Harbor Freight 79 vs Honda 50 and HS50

Discussion in '4-Stroke Engines' started by MotorbikeMike, Jan 9, 2010.

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  1. Hello all, there has recently been a lot of questions, comments, ideas, and stated ideologies about some of the small 4-stroke engines which are still very new to allot of owners of Motor Bicycles.

    I have ridden the RS35, and it was a nice smooth underpowered engine for my taste. I own and ride HS-50 and Honda gxha50, and I can tell you that both of these engines perform VERY well, and far above the results I had with RS35.

    However, most recently, there has been a bit of a buzz about HF's 79cc Greyhound 2.5 hp OHV. There have been statements made as to its performance as a superior Motor Bicycle engine, even though it is rather long, and actually pretty wide.

    What I propose is a chance to run these bikes together, and see what the results may be. So, I am in Sacramento CA., and there must be many 4-stroke bike owners within an hour or two of here?

    Stock engine, the only mods allowable are remove governor (if equipped), open the exhaust, and use any air cleaner you like. No disassembly, nor internal mods accepted, this is not to see if you, or your friends, likes to hop-up "stock" appearing engines.

    26 inch wheels, bicycle of any "normal" type (i.e. no plastic recumbents with streamliner bodies)

    ANY gear ratio you like, BUT no shifting, no CVT, no Nuvinci, just see what the engine will do, not what kind of transmission you might scare up.

    Anyone who wants to play, 4 stroke stock engines, BUT especially with the HF is welcome! I stock a lot of parts, and if you have trouble with your build I am willing to help you, no labor, just whatever parts used.

    One major problem area is exhaust on the HF and I have solution for that here.

    I await your entries!


  2. Nuttsy

    Nuttsy Member

    Apples to Apples

    Large Deal! Your V8 Muscle car can outrun my Cummins Turbo Diesel. Big whoop-D-freaking do! And my CTD can pull a house up a mountain! Ooooooh!
    You are talking about two very different motors built for very different purposes.
    People are gonna like what they like for what benefit it can provide for THEM! PERIOD! One engine is not superior or inferior to the other. Its just a matter of what one chooses for a given purpose. And what kind of half-assed challenge is it to say all things have to be equal? Again, would you put a Porshe engine in a Freightliner and expect it to turn in the times that the Porshe would. And vice versa?
    I may be Nuttsy, but I'm not STUPID!
  3. HoughMade

    HoughMade Guest

    I guess my question would be- when one puts an engine on a bicycle....what relevance does a sports car to semi comparison have? Frankly, a few people pull a trailer, a few build trikes, but I would venture a semi-educated guess that 95% of MBers want to run around on a bike with 2 wheels and no trailer. Probably 60-70+% would like to cruise close to 30 or a bit over. Given that background, a Greyhound to Honda/HS comparison with like bikes makes a lot of sense...especially with varying claims about speed, on both sides, out there. You aren't interested? One more topic you don't have to read.
  4. Nuttsy

    Nuttsy Member

    You are missing the point. The relevance is the fact that the engines were designed for different tasks. Now if you want to do this "challenge" with the HS v the Honda, all else being equal, OK. Or if its a comparison of what two HF engines can do with setup 'A' and drive system 'B', OK. Keep it apples to apples. But to tie the hands of either engine and not let them pull to their best benefit, then it's not a comparrison at all since one can spin to 8K RPM and the other 4-ish. What kind of contest is that? If what I have read about the HF 79 and all it's 'grunt' is true, then such a 'contest' on a steep hill with a load wouldn't be fair either. How can anyone not see that?
    H, when did you acquire the attitude? I probably won't follow this thread since the theory is flawed from the start, but who are you to tell others what they do and don't have to read? The new thread police?
  5. spunout

    spunout Member

    I think it's a great idea, mike, regardless of any potential naysayers. you are comparing two completely different motors and thats exactly the point. edit: the results of one motor may appeal to one, while the other may have benefits that are more of what someone else will be looking for. apples to apples.
    i'll keep watching this thread because i'm interested in the results. and thats great you're willing to help out with parts.
    Last edited: Jan 9, 2010
  6. Youngbird

    Youngbird Member

    Count me in too. I just got a HF 79cc today for $71.00 and change, so Im looking at all the comparables I can. Go for it.
  7. Tinker1980

    Tinker1980 Guest

    One thing I like about the HF engine is you don't have to get really elaborate with your gear reduction. If you only have to deal with gentle rolling hills, you can gear the engine to run 30 MPH at 3600 RPM and it will pull me (200+ Lbs) along just fine. If you've got a six or seven speed spare bicycle wheel, one can use the axle and cassette from that wheel, and using a 48 tooth happy-time style gear on the back wheel with a 10 tooth centrifugal clutch, you've got all the gearing stuff you need - just have to assemble.

    The engine starts very easily, even in this unusually cold winter (0 degrees F) that we're having. One pull at full choke and it starts; run the engine on half choke for a little while if it's very cold outside. (If the engine isn't warmed up, and you open the choke, it tends to stall out when given throttle.)

    The only complaint I have with this engine is the small fuel tank, and the screen inside that small fuel tank. There is a filter screen for when you put gas in it, it catches all the bad stuff that might get poured in. It makes it hard to fill up at the gas station.

  8. atombikes

    atombikes Member

    Mark, I recently purchased one of these HF engines, and am planning a build. Thanks for your insight; it sounds like you have already built one? I don't follow what you mean in the quote above? Are you suggesting using the 6 or 7 speed freewheel as a mid-drive (jackshaft)?

    I started a thread on my Harbor Freight build here:


    Thanks, ED
    Last edited: Jan 10, 2010
  9. Tinker1980

    Tinker1980 Guest

    You've got it - I plan to use the 7 speed axle as a jackshaft. I haven't yet finished my build, I'm working on it as time (and money) allows.

  10. snowbanana

    snowbanana Member

    does the harbor freight engine even compare with Hondas as far as reliability?
  11. Reliability?

    Hi snowbanana, no, I certainly do not think the cheap HF 79 compares with the Honda, on any level. But, apparently some do, and I plan to be ready for them.

  12. GearNut

    GearNut Active Member

    This sounds like it is going to be a good thread!
    I plan on building a 4-stroke in the future. I ride on mostly slight rolling hills, but I live on the top of a very long, steep hill. I need a powertrain that can do good on both.
    This compairison is just what I have been wondering about. Which engine could suit my needs? I am a bit leery about the HF engine though, the displacement is too large for Cali. I may still risk it though.
  13. jbcruisin

    jbcruisin Member

    there's a huge steep hill near my house & when I get to the top my Hueshang's doing 19 mph.
  14. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi GearNut,

    Sorry, but I answered your post earlier but I received 20 points and the post deleted. I made the mistake of mentioning a certain brand of product. It is OK to mention any brand except one. So here it is again without certain brand names, certain brand names now will be called brand W, or brand X. The names have been changed to protect the innocent.

    Hi GearNut,

    I live on the edge of the Atlantic ocean and is mostly flat, however there are a lot of bridges to connect the islands. The bridges are long and steep because large boats must pass under them.

    When I ride a stock 138 CC brand "W" [4 stroke], it is necessary to get a good running start before attempting the "hill climb" or it will run out of power just before cresting the top.

    Not long ago I decided to test the ability of the HS 49CC 4-stroke from a complete stop at the bottom of a very long & steep bridge.

    WOW! at the same point the Brand W started slowing down the HS motor simply "dug in", the RPMs slowed somewhat, but it just pulled like a tractor and went over the hill with ease. I was so amazed I repeated the ride several times, and each time the little motor "dug in" and easily pulled the hill. It seems the RPM slowed to the peak torque curve of the motor and just produced raw power [torque] when needed.

    The HS motor is legal in almost all US states because it is 49 CC and the HP is also within the guidelines of most states.

    The HF motor, however is above the HP & CC limit in the majority of states [not all].
    The HF motor hasn't been tested near as much as the HS motor, but the several HF equipped bikes I have ridden [with the same brand X drive as the HS motor for an even compairson] pulled good but ran out of RPMs early and had a much lower top speed.

    One problem about the HF motor that does concern me somewhat is the appearance. The motor is and looks large, and might be hard to convince someone it is a small CC motor. I know it is only a 79 CC motor but I think it was designed from the brand H 160 or 200 series motors, and could easily be confused for a much larger motor, whereas the HS motor is and looks small.

    Have fun,
    Last edited: Jan 27, 2010
  15. loquin

    loquin Active Member

    I believe the HF engine is copied from the Honda GXH100, Quenton. The mounting pattern and shaft size seem to point that way, anyway
  16. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Lou,

    After reading your reply, I searched the internet for information about the Honda GXH100. It is difficult to find information on that Honda Motor, and I only found it used with a generator and wasn't able to see the actual motor. Most of the information concerning a Honda 100 CC motor was the big brother to the GXH50 motor with the vertical cylinder. I am sure somewhere on the internet would be a picture of the motor you refer to, but I wasn't able to find it.

    The HF 79 CC motor has a tilted cylinder like the 160 & 200 CC Honda motor, and is much larger than the HS50 or the GXH50 Honda motors.

    If you could find and post a picture of the Honda GXH100 motor I sure would be interested in adding the information to my knowledge base.

    Have fun,
    Last edited: Jan 27, 2010
  17. snowbanana

    snowbanana Member

    I live is Salt lake city, Utah and there are steep hills! I don't live right in the valley, I live kind of on the side of mount olympus and everywhere I go there are hills that are really steep. Honda doesn't make a 2.5 HP motor so I was thinking that the harbor freight would help me get up some of those hills. Is there big difference in power between the harbor freight and the honda 50cc engines
  18. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi snowbanana,

    I have actual test results from the various motors. The HS 49 CC motor and the Honda GXH 50 have similar HP, however the Honda is rated higher on certain web sites. I have seen the Honda rated as high as 2.5 HP.

    After exposure to the HS, Honda, and HF motors, IMO all three motors could be "geared" to suite your needs. We tested all the motors with an indentical drive sytem [not allowed to mention the brand name without getting points on this site]. The brand of drive I can't mention allows the ratios to be changed to fit the power curve of the dis-similar motors. We [2 of our authorized dealers]tested the HF motor with different ratios because one of our dealers even had an adjustable drive pulley.

    One of our authorized dealers pulls a trailer up and down hills with the HS motor equiped with the same drive system [brand x] and will tell you quickly it works 100%.

    I know the HF motor has the torque curve at a much lower RPM and would only be worth considering if top speed wasn't an issue and you gear it to pull up the side of a building.

    The main reason I like the Honda & HS motors is because of the wide RPM range, which allows for great low end power and the ability to obtain a fair top speed. My personal proto-type motorbike [once again I am not allowed to mention the brand name] will easily take off from a stop, climb most hills with ease, and reach top speeds over 35 MPH [actually faster, but don't want to brag], in fact it cruises at 35 MPH without "winding" the motor up.

    The only advantage to the HF motor is price, but that is only true if you already have a lot of kit parts laying around. The HS and Honda motors are popular choices and many companies offer them in a complete kit [won't mention our company name as one of the suppliers] and therefore money can be saved compaired to buying all the parts seperate.

    Several companies offer kits with quality AMERICAN made parts [including brand X] and IMO offers the best "bang for the buck". Shop around, and you can find what you are looking for.

    Have fun,
  19. azbill

    azbill Active Member

    I have 3500+ miles on my brand 'X'...
    I expect my new 72T sprocket to pull the trailer/girls up a wall ;)
    I love my bike :)
  20. darwin

    darwin Well-Known Member

    Get caught once riding a 79cc engine on the streets and it can add up tp to 2000$ in tickets. Its the same as driving a car with no plates, reg or insurance plus no m/c endorsement. No thanks! 50cc is governed under different rules thank the LORD.