Are they supposed to vibrate this much!!!!!

[showcaller]

After years of wanting a gas powered bike I finally took the plunge two months ago. I bought a 26" beach cruiser three speed. I specifically wanted a three speed because I still had the fantasy of using it as a bike that I actually peddle once in a while. It has actually worked out okay, even though I had no idea how much friction would still be created when the motor chain is going through the clutch unengaged. For what it is worth, I bought a Firmstrong aluminum frame. Found a guy on Craigs list who was selling a bike and advertised he would put a RAW 49 CC on any bike you deliver to him. I had my Beach Cruiser converted. That was 180 miles ago. I am learning all about the RAW 49 CC, more than I thought, but in an odd way whenever somthing goes wrong I wonder if I can fix it myself. When the clutch cable went, I went back to the guy and he fixed it. I got a leaky fuel tank and the guy replaced that, no problem. The mounting bracket for the front fender broke, I fixed it. This evening I was riding, heard a pop, and then ironically the vibration stopped, (which is really where I am going here) to discover the bolt that attaches the front of the engine to the frame broke at the locking nut. The spacers used between the frame and the engine, (abou and inch and a half) were three large nuts. I replaced them using 20 rubber washers, my thinking being that if the engine has room to move a little, the stress at the head of the bolt won't be as bad since the rubber washes will absorb the shock of going over potholes etc.

The engine is pretty much broken in. I have had the bike up to 27 mph and the thing is vibrating and shaking so much I feel like a human milk shake machine stirring up a bunch of rocks and stones for a rock milk shake! The vibration is herrendous! I am fine up to 19, 20 mph, then after that things get wierd. The seat shakes so much it is almost impossible to sit down on it. I am not looking for speed though I do want to swap out the plug for a high performance one and I understand there is a high performance carb for the engine but I can't find it.

My question is, is there anything that can be done in eliminating the vibration. I hear about these guys that go 35, 40 mph. I can't imagine that without my rig dissintigrating!

Does anyone have any suggestions? better seat?

Look forward to the responses to this.

showcaller

 

[Goat Herder]

Here is a read for you. http://motorbicycling.com/f6/rubber-not-27364.html

 

[matthurd]

i wouldnt suggest running a front fender.

was enough to scare me away from em at least http://motorbicycling.com/f30/motorized-bicycle-front-fender-dangers-315.html

 

[earl.k]

Here is a read for you. http://motorbicycling.com/f6/rubber-not-27364.html

lol.. i was going to give him the same link.

 

[bairdco]

when you say "bolt" for the front mount, are you saying it only has one that was drilled through the frame and had three nuts for a spacer? and you replaced that with rubber washers?

if so, the reason your bike's vibrating, is because it's trying to tell you it's about to break in half and you should stop immediately.

 

[scotto-]

First of all, welcome to the forum showcaller! You want your engine to be mounted to the frame in a fairly solid manner as they tend to flex and twist from torque and vibrate like a mad hatter as well. My cure for this was a little expensive....I went to using 4-strokes and will not go back. The vibration factor alone was worth the switch....or should I say lack of vibration?

Mount your engine solid so too speak and hang on!

 

[LS614]

It's sounding like he's got that cheap through the frame front mount. he should go with the u bolt setup from Sick Bike Parts...Well worth $15

 

[showcaller]

Thanks guys.

I really appreciate the feedback. I know we are talking about two different things here, vibration and how the engine is mounted on the front. These may be related or not.

I am going to order the ubolt setup asap. As soon as I read a couple of you had done that I thought why isn't that arrangement a standard setup.

Yes, the guy used three nuts to make up the clearance between the frame and the front engine mount. It was only a matter of time (less than 6 weeks) before the stress got to be too much and it broke at the lock nut. I replaced it by making a rubber seal so there is a bit of absorption when I am running it. I see this as a very temporary solution (assuming it works, I did last nite and about to run it this morning to see what happens.) until the u bolt mount is installed. If I can figure out a way to reduce the vibration over 20 mph then I will think about the performance aspects. Right now I can run at 27 mph and I feel like I am about to break the sound barrier!

Show

 

[LS614]

Riding fast sure is a good feeling! You'll get used to it! My engine took me up to 29 the first time I rod

 

[MarkSumpter]

Show caller make sure that since your frame is aluminum when utilizing the U Bolt mount that you use a metal shim between the frame and the clamp and u-bolt as in this thread to prevent frame damage:

http://motorbicycling.com/f6/best-mounting-aluminum-frame-20262.html#post193211

I would also personally suggest that if the frame has been drilled to have the holes heali arced up by a welder that is good wit aluminum to restore its strength and stay away from Craigs list when looking for a reputable builder.

 

[LS614]

No problem use them in good health! They're really great!

 

[earl.k]

get the u bolt set up.. i have the SBP front mount and its great. also a shift kit held on by two more u bolts/clamps... i dont think my motor could be any more solid.

 

[LS614]

Unless you had someone who can weld put on mounts in the right place that's what I'm doing with my current build!

 

[biknut]

You probably have a bum motor that's out of balance. It is possible to balance these motors, but if you can't do it yourself, considering the cost it's probably more cost effictive to just get another motor and use yours for parts.

 

[flybytaco]

how can you balance theese motors yourself? I'd really like to know cause i just spent good money having mine done

 

[earl.k]

i would also like to know? im rebuilding the motor i ran last fall. the crank and all that is still in the case. when i spin it, you can see its off balance. when i get it out id like to know what im getting into. is it a matter of adjusting something or what???

if it casts alot to do. or is to much work for its worth, ill get a new one. but could i true it myself??

 

[msrfan]

You probably have a bum motor that's out of balance. It is possible to balance these motors, but if you can't do it yourself, considering the cost it's probably more cost effictive to just get another motor and use yours for parts.

Exactly right. I got two bum motors in a row from BGF and had to balance them myself. The cranks were way off. They were basically defective motors.

 

[msrfan]

how can you balance theese motors yourself? I'd really like to know cause i just spent good money having mine done

Check my threads titled "plagued by vibrations", and "no more vibrations". I figured a way to balance my own cranks using the standard formula without disassembling them.

 

[showcaller]

The latest update.

Since I already had started building a rubber mount/bolt/washer to replace the one that broke a few days ago, I thought I would mount it and see what happens. Mind you that 90% of you advised against any rubber mounts but I was/am curious about how it would perform. I just finished a five mile test run with it and much to my surprise the amount of vibration has been cut substantially. I topped out at about 26 mph which is about right. I could actually sit on the seat and the whole bike felt alot more solid. The vibration has left the seat but in the process has been transferred to the pedals giving my feet a workout! The U bolt and high performance spark plug has been ordered anyway. I don't see staying with the rubber support even though that engine is in there solid.

 

[scotto-]

Just balance the crank by drilling holes in the proper places and use a dial indicator and such for checking tolerances. Don't forget to stuff the holes with cork and epoxy to keep the compression up.

It's best to send to a machine shop to have it done properly as flybytaco does, or buy a new engine and hope for the best. These engines are pretty cheap ya know.....quality and price.