Freebeer's Mini Bike Build

[Freebeer187]

This first post will be updated as the build progresses​

I am upgrading my tired mini bike. This mini bike is roughly 7 years old and had a tired 3.5 hp engine. I will be upgrading the engine to a Honda clone 6.5 HP engine. It might be a breeze, it might be a little difficult, and it might be a a real PITA. After lots of planning, I finally began working on it tonight. Here is some info.

Parts list:

• Engine (6.5 HP Honda Clone) ($82)
• Throttle Kit ($18)
• Header in the works (being custom made)
• Clutch #35 12 tooth 3/4" ($29.99)
• Steel Sprocket - 66 Tooth / #35 Chain ($15.54)
• #35 Standard Chain ($16.50)
• Air Filter Angled ($10)
• Air Box to Carb Gasket - Honda GX200 / Clone ($2.90)
• Air Filter Adapter ($9)
• ARC Chain Breaker - #35 chain ($21)
• Choke Assembly Bracket ($2.50)
• BSP/Clone Main Jet .037 ($3.25)
• Exhaust Gasket ($1)

5/11/11
Starting from the top. Remove engine, chain, sprocket, and mount new engine. Prepare for incoming parts.​

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Old engine is gone!

New engine mounted Fits nice.

5/14/11
Installed Clutch, Sprocket, Chain, .037 Jet, Air filter Adapter and Air filter​

Sprocket installed

Heres the temporary throttle set up

Air filter adapter

Installing air filter

Done for the night!

5/19/11
Installed custom header. First start.​

No header

Header!

Done.

Started right up. The next day, after letting the engine break in a little, it was taken out for a few spins. Pulls hard as hell and is much faster than the engine before. It needed some fine tuning (tightening of the chain, and a little extra lube in some areas), but other than that it ran great. Thanks everyone for the help!

Click to read more...

 

[1quick]

why did you decide to go with the honda over the briggs 5hp, there is a huge aftermarket for performance on the brigs since its used for jr dragsters and gocart raceing, cool build, im going to be doing a go cart soon

 

[Bob Kazamakis]

why did you decide to go with the honda over the briggs 5hp, there is a huge aftermarket for performance on the brigs since its used for jr dragsters and gocart raceing, cool build, im going to be doing a go cart soon

This engine has just as much I not more aftermarket support. Ported head, big cams, stroker kits, etc. People make close to 18hp out of them.

 

[99PONTIACGP]

Why didnt you paint the frame while the engine was out?

 

[greasy]

Cool build Makes sure to clean off all the small flower petals from the tires, they will be no good for traction will all of the new found power.

 

[Freebeer187]

why did you decide to go with the honda over the briggs 5hp, there is a huge aftermarket for performance on the brigs since its used for jr dragsters and gocart raceing, cool build, im going to be doing a go cart soon

The engine was $80

Why didnt you paint the frame while the engine was out?

Paint? I like the color.

Cool build Makes sure to clean off all the small flower petals from the tires, they will be no good for traction will all of the new found power.

Haha thanks Greasy! Yeah ill be sure to take them off

 

[99PONTIACGP]

Oh... to each their own... Looks good though.

 

[Bob Kazamakis]

What size Is the old output shaft and the new output shaft? Can you make the stock clutch work?

 

[Freebeer187]

What size Is the old output shaft and the new output shaft? Can you make the stock clutch work?

The old clutch will not fit. The Output shaft on the 3.5 has a cut groove. The OPS on the 6.5 has a enlarged/exposed groove to fit the clutch.

 

[LSx S10]

cool build! If you want to save a couple bucks, a chain breaker really isn't necessary. You can use a dremel or a bench grinder just as easily.

 

[Bob Kazamakis]

The key in the new engine should come out...if I'm understanding your description. Are the diameters the same or similar?

 

[Freebeer187]

The key in the new engine should come out...if I'm understanding your description. Are the diameters the same or similar?

...damnit freebeer... What is the key?

Oh and the throttle kit came in today. Going to be working on it tonight

cool build! If you want to save a couple bucks, a chain breaker really isn't necessary. You can use a dremel or a bench grinder just as easily.

Thanks dude! Ah makes sense. I already bought the chain breaker though >:|

 

[Bob Kazamakis]

The little rectangle piece in the shaft.

 

[Freebeer187]

The little rectangle piece in the shaft.

Yes there is a rectangle piece in the shaft. I havent had to installthe clutch yet so i havent gotten there yet but this piece is to be removed right? I kinda checked it out and it was fitted pretty strong in there.

 

[radioguy6]

Looks like the shaft key is built onto the output shaft of the Honda from that picture. Normally they are 3/16" x 3/16" square keys. On the old engine it either has a removable shaft key with a set screw on the clutch or the clutch has its own built in key. Both shafts are 3/4" so the old clutch should work unless it has a built in key and the honda key is not removable. Either way a key is necissary for the clutch to work. Centrifugal clutches are so cheap though I'd just get a fresh one.

 

[Bob Kazamakis]

Then how would you put it through the case bearing? Im willing to bet it pulls out. The old one may be a bit rusty. Pb blaster and vise grips work well

 

[radioguy6]

yeah I agree it has to be removable.

 

[Freebeer187]

Oh ya know what now that I think of it, the old clutch had about half of a key (risend rectangle) in it. Something must have broken off...

 

[Bob Kazamakis]

Yea they can sheer.

 

[Freebeer187]

Know anything about band brakes? I need a whole new kit >:|

 

[Bob Kazamakis]

That I do not. We use disk brakes.

 

[Freebeer187]

That I do not. We use disk brakes.

Im going to be installing the throttle kit after the game. Ill let you know how it goes

Im just going to leave this here too. I need to build something similar to this. I dunno where to get the damn bolts n such for it. I can get the band brake pad. The loop at the end of the steel cable is not needed. I have a pim to fix that. Any ideas appreciated!

 

[radioguy6]

I have a band brake on my homemade gokart. My minibike has a scrub brake . I jerry rigged the band brake to the frame, but it stops good and has enough bite to lock up the wheel. Looks like you have the drum on the rear tire already, just need a replacement brake band. It looks like a horseshoe, it fits loosely over the drum with one end bolted to the frame and the other connected to the brake line. When brake is applied it closes around the drum, similar to a drum brake on an older car, but on the outside of the drum instead.

 

[LSx S10]

Harbor freight is closing out all of their "greyhound" clone motors, so I bought another one for my go cart. With a 20% coupon and their sale price, it was 74 bucks shipped. Couldn't pass that deal up.

I know you bought a throttle kit already, but this is how I set up mine. Its really simple and costs less than 5 bucks.

New motor mounted:

Remove the airbox and gas tank. The big black spring on the inside is the one that gets replaced with a solid linkage. The little spring on the other linkage can be removed, its not needed. Also the nut holding the throttle arm on needs to be loosened up so it can move freely.

Linkage made out of 14ga multi purpose wire.

All done, now the governor is completely bypassed. I reused the black spring as a return spring for the governor arm. Just needs to be shortened a little bit.

 

[Freebeer187]

haha niiiice!! Looks good man! Ill look into the governer soon enough