Preparing to go Big-Bore on my Buddy 125

GrantSR · Post by **GrantSR** » Mon Dec 12, 2011 3:39 am

OK, so I have been doing a lot of research on what I will need to install a Big-Bore kit on my 125. I have determined that a 59mm diameter cylinder is the biggest I can go without needing to bore out my crank-case. I will probably get the NYC kit as it seems to be the most popular and most recommended.

I have also decided that I might as well put a big-bore head on it while I am at it. I know it isn't necessary but while I have the cylinder apart, I might as well bolt on and break in that new head instead of the old head.

I also know I will need to rejet the carburetor. I have read recommendations that I start with the largest size hole diameter and work down till I find what works best. However, I haven't seen any recommendation as to what that largest hole size should be. I know altitude and weather makes a difference. I live in Tucson but plan to move to Berkeley. I have been told that in Berkeley I will need the largest hole size because I will be at sea-level. I'm guessing more air pressure means it requires a larger hole to get the same amount of fuel to come out.

Now, I know there are lots of other things that I COULD put on this scooter to make it faster. I could get a bigger intake and carburetor. I could mess with the weights, pulleys, and clutch. I could change out many parts of the electrical system. I will probably do all of those things, but not now. What I would like to know is: Is there anything else that I absolutely SHOULD do when I install this cylinder kit? Anything that will cause performance or reliability issues if I do not do it?

Thanks.

Post by **ericalm** » Mon Dec 12, 2011 4:33 am

I like (and recommend) doing these types of mods in stages rather than all at once. Getting the big bore kit is a good place to start because once broken in, you will have discrete results that are easy to use as a new baseline when you start messing with the transmission, which has less predictable results.

Kit, larger intake manifold, larger head are pretty much all you need! Not sure precisely what size jet you'd want (someone whose done this on a Buddy can recommend) but the jet and carb adjustment are the only other changes you should need to make when you do this. Sounds like you've got it all covered.

What kind of mileage will you have on the scooter when you do the modification?

GrantSR · Post by **GrantSR** » Mon Dec 12, 2011 4:40 am

ericalm wrote:What kind of mileage will you have on the scooter when you do the modification?

If you mean what kind of gas mileage can I expect? I have no idea.

If you are asking what my odometer reads: 12,000 miles. And I am still on my first pair of tires.

I use synthetic oil and the Lucas oil additive.

Post by **ericalm** » Mon Dec 12, 2011 4:55 am

Asking about odometer.

LunaP · Post by **LunaP** » Mon Dec 12, 2011 6:57 am

GrantSR wrote:
ericalm wrote:What kind of mileage will you have on the scooter when you do the modification?
If you mean what kind of gas mileage can I expect? I have no idea.

If you are asking what my odometer reads: 12,000 miles. And I am still on my first pair of tires.

I use synthetic oil and the Lucas oil additive.

Holy $#!%, what the heck kind of tires did you use? I just got told not to expect to go past 4k on my stocks...

GrantSR · Post by **GrantSR** » Mon Dec 12, 2011 1:28 pm

LunaP wrote:Holy $#!%, what the heck kind of tires did you use? I just got told not to expect to go past 4k on my stocks...

Stock. I don't weigh much. I used to weigh in at about 140 lbs when I first got the thing. Now I weigh about 160. But I do drive like a maniac and it is definitely time for new ones now. Almost no tread in center of back tire. I could just switch front to back but I have ordered Continentals. I have always had good luck with that brand on my bicycles.