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I searched through the old post but didn't find any info on jetting mikunis for a 450. I'm ditching my CV carbs for some 32mm VMs.

Do you have to rejet them and if so, what sizes do I need?

 

[UngaWunga]

My mains are 195's. Not sure about the needles, needle jets, or pilots.

 

[ohiocaferacer]

Try checking out this link on my website. There is some info for setting up Mikunis.

http://www.ohiocaferacers.com/MikuniJetting.html

Later,
Greg
www.OHIOCAFERACERS.com

Edited by - ohiocaferacer on May 26 2006 07:15:21 AM

 

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cool, thanks guys! UngaWunga, are you running 32mm or 34?

I'm going to use the recommmendations listed for the CB350 since it has the 32mm listed.

 

[UngaWunga]

32mm roundslides.

I also have a Dyna Gl1000 ignition on mine, but that shouldn't affect jetting much as I'm still using the stock coils.

When we ran the 450 on the dyno, it made the most power with the 195 mains. Anyone know what a good HP number is for these bikes? According to Pete's dyno, mine only made 30hp (no adjustments for temp or humidity). I'm thinking my exhaust is too restrictive.

I should probably do a compression check to see how the rings are doing.

 

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I'm running the GL1000 dyna and stock coils as well. according to my old stat sheet, the 450's put out 45bhp @ 9000rpm. The word "claimed" is also right before those stats.

 

[nf343vr]

I run 32mm VM Mikuni carbs on my CB 450 Race bike, spent lots of time trying to figure out the jetting and now have the bike running well. I have a smooth idle, no serious dead spots and great top-end! I am using the stock jet needle and needle jet that comes supplied with a new VM 32mm (you can look it up on Sudco or Pro Flows sites) and I believe I am in the third (middle grove with the clip). I am currently running 160 mains and 37.5 pilots. I started around 180s and kept going up. At one time I was up to 220 mains and the bike was terrible and getting worse. I finally realized I was going in the wrong direction. I may even try even smaller mains say 150 or 145. I must mention that I have made many other mods to the engine that may not relate to what you are doing. I have a +3mm piston kit (483 CC by my math) did some mild porting, added about a 40mm aluminum manifold extension, machined in two more spark-plugs and machined the intake cam to accept an exhaust cam sprocket so I could adjust the cam timing. The bike rips! But remember, the right way to go with jetting may be opposite of what seems logical. That is, increasing the displacement while using the same carb may mean you have to decrease the mains instead of increase them due to greater differentials in pressures and greater velocities in the venturi. Maybe the stock 444ccs would run better with 175 mains for example. Who knows!! Good luck with your project, and, by the way, I put VM22s on my 160 and not having the best luck getting them to run right, any Ideas?
Kevin.

KCampbellNH

 

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I installed the Mikunis this weekend. I thought my pod filters would work but they're way to small. Are you guys running filters or stacks?

Thanks for the advice about the mains and pilots. I'll order a few misc sizes and see what works best.

One thing I noticed is that the slides are open quite a bit with the throttle closed. I didn't see away to adjust the slide height besides the cable adjusters which are spun all the way in. Am I must missing something obvious?

 

[UngaWunga]

Yup, the big gold colored idle adjuster screws on the side of the carb.
Make sure they're even, and then use the cable adhjusters to make sure that the throttle pulls the slides up evenly. Do that by opening the throttle so that one slide is open the other way, then look at the other side to make sure its also open all the way.

My jetting is almost spot on. The bike starts easily, and the 1/2 throttle to full open work great. I have a stumble at 1/4 throttle that I need to figure out. I think the problem is caused by the size of the shield on the primary needle jet I'm using (these carbs were set up originally for a RD350).

http://www.sudco.com/cat32/56-58.pdf

Once the slide clears the needle sheild (1/2 throttle) the bike stops stumbling. Feels like a rich condition.

 

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Cool, thanks! I figured it was something right infront of me. The mikunis are definitly a bit of a change from the stock CVs. How did you guys get around the pain in the ass choke set up? Definitly not easy to undo the choke on the right carb.

I found a set of K&N tube style filters that I'm thinking about using. They're 57mm but the intake measures about 57.5mm if I remember correctly.

 

[UngaWunga]

quote:
Cool, thanks! I figured it was something right infront of me. The mikunis are definitly a bit of a change from the stock CVs. How did you guys get around the pain in the ass choke set up? Definitly not easy to undo the choke on the right carb.

Choke: take off the exhaust valve cover, counter sink the lower 4 bolt hole so that they sit flush to the cover, and use tapered allen head bolts instead. That'll give you enough room to install the carbs with the choke levers intact.

I don't need choke to start mine.

For the K&Ns, I just picked some out of the Parts Unlimited catalog that fit the carb mouths and the frame. Get the biggest ones that'll fit.

 

[UngaWunga]

Still a little rich...

[video=google;6875380637568407259]http://video.google.com/videoplay?docid=6875380637568407259[/video]

 

[UngaWunga]

So, took the carbs apart tonight. Here's the line-up:

VM-32
Needle jet: 159 Q-6
Main jet: 195
pilot jet: 35
air jet: 2.0

The needle jet is WAY too rich. Its also a primary choke type, not a bleed type. http://www.sudco.com/cat32/56-58.pdf
That big shield covers the needle until past 1/4 throttle I think, and it might be causing my stumble problem. Once past 1/4 throttle, it seems to run ok, but still a little rough.

I should at least go to a 159 Q-2 or 159 Q-4 if I stick with the primary type needle jet. According to my handly dandy Sudco tuning manual, that'd be equivilant to a 176 Q-2 or 176 Q-4 bleed type needle jet.

Anyone know how the two different needle jets work? Which one will work better in my situation? I know the primary needle jets are commonly called two-stroke jets and the bleed type a four stroke needle jet. But I have no idea why...

 

[UngaWunga]

Hmmm.... I shoved a P-2 needle jet in there, and the bike would start (pilot jets are correct), but any throttle and the bike died.

So, I'm guessing that this is way too lean. When a four stroke stumbles (four strokes... lol), is that lean or rich?

The reason why I thought I was rich was because I was seeing some black smoke at part throttle with the Q-6 needle jets.