Happy Time Mounts and Sprockets

Discussion in 'Frame Mounted Engines' started by Molotov256, May 29, 2010.

  1. Molotov256

    Molotov256 Member

    This is probably going to turn out as more of a "stream of consciousness" thing, but I've got a handful of issues brewing between 2 and a half bikes, and it's all leading me in the same direction.

    I've bought 2 generic brand Chinese made 2-stroke kits in the last couple years, and I've built maybe four or five bikes between the two by moving the motors and parts around on different yard sale bikes. Between all the frames, wheels, and sprockets I've combined in various backyard mechanic fashions, I keep on struggling with the same issues, so I want to use this post as a sounding off point for educated opinions regarding these struggles.

    The first matter is the engine mounts. I've mounted the motor on road bike, mountain bike, and beach cruiser frames. I've also broken or lost motor mount bolts an all but one build. I've broken more rear mounts than front mounts, but I have broken bolts on both. As an example, I currently have a motor in my garage with THREE OUT OF FOUR (yes, literally, three of four) bolts sheared off below the surface of the motor. That indicates a weak spot to me.

    The next matter is the engine-side drive sprocket mount. The stock "rag mount" system is really hard to true, and because the bolts which secure the sprocket to the wheel rely on friction and torque against the spokes, it totally destroys my back rims.

    I've googled my issues and used the search function on this forum as well as on another prominent MB thread. I've seen pictures of and read testimonials about the mounts and sprockets MANIC Mechanic makes out of Florida. I've also read posts about guys using U clamps and hockey pucks to hold the motor down.

    Some folks say the ragmount sprocket mount is fine if you spend enough time truing it and carefully counting sequential bolt rotations. Others say the ragmount is the spawn of Satan and must be replaced with a clamshell mount.

    My love for the motorbike is strong, and my path has been chosen. :Mr-T: I must now find my way. (looked for a ninja emoticon but all I could find was a ninja turtle and Mr T.)

    If I'm doing something wrong which is causing my repeated failure, I want to be corrected so I can progress. If I'm repeatedly failing because I'm overlooking a bare bones upgrade or improvement, I want to know about what I'm missing. I'm willing to accept that either my mechanical skills are lacking or I need to spend more money on better components. I'm also willing to accept that making motorbikes with a $120 universal engine kit is a bad idea which is doomed for failure, but if that's the case, I don't want to make them anymore :evilgrin:

    I'd like to hear success stories about motor mounts as well as successful methods of mounting sprockets to bicycle wheels.
    Last edited: May 29, 2010

  2. Al.Fisherman

    Al.Fisherman Active Member

    There you have in in a nutshell of my experience.... Not one failure other then a coil and blown head gasket on my first build out of five.
  3. Molotov256

    Molotov256 Member

    Thanks for sharing your experiences... you mention fabricating a front mount:

    Have you posted anything about how you go about making these front mounts and/or that torque bracket? I am interested... I know for a fact that the frame on which the motor broke 3 of the 4 bolts was not really accommodating the mounts flush. I spent hours trying to get it to line up nice and flush, but the frame simply wasn't built with the same angles the mounts are. I just did the best I could and hoped for the best, but that doesn't always pan out so well, heheh...

    As for replacing the stock studs with grade 8.8 - I might have, but I don't know. I replaced the studs with bolts from my local hardware store, but I'm not sure if they are grade 8.8 or not. I'll have to do a little more research to that end.

    It is also interesting to hear that the ragmount has been working so well for you... I've had some work better than others on a variety of wheels, but every time I remove a sprocket I can see the spokes have bent near the hub. Sometimes it's not extreme, but it surely has an effect on how true the wheel runs. I'm not saying I don't believe you, just that my experience hasn't been as successful.

    Thanks for sharing - you've given me a few things to investigate this weekend!
  4. Al.Fisherman

    Al.Fisherman Active Member

    I don't replace any stud on the engine with a bolt. I lock tite every stud, which you really wouldn't want to do with bolts. I use self locking nylon nuts or they are jam nutted....Each and every stud

    Bolt grade will be on the head of the bolt. A metric 8.8 is equivalent to a US grade 5... Anything over that is only a waste of money as the cast aluminum can't even take the torque that a grade 8.8 can withstand.

    Check out my photo albums in my profile...pictures of everything.

    As far as mounting the engine, I clamp the rear mount to the seat down tube first and make my front engine mount fit the frame. A Chinese HT engine has a 75 degree mounting angle. ANYTHING different (bike frame) gets a custom made front mount. I haven't to this day found a 75 degree bike frame.

    As far as the rag joint...I've never had to remove one. The wheel does need to be trued up before installing the sprocket. Thicker (12ga) spokes can replace the 14 gage, I haven't found a need as of yet.
    Last edited: May 29, 2010
  5. Molotov256

    Molotov256 Member

    Killer pics in your profile, but I couldn't find one of your customized front mount. I'm curious what approach you take since you've made so many of them.
  6. Al.Fisherman

    Al.Fisherman Active Member

    Look in the album.. "Mikes Bike"

    On Mikes, since it was new I taped the seat down tube. I slid the engine on the seat down tube and put on the clamp. I adjusted the engine to where he wanted it to sit, making sure there was plenty of room for the carburetor cable to work properly, and tightened the clamp. Next I measured the distance from the front mount to the front tube. Took a piece of angle iron and fitted it between the mount and tube. With the angle iron (bed rail) the right size I bolted the angle iron to the engine and loosened the rear mount to get a good true fit and re tightened rear. Took mental image of the angle of the tube to mount, removed the angle iron and tacked the mounting brace to it. Refit (easy to bend angle in a vise) until I got it where I wanted it, removed the bracket and wielded the flat bar to the angle iron. Trimmed corners and painted. Took a muffler clamp and secured the mount (flat bar) to the bike. The flat bar was gage 14 and when the clamp was tightened it formed a curve around the tube.

    Notice...all studs are double nutted (except head...locking nuts). Mike cut the cylinder case studs too long, they were lock tited in and not discovered till we put the head on the next day. I was going to remove them (heat needed) but he said they were fine by him.

    Attached Files:

    Last edited: May 29, 2010
  7. Molotov256

    Molotov256 Member

    Cool - nice pics again! I think i could pull all of that off, only I don't have access to a welder.

    I came across this approach on another message board:

    Hockey Puck Mounts

    What's your opinion on this style of mount? I'm intrigued because it doesn't require use of tools I don't have, but if it's doomed for failure, then I don't want to waste my time on it.
  8. Al.Fisherman

    Al.Fisherman Active Member

    That would be just fine. It's a very unique idea, amazing what people come up with. I have never seen a hockey puck, so the idea would of never crossed my mind. He's has had it installed long enough to give a opinion...if he's still a member there PM and ask how it has held up.
    Last edited: May 30, 2010
  9. Molotov256

    Molotov256 Member

    Sweet, I think I'll try and give it a go then. Thanks for all your input, and I'll try and post some pics as I make my attempt.
  10. Molotov256

    Molotov256 Member


    Okay, I solved my ragmount sprocket issues by getting my hands on a Schwinn rear wheel with a Modus hub and ordering a MANIC Mechanic Clamshell Mount for it from pirate cycles. Kinda pricey, but it came with a customized sprocket, so I can't complain, and I got the wheel from a buddy in exchange for some other spare parts, so hooray for bartering!

    As for the mounts, I tried the hockey pucks and didn't meet with much success. I did, however, concoct a solution that worked out better for me. I posted some more details and pics in a new thread dedicated more to the mount solution than my inane ramblings:

    Overkill Rear Mount

    Thanks for your input, Fisherman!