Mikuni jetting

[firko]

I've fitted brand new 36mm Mikuni VM carbs to both my open class piston ports, the Cheney Yamaha RT1 360 and Boyd and Stellings Suzuki TM400. I've run either Bing, Amal  or Mikuni flange mount carbs for the last few years so I've fallen out of touch with the big body Mikuni's. Both carbs are identical, brand new and have the following jetting.
Main: 310
Pilot: 35
Needle: 6F
Slide: 2.5
I'll be spending next weekend at the farm to get them ready for CRC, CD10 and later the CMX Nats (if it happens) so is the above jetting a reasonable starting point? I've got most main jets from 240 through to 380 and a few different needles. I've also got a new 3.0 cutaway slide. Unfortunately I haven't got any spare pilot jets so in addition to the above question, can anyone recommend a few different sizes of pilot and needles that I may need? Would it be worth getting a 2.0 slide or perhaps a 3.5? I'm going to spend three days plug chopping and running in both engines....I want these bikes to be as crisp as a Jatz cracker before they get anywhere near a race track so any advice will be gladly accepted.   

[oldyzman]

Mark, The 35 pilot is way too small
I would start at 340 Main and 55 Pilot.
Pls note there are many more people on this forum much better qualified than myself to answer this question.
Brett

[tony27]

As an example for open class piston port bikes running the mikuni you have Firko, my 73 CZ400 has a 45 pilot & 280 main, needle jet & needle & slide are still the same yours. Seems that the needle & needle jet are pretty much on the money as fitted

[oldyzman]

So Tony thats a 36mm carb?

[tony27]

So Tony thats a 36mm carb?

It is, manifold a got off ebay had the stud spacings & bore size for the 36mm rubber mounting so that's what I bought to fit

[BETRIC]

Firko, my Yamaha MX360A runs the standard 34mm Mikuni carb with a 290 main jet, 70 pilot jet. standard needle ( clip in centre pos), standard slide, 32:1 fuel mix, did have 65 pilot but would run lean (running on) when hot, I use DT360A barrel (Greg Ball) ported to MX360A spec's, Webco head, Circle F pipe, runs very crisp. see you at the CRC  

[firko]

Thanks Dave......I seem to recall that reed valve engines and piston port engines had very different jetting requirements. I first discovered this when I fitted a 36mm Mikuni from a YZ400 to my 400 Maico Magnum. I'd assumed that the jetting would be in the ballpark but I ended up changing everything before it'd run well enough.....and eventually went back to a 38mm Bing (but that's another story). I'm assuming that there'd be a fair change between a 34 and 36 as well.....Yeah, looking forward to CRC.

[Slakewell]

Regarding jetting an old bikes. You cant jet your bike correctly with old worn slides and needles and tubes it just lets to much air in at the wrong time. Given that a new Mikuni are on ebay for under $200 there is no excuse

[firko]

Regarding jetting an old bikes. You cant jet your bike correctly with old worn slides and needles and tubes it just lets to much air in at the wrong time. Given that a new Mikuni are on ebay for under $200 there is no excuse

Absolutely. I've been through the used carby dramas....I've got a box full of 'em. Once I bought my first shiny new carburettor my world changed forever. My new 36mm were closer to $100 than $200 Micky, money well spent. I love Bings too but they wear in the slide area like all buggery so I'm going to bite the bullet and buy a new 38mm Bing type 54 for the upcoming 360 Oval Maico project. They're not cheap so I'd better start saving .   http://bingcarburetor.com/index.html   

[oldyzman]

So where are you buying the carb from Mark?

[Tahitian_Red]

I thought there were no more Bing 54's, just kits.  Email me the price list Firko. 

[firko]

So where are you buying the carb from Mark

I thought there were no more Bing 54's, just kits.  Email me the price list Firko

http://bingcarburetor.com/index.html    The link is in my previous post. As you can see on the website Red, the type 54 are listed but I haven't got a price, you can email them and they'll get right back. I'm assuming they're expensive based on a conversation with my cousin who recently bought a couple for his BMW R90. I can't recall the price but remember gasping when he told me .