28mm Mikuni Flatslides

[Heb]

I picked up a set of Mikuni 28s for a pretty good price and would like to try running them. I was running stock carbs with stock 25 pilots, stock needles on the middle clip and 320 mains and the plugs always looked good and felt like it was jetted well. Mods were FMF fattys with powercore 2 silencers, advanced timing +4 degrees, proflow with K+N and outerware, no lid, stock head shaved .030. Now I'm doing a rebuild and adding a set of VF2 reeds, aggressive dune ported cylinders, cool head with 19cc domes. The 28s came with needles that read 5f21. I have 25 and 27.5 pilots to try and 260 through 330 mains to try. Mostly I was wondering what needles I should try, since looking at the Sudco website makes me think the needles I have may be an outdated part #. I have done a search but these are not the most common carbs and I got some contradictory information, I'd really like to hear from someone else who is running them. Also they fit loosely in the stock manifolds and the stock clamps will not tighten enough, can I get away with using regular hose clamps on stock manifolds or do I need aftermarket manifolds. Any suggestions will be appreciated

[Yaxy]

Congrats on your purchase of the 28s. They are awesome carbs that I use on my RZ shee and my other shee. The needle you have mentioned is not the original needle that comes with those carbs. If I recall the needle is a 5DP39. If you would like you can call any Mikuni dealer and they will tell you.

 

Also I think you are going to rich on the pilot. Both my foll mod motors run a 20 pilot and they run rich.

 

As far as the mains go. I run 280 with the FMF's on the shee and 340's with Rockets on the RZ.

 

The ID on the 28 carb inlet flange is smaller than on the 26's. There are no smaller boots you can get. Back 10 years ago or so White brothers sold a sleeve that pressed over but no longer. Earier this year I went to a local machine shop and they made me 6 of them at about $20 a piece. They press right on and work great, no more slop and ripped boots.

 

Also, I run a airbox and lid so the jetting above may vary from what you need to use

 

Chris

Edited October 17, 2006 by Yaxy

[Heb]

Thanks Yaxy- Glad to hear someone else is having good luck with these carbs! So you are running the stock needle that comes with these carbs? It sounds like that may be a good place for me to start as well, thanks for the tip.

 

I will start off with a 20 pilot and see how that works with my set up too.

 

Sounds like you found a great solution to mounting these carbs, I may have to look into getting my hands on some adapters like the ones you had made. On the pro-design website it shows that they sell boots for their manifolds to fit 26-28 mm carbs, maybe they only fit stock carbs and Keihins? Actually I was hoping that I wouldn't have to spend too much to get these carbs woriking well, I was looking at them as a temporary step between stock and getting a set of bigger carbs. But maybe if they end up performing well and I like them I'll keep them for a while.

[Yaxy]

Heb

 

I am running the stock needles, 5DP39, and they work fine. When you order needles from a Mikuni Distributor make sure they send them regular mail If not, the shipping charge will be more than the damn needles costs. I have a pro design system and same issue with the boots. If you plan on running an airbox in the future the fit up between the large carbs, will be a pain. If you run pods than no issues. Also with larger carbs you may have to bend the shift arm or get reed spacers.

 

The sleeves I have make a big differences. Unfortunately to keep the costs down I bought 6 at $20.00 each instead of $40.00 each for 2. They are still alot cheaper then buying new intake boots every 6 months. Plus the 28 FS are great carbs and are relatively cheap. I have a new set coming in today and they only costed me $180.00 for the pair. For my application of riding they work really good and personally I feel as long as you are not strictly drag racing these carbs are the way to go!

 

Chris