30mm CVK Fitting help

[pdaddy]

Here's some of my tips if you cant fit youre newly bought 30 mm CVK Carb.

There are some diffrences betwean carb brands, and i think the OKO brand can be the hardest (maybe).

Well i got a 30mm OKO CVK carb from "Autotech355" @ ebay.
Also bought the alu intake.
My scoot is a small frame 125cc (Same size as alot of 50cc mopeds), i also have a brand new 59mm bore kit installed + filter and race exaust.

The biggest problem ppl have is getting the f**ker in there, it just wont get in the right place.
Sd in Big Daddy Dawgs installation manual you can see that the acc pump is going under the mounting bracket.
But for me that wasnt all, i needed to cut away some plastic that cover the cam chain tensioner.

With the new manfoil intake you dont use any spacer, and you must put it on the carb with the rubber fittings before you install it (in my case). But that cuases another problem that is solved by removing the intake dubble sided screwes from the head, that way you can slipp the carb in and attatch screws later.

Even doing this my carb was placed 5mm to far back, so that one of the bowl screwes hit the frame and intake didnt want to align with the head.
This is the thing that can differs with diffrent brand of the carb. My carb had 3 mounting screws for the bowl, my old had 4 so it didnt stick out.

Anyway, if this is the case you have to modify the rubber fitting that is seated on the intake. Just remove it and cut it down about 5 mm, dont forget to remove the rubber that sticks out on the inside of the rubber tube. When you have removed 5 mm you can still have to hose clamps on it, but just barely.

Hope this helps, i know several other ppl who have scraped theire new 30mm carbs cuase of not getting it to fit.
IT CAN BE FITTED, it just needs some lovin to get in there .

I will take pictures when i have bought a new tube for my airfilter.

BR

Marcus

BTW.. It started up after 5 trys, idle is way to high, so i think i need to adjust my fuel/air mixture screw. Think main jet is 128, but no idea what low is.

[natefromogden]

You're absolutely right, fitting a larger carb and the alloy intake manifold under, around and through the motor mount is a major pain. You figured one thing out already, dump the intake mounting studs and get some socket headed cap screws that install from the top.

Also, sometimes, using a phenolic spacer, (I made mine) raises the manifold enough to allow clearance on the carb where it contacts the engine mount. Your mileage may vary...

I also found it neccesary, before I built an entirely new engine mount, to grind off some of the plated portion of the hoop that the carb mouth fits through, to give adequate clearance. I used a die grinder to remove portions of that boxed in part of the motor mount.

While I can't recommend it except to the really motivated and frustrated, I made a motor mount using two stock mounts, lots of welding and grinding to build a mount that now provides enough room that you can almost throw the carb into the engine bay and it will fall into place.

Basically, I cut the ends off the hoop of one mount, aligned it behind the original, welded the two together, added braces and a new bolt sleeve on the bottom, then cut away most of the front hoop. It was a bunch of work but it turned out to be the right solution for that carburetor and engine mount interference problem.

[earlwb]

Insane thought for the moment before the coffee has taken effect.
How about putting in dual or triple 50cc carbs? Granted lots of problems getting it all to fit, plus needing a special intake manifold and air filters, but it would sure look neat.

[natefromogden]

Earl, you must like walking because building a multi-carb solution sounds like you would be on foot a long time- first building it and second getting it to work!

A real solution would be a downdraft carb that could be fit to the existing cylinder head flange but I can't think of any modern, small engine applications we could rob from. Everything I can think of is sidedraft like our current carbs.

Anybody?

[natefromogden]

As usual, I wrote something before Googling... Check this out:
uas.co.jp/SHOP/FCR28D-A.HTM
Here's a source: www.motorcyclecarbs.com/CARBURETOR_KIT_HONDA_MONKEY_F_P9155.cfm These might be an interesting possibility for an alternative carb.

[earlwb]

I wonder how big this Weber downdraft carb is www.webercarbsdirect.com/34_ICT_p/15290.027.htm
That looks promising if it isn't too big.
I haven't kept up on Weber carbs, but I always liked the look on some cars and motorcycles.
They seem to have made a lot of different venturi sizes, so maybe this is possible. members.aol.com/dvandrews/webers.htm

[pdaddy]

it looks promesing, maybe it's 34mm as in the name !!

M

[earlwb]

Wow this might work Ok.
According to this PDF file on the 34 Weber ICT carb www.racetep.com/weber/34_ICT.pdf the venturi is 29mm. the trick is if you need to reject it ot not. It also has a accelerator pump too. A ICT does not have a manual choke whereas the ICH has a manual choke.
This is cool, with an adapter plate one could bolt it right on to the engine. Heck the bolt pattern might even be close enough to work too.
This does look really promising. You just clamp on a K&N filter right on top sticking straight up.
Cool.
Humm the throttle arm is on the back of the carb. Maybe some creative engineerinmg is needed or not, i am not sure.

[earlwb]

I also ran across this carb here:
REVFLOW carbs sidedraft floatless:
www.revmasteraviation.com/products/revflow_injector_carburetor/index.htm
they have a 28mm size and a 30mm size that would be of interest.
According to the manual usually gravity feed works just fine with them too.
It does look pretty cool as well.

[natefromogden]

Earl, I can't get the website to open from here on the job so I can't verify but these carbs sound like a design I saw used on Japanese 4 cyl bikes years ago. While they did perform remarkably well in racing use, they were less friendly for street use. In particular, I remember that you could NOT crack the throttle when starting because the way the venturi pulled fuel it would flood immediately. Basically, opening thr throttle allows fuel to start flowing and if there's no combustion taking place to burn the fuel, it just pours in.

I'll look at these tonight from the house. Maybe there have been some interesting improvements over the past years.

[earlwb]

Well they are used mostly on aircraft engines. Being floatless makes them nice for aerobatic manuevers. But you are right about opening the throttle would allow the fuel to pour in. On the aircraft engines they mount the carb below the engine, so if fuel flowed freely it would dribble out of the front of the carb onto the ground. I'll have to think about that too. The feature I thought was nice is the ability to control the air fuel mixture remotely. That could be pretty handy if you use a oversized carb on a engine as you can tweak the air fuel mixture easily. Granted we don't have huge altitude changes like they do on a airplane, but you don't have to take the carb apart to change jets either.

[natefromogden]

Earl, I finally got around to looking at that Revmaster from home. It is similar to the old carbs I was familiar with with the addition of that second throttle cable controlling the fuel flow cutoff. Since they require solid wire control cables they wouldn't work too well on scooters but rather for the aircraft they are designed for that use a (semi) fixed throttle position for most operations. Pretty neat design though.

[natefromogden]

Earl, here's a carb that I have actually held in my hand. They are made in my town! www.psipowerinc.com/mxAtvCarb.htm They actually make a model designed so that it is designed for smaller engines that might be perfect for our scoots or perhaps the 125cc version mentioned on this page. They are very neat in that all the adjustments- idle mixture and high speed fuel mixture are controlled from outside the carb. There's no removing the carb and spilling fuel on the bench to switch out a jet with these carbs.

That's the good news. The bad news is the price- about $600 when I asked last summer. They are beautifully machined and assembled and I really like the triangular throat concept. But its out of my price range for my scoot.

[earlwb]

Nice carb, nice price too.
I always had a thing for CNC machined parts like carbs.