extended intake for more low end power



Kpi890

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#22
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Just stumbled across how awesome this stuff is and what a great application it makes to an extended intake. I cut 2 nine inch sections of the tape and stretched and wrapped it tightly over top of my two connections of radiator hose to extend my carb and then just secured the stretched tape with a zip tie. This has been the only solution that has worked to completely eliminate air leaks since I couldn’t find a decent hose clamp that would keep a vacuum leak out. I just installed the intake earlier today so the test of time is still out there but I rode it for about 30 mins and it’s held up perfectly! Now I’m just looking for a better, no so ghetto, way to secure the extended carb to the bike lol, open to suggestions!
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Joined
Jan 15, 2018
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#24
I want to make my engine to work at low RPM, I'm using a 32T sprocket and 28" wheels and a sleeved cylinder. The timing is the same as stock, but I have a 44 mm stroke and 47 mm diameter piston which equals 76cc. The sleeved cylinder and the longer stroke gave me more low end powed and I want to boost it more, because when I reach 60km/h (~6500RPM) my seat starts to shake like crazy and the engine gets louder too. I also have a 27 T sprocket, the 60km/h speed was fine, but I had to pedal more. So I want to make my engine work in a 2000 - 5000RPM range. The last time I used my 27T sprocket, the engine holding bolts broke, one on each side, so now I have M8 bolts holding the engine. I also put rubber between the frame and the engine, and the crank is trued, so the stock cdi might cause the vibration. I will try out the intake extension, because I've never tried it before. And a larger sprocket doesn't give you low end power, you just run your engine on a higher RPM try to cruise within the 2000 RPM range, I did that on this video.
 

FurryOnTheInside

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Sep 23, 2013
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#25
I want to make my engine to work at low RPM, I'm using a 32T sprocket and 28" wheels and a sleeved cylinder. The timing is the same as stock, but I have a 44 mm stroke and 47 mm diameter piston which equals 76cc. The sleeved cylinder and the longer stroke gave me more low end powed and I want to boost it more, because when I reach 60km/h (~6500RPM) my seat starts to shake like crazy and the engine gets louder too. I also have a 27 T sprocket, the 60km/h speed was fine, but I had to pedal more. So I want to make my engine work in a 2000 - 5000RPM range. The last time I used my 27T sprocket, the engine holding bolts broke, one on each side, so now I have M8 bolts holding the engine. I also put rubber between the frame and the engine, and the crank is trued, so the stock cdi might cause the vibration. I will try out the intake extension, because I've never tried it before. And a larger sprocket doesn't give you low end power, you just run your engine on a higher RPM try to cruise within the 2000 RPM range, I did that on this video.
Do you really want it to run at lower rpm or do you want it to not vibrate at its top end?
I would rather solve the vibration issue, personally..
The crank needs to be spinning to work as a flywheel, it's inertia helps to smooth the rotation between the combustions, and the intake airflow needs velocity to draw fuel through the venturi and to keep it moving in one direction rather than it reversing its flow when the piston is descending.
A reed valve would help to avoid the excessive reversion from the lack of intake gasses inertia, but that lowers the intake velocity even more when you pair it (as you should) with a windowed piston that increases intake duration. You will need a large jet to get the right amount of fuel.

Above all, lowering the rpm further will make less power or make it harder to get the same power.

There are many ways to reduce engine noise and vibration while keeping a reasonable engine speed. Even a cheap generic "happy time" can run smoothly and quietly above 6500rpm if it's well built, balanced and mounted to the frame rigidly.
Lose the rubber! :p
 

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#26
The crankshaft isn't balanced, that might cause the problem. I found out today, that I need a larger main jet, because above 50 km/h the engine loses it's power, but when I pull the choke throttle (Yeah, I have a throttle for the choke too on the handlebar it opens another jet so the mixture will be richer) it accelerates like crazy. Once I was brave and with the choke on I accelerated to 70 km/h, but I think it could go faster. I'm not a fan of the big RPM, this engine is not designed for crazy high RPMs, the RPM was 70 km/h was 7500, with stock CDI. The bearings are too small, the wrist pin is too small and crankshaft is not balanced well, if I could do that I could be braver to make it go faster. I'll try to make a shift kit, so I could test is I can go faster if I lower the RPM, because with the 27T sprocket, it still got up to 60km/h but it was better to hear the engine running. I'm not a fan of the high RPM, there are motorcycles around here they have annoying noise, goes around 40km/h but already in the 5th gear. That's just ridiculous. I know it's only 50cc, but that buzzing sound is annoying. I love this engine's sound in the low RPM range, but there are other noises too, but there aren't much I can do about it, the clutch plate amplifies the clutch's noise, if there would be enough place I could put some sponge into the clutch plate to reduce the noise. It revs up nice, there's a range around 4000 - 5000 RPM when it accelerates like crazy, but after that the main jet seems to be small, because I can feel the mixture is too lean. Here's another video showing how it accelerates, even though the clutch was slipping, I solved that problem, but now it does a whine noise now.
The camera stand was sh*t, I mounted on the handlebar and the screen shakes like crazy at certain RPM, the crankshaft wan't trued when I took the video, it's a little better now. I forget to mention it revs up like crazy, because the bike weights 25 kg, and I weight around 60 kg.
 
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FurryOnTheInside

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#27
The crankshaft isn't balanced, that might cause the problem. I found out today, that I need a larger main jet, because above 50 km/h the engine loses it's power, but when I pull the choke throttle (Yeah, I have a throttle for the choke too on the handlebar it opens another jet so the mixture will be richer) it accelerates like crazy. Once I was brave and with the choke on I accelerated to 70 km/h, but I think it could go faster. I'm not a fan of the big RPM, this engine is not designed for crazy high RPMs, the RPM was 70 km/h was 7500, with stock CDI. The bearings are too small, the wrist pin is too small and crankshaft is not balanced well, if I could do that I could be braver to make it go faster. I'll try to make a shift kit, so I could test is I can go faster if I lower the RPM, because with the 27T sprocket, it still got up to 60km/h but it was better to hear the engine running. I'm not a fan of the high RPM, there are motorcycles around here they have annoying noise, goes around 40km/h but already in the 5th gear. That's just ridiculous. I know it's only 50cc, but that buzzing sound is annoying. I love this engine's sound in the low RPM range, but there are other noises too, but there aren't much I can do about it, the clutch plate amplifies the clutch's noise, if there would be enough place I could put some sponge into the clutch plate to reduce the noise. It revs up nice, there's a range around 4000 - 5000 RPM when it accelerates like crazy, but after that the main jet seems to be small, because I can feel the mixture is too lean. Here's another video showing how it accelerates, even though the clutch was slipping, I solved that problem, but now it does a whine noise now.
The camera stand was sh*t, I mounted on the handlebar and the screen shakes like crazy at certain RPM, the crankshaft wan't trued when I took the video, it's a little better now. I forget to mention it revs up like crazy, because the bike weights 25 kg, and I weight around 60 kg.
I can't hear the whine but it does seem to be four stroking a lot.
 

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#28
But it wasn't four stroking at all, and the clutch was okay on this video, it was just slipping. The audio is recorded with my phone which was in my pocket so it has a different sound, when I sit on the seat.
There's this video with the 27T sprocket. It was in the break in period so I was very gentle. You can hear the engine better it's not four stroking, it's just the way it sounds. Maybe the exhaust changed its sound.
 
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Joined
Jul 14, 2018
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#30
Extended the intake to a total of 6 inches including the stock intake manifold and I saw very large power gains like around 15-20 percent. It just could not idle. But my engine never idles anyway.
 

Joined
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#31
Forgive me if I missed this somewhere in the thread, but what exact automotive hose are you all using? I did find some radiator hose with the proper ID/OD, but it is made of EPDM, which has a very bad rating to be used with gasoline. I looked at silicone tubing as well, but it seems to also exhibit poor compatibility with gasoline. Any advice would be great, thanks in advance.
 


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#33
Forgive me if I missed this somewhere in the thread, but what exact automotive hose are you all using? I did find some radiator hose with the proper ID/OD, but it is made of EPDM, which has a very bad rating to be used with gasoline. I looked at silicone tubing as well, but it seems to also exhibit poor compatibility with gasoline. Any advice would be great, thanks in advance.
I'm using reinforced silicone hose. It seems to be fine with the fuel, maybe won't last forever but I can afford to replace it after a year or whatever. The thickness and reinforcing is important, makes it not collapse from the vacuum inside.
 

Frankenstein

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#34
Forgive me if I missed this somewhere in the thread, but what exact automotive hose are you all using? I did find some radiator hose with the proper ID/OD, but it is made of EPDM, which has a very bad rating to be used with gasoline. I looked at silicone tubing as well, but it seems to also exhibit poor compatibility with gasoline. Any advice would be great, thanks in advance.
We have found that home depot has heater hose available, https://www.homedepot.com/p/UDP-5-8-in-I-D-x-10-ft-Rubber-Heater-Hose-T62006002/304185176?cm_mmc=Shopping|G|Base|All-Products|All|All|PLA|71700000014585962|58700001236285396|92700010802552406&gclid=Cj0KCQjw77TbBRDtARIsAC4l83nFXdARxlHy0vm-BAm19K0aWqyPc7RaM6S4CrW9bEACfSnOw4SiA4caAjFjEALw_wcB&gclsrc=aw.ds&dclid=CJbL4pTp49wCFdFTDAods1gAfA, it's cheap enough and fits over the stock intake rather nicely, clamp with a clamp of course.

I would not be concerned with gasoline compatibility, it's too thick and reinforced to break down, and doesn't come in contact with enough straight gas to even begin dissolving. It's basically stable, maybe not good enough for NASA, but surely good enough for the average joe with a cheap bike and an engine that didn't cost 3 times as much as Bill Gates' house.
 
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