CafeAddict
CB750 New member
Hi,
New to the forum, but have done a couple of rebuilds before, so not a complete newbie. I have three projects at present; Cx500 Cafe, Thruxton 2008 Cafe and now a 1975 CB750. The engine number suggests it is a K5, but the livery suggests it is a K2 as it doesn't have the K5 decals, etc.
The CB750 is in very 'original' condition (even has original owners manual under the seat) - only one owner and due to him aging and passing it on to other family members has not been running for approx 5 years. It has 30,000km = 20,000 miles. It does have a 4n1 exhaust, although I am not sure of the brand. If anyone recognises it in the pic, I would be pleased to find out....
I did get it started, but wouldn't idle and one carb was leaking fuel out of the bowl. So the carbs need a rebuild. As it will cost me approx A$150 plus a lot of time to rebuild the original carbs, I am considering upgrading to aftermarket carbs to get the 10% to 20% performance improvement, etc, etc.
So, I am tossing up between the Mikuni RS34 and Keihin CR29. Although the bike is stock 750cc at present, I will want to install a big bore kit at a later date to either 836cc (most likely) or possibly to 915cc. So I want to make sure that if possible, I buy carburettors now that will work well with both the current 750cc engine as well as a future big bore kit. So I am not replacing the carburettors in 2 years time.
Does anyone have any experience to enable some comparison between the two carbs? For example, I heard the Mikunis have some binding on a trailing throttle? I also heard that CR29s are actually faster than CR31s, especially for stock engine and road or non-race applications.
I have seen some other posts, but typically low on detail and without any comparison. Some just like the Keihins, while others like the Mikunis. One big benefit for me is the Mikunis are much cheaper, which makes a bigger difference in A$. But i gather the Mikunis have a rectangular body, so don't retain the 'stock look'.
Does anyone have any other recommendations or advice?
Many thanks
New to the forum, but have done a couple of rebuilds before, so not a complete newbie. I have three projects at present; Cx500 Cafe, Thruxton 2008 Cafe and now a 1975 CB750. The engine number suggests it is a K5, but the livery suggests it is a K2 as it doesn't have the K5 decals, etc.
The CB750 is in very 'original' condition (even has original owners manual under the seat) - only one owner and due to him aging and passing it on to other family members has not been running for approx 5 years. It has 30,000km = 20,000 miles. It does have a 4n1 exhaust, although I am not sure of the brand. If anyone recognises it in the pic, I would be pleased to find out....
I did get it started, but wouldn't idle and one carb was leaking fuel out of the bowl. So the carbs need a rebuild. As it will cost me approx A$150 plus a lot of time to rebuild the original carbs, I am considering upgrading to aftermarket carbs to get the 10% to 20% performance improvement, etc, etc.
So, I am tossing up between the Mikuni RS34 and Keihin CR29. Although the bike is stock 750cc at present, I will want to install a big bore kit at a later date to either 836cc (most likely) or possibly to 915cc. So I want to make sure that if possible, I buy carburettors now that will work well with both the current 750cc engine as well as a future big bore kit. So I am not replacing the carburettors in 2 years time.
Does anyone have any experience to enable some comparison between the two carbs? For example, I heard the Mikunis have some binding on a trailing throttle? I also heard that CR29s are actually faster than CR31s, especially for stock engine and road or non-race applications.
I have seen some other posts, but typically low on detail and without any comparison. Some just like the Keihins, while others like the Mikunis. One big benefit for me is the Mikunis are much cheaper, which makes a bigger difference in A$. But i gather the Mikunis have a rectangular body, so don't retain the 'stock look'.
Does anyone have any other recommendations or advice?
Many thanks