My Harbor Frieght Greyhound full suspension Mongoose build

4

4950cycle

New Member
Hi, I'm gonna post my rack mount, V-belt drive, 4 stroke build to show there are other ways to skin a cat. For those that are interested, my technically challenged butt will be attempting to put the thread together today and super near future. I have pics but no video yet. Mad MAverick AKA 4950cycle or just plain John cvlt1
 
The pics are big so I had to put them in photobucket. Here is some pics of the almost (aside from elective improvements) the finished product. As I have said it has a 2 1/2 hp 79cc OHV slant cylinder Harbor Freight Greyhound engine. I took the gas tank off the top of the motor to lower the profile so my rear suspension has some leaway. Trimmed the plastic petcock and switch panel so it would look right after removeing the gas tank and welded a new exhaust configuration using the factory muffler can and a section of seat post. I will put together the following post to show the build in stages for those who may be interested in how I got this most excellent full suspesion two ratio motorbike together. Thanks for the encouragment cvlt1





Pictures by Patriotrights - Photobucket
 
That looks great! I just bought one of those little HF 2 1/2hp greyhounds and put on my rototiller. Now if the tiller breaks.....you have given me a great idea for the engine. Thanks for sharing.
 
John

looks like a dependable ride. The double pulley is a great idea. Looks like a spring tensioner on the wheel drive belt, that will save the spokes if spring is not too strong. Great build. Probably goes faster than needed!! Lol.

Thanks for sharing.

Ron
 
I appreciate the encouragement, Some have asked for top speed and why no rear fender. I have a matching rear fender that needs modified to allow for the belt drive. Just havn't reinstalled it yet. Got them off a Huffy Cranbrook. A real beaauch to install on a suspension bike BTW. That is why I have been procrasstinating on that. Top speed in high gear is about 35 mph now (motor not totally broke in yet) . I can tell potential for at least 42-45 with a minor ratio adjustment. Might even do that when over revving once broke in without overall ratio change. I am tall and 230 lbs. And don't ride in a tuck. Would be better with average Joe. But I don't want to run the motor to death. Remember these HF OHV Greyhounds don't have a braod a power band (rev range) as the Honda/Haushang 50cc motors. That is why it is almost essential to have more than one ratio for Greyhound powered MBs to be entertaining. Good and powerful, just not very rangey if you know what I mean. They run out of speed if you don't have another gear/ratio to go to. I think my high ratio is about 9.5 to 1 . But to be sure I will do a pulley revolution count test tomorrow to not make any false statements. cvlt1
 
Yea Ben/Cannonball2, It will strike if you really ask a lot of the rear suspension. But it is still way better than not having it. Seat post is not as close to motor as it looks. There is a natural slot in the way the engine is put together that gives the seat post a place to go when suspension compresses. I won't lie though, It did loose "some" rear suspension travel.
 
4950cycle said:
Yea Ben/Cannonball2, It will strike if you really ask a lot of the rear suspension. But it is still way better than not having it. Seat post is not as close to motor as it looks. There is a natural slot in the way the engine is put together that gives the seat post a place to go when suspension compresses. I won't lie though, It did loose "some" rear suspension travel.
Click to expand...

I thought probably so. I had a to tighten the shock on my Mongoose FD so when I lifted the motor the suspension wouldnt compress. Suspension bikes are great but some times the suspension can work against you. Still that a great well thought out build, love the two speeds. I am contemplaring a 2.5 Lifan on the front of an upscale MTB as my last build. Something similar to Lowracers build. The engine is on the way atleast.
 
I thought that sounded a lot like Alex Lowracers bike ? Yea, before he got his setup dialed in and fell in love with it, you could have bought his 2.5 side valve Lifan motor. He was going to sell it to me then he got it right. Then all bets were off. lol My first rear rack 8inch friction wheel build was a flat head (side valve) motor. They have a lot of oommph. But I find the type of power they have to be a bit hard on a bicycle drivetrain. To pulsey and jerky if you know what I mean. The Over head Valve (OHV) and Over head cam (OHC) motors have the smoother power delivery IMI. I think these shocks that come on these suspension bikes can be replaced. The color of the spring usually determines the strength or how many LBS. the shock is rated for. My D50i I think it is came with a Black spring. It says 750 lbs. on it. And I have adjusted it as you have mentioned for more preload already. Maybe I'll go to a different color if there is a heavier one ? Where is a pic of your bike located Ben ? I want to see it if I could. cvlt1
 
My bike has the 750in/lb spring also. I screwd it in all the way and the backed it out a little at a time til I found the balance I needed. The only problem I have had with the Lifan is the Gonernor slipped on its shaft. Once readjusted and set I have had no other issues. I run it governed, works like cruise control, set it and forget it until you have to stop. The HF is ungoverned. While I find the Lifan very smooth, the HF is smoother and winds higher and more freely. I like the upright compactness of the Lifan though, the HF is kinda stretched out. Both are great engines. My bikes are in DIY under: HF friction Drive a different approach and Lifan 2.5 Friction drive. Check out the Easy Variable Pulley too, a different spin on multi speeds.
 
I like it! Looks like a nice tight build, I know its a smooth ride.
I used a modified Island Hopper friction
drive on my old Pacific dual suspension and it was sweet, if not just a bit tail heavy.
Enjoy the ride!
FR
 
My Mongoose is a bit tail heavy. But I made it as light as I could and it is only a bit awkward when pushing the bike by hand. You know, taxiing the MB around the garage by handlebar. When I'm riding it my 230 lbs. dominates any incidental weight the tail of the bike my have. Its worth it to have all the motorized stuff out behind you. You still feel like you are on a bicycle instead of a makeshift motorcycle like my dads China girl Huffy Cranbrook. cvlt1
 
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