Harbor Freight Greyhound 79cc engine

GoldenMotor.com
W

WayneC

New Member
Aug 2, 2009
173
0
0
Clearwater, FL
Hi guys,
I have had this Greyhound engine in my shed for just about a year now and am finally gonna use it on a project. After reading through this thread tho I'm wondering 2 things:

1. You guys who are posting of RPMs, Are those ACTUAL running RPMs? As in, you are reading this off of a tach while riding. I'm curious/skeptical if the engine will actually hold on to 3600 going down the road pushing a 26" wheel or even the 4000-4500 RPM some are claiming (ungoverned). I could see it in a case like that last post on a pusher trailer with the small go cart or mini bike wheel.

2. Has anyone seen a performance chart for these engines? I wonder where peak torque and peak power bands are in that 3600 RPM range? No performance data in my printed material. I haven't been able to locate anything else on the web either.
WC
 
Quenton Guenther

Quenton Guenther

Dealer
Feb 21, 2008
686
1
0
Outer Banks of North Carolina
Hi WayneC,

The HF motors were tested with the Q-matic drive from EZM. The Q-Matic clutch is custom made to enguage at a specific speed, unlike standard cent. clutches.

In order for the HF motor to be "geared" correctly it is necessary to alter the final ratios to use the limited power band. If you mount a clutch on the drive shaft of the motor it will present 2 problems, first it will be too wide, and secondly it will be very difficult to arrive at the correct ratios without a reduction shaft.

The motor is rated at 3600 RPMs, however it will easily spin up to 5600 RPMs without the governor. I rode two different bikes with the HF motor and Q-Matic drive and both easily cruised at 25 mph. The actual numbers are 4750 RPM @ 25 MPH. Both bikes could exceed 30 MPH which means the motor actually peaked above 5600 RPMs under load.

The additional torque allows the motors to be geared differently than the hi RPM Honda or HS motors.

The HF motor produces a little more torque at lower RPMs making it a great choice for heavier riders or hilly terrain.

Have fun,
 
tyrslider

tyrslider

New Member
Sep 26, 2008
958
2
0
RainCity
Not seen specs on the greyhound but these are pump motors and the governers aren't really governers so much as they are turtle/rabbit controls. The manufacturer has determined the 3600 (rabbit) rpms to be the most efficient/ peak hp speed for that motor.

There's no real reason to doubt that you can reach those motor speeds if your reduction ratios are correct.

If its a one speed (and you gear it for top speed) you'll likely not max out up hill but you will down hill. If it's a shifter it depends on the ratios.

Lot of confusing ratio info on this thread for the layman.
 
W

WayneC

New Member
Aug 2, 2009
173
0
0
Clearwater, FL
Thanks for the responses guys. I was planning on using a jack shaft and have gearing options in my stock for ranges from mid 7s to mid 9s:1 overall ratios. I'm thinking the 9.5:1 will be the better choice, but, I'll be able to play with several different combos and go lower if need be.
I have read on kart forums and others that these motors will crank over 5K but again with smaller wheels and again ungoverned. I'd be happy with a 30 MPH bike. My 200 lb self and about 100 lb bike (loaded for full day commuting) need the grunt to get up over some high bridges in my area. I don't expect the bike to fly over them but some good power would be nice.
Thanks again.

edit: Oh by the way, what do these motors idle at and what would be a good clutch engagement RPM? The on clutch I'm looking at engages at 1800.
 
Last edited:
Fossil

Fossil

New Member
Mar 15, 2008
228
2
0
Guthriesville Pa
I have one of the bikes Quenton spoke about in his post. The motor has a good amount of torque and I think you will be happy with it. I am experimenting with a variable front pulley to help get the clutch engaged at a lower rpm but I have been so busy with work that I have not had the time to finalize the build.

Jim
 
Quenton Guenther

Quenton Guenther

Dealer
Feb 21, 2008
686
1
0
Outer Banks of North Carolina
Hi WayneC,

You might want to re-think the ratios. 138 CC Whizzers are usually geared in the 9s and it is too high for riders over 175 pounds.

You also need to consider the width of the motor, and the exhaust exit point during your build. The motor is very wide on the rope start side. Because of the length of the motor you will need to mount it high in the frame to clear, however it makes it easier to make the pedals clear.

Look at the pictures of RusticRay's & Fossil's bike with the HF motor installed to see the frame clearance.

http://motorbicycling.com/attachmen...-freight-greyhound-79cc-engine-0919091149.jpg

http://motorbicycling.com/attachmen...or-freight-greyhound-79cc-engine-img_0751.jpg

Have fun,
 
Last edited:
Dan

Dan

Staff
May 25, 2008
12,765
115
48
59
Moosylvania
Thanks Ray. Dunno how I missed it. Gonna snatch up DV8's.

OT, think I mentioned or posted links to your atlas builds about 3 or 4 times today. The Velcro thing for the GPS is just brilliant. I still have not called our friend about getting one.

On your Atlas's, are those stock seats?
 
R

RusticoRay

New Member
Oct 3, 2009
170
0
0
6mi. from the Old North Bridge
Dan said:
Thanks Ray. Dunno how I missed it. Gonna snatch up DV8's.

OT, think I mentioned or posted links to your atlas builds about 3 or 4 times today. The Velcro thing for the GPS is just brilliant. I still have not called our friend about getting one.

On your Atlas's, are those stock seats?
Click to expand...
Yes those are the stock seats for the atlas. Speaking of Atlas I installed Adapter and Sprocket from Creative Engineering yesterday, no more hop what a beautiful thing.
Check to see if the workman sattle is the stock 11" wide or the wider one at 13". Either one at 20.00 is a good saddle at a good price.
The push trailer ( 79c.c. Greyhound H.F. formally on the Atlas ) will be attached to a 79 Batavus Moped(no shame just fun) with a bad cylinder. It is the bad sister of a set of twins I picked up a while back. Was going to use for parts but maybe a second life. If it works out I'm going to register it in Ma.(not sure about the third wheel being a pusher). The whole mess will be paying you a visit soon as I get back from Fl. trip.
 

Attachments

Dan

Dan

Staff
May 25, 2008
12,765
115
48
59
Moosylvania
Ray! when ya going down? Carol and I are planing to go around March 4th to visit Mike and Ron (Neat times) Some other folks might be going.

"Hop"? Dununderstand

Just got back from the store. Is 68* and I wore shorts and a Tshirt! Be a great day for a ride. My car is at the shop. My 2 smoker has a broken mount and my 4 stroke is in MI being used as a tester for a tranny. I am bummed! lol (I was sad because I had no wheels. Then I saw a man who had no bike)
 
KilroyCD

KilroyCD

New Member
Jul 22, 2008
279
0
0
65
Lancaster County, PA
Last edited:
R

RusticoRay

New Member
Oct 3, 2009
170
0
0
6mi. from the Old North Bridge
I'll have one of those large seats with my cup of coffee soon. Thanks for the link Chris.

Dan the chain hop I got when my limited machining ability(dremel)of the sprocket axle hole. The sprocket needed a little work to get over axle bearing cap of Shimano CB110 hub. The chain would slacken then thighten up per revoltion of wheel multiply by 35mph and you got a noisy situation. I put thirty miles on yesterday and becides the motor I heard a small chatter of the chain. Creative Enginnering adapter and spocket as stated by many the best. Dan have you seen my muffler?
 
Dan

Dan

Staff
May 25, 2008
12,765
115
48
59
Moosylvania
Kool Ray! Is that the same muffler and is there a thread? Wanna ask a bunch of ?s and dunwanna trample.

Post Script, looks awesome.
 
D

dv8cam

New Member
Dec 15, 2008
84
0
0
Los Angeles
Dan said:
Thanks Ray. Dunno how I missed it. Gonna snatch up DV8's.

OT, think I mentioned or posted links to your atlas builds about 3 or 4 times today. The Velcro thing for the GPS is just brilliant. I still have not called our friend about getting one.

On your Atlas's, are those stock seats?
Click to expand...
Did you ever get my email? I will PM you about the seat.
 
You must log in or register to reply here.
Top Bottom