KZ1000 MkII (A3, 1979) aftermarket carb sizing advice

[JamesH_Sussex]

Afternoon chaps.

I’ve managed to acquire an original, low mileage 1979 KZ1000 MkII just after the owner started stripping her for spares.

She’s complete aside from the original body set and original VM28 carbs.

I’ll probably end up sourcing a new body set from PmC/Doremi but wondering what the general concensus is on correctly sized aftermarket carbs for a stock bike with stock exhausts.

I’m thinking something along the lines of Mikuni RS34’s which from the research I’ve done seems to be the best bet for a stock bike?

Any advice / input from those of you that have been there / done that would be really appreciated.

[Pigford]

RS34 will be ideal

[JamesH_Sussex]

RS34 will be ideal

Awesome thanks for the quick reply.

Anyone else have any experience running RS34’s on a MkII?

[Ultim8pc]

Not restoring to standard James?

[Ultim8pc]

I've seen a NOS tank advertised for 1200Euro!

[zed1015]

The stock 28mm carbs are plenty for a stock motor and exhaust and still give good results even with a port job and open pipe etc.
34mm slide carbs are overkill and really the largest you would need for any state of road tune.
If going for a 4-1 pipe, cams and pods etc at a later date then 29 or 31 smoothies will let it breath better at top end without sacrificing bottom end tractibility.
Sticking RS34's on your stock motor is a waste of time and money.
Bigger is not always better.

[8 Valve Mark]

i agree about the 28mm carbs, they're more than enough, BIG saving over rs jobbies too, I'd go for 28mm pumpers.. m

[JamesH_Sussex]

The stock 28mm carbs are plenty for a stock motor and exhaust and still give good results even with a port job and open pipe etc.
34mm slide carbs are overkill and really the largest you would need for any state of road tune.
If going for a 4-1 pipe, cams and pods etc at a later date then 29 or 31 smoothies will let it breath better at top end without sacrificing bottom end tractibility.
Sticking RS34's on your stock motor is a waste of time and money.
Bigger is not always better.

Really useful, specific feedback, many thanks.

The problem I have is the original carbs to the bike have been sold, along with the body set. Long story short, I bought the original seat from the seller and then it became apparent he was breaking a lovely original bike - by the time I'd agreed to buy the bike he'd sold the body set and carbs.

My concern is finding a correct, decent set of VM28ss's with the pumper/enrichment circuit in perfect operating order without an off-idle stumble. The last MkII VM28ss carbs I did were a total nightmare - I probably sank ~ 20-25 hours into getting them right and really don't want the hassle again :-).

The big attraction with buying a new 'virgin' set of carbs is knowing they are properly clean from the outset, and can be adjusted to perfection to suit the bike. Or am i chasing an impossible dream lol?

[zed1015]

The problem I have is the original carbs to the bike have been sold.
My concern is finding a correct, decent set of VM28ss's with the pumper/enrichment circuit in perfect operating order without an off-idle stumble. The last MkII VM28ss carbs I did were a total nightmare - I probably sank ~ 20-25 hours into getting them right and really don't want the hassle again :-).

Ok. if using pods the off idle stumble is caused by a fuel drop just coming off the pilot circuit and is cured by fitting air corrector jets.
If you are set on a new set of slide carbs then go for the closest size to stock to keep the air velocity at the venturi up at low speed otherwise you get bottom end throttle lag.
29mm smoothies would have been the choice back in the day and properly set up they did make a difference but they are NA so 31mm's would probably be the closest you can get new.
I have Katana 1000 32mm Mikuni smoothies on my Z1R and they are more than enough with 1075 wiseco's and 1mm o/s valves.

[Philippe]

Hi James
find a set of VM28SS mikuni carbs, from an ST or from a MK2, they're the same exept for the main jets. (ST has 110, MK2 has 105) They're identical and not really hard to give an initial synchronisation. Use the workshop manual and follow it step by step. If done correctly your engine will run from the first time you fire it up!
What's the use of using 34 mm carbs when the ports in the cylinder head have a smaller diameter? If the ports and valves are adapted (made wider) it could have some sense, if not, it's useless.
GrtZ
Philippe

[johny brando]

Afternoon chaps.

I’ve managed to acquire an original, low mileage 1979 KZ1000 MkII just after the owner started stripping her for spares.

She’s complete aside from the original body set and original VM28 carbs.

I’ll probably end up sourcing a new body set from PmC/Doremi but wondering what the general concensus is on correctly sized aftermarket carbs for a stock bike with stock exhausts.

I’m thinking something along the lines of Mikuni RS34’s which from the research I’ve done seems to be the best bet for a stock bike?

Any advice / input from those of you that have been there / done that would be really appreciated.

Hi it's my personal opinion that if you want to detune your MK2 fit those 34's......... even 26mm carbs would perform better than those on a Std Mk 2. Save the agro find some 28's.

[JamesH_Sussex]

Many thanks for the feedback.

Looks like my future will involve rebuilding another set of VM28ss carbs then :-)....

Really appreciate the guidance.

James