Honda Spree and Elite 50 Forums

Hi everyone, im new to the fourm and wanted to share a mod i have done. i believe a good way to get more air and fuel into the engine is to increase intakr velocity. so i cut about 4 inches if rad hose that necks down to the carbs size. i use some wash cloth from work as a filter and it provides enough negative pressure to idle. i lost my air/fuel mix screw and just capped it off. i thought it would run worse but it runs faster now and still idles. i believe i have to upjet because it runs better in warmer weather and the extra fuel from the missing screw aids the lack of jetting. I went fron 26 spreedo mph max to 30-31 spreedo mph. down hill i have hit 35 spreedo mph, all on stock gearing. It was SCREAMING!!!!. Im also running 91 octane, 1-2 oz of seafoam and husqvarna synthetic oil. im 1000ft above sea level aswell, to run properly, the clip on the throttle needle is set to as rich a possible. 1 kick starts all day aswell. im heading out to gps my speed so i will post back later with results and images. its very ghetto lol.

It tops out on flats at a whopping 30mph gps. i have an 87 dri drive gear that i will try when i grt my gasket kit

Haha nice, IÔÇÖm interested to see the pictures of what you did with the carb

my bystarter also is disabled to allow more fuel while running

If you got a speedup increase with that setup, you are more then likely running lean. I thought when you meant intake you were talking about the actual intake. That rig is destined to seize the piston, would REALLY recommend you put the airbox back on.

P.S. Doing what you did will not increase air velocity, would explain more but I am at work, Google Bernoulli's principle.

Also, from looking at the pics, I see a kick start. Unless you have done a kick start conversion, what you have there, is an 86'. The gear from an 87' will do you no good as it is the same thing (13T). You are not helping your bike in the slightest, in fact, you are going to blow the engine with what you are doing. Don't let the speed increase fool you and don't think that increasing the jet size will help the lean condition. You are lean because you decreased vacuum in the venturi, so bumping up the jet will do very very little for you. When you pull back the throttle you are not letting in more fuel, you are letting in more air. The fuel resides down in the bowl and the venturi effect caused by the vacuum created by the piston will draw in the fuel and outside air. The reason it's running now is because you are pumping all the fuel it can take with the needle settings and the air/fuel mix. That's semi compensating for the lost vacuum, but you are still lean. I know this because of your speed increase. Lean running bikes will give out more power once they reach their lean condition at higher rpm. You seriously need to correct this and get rid of that ghetto rig before you cause more serious damage to that engine. Increasing the jet size does nothing because the vacuum power is lost, so it doesn't matter how big the jet is, the bike is unable to pull the fuel it wants from the bowl because of what you did to the air intake. Hope that makes sense, and hope you get this corrected.

eclark5483 wrote:Also, from looking at the pics, I see a kick start. Unless you have done a kick start conversion, what you have there, is an 86'. The gear from an 87' will do you no good as it is the same thing (13T). You are not helping your bike in the slightest, in fact, you are going to blow the engine with what you are doing. Don't let the speed increase fool you and don't think that increasing the jet size will help the lean condition. You are lean because you decreased vacuum in the venturi, so bumping up the jet will do very very little for you. When you pull back the throttle you are not letting in more fuel, you are letting in more air. The fuel resides down in the bowl and the venturi effect caused by the vacuum created by the piston will draw in the fuel and outside air. The reason it's running now is because you are pumping all the fuel it can take with the needle settings and the air/fuel mix. That's semi compensating for the lost vacuum, but you are still lean. I know this because of your speed increase. Lean running bikes will give out more power once they reach their lean condition at higher rpm. You seriously need to correct this and get rid of that ghetto rig before you cause more serious damage to that engine. Increasing the jet size does nothing because the vacuum power is lost, so it doesn't matter how big the jet is, the bike is unable to pull the fuel it wants from the bowl because of what you did to the air intake. Hope that makes sense, and hope you get this corrected.

My scooter is an 85 that i put a kickstart on. made this intake with negative pressures in mind, the fabric used is not free flowing by any means and the green foam part is just a dirt catch, the actual filter medai is 95% taped off for vacuum required to run "kind of" properly. i am aware i am running lean but i plan to keep testing. It smells very rich however when running and will smoke lightly to show it. once i get my cht and rpm gauges im raiseing the compression. im swapping so this motor is just a test bed. Another thing is with the set up, i have yet to have popping from the exaust and have not soft seized. the longest i went so far wot is a mile and some and could have kept going.

eclark5483 wrote:P.S. Doing what you did will not increase air velocity, would explain more but I am at work, Google Bernoulli's principle.

I was just reading up on the principle, it is interesting bit i had read this aswell "The main disadvantage of basing a carburetor's operation on Bernoulli's Principle is that, being a fluid dynamic device, the pressure reduction in a Venturi tends to be proportional to the square of the intake air speed.". if im interpting that correctly, the higher the airspeed before the venturi the lower the pressure in the venturi. i read this shortly after "Bernoulli's principle, which is a function of the velocity of the fluid, is a dominant effect for large openings and large flow rates, but since fluid flow at small scales and low speeds (low Reynolds number) is dominated by viscosity, Bernoulli's principle is ineffective at idle or slow running and in the very small carburetors of the smallest model engines. Similarly the idle and slow running jets of large carburetors are placed after the throttle valve where the pressure is reduced partly by viscous drag, rather than by Bernoulli's principle."

Well, I'll tell you what. I have learned to never argue with people who think they have defied the laws of physics. I just move along and won't even give them an "I TOLD YOU SO". But I can say this... There is about a decades worth of reading on this site from people who have tried this and that and all claim to have great improvements... needless to say, we don't hear much from them anymore unless they need help with an engine swap because of "issues" with their last experiment.. good luck.

Greetings:

Following this with great interest. Is it worth purchasing a CHT gauge so you can have a better idea what temperatures you're running at various speeds?

eclark5483 wrote:Well, I'll tell you what. I have learned to never argue with people who think they have defied the laws of physics. I just move along and won't even give them an "I TOLD YOU SO". But I can say this... There is about a decades worth of reading on this site from people who have tried this and that and all claim to have great improvements... needless to say, we don't hear much from them anymore unless they need help with an engine swap because of "issues" with their last experiment.. good luck.

I set this post up to simply explain what i have done and the results, im not saying my "GHETTO" rig makes more power or is more effective than a normal operating carburator. weither or not its an improvement this was an EXPIREMENT and will still be held as one. i have multiple filters, intake lenths to try for diffrent reasons. If you truly feel like im going to blow it up keep your fingers crossed then. I also never said you were wrong, i just saw conflicting data is all.

Wheelman-111 wrote:Greetings:

Following this with great interest. Is it worth purchasing a CHT gauge so you can have a better idea what temperatures you're running at various speeds?

Im getting the cht gauge to see my max possible temp at wot with the set up before i make any more changes. if im running lean like said above then my cht will def be higher. i have other expirements lined up after the gauge comes in. im curious to see part throttle temps are like.

Ive been out testing it tonight, the old filter filled with oil and gas when my bike fell so i chucked it. im currently on my spree now with a food service wash cloth as the filter and it works a little better than the media filter, it can idle very low and i was holding 25mph at quarter throttle, 30 at full. i hope to get a helmet cam to get some videos up. im going to link one of how its idling, at its lowest idle.

https://youtu.be/SsEVDMlXQEM
Video of idle after uphill wot runs