Can't get bike over 23MPH

Emcee

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I wanted to run the bike on a few more tanks of gas before making this post but the time has come.

I can only get to 23 MPH WOT. I am on my 6th or 7th tank of gas. I have a stock NT Carb, 80cc engine and am using the stock 44T sprocket. The bike has 26 inch wheels running 26 x 2.125. I run 93 using Lucas at 32:1. I'm roughly getting 70MPG, I weigh 220. I thought maybe I wasn't getting enough air so I drilled a few holes in the filter two tanks ago and it didn't help.

The land elevation is 505ft where I live. Lowest I go to is 398ft, so average 452ft.

The thing that scares me is how high im revving is just to get to 23MPH. I don't want to fry my engine.

I'm not sure where to begin troubleshooting. Any help will be greatly appreciated.



UPDATE :

Got my tach today and here is what I'm reading. I pulled my spark plug out and it was very rich and fouled. Moved the needle to the 1st notch and my engine is responding well to that and to the 90 Octane ethanol free I put in. Top speed is still 23 mph



When I spray the carb where it meets the intake manifold it stalls out. Sprayed it on the intake manifold where it meets the engine and it's fine.

That weird square bolt and Phillips head that tightens it, should I replace it with something better like a hex bolt and nut?

1690 idle

2190-3100 RPM 10mph

4100 RPM 15mph

5100 RPM 20mph

SECOND UPDATE :

So I sealed off the air leak, it preforms better. It would make that sound but not anymore. Instead of stalling the RPMs would drop from 1650 to 1630 slowly so I'm not sure if some of it is going into the air filter.

Still can only top at 23 MPH. It just sounds horrible, unless the engine sounds that way at higher RPMs. Tomorrow I'm going to put my old exhaust on to see if that is creating some sort back pressure problem. I have the viper flex exhaust on it. In addition, I am going to follow what someone else did when this same issue happened to them and I'm going to see what happens. I have an extra carb I can bend the arms on. I'm not exactly sure what happens mechanically that could help it, but I love learning in the process of it.
 

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Sidewinder Jerry

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I wanted to run the bike on a few more tanks of gas before making this post but the time has come.

I can only get to 23 MPH WOT. I am on my 6th or 7th tank of gas. I have a stock NT Carb, 80cc engine and am using the stock 44T sprocket. The bike has 26 inch wheels running 26 x 2.125. I run 93 using Lucas at 32:1. I'm roughly getting 70MPG, I weigh 220. I thought maybe I wasn't getting enough air so I drilled a few holes in the filter two tanks ago and it didn't help.

The land elevation is 505ft where I live. Lowest I go to is 398ft, so average 452ft.

The thing that scares me is how high im revving is just to get to 23MPH. I don't want to fry my engine.

I'm not sure where to begin troubleshooting. Any help will be greatly appreciated.
How do you know you're only doing 23 mph? Are you using a bicycle computer? How do you know you're revving high? Are you using a tachometer?

With your setup, it takes 5365 rpm to do 23 mph. If you're going over 5365 rpm and are only doing 23 mph it means either something is in a bind somewhere. Or you simply don't have enough power for the weight being propelled.
 

Wolfie65

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On just a regular bicycle, I do about 12-15 mph without any special effort, but only half that when returning from Homeless Dump (formerly Home Depot) with cat litter, aka play sand.
 

Emcee

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How do you know you're only doing 23 mph? Are you using a bicycle computer? How do you know you're revving high? Are you using a tachometer?

With your setup, it takes 5365 rpm to do 23 mph. If you're going over 5365 rpm and are only doing 23 mph it means either something is in a bind somewhere. Or you simply don't have enough power for the weight being propelled.
My GPS matches a radar gun. I'm going off of sound for the high rev.
 

Sidewinder Jerry

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My GPS matches a radar gun. I'm going off of sound for the high rev.
Bicycle computers are very affordable and far more accurate than GPS devices. A tachometer is also very affordable; both can be purchased on Amazon and eBay.

You can look for binding things on your bike. The tachometer will let you know exactly what your engine is doing.

20220524_184552.jpg
 

Emcee

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Bicycle computers are very affordable and far more accurate than GPS devices. A tachometer is also very affordable; both can be purchased on Amazon and eBay.

You can look for binding things on your bike. The tachometer will let you know exactly what your engine is doing.

View attachment 178842
I appreciate your help. Radar gun is accurate. I mean, if my GPS says 23 and his radar gun says 23, I feel confident that I'm not going 30 and both my GPS and his gun were wrong. I have good ears, I can tell the difference between when the engine sounds stable and when it sounds like it's going to blow up any second.

Quick question and I don't mean this to be argumentive. What will me having the rpms do exactly? In the sense of diagnosing. Is this where to start?

I only get $200 a month after expenses so I'm pretty strapped for cash at the moment.

Edit : I could buy one and use it and return it 😭
 

Sidewinder Jerry

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Ok on 26" wheels with a 10\44 at 23 mph the engine should be doing 5365 rpm. If the tach is reading more than that it means your speedometer is off and/or your tires are less than 26" and/or something is in a bind and/or your engine lacks the power for the load being put on it and/or the clutch is slipping.

Why would you return such a useful device? With motorized bicycles, you're going to need quality tools, specialty tools, and devices.
 

Sidewinder Jerry

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Are you using 100% ethanol-free gas? This has nothing to do with octane level. Have you checked for air leaks? You can do this with smoke. Did you clean up the inside of the engine or simply put it on the bike?
 

DAMIEN1307

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Why would you return such a useful device? With motorized bicycles, you're going to need quality tools, specialty tools, and devices.
Because he is in a "living situation" where he really cannot afford what you and I would take for granted as not being expensive...for him right now a pack of chewing gum is expensive.
 

Sidewinder Jerry

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Because he is in a "living situation" where he really cannot afford what you and I would take for granted as not being expensive...for him right now a pack of chewing gum is expensive
Once they run right, our bikes are fairly affordable. However, chances are you're going to have to spend money to make them do that. It's a sad fact, but just the way it is.

My neighbor's mower I got for him won't crank now because he didn't listen to me and put ethanol-added gas in it. He did this because it was cheaper than 100% gas.
 
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