Sportsman 80

GoldenMotor.com
S

sportscarpat

Bonneville Bomber the Salt Flat record breaker
Jun 25, 2009
1,839
471
83
california
Sportsman 80 because it has a 79cc Harbor Freight engine. I have floated pictures of this bike around while it's been going through development, but after the lastest couple improvements I can say it's (possibly) finished! I have added a simple clutch guard, increased the size of the second primary drive sprocket, and added a real exhaust pipe. Ever stuff a set of headers on a muscle car? Same effect here. Louder and faster! Just the pipe alone has increased the cruising speed by 8-10 mph. So my internally stock HF79cc engine with 19mm Mikuni and performance intake and exhaust can cruise at 40 mph. It is really a go anywhere bike! It's fast, smooth, very easy to start, handles great and is super strong.

Sportsman 80 by Sportsman Flyer, on Flickr

Clutch guard, exhaust system, and modified gearing so it will rev. My calcs at 40 mph show 6000 rpm.

Sportsman 80 by Sportsman Flyer, on Flickr

Probably the coolest feature is the entire engine package is a bolt-in. The engine cradle straps to the frame and carries the engine and the engine mount bracket has about 1 1/2" of adjustment for chain tension.

Sportsman 80 by Sportsman Flyer, on Flickr
 
wheelbender6

wheelbender6

Well-Known Member
Sep 4, 2008
4,059
221
63
TX
Your HF engine looks a lot like a Jawa speedway engine the way you mounted it with the cylinder vertical. Beautiful build.
 
RicksRides

RicksRides

Member
Feb 22, 2012
864
6
18
osceola IN
I concur with the bear. SB, I was listening to the radio the other day they were playin an old Jim Croce song " Hard time losing man" 1 of the lyric is "Sometimes you eat the bear sometimes the bear eats YOU.

Pat as always FANTASTIC work!!!!
 
C

curtisfox

Well-Known Member
Dec 29, 2008
6,046
3,948
113
minesota
This is a AWESOME build, proof you don't need a big engine to build a good bike. Is that exaust pipe strieght through or do you have baffles in it?............Curt
 
S

sportscarpat

Bonneville Bomber the Salt Flat record breaker
Jun 25, 2009
1,839
471
83
california
Thanks for the comments, guys. I agree about not needing a big engine. With my bigger bikes I kind of limit where I ride, staying out of the busy areas. This thing is so legal I ride it anywhere and don't worry about it.
Exhaust is a couple long elbows so they have straight sections on either side of the 90. Welded together they are a perfect length for a forward facing pipe. Just roll each 90 where you want it to point and then weld together. I used a 1" kart muffler that is straight through with a couple perforated screens inside and no packing material. A little loud but acceptable. Actually sounds really cool!
I did find after some extended runs at 40 mph that the engine vent hose would drip a little oil. I mounted a catch can in the tool box last night. I also went back to the stock 12 oz of oil. I was running 14 oz. I hate oil drips on my driveway. I think we have put the vertical cylinder and oiling issues to rest. I have never had a lack of oiling issue. I know, long rant. Just trying to share what I have learned. That's why were here, right?
Oh, the clutch, yeah it's a custom single disk Bully with 5/8" bore made special for the HF79cc engine. Set at about 3000 rpm engagement to let the little engine spin up a bit before lock. Works great!
 
Last edited:
C

curtisfox

Well-Known Member
Dec 29, 2008
6,046
3,948
113
minesota
so you must be useing 1" pipe, what size is the engine port hole? or did you hone it out? Use old north woods guys have to learn to
 
F

fasteddy

Well-Known Member
Feb 13, 2009
7,445
4,888
113
British Columbia Canada
My thought when I first saw it was that the motor was a perfect size for just riding around and enjoying it. For my way of thinking and my needs I could add a sidecar to it and it would still have plenty of power to carry two people I would imagine.

Of course it would require all stops being pulled out to make a sidecar that would be equal in beauty to this bike but I may be up to the task. Then again if my son heads out to South America on his motorcycle this fall as he plans he may find someone who does wicker and rattan and I could get a flashy wicker sidecar built and shipped.

I think a Sportsman bike from Worksman is in order this fall and then work from there and just when I thought it was the right time to retire.

Steve.
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
fasteddy said:
My thought when I first saw it was that the motor was a perfect size for just riding around and enjoying it. For my way of thinking and my needs I could add a sidecar to it and it would still have plenty of power to carry two people I would imagine.

Of course it would require all stops being pulled out to make a sidecar that would be equal in beauty to this bike but I may be up to the task. Then again if my son heads out to South America on his motorcycle this fall as he plans he may find someone who does wicker and rattan and I could get a flashy wicker sidecar built and shipped.

I think a Sportsman bike from Worksman is in order this fall and then work from there and just when I thought it was the right time to retire.

Steve.
Click to expand...
Oh boy! I can see it now with a wicker sidecar...
SB
 
runnermike

runnermike

Member
Nov 18, 2012
936
0
16
Sanford, FL
Hey Pat

What type of tubing is that you used for the exhaust? I know its 1" O.D., but it almost looks like copper.....

The exhaust looks sweet!
 
S

sportscarpat

Bonneville Bomber the Salt Flat record breaker
Jun 25, 2009
1,839
471
83
california
runnermike said:
Hey Pat

What type of tubing is that you used for the exhaust? I know its 1" O.D., but it almost looks like copper.....

The exhaust looks sweet!
Click to expand...
I was a pipe fitter and welder for a few years working with thin wall stainless tube. The 1" o.d. tube is 304 stainless in .065" wall. I tig weld it. Here is a close-up of the pipe on my bigger bike. Lot's of joints here so this one takes time to fit and weld.

Keystone Flyer by Sportsman Flyer, on Flickr

The copper color shows up after a few heat cycles. Here is the 80cc pipe. Short but sweet. One weld at the flange and one butt weld between the two fittings. Doesn't get any simpler than this!

Sportsman 80 by Sportsman Flyer, on Flickr
 
Last edited:
You must log in or register to reply here.
Top Bottom