TOPIC:

wrote:

Thanks to everyone who posted comments, I have owned ten z1's but never had a set of these carbs and know nothing about them.

New in 1979 I paid about 300 Bucks for my 29s

$300*6 = $1800 (today) so they were expensive back then.

 

Actually, $300 in 1979 = $1,148.55 today.  And that's just about what a really nice set that's been restored to new condition is worth.  

 

Love my 33's now I have them dialed in.
Steve

Being an old man and having many kz's with 29s and accell coils,kerker header and derale oil cooler back then was the shit.I have a restored set of 29s waiting for my next project.

I sold my 29vm and bought rs34. had money left over. never looked back.

So the Z1/900/1000 came with 26 or 28mm carbs, but the 29mm were the cool period upgrade. These days it's pretty common for folks to run RS34.  That seems like a pretty big jump from 26mm to 34mm.

I know the 80s bikes went to BS34 carbs, but my impression was that CV carbs avoid bogging and lean condition when whacking the throttle open by controlling the slide with vacuum.  And they had better flowing heads too.  I believe the RS34 is still a slide valve carb like the VM or CR series, just with a different shaped slide.  It seems like it behave similarly to a the VM (or the VM with accelerator pumps), but likely with more flow for a given size.

Lots of sources say that using a carburetor that is too large will give poor low and mid speed performance.  How is this problem avoided with the RS34?

Do folks go with the RS34 just because it's the smallest size available and just make it work?  Do you need a built or bored motor for them to work well?  

Hmmm....  Poking around a bit, it seems like there are some rules of thumb to estimate carb sizing if you know the CFM of the carb.  Anyone know the CFM for an RS34 and VM29? 

performanceimprovements.com/blogs/news/c...carburetor-do-i-need
 

I am not an expert on this subject, but from what I've read, the RS34 performs much like a VM29.  Your questions are good ones, and I can't answer why, though.  

I have a set of RS34 carbs that went on my 831cc 650 this summer, they ran very well only because the motor has been built to flow lots of air.

I am currently building a KZ1000 motor for another project, it will use MTC 1197 pistons, thought I could use the RS34 carbs on that build but the guy doing my cylinder head (porting, big valves) suggested using VM33 smooth bores if I could find a set at a reasonable price. With that built 1200 motor he said the RS34 would be too small and he has built similar motors using the VM33 carbs. He said they seem to work better on motors over 1200 when they are ported and big valved. For a flat slide he suggested at the minimum the RS36.
The vintage road race guys seem to have plenty of VM29/VM33 carbs so that is a good source to look to buy them.
VM33's are on the way.

wrote:

I have a set of RS34 carbs that went on my 831cc 650 this summer, they ran very well only because the motor has been built to flow lots of air.

I am currently building a KZ1000 motor for another project, it will use MTC 1197 pistons, thought I could use the RS34 carbs on that build but the guy doing my cylinder head (porting, big valves) suggested using VM33 smooth bores if I could find a set at a reasonable price. With that built 1200 motor he said the RS34 would be too small and he has built similar motors using the VM33 carbs. He said they seem to work better on motors over 1200 when they are ported and big valved. For a flat slide he suggested at the minimum the RS36.
The vintage road race guys seem to have plenty of VM29/VM33 carbs so that is a good source to look to buy them.
VM33's are on the way.

VM33's are famously difficult to tune on the low end.  With a 1200cc engine it should be possible to make them work, but the RS family carbs would save a lot of time tuning.

I have two VM29 sets, one with the accelerator pump and one with no pump. I ride with the pump at the moment on my Z and it works very well. In the beginning problem to tune but after replacing the choke plungers and cleaned every thing they run like hell. 

wrote:

wrote:

I have a set of RS34 carbs that went on my 831cc 650 this summer, they ran very well only because the motor has been built to flow lots of air.

I am currently building a KZ1000 motor for another project, it will use MTC 1197 pistons, thought I could use the RS34 carbs on that build but the guy doing my cylinder head (porting, big valves) suggested using VM33 smooth bores if I could find a set at a reasonable price. With that built 1200 motor he said the RS34 would be too small and he has built similar motors using the VM33 carbs. He said they seem to work better on motors over 1200 when they are ported and big valved. For a flat slide he suggested at the minimum the RS36.
The vintage road race guys seem to have plenty of VM29/VM33 carbs so that is a good source to look to buy them.
VM33's are on the way.

VM33's are famously difficult to tune on the low end.  With a 1200cc engine it should be possible to make them work, but the RS family carbs would save a lot of time tuning.
 

That might be true, don't really know as this will be my first set owned. I am probably going to rely on big CC and more HP on the bottom end to pull me thru any low end issues. Expecting motor to be at 120HP/80FTLBS of torque on a low end estimation, the guy that suggested them has less luck with carbs than I do and his similar motor ran fine (his a bit wilder than my setup head/HP wise (~150) but still a street bike. He is giving me his jetting notes so I can me fairly close on first start.
All those GS1100/1150 guys can't be all that wrong about the 33's.
 

wrote:

wrote:

wrote:

I have a set of RS34 carbs that went on my 831cc 650 this summer, they ran very well only because the motor has been built to flow lots of air.

I am currently building a KZ1000 motor for another project, it will use MTC 1197 pistons, thought I could use the RS34 carbs on that build but the guy doing my cylinder head (porting, big valves) suggested using VM33 smooth bores if I could find a set at a reasonable price. With that built 1200 motor he said the RS34 would be too small and he has built similar motors using the VM33 carbs. He said they seem to work better on motors over 1200 when they are ported and big valved. For a flat slide he suggested at the minimum the RS36.
The vintage road race guys seem to have plenty of VM29/VM33 carbs so that is a good source to look to buy them.
VM33's are on the way.

VM33's are famously difficult to tune on the low end.  With a 1200cc engine it should be possible to make them work, but the RS family carbs would save a lot of time tuning.

 

That might be true, don't really know as this will be my first set owned. I am probably going to rely on big CC and more HP on the bottom end to pull me thru any low end issues. Expecting motor to be at 120HP/80FTLBS of torque on a low end estimation, the guy that suggested them has less luck with carbs than I do and his similar motor ran fine (his a bit wilder than my setup head/HP wise (~150) but still a street bike. He is giving me his jetting notes so I can me fairly close on first start.
All those GS1100/1150 guys can't be all that wrong about the 33's.

 

Fortunately, the 33's are much cheaper than the 29's.  It's still going to set you back about $600 if purchasing on ebay.  Then you get to spend more and replace all the old O-rings and gaskets.  A set of RS36's sell for about the same amount, and since they are newer you shouldn't have to spend as much time refurbishing them.

And regarding the GS1100's, this thread may help you since the owner used VM33's on his Katana 1100.  He had to jump through hoops to get it to run right, but he got it in the end and posted most of his carb jetting information.

www.thegsresources.com/_forum/showthread...697-1984-Katana-7-11

Got them for $450 Canadian off a local road racing guy. I think they just need a good cleaning, hopefully nothing to replace but have not tore into them yet.

Thanks for posting that link.