1978 Chappy LB50 Derestrict

Curtis Riendeau /

I Have a 1978 Yamaha Chappy LB50. I would like to get a little more power out of it, I'm not all that worked about top speed but I would like better acceleration for hills.

I pulled the carb and noticed that it is only around a 12mm, I have a vm18 would that be something that would be helpful?

I also ordered a high compression head since my compression was only around 100psi with a mint cylinder bore. I am pretty sure it was meant to be low compression, but I feel higher compression will help my low end quite a bit.

What about a lb80 muffler? would that be less restrictive ? Since the lb80 would do 40-45mph. Im guessing that the 80cc had different gearing as well.

I don't really care all that much if it only does 20-25mph since it is really only for in town, but if I can get it to do 40 like the 80cc then I will.

Is there any cheap aftermarket pipe for the chappy or would I be better to make my own? Would a pipe and baffle be sufficient? I hope I don't sound dumb for asking that!

So honestly I am looking to derestrict the lb50. I know that these bike can scream when set up correctly. I mean I have a 1960's Honda 65cc 4-stroke and it has plenty of power and does 60mph.

Re: 1978 Chappy LB50 Derestrict

Curtis Riendeau /


Re: 1978 Chappy LB50 Derestrict

Curtis Riendeau /

Tonight I'm letting the original muffler soak in drain-o. because If I shake the muffler I can hear carbon but I can't get any out.

I was hoping to get a less restrictive muffler and run a larger carb, but I wouldn't even know where to begin. The problem is I am cheap, so the Giannelli pipe for $130 just is too much, plus I don't want to lose my pedals.

Is there any muffler that is bolt on without losing the pedals? Could I modify my original muffler.

I have a vm18 carb would that be fine if I run a less restrictive muffler?

Re: 1978 Chappy LB50 Derestrict

Bill Habekost Jr. /

I hear you Curt & if I knew I'd help;just wanted to bump this again for you.

Re: 1978 Chappy LB50 Derestrict

Curtis Riendeau /

Well I installed the High Compression head from treat land last night. I had to use spacers on the studs since my threads ran out. But other then that it went smooth.

I took it for a spin around the block since it was dark and I don't have any lights. And I do notice a difference in bottom end, I haven't checked my compression yet with the new head.

Maybe my rings are worn and that is the main issue I have , but my speed is right where it should be.

I also went up one size main jet since my plug chop showed a white plug, that was starting to turn brown.

Now the plug is chocolate brown, but I lost 1-2mph top speed.

Would a cylinder from a lb80 fit on my lb50 bottom end? or is the stud spacing different?

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account