New Build!! Harbor Freight 52cc and BMP kit....

[5-7HEAVEN]

New Engine Overrevving?

Aren't you afraid you're overrevving your brand new engine? How fast is that 52cc engine spinning at 39mph with 1.25" roller?

 

[happycheapskate]

I'm sold. It sounds like this blows the happytimes away. I love how you can just flip a QR skewer and pedal freely. This is the wave of the future.

 

[andyszyd]

Ok so I bought the following:

BMP kit with the 1.25 roller
Harbor Freight Auger

Wow!! This thing fly's!! This is my second day testing this engine with this kit and I have hit 36.1mph according to my Trek Computer. This could be off a few, but anyway I highly recommend this kit and engine. My only concern is that some guy up here with the exact same setup posted that with a 280lb rider, his bike hit 34.5mph. Now I weigh 160lb. Does this sound right? I figured I could have hit around 40mph since I weigh around 100lb's lighter. Can anyone explain this?

Yea I am a guy who posted doing 33 MPH with 1.25 roller, being 280 lb.

You will hit 40 MPH or more but you need 1.5 roller.

BMP spins about 10000 rpm at 33 MPH using 1.25 roller. Although 52cc got some torque and power, but it is no Morini. So to go faster you need larger roller.

 

[happycheapskate]

re: 100 lbs lighter

Several things can affect the top speed of your bike on level ground:

Friction of the tire against the roller (necessary but draws some energy from the engine) Make sure brakes are not dragging and hubs roll freely.

Rotating weight of the wheels and tires

Tuning and break in condition of the engine

Gasoline quality and oil mixture

Altitude and humidity

Air and fuel filter conditions.

Spark gap and conditions

 

[cycledude]

Small difference - the bigger rider has more cross-sectional area, thus, more drag due to air resistance. However, weight increase is proportional to the volume (centimeters cubed) of the individual (all other factors being equal,) whereas the cross sectional area is measured in centimeters squared.

For instance, a male Gorilla could weigh 400 pounds, but be shorter than you (just significantly wider and deeper!)

For a cube, the ratio for weight to cross-sectional area would be proportional to (X * X * X)/ (X * X)

I've thought about that, it is one of the reasons why I ride sideways.
Some people have the right body structure for bike riding, and the weight.
When I ride my bike over 60 mph I feel like if I let myself go my body would gradually begin to float and the only thing connecting me to the bike would be the handlebars. lol

BTW I know about the more cc faster experience but I'm tring to find out how small I can go with engines.
Does anybody know where I can get a weedeater engine by itself?

 

[Porkchop]

I just saw this. Yeah, I know it was posted back in February. I know you’re not hitting 36 MPH in that snow ! Hee ! Hee ! Friction drives and wet tires go no where in a hurry. I have the exact set up you have. I swapped my HF engine for a Honda GX35. Believe me, the HF will blow away the Honda. I’m using the 1” roller with the Honda. I wouldn’t think of trying the 1.25” roller. Honda would be straining her guts out, but not an issue with the HF 50cc. The fastest I ever got my bike on level ground with the HF engine with 1.25” was around 28-30. I’m pretty sure I had my Schwinn speedometer calibrated precisely, but wouldn’t bet on it. But that is one strong engine. Everyone I know that has used one swears they get faster with use.

 

[Porkchop]

I've thought about that, it is one of the reasons why I ride sideways.
Some people have the right body structure for bike riding, and the weight.
When I ride my bike over 60 mph I feel like if I let myself go my body would gradually begin to float and the only thing connecting me to the bike would be the handlebars. lol

BTW I know about the more cc faster experience but I'm tring to find out how small I can go with engines.
Does anybody know where I can get a weedeater engine by itself?

From my personal experience, I would not go less than 35cc on engine size. Any of the common Japanese engines are pretty easy to find. I paid about $200.00 for my Honda GX35, ordered on line. The best price I got locally was $350.00. I ordered mine and got it quicker and $150.00 cheaper.
Click on the attached link. It’ll take you to BMP’s site, straight to engine vendor info. This will at least give you a starting point.

http://www.bikemotorparts.com/ENGINES.html

 

[happycheapskate]

re: weedeater engine by itself. I do not think any common weedeater engines will fit the BMP kit, but if you are planning to make the old home-style weeder with bmx roller, you can find them easily. Look in the phone book for lawn mower repair. The biggest and smallest shops will have "junk" weeders and a ready supply of used engines. If you buy only the engine new, nearly any commercial brand, it will be $150 and up.

You can find a bunch of weeders on Craigslist etc, but buyer beware. If anyone is selling a weeder, there is probably something wrong with it (bearings or carb usually, sometimes the shaft is broken or clutch is fried.)

 

[happycheapskate]

I'm still goofing around with my happytime. I am out of work so I have no play money. I canniballised a dead groobee and I think I have the garage sale groobee ready to run. We'll see at the car show!

I think the roller drive is the way to go for a pit bike or 25mph commuter bike. Slow as molasses but saves on the taxes!

I'm saving change in a jar and when this grubee BTD (hopefully at least a year away!) I'm going to get the Harbor Fart and the BMP kit.

 

[Porkchop]

Harbor Freight 50cc water pumps are no longer available. You might get lucky and find a left over. Their auger has almost the same engine. I'ts 100% plug and play with the BMP friction drive, but to costly just for the engine. You can get that same engine though for about $120.00 from monsterscooter.