Mikuni carburetor flow diagrams

[Snipescastle2]

Hello all, I would like to know if anyone has a flow diagram of the mikuni carburetors? Basically, I just want to know if the internal filter, if it's clogged or partially clogged,will this block both jets or just the high speed jet? common sense tells me it will block both, but I'm just curious. after siezing two engines, I found my internal filter almost completely clogged. I am removing the internal filter and installing a good, inline filter prior to the pump. I also have the black fuel lines, not those horrible grey ones, so I doubt they are washing trash into my carb.
the shop I had rebuild my engine told me to adjust the high speed adjustment crew 1/8 turn on top of the 1/8th that was already open, but that was before I found the filter clogged.they said I was having a lean condition and needed to richen up the fuel mixture,they told me to investigate my fuel system.
everything I have read here on the forum, says that adjustment screw needs to be closed, or 1/8th turn max. any suggestions? Just to let everyone know, I have two 2003 GTI LE's with 718 rotax, stock engines, mikuni super BN carbs (44) and no other mods.

[dsolie]

Re: Mikuni carburetor flow diagrams

The internal filter feeds both jet cavities..

I can't beleive that a shop would rebuild a motor without fixing the cause of the originals failure.. Shoddy work.. Carb rebuilds are supposed to go hand-in-hand with motor rebuilds.

[Snipescastle2]

Re: Mikuni carburetor flow diagrams

Dan,
I sent the motor to a shop in PA. I live in Missouri, so they only handled the rebuild, not the carbs. I assumed there wasn't a problem, and you know what happens when you assume.......well, that was a big mistake on my part, an expensive one. I am shocked that they are covering the warranty work.
It's been a learning experience, that's for sure. If I would have spent another $1,000 I could have had a new Bombardier engine, but the carb problem would have certainly wasted that engine too. I have a small claims case with the prior owner over all this as we speak, it's been nothing but a royal P.I.T.A that's for sure.
In hindsight, I will allways rebuild the carbs when rebuilding any of these engines, these two-strokes are a new thing for me. I have been rebuilding gas and diesel engines for 30+ years and this got the best of me.
I did have a similar situation before and not to ramble on, but I had just replaced a Cummins 6BT5.9 diesel in a 7 meter RHIB and it ran just fine in the shop, but would never plane out in open water, I replaced the injection pump, filters,injectors....everything.. but had same problem, fell on it's face. Started pulling every fuel line off and blowed them out, nothing,untill the last one.....when I got to the 90 degree fitting on the fuel tank, I pulled the suction line off, it looked like someone had stuck a cigarette in the line, it was like 3/4" long when I took a closer look. I went to pull it out and it crumbled. Come to find out, when the company that built this boat drilled the gas tank's inspection cover, they never vacuumed the shavings out and they wound up getting stuck in the 90 degree fitting (sharp turn radius) and all the dirt and sediment pulled in behind it. the fuel would get by at low speeds, but when you nailed it, it would choke off the fuel. cleaned out the tank, flushed the lines and refueled, it ran like a scalded dog.....

So, I should have spent a few minutes inspecting my fuel system before firing that engine for the first time.I have since checked the strainer, the fuel lines and the internal filter and once my rebuild kit arrives, I'm rebuilding the carb too.

So, the shop who did my engine work, did exactly that, the rest was a pre-existing condition that was unknown to them. my fault.

[dsolie]

Re: Mikuni carburetor flow diagrams

Gotcha... It's not a PMC is it?

[Snipescastle2]

Re: Mikuni carburetor flow diagrams

Dan,
Had the work done by East Coast Cycle center, Warrington,PA.
What's PMC?

[dsolie]

Re: Mikuni carburetor flow diagrams

A cheap rebuild company..