Mikuni VM 29's or RS 34's or Keihin 29's

Ive had both the 29 & 33mm smoothbores on my 1105 and much prefer the 29s for everyday riding. Wide open its a tossup

I have RS34 carbs on my 1075 with andrews 2x cams and they absolutely haul on the top end, but they are definitely "fluffy" if not downright boggy below 5k. A big handful below that speed will get you a bog and a leap.

Basically, I would stay away from them for most street riding, unless you are running a setup that can REALLY flow some serious air, like a ported head with big cams.

On the plus side:

They are great for getting on down the drag strip, when you are really on it and keeping the r's up

They are very easy to tune, being very forgiving with jetting, and the accelerator pump works well to cover up most of the serious sins of overcarburation.

-Dave

mtkawboy wrote:

Ive had both the 29 & 33mm smoothbores on my 1105 and much prefer the 29s for everyday riding. Wide open its a tossup

Do the 33's lack bottom end/midrange? Ive been seeing them go for ALOT less than the 29's and am kinda curious why that is..

I have the RS34s on my 1105 with stock cams and have great response through the range. Whack the throttle past 3K and the front end lifts. Maybe yo have a jetting issue?

"Do the 33's lack bottom end/midrange? Ive been seeing them go for ALOT less than the 29's and am kinda curious why that is.."

Here's how it was explained to me by Larry C and Buzz @ Dynoman...

Larry C:
Head porting for CFM flow... Unless your build over a 1075, .385 or larger cams you'll just not be happy with the low to mid range results... 3/4 to WOT, yeah you'll feel the difference no doubt.

Bigger is not always better... Depends on your engine build and riding style.

Buzz:
Almost 100% the same as Larry, "Word for Word", was kind of eerie as they where reading off the same card....:blink:

Anyhow, Buzz added... "I'll sell you what ever you want for they're ~ the same price but for what I had described in riding style and desired performances low to mid range and for what I had in mind on my mild performance build, go with the 29mm"....

He also added that the Miks are a great carb but they are a racing carb! Basically meaning 3/4 to WOT! Unless your truly riding in this range, you'll just be pissing in the wind...

Now if mikuni was smart enough to manufacturer a 29-31mm carb, may have gone that way as well, who knows but they don't....

In answering your question, the PO most likely didn't like the results they were receiving off the larger carbs in their build configurations and are letting them go cheap...

Damn, that was an expensive lesson for them to learn....:ohmy:

OMR

Since we have all added our two cents I concur with everyone. For a stock setup the 29's are what you want. 34's are too big unless you have the head worked nice and some big cams. Big cams lessen chain life and valve springs so if you don't like taking apart your bike every 10k to replace those things then I suggest you stay with your 1015 and 29's vm's make a big difference over the 26's but the crs are a guaranteed thing and yes 34 miks are better than the crs but they don't make them smaller so that is what the choice you should make would be cr. They are better than the 30 year old 29s
I opted for the 31's cr I have a 1075 with .410 cams and had 29's and took them off. Carbs that are 30 years old will not run as good as new ones with newer technology. The crs are much easier to setup and tune than those 29s.
For the price I would go new rather than old with the potential of getting a set that don't function as they should. They have moving parts that do wear after time slides you know don't last forever. And while you can replace stuff on the old ones if you have to pay new prices then buy new carbs and be done with it. You will have to buy new pods of course as I think the diameter is bigger on the outside than the vm 29's
On a side note. The exhaust note changing from a set of 28's to 29 crs is much different and sounds downright NEWICE and the throttle response is crisp.

How are the 31's on your bike vs. the 29 smoothbores??

In my opinion we are looking for improved airflow. This thing is designed like a musical instrument with the opening smoothly tapered as opposed to the more blunt and abrupt change in the miks. I think 30 years of improvements is a good thing and if they made new 29 mikunis I would opt for those instead but they don't so I got these instead.

Well the shape alone on the crs sucking the air much smoother. I have my bike completely apart at the moment, doing a complete rebuild. I have the frame sent to powdercoater and the cases are all apart getting powdercoated as well.Going to get the tapered bearings and a two inch over swing arm. All black stainless braided lines and I'm rebuilding and anodizing the calipers and basically going apeshite with it. The top tree I will polish and have it anodized black.
Since my chain went from virgin status to loose after three sets of twins I decided to get the crank knife balanced and welded and thinking about having the gears back cut.
So to make a short answer long no I have not yet tried them on my bike but my buddy switched his and I noticed on his stock motor a whole different sound and attitude which thereby promptly persuaded me to make the switch. His bike sounded mean and the bike idled like butter. I thought it was impossible for these old dogs to idle so smoothly. He smoked the tire coming off and said that the bike launched much noticeably harder so he convinced me by showing me the results. No one had to tell me differently. So off with my 29s which I liked and onward and upward with the new carbs. I'll post pics of the progress as it comes along. If you look at the rat that I bought to now with my pics you can see I have done quite alot to her in just a short time.

Didnt you go from vm29's to 31 mm crs? Any noticeable power difference??

will61310 wrote:

Didnt you go from vm29's to 31 mm crs? Any noticeable power difference??

Apples to apples. I wouldn't even try to compare any different. 31's are going to provide more juice for sure. I think you would be happy with 29s unless you are going to do some headwork and put bigger valves and cams. I think I went overboard with my setup for the street but I can say that 29s over stock on the stock motor the 29s are noticeably different in many ways. Much better than 26's or even 28s with the pumpers but for sure 26's
I couldn't begin to tell you honestly with my setup as it will be different with yours. But 29s for stock I have heard since I was 16 over 24 years ago that those were the hot setup for that stock motor. If you plan on going larger later then maybe opt for the 31's 34's are way to big for stock motor and no head work.
Try a vance and hines pipe with a comp baffle and the baffle alone will make a big difference. Man! The baffle when I experimented open closed and then decided to try the comp baffle. Woh is all I have to say.

saxjonz wrote:

will61310 wrote:

Didnt you go from vm29's to 31 mm crs? Any noticeable power difference??

Apples to apples. I wouldn't even try to compare any different. 31's are going to provide more juice for sure. I think you would be happy with 29s unless you are going to do some headwork and put bigger valves and cams. I think I went overboard with my setup for the street but I can say that 29s over stock on the stock motor the 29s are noticeably different in many ways. Much better than 26's or even 28s with the pumpers but for sure 26's
I couldn't begin to tell you honestly with my setup as it will be different with yours. But 29s for stock I have heard since I was 16 over 24 years ago that those were the hot setup for that stock motor. If you plan on going larger later then maybe opt for the 31's 34's are way to big for stock motor and no head work.
Try a vance and hines pipe with a comp baffle and the baffle alone will make a big difference. Man! The baffle when I experimented open closed and then decided to try the comp baffle. Woh is all I have to say.

i had the vance and hines with comp baffle.....not bad...i pulled the baffle, took all the insulation off it, and stuffed the metal core back in....now we are talking.....gotta flow way better and surprisingly not too obnoxious....i tried it with nothing in it and it was just plain unrideable..popping bad on decell...with just the core in it, its just a tad louder than comp baffle and no backfiring on decell(if jetted right).....