GPZ1100 B2 Carbs

[jacobb]

Hey guys,

I'm running some 26mm smooth bore Mikunis on my B2 at the minute and am not quite happy with them... Does anyone have any suggestions about another type (I have contaced a guy about some 34mm CV Mikunis that were off a Kat), or does anyone have any lying about in the shed that they could be convinced to part with?

[Gosling1]

are you sure they are smooth-bore Mikunis ? These normally were available in 29, 31 and 33mm - not as small as 26 ? There are heaps of 26mm carbs floating around because most punters wanted the larger 28mm carbs.

26mm Mikuni carbs were found on the 1976 Z900A4 model - earlier Zeddies ran 28mm carbs. If you can bung up a picture of the carbs I can tell you what you are using.

The best conversion for old B-model 1100's are the OEM 34mm CV Mikuni's from a Z1000J model. They almost need no jetting changes at all to work fine on the 1100 B-model motors. You can use other 34mm CV's from other bikes ( like the Kat) - but you would need to check the jetting first to get them to J spec.

[jacobb]

Ok yeah my bad- they are probably not smooth bores... As you said Gos, I think they are 26mm Mikunis of the 1976 Z900A4 model, or even off an early GS750? Admittedly, they need to be cleaned, as they leak when i leave the fuel tap on... there's a huge flat spot just as you take off - I need to blip the throttle before I take off or I stall the bike. This in combination with the bike not idling well has made for extreme concentration and on the odd occasion embarrassment at the lights

[jacobb]

and from the other side

[Gosling1]

.... I think they are 26mm Mikunis of the 1976 Z900A4 model, or even off an early GS750? Admittedly, they need to be cleaned, as they leak when i leave the fuel tap on... there's a huge flat spot just as you take off - I need to blip the throttle before I take off or I stall the bike. This in combination with the bike not idling well has made for extreme concentration and on the odd occasion embarrassment at the lights ......

OK - I think you may have the GS750 carbs, here is a pic of a set of 26mm Mikunis from a 1976 Z900A4.




You can see in this picture - although the carbs look really similiar - there are some slight detail changes in the internal drillings ? There are some additional inner drillings on the carbs you have, which are probably specific to the GS750 jetting (if these are GS carbs - I don't have any good close-ups of much Suzuki stuff unfortunately...) - you can see these clearly right under the choke lever.

The flat-spot is a massive leaning out, due to the use of the pod filters. You can dial this out by richening up the idle mixture and fitting bigger pilot jets.......but its a bit of mucking around to get it right with these filters. Better bet by far, is get some Z1000J carbs from a wreckers, and fit those up heaps better performance all round, better fuel economy etc - money well spent.

[jacobb]

ahhh... ok then... Yeah, that kind of makes sense because I enriched the idle mixture a touch and it has helped... Enough to make my life a little easier - but now I will know what to do with my spare time, hunt down some z1000J carbs!

Thanks heaps for your help Gos!

[jacobb]

Yeah, actually I'm pretty sure they are from a GS750 - dad has one lying in bits and pieces in his shed they are pretty much identical (actually dads are in heaps better shape hmmmm.... )

[Gosling1]

no worries mate - good luck with it. If you do keep those 26mm carbs on the B1 for any length of time though - richen up the mixture right through - they were only designed for 900cc, not 1100cc, so they will likely be lean *everywhere* in the rev range......

[bonester]

With your pic there Gos I got a little tingle. Reminds me of the early scene in Stone where the dude starts the Z up...

[jacobb]

Hey Gos,

Do you whether the z1000j/gpz1100 34mm Carbs had two or four jets? I'm only asking this as two sets have come up on ebay... and I'm thinking about bidding on one. Is there any way to identify whether it came off a kwaka? Any ideas?

This is the link to the auction...

http://www.ebay.com.au/itm/Mikuni-34mm- ... 3f12bdaec0

[Gosling1]

Most 4-cyl bike carbs have 1 each of individual jets or mixture screws for each individual carbie - so you will have 4 x pilot jets, 4 x main jets etc. ( One of my early z750 34mm CV carbs has 2 main jets circuits - a primary main and a secondary main - you don't want to get a set of these )

Not sure at all what that ebayer means when he says it only has 2 jets in front ?? sounds weird to me but you get that with some ebayers who know SFA about what they are actually selling.

A set of those 34mm CV carbs will do the business on your B2, but will need to be jetted properly. If you can get these for <$100, grab them. If not, save your $$ and get some dinkum Z1000J CV's.

Have you tried putting some feelers out on findapart.com yet ? Keith at Vic Wreckers is bound to have a set of J carbs.

[jacobb]

Yeah right, No I didn't try findapart... It sounds like a better option that trying to piss fart around with the jetting... Thanks again for your help mate

[Gosling1]

no worries - if you get stuck with jetting or anything just yell out

[jacobb]

Thought I'd give you an update Gos,

So I took your advice and chased down a set of KZ1000j carbs and an airbox. I disassembled them, cleaned them with an ultrasonic cleaner and rebuilt them with new rubber bits - and dropped them off to my mechanic to chuck them on and tune them. He pulled of the suspected GS750 carbs and the inlet size is 33mm and the outlet size is 29mm - do you reckon these are 29mm smooth bores?

Anyway, he reckons that they will come up good with a bit of jetting... So what do you reckon these 29mm jetted right or the CV 34mm?

[Gosling1]

The 34mm J carbs are heaps better for everyday riding. CV carbs give you good economy but still plenty of mumbo when you pull the pin. Jetting these should be pretty easy. I would probably go with these - especially if you are setting them up with an OEM airbox - this is by far the best way to set up CV carbs, it evens out the airflow into the carbies which is important for CV carbs....

29mm smoothies are better for racing or track riding. They still work OK for road work, but generally give you less economy than a CV carbie. They are designed to give really good response when you are on the gas.