Honda Spree and Elite 50 Forums

I guess my own personal takeaway I think you need to consider, is whether or not you do or do not believe Bernoulli's principle applies. Once whatever stream you are feeding it reaches the venturi in the carb, you have negated all that air you wished to come in by decreasing the atmospheric and vacuum pressure that it needs to suck up fuel from the bowl. This is supplied by the intake's vacuum and it's efficiency in receiving the charge from the venturi. This is where the Bernoulli's principle and the guy the Venturi was named after's theories, intersect. Bernoulli's principle can almost always be proven, even with smaller diameters. Crazy to think smaller is faster up goes down and all the other weird science behind it all, but if you apply it, you get better results.

eclark5483 wrote:I guess my own personal takeaway I think you need to consider, is whether or not you do or do not believe Bernoulli's principle applies. Once whatever stream you are feeding it reaches the venturi in the carb, you have negated all that air you wished to come in by decreasing the atmospheric and vacuum pressure that it needs to suck up fuel from the bowl. This is supplied by the intake's vacuum and it's efficiency in receiving the charge from the venturi. This is where the Bernoulli's principle and the guy the Venturi was named after's theories, intersect. Bernoulli's principle can almost always be proven, even with smaller diameters. Crazy to think smaller is faster up goes down and all the other weird science behind it all, but if you apply it, you get better results.

Regardless, the intake was made with WOT in mind. I know it would be ineffective at part throttle. One of my goals was maximum rpm because it felt like it lost breath when at max speed. At 35 downhill its very zingy sounding.

With my next test i had lined up, i wont be able to properly run it until i get my air mix screw and bystarter. I installed a power jet to see if i can supply fuel at higher rpms using vacuum. If i installed the jet in the carb throat, fuel would pull at a ssooner rpm, i installed it 1/2 an inch from the carb hoping to see it pull fuel under wot. It did just that! with the power jet active i didnt have a zingy 35 anymore and was much slower to get there. i can tune the jet by rotating the drain screw to set how much fuel is vacuumed in. its a 42 pilot jet aswell.

the pilot jet

Greetings:

What an inventive, unique idea, Spree O' Joy! I'm eager to see your results.

Dude, you're freakin me out!

I got my small parts in so ill be doing some runs once im out of work. The longer intake in the picture made the clutch lock up slower, it was causing turbulance at lower speeds. I made a smaller version that is essentialy a big elbow to the carb with a filter on it. It ran alot better. The new filter i have has an hole smaller than the carbs inlet, when i ran it as it it bogged heavily like it was choking. i drilled out the inlet until it was able to achieve prior speeds. it runs the new filter without having to restrict the filter with tape. I have plenty of pics and if it doesnt rain ill try to upload a video of the power valve in action. once the carb is working properly i would like to start some trials and run it.

I will be uploading a test video of the valve shortly, here are a few pics of the set up.

Some juicy high rev test video for you guys, i used longer hose for the jet to delay the fuel delivery, the previous hose sucked too fast.

https://youtu.be/NAljMTs5nR0

In the video, i showed the power jet sucking fuel but only at higher rpm and wide open throttle. when i bring it to half throttle flow is immediately stopped.

Just got my 86-87 spree reeds in, the petals seal very well on them. I thought they would only be a little bit bigger but it is actually a lot bigger than my 85 reeds. With the expansion chamber I made as well I need to rejet badly as my #65 jet is sounding zingy,but its beefy in the half throttle range with the clip on the richest part of the 5 slotted jet needle. also ordering an adjustable powerjet system.

What's cool about the next prototype is that the fuel provided will be from a source other than the carb. I was going to run oil and gas in a separate container to supply the power jet. That way I can keep my oil pump, fill my gas like normal, and have extra oil only in 3/4 to WOT when I need it. I will be using 0 ethanol gas soon as well because it is available to me.

You seem to have educated yourself to a point to put your knowledge into real world testing. Hats off to you, sir. Thinking outside the box is what blossoms creative ideas and produces advancements. Regardless if what youre doing works or not, never stop trying new things and going out on a limb. Unlike billion dollar companies with seemingly unlimited resources to dump into R&D of new designs, us normal folk just have use the tools (and filter materials) we have and give it run! Keep on having fun being creative and never let nay sayers distract you from enjoying doing what keeps the Spree spark alive for you. Bravo.

Thanks for the inspiration meatball! Got around to doing some porting for the reeds, I'm so picky about my measurements that every 5 seconds I pulled my dremel back to compare the reeds opening to the manifold with calipers. Needless to say I matched it up near perfectly. I also took a lot of material from the bend right after the carb. I ate into the back of the flange on the inside to make as nice as a transition as possible.

After a few silly errors I got it running and man does it have response. The literal moment you crack the throttle all you feel is a snappy response. With the jet needle at max rich, all my throttleage was within the 1/4 to 1/2 zone, anything after that it just made more noise. Now I know I'm very lean. I had a random #78 jet laying around so I slapped it in and felt much more torque. I didn't change needle setting( I should have) and it stuttered little at 15mph but after it kept rising in rpm. I topped out at 30 mph on stock 85 gears. I feel like if I lean it out to a #70 or #72 it will be right where i want it.

Ok, so I've been pondering some ideas. I was doing some port reading and the port timing for the 84-85 is slightly different from the 86-87. If I raise my intake port to match the 86-87 it will have the same timing but would flow just a tad bit more as well due to having to grind material out to time the port. Same for the exhaust as well.
it went from a DIY intake to me just going down the line with mods for higher rpms. While there isn't really any power to be made in the higher revs, it's the only way to go faster........(without swapping or gearing)

I bought a spare jug and piston (85) for some crazy port action, gotta try to make it to the higher revs. I'll be opening up the exhaust as much as possible as it's very pinched on the inside where the muffler bolts to. As a precaution I'll be welding extra material around the exhaust to make the port as round and open as needed without fear of grinding through the walls. I've got this big expansion chamber and a pinched exhaust port feeding it .

On a side note, I will be swiss cheesing the spare piston and ramping the piston to test more aggressive port timing as per http://www.dragonfly75.com/motorbike/pistonramp.html.

Just got my jug and piston in and they are in great condition. Paid 25 for everything, only downside is it's the 86-86 jug and domed piston so the ports are already raised higher than mine. However I will try to go as aggressive as possible with exaust port timing while keeping the intake and transfer ports times slightly less aggressive. If I raise it by 2 rings worth of metal it should free it up, but on my 85 I'll have to go up 3 rings worth of a little more to achieve the same timing but will flow more for that same reason.

I found a page in a Yamaha 2 stroke book online about small mods n such. On the plus side, the domed piston may help the cuts on the top flow better rather than cutting into a dished piston and it will raise my compression without cutting the heads(yet)