Topic: carb options ???

[trueblue]

I'm doing a go fast project on my 650z, it's going to be an as funds allow project, I already have a NOS 61mm wiseco kit, according to an old wiseco catalogue a mate of mine has it gives 10.25:1 compression ratio.  I'm planning on sending my head to MReick to get some port work done.  I went for a drive out to the local bike wreckers today to look for some other options for carbs, he had a set out there off of an 81 GS650E screwsloosy, they are 32mm minkuni CV style, they line up perfectly with the ports on my head, I was wondering if anyone has had any experience with putting these carbs onto a Honda 650.  The other question is will these carbs be too big for the honda which only had 26mm carbs on it standard.  I'm a mechanic by trade, so I know my way around an engine, but have never really played with engines to make more power, so I'm not really sure on what will work in these regards.

[turboguzzi]

not a bad idea, but just take into account that CV's dont flow as well as good old round slide carbs

back at the time, when CV's broke into the scene, it was sort of common to assume that for same nominal bore, say a 26mm slide carb vs. a 26mm CV, a CV would flow about 20% less. That means that your nice 32mm CV's equal about 26mm slide carbs in flow potential. makes sense, both bikes are 650's.

Would try look for at least 34's CV's (maybe from a Gpz600R) if I was going that route, but if I was you, i'd look for GS750 26 VM slides (actually 27's) that have quite good flow.

If you have more money to burn, then of course there are the big 900-1000 kawi 28-29's and Keihin CR's.

TG

[Tim2005]

I agree, if you are after performance then 32mm may be too small - for instance Rudi on here is running 31mm CV's on his 460/4.

[trueblue]

Gpz600r carbs are 32mm anyway and the Keihin carbs have issues with the diaphragms going to holes, which the doesn't seem to be an issue as much with the Mikunis.  I'm not trying to achieve crazy amounts of performance on this build, but I thought this would be the best place to ask these questions because I have found on the other boards of this forum there are a lot of people who think they know what they are talking about, whereas on this board most people seem to have an idea what they are on about.  Even though they both say 650 on the sticker the GS650e zuke is actually 673cc, compared to 626cc in the Honda, and produces an advertised 73hp compared to the advertised 63hp of the Honda.  How accurate these numbers are I don't know, I believe these are crank figures not rear wheel HP.  I know the carbs aren't the only thing that give the increased HP in the Zuke but they are both 8 valve engines even though the suzuki is DOHC and it is also close to the capacity that my bike will be when done.  This bike will be used on the street not the track, and as such needs to be fairly civilised, what I'm trying to achieve is a bike that goes like a dog shot in the ar$e but can still be comfortably ridden with the missus on the back and handle a few long jaunts down the highway.  From what I have read and been told the CV's help achieve this result, but if I'm wrong please correct me. 

[turboguzzi]

yep, you are right, the 34's i have here were off a 750, not a 600... too much parts lying around, too many bikes taken apart

but at the end of the day, for the type of tuning / riding you are planning, CV's are a good idea, just take into account that if you do need to go into re-jetting, different needles will not be easy to find compared to a set of CR's for which SUDCO will have everything on the shelf.

good luck with your project!

[trueblue]

Hey TG stop bragging, you wouldn't happen to be able to provide the measurements for those 34mm carbs by any chance.  These are the ones I need.
depth (front to back)      -
OD (motor side)              -
OD (airbox side)              -
#1&2 and 3&4 (c to c)     -
between2&3  (c to c)      -
The only problem with CR's is I don't think my wallet is fat enough to accomodate them.

[turboguzzi]

Hey TG stop bragging, you wouldn't happen to be able to provide the measurements for those 34mm carbs by any chance.  These are the ones I need.
depth (front to back)      - 112
OD (motor side)              - 40
OD (airbox side)              - 55
#1&2 and 3&4 (c to c)     -75
between2&3  (c to c)      - 95
The only problem with CR's is I don't think my wallet is fat enough to accomodate them.

now that i measured them i noticed that these 83' Gpz750F carbs are actually mikuni's

[trueblue]

Thankyou very much TG, everything was looking good for a match up with my head except the 2-3 measurement is 14mm too wide, so it would take a little creative thinking to make it all fit as 1-4 would also be too wide, I know the GPZ600 boots are offset a little so they may do the trick.