A previous owner installed a 1993 engine in my 1990 Cbr 1000f. Recently I noticed that a vaccum line coming from a nipple under the # 1 intake ( on the block) is plugged with a screw. I cannot find any info telling me what this goes to. Can anyone tell me what it goes to or what it is? thank you for your help.

 

I don't have a Mark 3 but here's my best guess. The vacuum port is not needed unless you are setting the carbies for air flow. So the rubber tube has been sealed with a screw.




You can see from the above picture, the vacuum lines come off the bottom of the 93 carbs.

Sprock would be the man to give the definitive answer but I think he's just about to - or even may be - winging his way to Europe.

Cheers, SB

 

Ok, just did a bit more of a search this is what I found.

Information from a post by Naga_Thai in a much earlier thread.

Carburetors’ Synchronization:

Different method for different models (as stated in detailed "How-to's" and Honda Manuals).

There are 2 different sets of carbs on the CBR1000F series. Accordingly;

• On 1000 H, J, K, L, M, N models, remove the rubber plug from the vacuum take-off point on the top of each carburetor and connect the vacuum gauge hoses to the take-off points.

• On 1000 P models onward, release the fuel tap vacuum hose from No. 1 cylinder take-off point, the rubber plugs from Nos. 2 and 3 cylinder takeoff points, and the screw and washer from No. 4 cylinder take-off point. Screw an adapter into No.4 take-off point and connect the vacuum gauge hoses.

Number two cylinder (all 1000 H, J, K, L, M, N models) or number three cylinder (1000 P models onwards) carburetor should be used as the base setting; and the other three carburetors should be adjusted to be the same.

For detailed links to "HOW TO with pictures"...

• 1000 H, J, K, L, M, N models - see my links below or HOW TO - CARB SYNC / BALANCE - MANY PICTURES - CBR Forum - Enthusiast forums for Honda CBR Owners & YouTube - ‪CBR1000F - L (1990) CARB SYNC BALANCE 2‬‏
• 1000 P models onwards - Farkles

I hope this clarifies for all.

You can see from the highlighted text above, carb 1 - closest to the fuel petcock, the vacuum line GOES to the petcock. Carbs 2 and 3 have rubber covers, and Carb 4 has a screw and washer.

Cheers, SB

 

Thank you for the information. I just wanted to make sure it is an extraneous item. My question has been answered.

 

Exactly! Unless you plan on opening a vacuum operated fuel petcock, its not needed and should be sealed.

 

So winged and yeah I'd agree - no vacuum actuated petcock so no need for that port
to be open