This build is all over the place

[4950cycle]

Hi fellow MBers, My name is John and I even have a FL. Drivers license. But I just like bicycles with motors in them. Currently I am building a HF 79cc Aluminum Mongoose full suspension rack mount. It is a real challenge trying to keep the weight down while designing a muti-ratio 80cc 4stroke rack mount motorbike. I like the fact that this site seems to allow more free thinking and dosn't steer you towards existing MB kit companys to much. I notice a lot of the in depth posts and threads at least a couple are years old here. I hope I didn't miss the boat on this motor bike thing.

 

[professor]

Hi John, welcome to Motoredbikes!
I have a HF 79 and initially had it on the back rack. Was just too heavy, the engine weighs about 24# and you need a hefty reack to hold it. You could actually feel the frame flex side to side.
Ended up putting it in a legnthened frame. Huge difference where the weight is placed. I really really like the motor, has good power and doesn't vibrate much.

 

[Dave C]

Hi and welcome. My best advice is to pre-flight the bike before you go out everytime, just like the bike was an ultralight airplane. What your looking for is loose nuts and bolts on the motor and bike frame. These things tend to back out if not properly tightened. Blue LockTite is your friend.

Check the frame weld points. There have been reports of aluminum frames having a problem with cracking and breaking. If you have fenders always check the support rods for cracking. If detected remove and replace or remove the fender until repaired. Wadding a loose fender up in your spokes will ruin your day, guarenteed.

Keep it locked up. Get a bigger chain or cable than you think you need and use it all the time.

Have fun. Use the search feature to find things then if you can't find an answer that way ask away.

 

[Motorbikemadman]

Hey Dave thanks for the tip on Blue locktite. I have been wondering which was the preferred type for my build also. I am currently building an old military replica bike but making it a more functional bike. Mine is a kit, but I am modifying the kit quite a bit. Going with 66cc and chain drive though. I do see alot of people on here going with belt drives though. Good luck 4950cycle with your build.

 

[4950cycle]

Thanks Guys

Thanks Guys, piont taken on every bit of the advice recieved. Thanks Dave On the blue locktite tip, Learned that on my Dad's 66cc China Girl. Everything tried to fall off of it every mile and a half.Now, on the weight issue, I built an all steel 3 1/2 HP Briggs with an 8 inch industrial trolly wheel for a friction roller/with jackshaft, sprockets (all 3/4 steel) shaft that is. And the strong steel rack needed to feciletate this monstocity of mine 11 yrs. ago. 45 MPH ,You want to talk about Heavy!! Live and learn. On this build I'm going aluminum 1/2 jackshaft, Nylon (33% glass fiber) pulleys,. Thick gauge aluminum angle rack, light pillow block or equivelent bearings for jackshaft. I'm calling Station to see if I can respring a little pocketbike style Centrifical clutch instead of that big old heavy Max torque clutch so it will operate properly on a four stroke. My only concern is there will be a lot of aluminum. Aluminum doe's not handle vibration stress very well as one of you have stated concerning the aluminum Mongoose. But they still make air planes out of the stuff. No doubt it will still feel a little Butt heavy also. And won't stand on a regular kickstand. It will need a workman type kickstand jobby. Anyway, it all works on paper. Oh, and don't forget that my swingarm is strong steel,probably chromemolly. My whole drivetrain will be built upon this platform. Nothing but me and a couple 1/2 pound parts are directly on the aluminum portion of the bike. I'm not a fan of unsprung weight but this is not a $20,000 superbike either. That dosn't mean Professor isn't correct in that most guys might still find it to Butt heavy. I am 6'3 235 lbs. I think I will still dominate the bike. I just like nothing but bike in front of me. Go figure