pictures for reference. There aren't hardly ANY good pics of these Keihin CR carbs on the internets so here you all go! I have many more pictures coming up of the intense cleaning that these went through. Lots of work.

Not exactly sure about how that little guy on the left works so I just threw on a clear hose for now so I don't light up on fire from fuel lingering around the engine.

Too lazy to make an IV bottle for fuel so I just set the tank to the left on a folding table to start it up.

Smithers · Post by **Smithers** » Sun Dec 26, 2010 4:52 pm

Ok I got the bike running and it runs much better with the airbox on by the way. It just doesn't have much throttle response at all and the rpms go up and down when you use the choke but nothing is very consistent at all. These carbs need to be tuned by someone with some experience so unless some magic book falls into my hands about how to tune these things I'm going to be looking for someone to take it to in order to make it run nice and smooth.

57x · Post by **57x** » Sun Dec 26, 2010 8:09 pm

Start with vacuum leaks. Spray carb cleaner all around and under the carbs. RPM rise means leaks. Do you have the tubes under the carbs plugged? Are the plugs tight?

Next, have you sync'd the carbs after the cleaning?

Worst case, take the bike up to Jojo at Superbike in San Jose and have his set it right. Long trip, but worth it. He does know them well. Then you can come by my shop and see the stupid number of ZX7s that I have now.

Smithers · Post by **Smithers** » Sun Dec 26, 2010 11:37 pm

I'll be addressing all these issues during the next round of ZX7R work. I'll get some pictures and such. The airbox is the biggest pain on these bikes... you know why already but I'll get pictures to illustrate. Any way that the newer airboxes will fit on the older ZX-7R so that you can top load the air filter into it instead of having to take the whole thing out and splitting it in half? There is no way I could get a proper seal on the carb inlets with the airbox assembled - those two screws on the bottom side of the box/carb rubber boot area are a big problem. If I assemble the whole thing and heat up the carb inlet rubber the chances of it getting a complete seal around the top and bottom of each carb is not good. I heated it up next to my heater and if I put a lot of grease on it then it might slip on but the rubber is old and super hard even at room temp.

How much do you think JoJo would charge for the sync and adjustment? I'll need his contact info for sure.

57x · Post by **57x** » Tue Dec 28, 2010 8:15 am

You can swap the 96-up to a 93-05 but not the 91-92. The bottom of the tank is a completely different shape. What I am doing is putting the Airtech airbox on. Better design and adds ram air. Putting on an air filter is a pain on the Airtech though as they copied the Superbike box which had no filter.

Smithers · Post by **Smithers** » Tue Dec 28, 2010 9:41 am

Good to know, thanks for the info. Yeah this airbox on the early models is a big problem. I'm going to do some thinking on this one... I could modify it maybe... but i wouldn't want to hack it up so I wonder if I can talk my carbon fiber friends into molding one for me. If it was my own I would so I'll see if the owner wants to go further into this project or just get it running. Damn I can't wait to go get mine. I'm selling two cars at the moment, buying a Cummins diesel tow vehicle and putting a roll cage into my Tacoma right now so it's very hard to spend time on this! haha Trust me tho... we'll meet up and ride this summer on ZX-7s tho at some point.

Smithers · Post by **Smithers** » Thu Jan 06, 2011 9:34 pm

So here is what I did tonight finally. Carb teardown part II. What a ton of work. I already had these apart before so everything came apart super easy this time! And it stillll took hours to disassemble everything properly and in order.

I handed over the carb bodies to my friend tonight who's going to dip them in a huge heated commercial ultrasonic cleaner tomorrow. So there won't be ANY question on if they are clean enough. I also need to order some seals for the old Keihin flatslides as well.

And there are a ton of little jets and things in the zip lock baggies. ALWAYS keep things together in zip locks or plastic trays. I get really nervous with all these little parts considering they cost between 2 and $25 bucks a pop!

57x · Post by **57x** » Tue Jan 11, 2011 12:44 am

Smithers, it is time to get that thing running. I am getting close with all three of my R version bikes (K1, M2, N1) and thinking of a ride down the coast in the spring. Let me know your progress. The 96 RR (N1) is the most likely candidate for the journey. The M2 will be track duty only (Buttonwillow here I come in April).

Smithers · Post by **Smithers** » Wed Feb 23, 2011 1:17 am

Well I got a little list of rubber seals that these carbs need. I'm waiting on a quote for some of the complicated looking seals. I might just have to use The Right Stuff sealer on these and put them back together very carefully.

Smithers · Post by **Smithers** » Wed Feb 23, 2011 1:19 am

Someone else had tried to repair these carbs by using a t-fitting that wasn't meant for these carbs. It might have worked for the short term but it occasionally lets fuel slip by (which = fire inevitably).

Smithers · Post by **Smithers** » Wed Feb 23, 2011 1:21 am

I need 8 of these o-rings as well. There's just no sense in assembling these things with these old hard o-rings when they only cost $1.75ea.

Smithers · Post by **Smithers** » Wed Feb 23, 2011 1:22 am

Here is another tricky part. They don't sell these tubes anymore, discontinued. I'll probably just use some fuel line for power equipment in place of the factory tubes. Small machine fuel line should work fine while staying nice and tight.

Smithers · Post by **Smithers** » Wed Feb 23, 2011 1:36 am

The parts that I have to contact a specialty supplier for are the 2 accelerator pump diaphragms and o-rings. If I can just at least get the diaphrams I would be happy. If worse comes to worse I can try and recondition them by softening them up a little bit with some grease. They look slightly deformed for the time being and I would hate to have to try and re-use them.

57x · Post by **57x** » Thu Feb 24, 2011 5:18 pm

Smithers wrote:I'm going to be a carb pro by the time this bike is running in top shape again. I never thought it would be this much work to recondition these Keihin CR carbs. And I have another issue that I thought was kind of odd. This brass nipple is leaking fuel from it when I pull the throttle quickly to activate the accelerator pumps. It was really leaking down on the engine so I put a long clear fuel hose on it to route the fuel to the side of the bike while I worked on it.

I finally got an answer on that nipple. It is for the fuel enrichment circuit. Muzzy recommends to plug it and remove the TPS on the top of the carbs when adding jet kits. That is what I am doing to mine. I called Sudco and they did not even know what it was since it is only on stock carbs.