MOPED ARMY

What what would be really cool, is to have the valve solidly mounted as close to the carb as possible and have a device/adjuster at an easily accessible place, so you can adjust the valve similar to how the MotoGP guys adjust their front radial brake with their left hand while during a race or practice. Used in conjunction with a temp sensor, you could dial it in any time you need. And by the way, I think your idea is great!

JBOT Is bored so I'm back to troll you Wrote:

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Well, I think you're basically right. Except, I'm getting the same performance and speed I was getting with the jets, minus a very slight lag. It hauls me up and down the block the same. Perhaps it will be different in warmer weather. We'll see what shorter tubes do. The one for my brother will be as short as it gets as I'll mount it directly to the float bowl.

@Charles Cole Your wish is granted. The needle valve I'm using is from O.S. Engines and has a set screw in the knob, and a hole in the end. Simply loosen the set screw, insert cable, and tighten set screw.

I didn't go this route because I was using just what I had lying around, and what one really nice guy sent me in the mail. I may end up getting there for the reason listed above. R/C airplanes have remote needle valves set up like this, but they are usually attached to the back of the engine and so are not far away from the carb.

I moved the needle valve much closer, and I trimmed about 8 inches of tubing. I used a bit of plumber's pipe hanger strap to attach it to one of the float bowl screws.

No testing as it is dark and cold.....cold....cold. Maybe tomorrow night.

Good, how are temps?

Well, kinda hard to tell real working temps whenever its so cold out.

JBOT Is bored so I'm back to troll you Wrote:

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That is an excellent question. I wish I had a way to answer. At the moment I have no practical way of answering. Could I touch a meat thermometer to the head and make that work?

The only thing I can tell for sure, is that it is running at least as well as it did with the jet. I let it sit for 6-8 minutes after starting 'cause someone wanted to talk to me. It ran fantastically. I then drove up and down the block for a good 10-15 minutes. If I was running lean, I'm pretty sure I would have started bogging down, right? Even at this air temperature, it would be over heating if I was too lean, right? Also wasn't going super slow or sluggish like I would expect if it was too rich. Also no major visible smoke coming out of the tailpipe.

I should have told you that it warmed up a lot today. It was probably 35-40 out there when I was riding. Supposed to be in the 50s tomorrow, so I'll go ride some more and see what happens.

Very cool! well done!

I wonder if you could use some of the tech that's used with the dial a jet stuff.

Have you seen their setup?

I guess I’m not the only person to read in thread view haha

With a Grande/Bravo set up you don’t even need to remove the carb from being attached to the motor to rejet/upjet. (edited)

JBOT Is bored so I'm back to troll you Wrote:

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I did look at the dial-a-jet. Problem 1 is that it costs about as much as a whole fancy carb for a moped.

They do it weird, too. They tap the float bowl same as I do, but instead of replacing the jet, they pipe the gas into the venturi. I don't know exactly how it all works, and why it isn't just rich as crap with two fuel sources... They advertise that it can be installed without disassembling the carb.

They also say that they have five settings. I don't know if there is a way to get more variation out of it or not, but five settings, while an improvement over just jets, seems a bit limited for an add-on that costs $80. The mod I've presented costs under $20 and gives you infinite control.

I SHOULD asterisk here and point out that the $20 price tag is using that needle valve from Traaxas. The needle valve I have is more expensive and comes from OS Engines. The ONLY reason I have it is because my dad had a scrap one lying around. I do think the Traaxas one will work just as well, but I can't guarantee it. I plan to order one and install it on my brother's bike in the next month and then I can report back. Ponch got one and said he'd post pictures, so we'll get some good info there as well.

Tuning Notes:

R/C engine instructions tell you to open the needle valve about 3-4 turns for starting, throttle up to WOT, then close the valve 1/4 turn at a time until you peak RPM. This is the ideal mix. Once you pass it, the engine will slow again, and you'll be leaning out. I recommend finding your peak, then opening a little to the rich side as a cushion.

On my Bravo, with a completely stock 50cc engine, a bored out 13mm carb, and a basically stock exhaust, at 40 degrees F, my ideal setting was somewhere around 2.5 turns open. Keep track of these settings, and set the mix while running on the center stand. Once you set it, you should be able to just adjust each time you want to, and not start at the beginning.

@ Charles Cole

Picked up tygon tubing today, hope to install a little later tonight. :)

I do really dig this though. I have a 28mm power jet oko on my bravo race bike, I'm gonna get one of those adjustable valve deals for the power jet for sure now! What was the one you are currently using? And in what ways is it nicer than the traxxas one?

@ Tyler

The Traaxas needle is made for a smaller engine than the one I have. Bear in mind that many of the needle valves on smaller engines are also used on larger engines of the same brand. If you can have a look at them in real life, you could probably measure the orifices and see if there is a big size difference. I didn't think it mattered much when I started, and still don't, because the size of the orifices inside the carb (float needle hole and jet hole) are smaller than the orifices of the needle valve. You want to control the flow, not permanently restrict the flow. The jet I used was a 94, which should be bigger than just about any jet anyone will ever use on a moped, and the hole was still smaller than the needle valve orifices. Conclusion: I think pretty much any of the needle valves will work for this project.

The other difference is that one end of the Traaxas needle valve body is threaded. That's a good thing because you can drill a hole in the bowl, pop a rubber washer on the needle valve body, and screw it in. (The steel threads will cut into the soft aluminum easily.) You can mount the needle valve directly to the float bowl anywhere as long as you don't stop the movement of the float, and save yourself some effort trying to mount it elsewhere on the bike. On my Bravo, mounting directly to the bowl isn't an option because then I can't get to it. The OS valve body has two nipples instead, so I could just do what I did. I bet you could find a way to use the Traaxas one in the same way I did, if needed.

@ Scooter

How cheap is cheap? I'd be interested in such a thing later on.

That has lots of adjustments. The screw pointed up at an angle is the slide screw? Is that big black knob a mixture control? And the slotted screw on top of the power jet hose, what does that do?

It looks like a pretty awesome setup!

I know you already purchased a needle valve but I found this on an RC site. Has mounting cast into it & only $10.

If you need a cylinder head temp gauge, there's plenty of ebay listings for under $40 for a Trail Tech. Together, you should be able to super dial it in.

http://www.amainhobbies.com/rc-airplanes/evolution-remote-needle-valve-assembly-tps4046-evo046874a/p33279

compression barb fitting modified like jbot suggested

Do you keep same line /fuel pressure? Pressurize tank? Fuel pump? Or just adjust needle on the fly when tank gets low?

Found this grommet at the hardware store. It might be a good option for sealing up the bowl.

I'm getting good at making these.