My four stroke build- observations

Discussion in 'General Questions' started by HoughMade, Oct 22, 2007.

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  1. HoughMade

    HoughMade Guest

    I have come pretty close to completing the mock up of my build so I could get everything working before I blow it apart for paint. You can see a couple of pics in the gallery section under "HoughMade Cycle Works". I just wanted to toss some things out that I learned along the way.

    First off- I started with the Grubee Skyhawk II- some refer to as the Whopper Stopper II. I used a Honda GXH50 I sourced from Small Engine Warehouse- there is another topic dedicated to that, but suffice to say- it works well.

    A few points-

    - Buy quality bolts, screws and nuts. The gold colored, slotted head bolts used to attach the gearbox to the engine are decent, but everything else needs to be replaced. They are soft and strip or break too easily. No surprise there.

    - They say you can install in 3 or 4 hours- HA. Maybe if you do not want to be careful, but I worked on this thing for weeks (an hour or two at a time). Not everyone will take that much time, but 3 or 4 hours seems optimistic to insane to me.

    - I did several things 3 or more times to get it just the way I wanted it. I replaced the plastic air cleaner with a fabricated metal "can" to look more vintage- that alone went through 4 version and about 5 hours. The throttle linkage took me about 6 to 8 hours (and about 6 versions)- I started with just attaching the cable to the stock lever, but I liked neither the way it worked nor the way it looked. I wanted the throttle to snap closed when you let go- I consider that essential for safety. In the end, I eliminated the stock lever, all of its linkages and the governor (which I had planned anyway). What I have now is very simple and works great (40 mph w/ a 56 tooth sprocket with a hair more left on top- without overevving the engine).

    - I am running the gearbox with grease only. I know there has been a lot of discussion about this. Mine was never really noisy as some describe it, but I could hear it when it engaged, but the more I use it, the quieter it gets- I'll stick with grease (I use high temp wheel bearing grease).

    - If you want a clean looking build- be prepared to shorten cables. I shortened the throttle cable by almost a foot- I had a screw on end to use- I wish I could tell you where I got it, but all I can say is I think it is a lawn mower throttle cable piece.

    - The engine runs quite smooth- no complaints.

    More thoughts as time goes on, and if you have any questions about the kit, feel free to ask and I will handle them if I can.

  2. Alaskavan

    Alaskavan Guest

    You demonstrated an amazing amount of patience with your build. It shows in the finished product.
  3. Dockspa1

    Dockspa1 Guest

    The time and patience that you have shown now will no doubt pay off in the end.
    I have a few projects in the workshop and I will tinker with them a little at a time but when I'm done, I know i'll have done my best.
    Looking good man.
  4. HoughMade

    HoughMade Guest

    Now this is humorous- I mention how detail oriented I am- and leave a typo in my topic title....great.

    -A few more observations-

    - The engine mounting plate (with adjustable ends) is quite well made provided you do not use the bolts provided. I would think that using a plate without the ends that adjust would be asking for trouble with the number of frames out there.

    - Also, I am using 2.125 tires- the chain comes very close (a little too close at times), but I will make it work- using at least that size of tires is critical to the look I am going for.

    - The in-out control for the gearbox seems backwards (to those of use used to a motorcycle clutch)- to engage the gearbox, you squeeze- I am probably going to reverse it so it engages when you let go and disengages when you squeeze- if you use the bike to pedal without power a lot, I would understand why the operation would be as it is, but I am using the pedals only to start (though it will move me from a dead stop).

    - Whoever says coaster brakes are not enough is right. They will work fine to gradually slow down when you can plan ahead, but I would not want to try to stop fast with them. I added a standard caliper brake to the back- but I am replacing that soon with a decent V-brake. I likely will add a front drum when I can find a decent price on one.

    - I had issues getting the standard supplied gas tank and petcock to work. With the petcock (with its pitiful screen "filter") screwed into the bung, the tank would not sit straight on the top tube because the hose barb hit the smaller diameter frame tubes that curve from the front down tube to the rear wheel. So, I ditched the petcock (there is a fuel valve built into the engine) and put a 90 degree brass fitting on the tank with faces mostly forward- I fit some 1/4" soft copper to curve it underneath the tank (and forward), where I pick it up with 3/16" fuel hose and route it back to the carb- with a Briggs and stratton fuel filter on the way. The entire fuel line run is tucked up under the tank between the small frame tubes. The only thing that currently shows is the short run of copper which will be covered by my tank cover when it is finished.
    Last edited by a moderator: Oct 22, 2007
  5. drimpact

    drimpact Member

    Typo fixed!

    Awesome build! I find I do my best work when I take my time...
  6. HoughMade

    HoughMade Guest

    Many thanks!

    RATRODER Guest

    HoughMade has front drum wheels at nice prices.louis
  8. fredbert

    fredbert Guest

    Hi HoughMade,

    Did you find that the hole on the grubee 2 gear box line up, I have a GXH50 and a Grubee 2 gear box but it is badly out of line with the holes.

    Are the holes for mounting threaded or did you have to thread yours?

    Thanks Ed
  9. Bean Oil

    Bean Oil Guest

    I wanna see!!!

  10. Herrmanator8

    Herrmanator8 Guest

    oooooohh!!! :D this new thread makes me sooo eager to build my new
    4-stroke project!!!:rolleyes: your project sounds great so far, cant wait to see pics when it's done!

  11. fetor56

    fetor56 Guest

    "They say you can install in 3 or 4 hours- HA.".....sounds familiar...........3 or 4 hours if i know aliens are coming to abduct me. :eek:
    Last edited by a moderator: Dec 20, 2007
  12. fredbert

    fredbert Guest

    may help UK members

    Here is a difference between the GXH50 sold in US and that sold in UK first is the QED4 version bought in the UK and the second is QXA sold in US I am not too sure if this is sold in UK but it is something to look put for.

    I asked HoughMade "Did you find that the hole on the grubee 2 gear box line up, I have a GXH50 and a Grubee 2 gear box but it is badly out of line with the holes."

    My problem was due to the mounting holes to allow the engine to be bolted to equipment like the cement mixer etc. These prevent a snug fit and keep the holes of the Gear box from lining up.

    Just some info I hope may be useful to others, for what it is worth.


    Attached Files:

  13. ocscully

    ocscully Member


    I was just looking at the two photos above and am wondering, it appears to me that the UK engine has two sets of mounting holes. Don't the set of holes just outside of the circle match the set of mounting holes shown on the US version of the GXH50? So is what you are saying is that this surface is not flat and the outer mounting holes keep the gearbow from seating up flat? Or are the inner set of holes not drilled and tapped for mounting? I have the US Honda GXH50 but have not mated it up to any gearbox as yet.

    Last edited: Dec 27, 2007
  14. fredbert

    fredbert Guest

    The inner holes are not tapped ocscully, the surface is flat and the supports for the outer holes prevent the grubee gear box from matching up. The housing of a bearing sits proud on the back of the gb and prevents it from sitting flat as it hits the outside hole supports.

  15. HoughMade

    HoughMade Guest

    All I can say is that the gearbox lined up and bolted up perfectly without modification.

    I have been looking for a photo of the PTO side of an engine like mine, but so far I have not found one. There are four mounting holes on a raised "ring" of about 4" diameter with the shaft at the center- perfectly on center. All 4 of the holes on mine were tapped and where the shaft emerges, there was no raised portion.

    Unfortunately, work issues, the holidays and weather have placed the bike-cycle lower on the priority list lately. I have a couple of more modifications to make and I think I will be getting new wheels, then when it is all mocked up and straight....again....time for dissassembly and paint.

    Below are pictures from the fall. Since then, I have built new handlebars that go straight out and down instead of down and back like regular handlebars upside down.

    Attached Files:

    Last edited by a moderator: Jan 7, 2008
  16. ibdennyak

    ibdennyak Guest

    Hey....thanks for that post. You may have just explained a problem I am having with a GX25 I have. It is set up to be mounted on a tiller, and has what looks like the mounting in your first picture. Did I understand correctly that I can purchase the US version of the mounting plate?

    Last edited by a moderator: Jan 7, 2008
  17. HoughMade

    HoughMade Guest

    I found a picture- this is what my PTO side looks like. You can see the obvious differences.

    Attached Files:

  18. Herrmanator8

    Herrmanator8 Guest


    hey there, this is jon. i just bought a brand new honda gxh50 engine from for $300, with a 2 year warranty. in addition to that i bought the mounting kit from i will be purchasing a bike soon. anyway, i would like to know if any of you guys out there know of the best/simplest way to setup the throttle system. ive been looking around the site for good ways but they include taking parts off and getting rid of the governet. i was just wondering because i do not want to void the warranty by performing these mods. so if anyone could get back to me on some info on the throttle in addition to some good tips for performance, that would be great.:grin:

    Thanks, Jon Herrmann