New to the board, new mb owner, modifications

[ratty]

Hey everybody.

I'm a new mb owner, got it last Saturday. It is an old ratty 12 speed bike with the 80/66cc HT engine kit. I bought it with the kit freshly installed and didn't get much with it. It has a 44t rear sprocket. I weigh +/- @240 lbs . Now....here is what I have experienced so far. I need the bike to go uphill halfway decent because I will be using it for a short commute to work. In stock form, it would barely make it up hills. Not good, some of my commute is uphill about a couple hundred meters or so. I decided to do a rear sprocket swap to a 60t that I found locally at Northern tool. After I bought the sprocket, I decided to do some exhaust and intake mods to increase my performance before swapping the sprocket. Today, I took the muffler apart, it is a black one. It was welded together. After grinding off the welds, I noticed what looks like an extremely crude catalytic converter insert at the end of the pipe. It was all held in, converter, baffle, and all by some spot welds inside the pipe. I removed everything (please no environmental speak about the converter removal. It really is a sorry excuse for one anyway) Then I opened up the exhaust and intake gaskets and did some contour work on the intake and exhaust pipe with a die grinder with a cone shaped carbide tip. Now, I can climb the same hills no problem at a decent speed and actually gain speed going up hills, although vveeerrryyy gradually; top speed is about 20 without really spinning up the motor. The power increase is VERY noticeable, but now its kind of loud for my taste; I will address that issue shortly with some kind of home made silencer added to the muffler somewhere. I feel like I need a little more grunt up those hills. How much difference would a 54t rear sprocket be? I think the 60t is overkill, and its going back tomorrow, but they stock a 54t one too. Will it give me a noticeable amount of torque? Top speed does not concern me, I will be driving it downtown.

[NunyaBidness]

Sounds like you know what you're doing so far. The 54 tooth sprocket should do just fine for what you need it to do.

Nashville hills shouldn't give it any problems at all.

[2door]

Ratty,
Welcome to the forum. I think you'll be very pleased with the 54T and it should carry you up those hills with no problem. My first bike was set up with a 44T and here in hilly Colorado it pulled my skinny butt up every hill I encountered. You're like me being unconcerned with top end speed but you might also consider a 48T. It could be a good compromise between that hill busting 54 and your current 44.
As for the muffler, some guys have had good luck using course steel wool or fiberglass as a sound deadner. Goes without saying that you'll need to fabricate some kind of cannister, maybe your old cat will work, using a thru pipe, drilled then wrapped with the material and a tail pipe of sorts. Good luck.
Tom

[ratty]

Thanks for all the input so far. I have a lot of 'hobbies', but this motorized bike thing is extraordinarily cool. Just getting back on a bike reminds me of the younger days!

[Dan]

Originally Posted by ratty

Thanks for all the input so far. I have a lot of 'hobbies', but this motorized bike thing is extraordinarily cool. Just getting back on a bike reminds me of the younger days!

Know what ya mean. Funny eh?

[Finfan]

With the 54 tooth sprocket your top end would probably be about 20 mph wide open on flat ground. If you are happy with putting along at 14-15 mph then it is a good choice since it will definitely torque you up those hills. If you want to go faster you might wear the engine out quicker by winding it out too much.

[dag_29307]

First: welcome to the forum

Second: I live in SC. and I have the 54t sprocket installed on a 24" mountain bike along with the 80cc. and I haven't done the intake or the exhaust mods yet but I can say the 54t gives a nice balance for both torque and speed for the bigger guys I weigh around 300 and I do 40mph. on the flatland. Another thing you might also want to check into a boost bottle it might just give you that little extra your looking for.

Hope it helps.

[Dan]

Dag, on an "80cc" 2 stroke with a 54T rear sprocket, your getting 40 MPH? I have to ask, you are saying this is due to a boost bottle? I have never tried one as they were widely thought to be no good. Just asking here.

[dag_29307]

Sorry I confused you No I don't have a boost bottle on my bike but from what I've seen they appear to have an effect I could be wrong. My bike is a 24" Huffy mountain bike I had for years. I have had my motor mounted for about 2 months now and I love this thing I am looking for "Hop ups" or Mods to improve the performance. I have nowhere near the amount knowledge of these motobikes many others have here but with the gear being my first I just thought I could shed some light. Sorry if I gave the wrong impression.

[city of angels]

if you are looking for a silencer sick bike parts sells one also welcome to the forum will love tosee pics if you can