Mikuni 28mm vs 29mm smoothbore

I purchased a 1978 kz1000 ltd. with no coils,no seat, and carburetors that eventually I am going to fix up, I know these bikes came with Mikunis 28mm smoothbores, what I like to know is how much better performance will I get with the 29mm smoothbores. Thanks for the help.

A bunch...most serious KZ guys are running them.

They are bigtime money.....$500 to $700 plus If you have to do a total rebuild....could go over $200 in parts.

been there done that...... :sick:

Most 1978 kz 1000 came with 28mm carbs but were not smoothbores. The only difference you will notice is better mid range to top end power with the rest of the bike pretty much stock. Pods and a header will help no doubt but if your looking for 10 or 15 hp, need a good cam and a hell of a tune-up. The smoothbores will track a little better if you jetting is spot on. The 28 mm carbs had a lean symptom from 2000 to 5000 that could be corrected with a needle change (5dl31) using 3rd position on the clip. Happy tuning.

1978 LTD should have come with 26mm non-smoothbore carbs. For the record, the 28s are not smoothbore either. If you have 26s then the smoothbore 29s make a big difference. I have never run 28mm carbs on my bike so I don't know how much difference the 29s make from the 28s. That is, if you do have 28 mm carbs now. Keep in mind that there are a few different varieties of 28mm Mikunis.

IM going to agree with you on this one. The ltd did come with 26's So compared with 29's you will get a noticable increase in power.

The 77-78 kz 1000 a1 and a2 came with plain old 26mm mikunis,basically same carbs as the 76 900a4/b1.
78 z1r may have came stock with 28s,cant remember off top of my head.
The 79-80 kz/mkII had 28mm carbs ,I think the ltd got them in 1980.
Anyway the 28 carbs from are just standard vm series carbs just bigger versions of 26s with accel pumps,theyre good carbs.
Unless you've got a good set of 29 smoothbores sitting on a shelf the prices to buy used ones are right up there with new carb prices

Yeah like going from a two barrel to a four barrel on a smallblock V-8.

wireman wrote: The 77-78 kz 1000 a1 and a2 came with plain old 26mm mikunis,basically same carbs as the 76 900a4/b1.
78 z1r may have came stock with 28s,cant remember off top of my head.
The 79-80 kz/mkII had 28mm carbs ,I think the ltd got them in 1980.
Anyway the 28 carbs from are just standard vm series carbs just bigger versions of 26s with accel pumps,theyre good carbs.
Unless you've got a good set of 29 smoothbores sitting on a shelf the prices to buy used ones are right up there with new carb prices

BTW I completely agree with this statement. If I didn't get a screaming deal on my 29s then I would have bought new carbs.

Wireman is correct

78 LTD 1000 did come stock with 26mm The 29 smoothbore really woke up the bike with or without a good pipe. Pipe just made it even better ( Voice of personal experience)

78 Z1R came with 28mm carbs

testarossa wrote: Yeah like going from a two barrel to a four barrel on a smallblock V-8.

It depends on which 2 barrel youre talking about,some of those old rochestor 2 barrels were huge! :woohoo:

testarossa wrote:

wireman wrote: The 77-78 kz 1000 a1 and a2 came with plain old 26mm mikunis,basically same carbs as the 76 900a4/b1.
78 z1r may have came stock with 28s,cant remember off top of my head.
The 79-80 kz/mkII had 28mm carbs ,I think the ltd got them in 1980.
Anyway the 28 carbs from are just standard vm series carbs just bigger versions of 26s with accel pumps,theyre good carbs.
Unless you've got a good set of 29 smoothbores sitting on a shelf the prices to buy used ones are right up there with new carb prices

BTW I completely agree with this statement. If I didn't get a screaming deal on my 29s then I would have bought new carbs.

And if you need jet blocks or any other odd ball stuff made for 29s Testarossa is da man!

Never no luck with smoothbores. I just bought and sold a set that were good but I don't need $500 carbs on a stocker Kz. Joy riding is Ok with me I'm not racing anyone. Beside any punk on a new 600 rocket will blow a kz away.
I opted for 28's paid $100 and my buddy gave me some velocity stacks. Needle on the 4 clip 120 main jets 20 pilots seemed to test ok w 14x35 sprockets.Weather finally went to crap o la around here
think spring