Modern Buddy

so I rejeted my Buddy 50 yesterday. I went from the stock 75 jet to a 85 jet when I installed the prima pipe. The 85 jet was recommened by my dealer as this is the set up they generally use. I raod the scooter for about 10 miles yesterday but it was too dark to check the plug so I just did it today. The plug is kinda dark around the threads but the ceramic is still very light. Am I running too lean?

How do I properly do a plug chop for a scooter? I found a site that shows how to do one for a dirt bike but they talk about running through the gears and we have CVTs.

One of my friends thought that, at least by smell, I may be a bit too rich so this result is a bit suprising to me.

A proper plug chop is easy to do.

Step 1:

Bring scooter up to operating temp

Step 2:

Run wide open for about a block

Step 3:

While holding the throttle wide open shut off the scooter and coast to a stop.

Step 4:

Inspect plug


While working with a few different setups on Frenchy I found out the 95 main works the best with a de-restricted air box and prima pipe.

what do you mean by derestricted air box?

If you pull the airbox off you will see the intake hose held in with two philps head screws. Thats the restriction I am talking about. We used a free flow performance air filter vs a de-restricted air box. We had better results with the airbox since the carb and intake runner is so small. There will be a full writeup on this tomorrow.

NASRA wrote:If you pull the airbox off you will see the intake hose held in with two philps head screws. Thats the restriction I am talking about. We used a free flow performance air filter vs a de-restricted air box. We had better results with the airbox since the carb and intake runner is so small. There will be a full writeup on this tomorrow.

Cool I look forward to reading about it. Not sure if I'm up to messing with the air side of this whole scooter modding thing just yet. I've heard its much more difficult than the fuel side of things

I've been trying to think of a good stretch of road to do the plug chop. Its kind of hard to find a place around here were you could safely hit the kill switch and then get under the scooter to check the plug. Is there a way to do the plug chop with the scooter on the center stand or would this harm the engine reving so high without pressure on the back tire from the road?

jasondavis48108 wrote:I've been trying to think of a good stretch of road to do the plug chop. Its kind of hard to find a place around here were you could safely hit the kill switch and then get under the scooter to check the plug. Is there a way to do the plug chop with the scooter on the center stand or would this harm the engine reving so high without pressure on the back tire from the road?

They run different under load so it doesn't work right

Thanks ScooterTrash I figured that idea was too perfect to actually work

Guess I'll have to search for a good paved backroad to try this out on. Also how long would you suggest being WOT in miles or minutes?

jasondavis48108 wrote:Thanks ScooterTrash I figured that idea was too perfect to actually work

Guess I'll have to search for a good paved backroad to try this out on. Also how long would you suggest being WOT in miles or minutes?

seconds, I do it in the matter of 2 city blocks. Or I go exit to exit on the highway and check the plug off the exit

thanks, Thats two folks here (which I trust a whole lot more than the wild web) that have stated very short distances. This will make it easier as I have a park with a parking lot near my house that is on a stretch of 45mph road. I'll have to give this whole thing a fresh try tomorrow. I thought I had really screwed up my jetting (too lean) somehow but now I realize I was just doing it all wrong

o.k. so I woke up this morning to a heat advisory. I'm assuming that 90+ degree weather is not the best time to push your air cooled scooter hard after rejeting. Can anyone tell me whether it is safe to do plug chops in 90 degree weather? Also, is there a temperature cut off at which you shouldn't do plug chops?. It looks like its gonna be in the 90s here for about three days and then drop back into the 80s.

jetting is temp sensitive i like to jet when its about 40 or 50 out that way its spot on when its cold and rich when its hot

but if you have no choice but to work on jetting when its hot and humid make sure its rich so it doesnt lean out when it gets colder

jmkjr72 wrote:jetting is temp sensitive i like to jet when its about 40 or 50 out that way its spot on when its cold and rich when its hot

but if you have no choice but to work on jetting when its hot and humid make sure its rich so it doesnt lean out when it gets colder

I do the same

jmkjr72 wrote:jetting is temp sensitive i like to jet when its about 40 or 50 out that way its spot on when its cold and rich when its hot

but if you have no choice but to work on jetting when its hot and humid make sure its rich so it doesnt lean out when it gets colder

That makes a lot of sense. Thanx

well I went out this morning and did the plug chop. I put a brand new plug in the scooter, let it warm up for about 5 or so minutes I got up to WOT for roughtly a quarter mile and hit the Kill switch. I had to use my brakes a bit so that I didn't coast past the parking lot that I wanted to pull the scooter into to pull the plug (hope this doesn't screw things up). I pulled the plug and put in the old (1 day old) plug and road home. After cutting away as much of the threaded portion as I could with the hack saw I could barely see a wisp of light brown so I'm too lean at an 85 jet. I just put the 95 jet in and we'll see how that does. I certainly hope I'm not still lean at the 95 jet as thats the largest one that came with the kit.

Thank you all very much for your help as I learn how to do this stuff.

jasondavis48108 wrote: After cutting away as much of the threaded portion as I could with the hack saw I could barely see a wisp of light brown

WTF? hack saw?

Ray Knobs wrote:

jasondavis48108 wrote: After cutting away as much of the threaded portion as I could with the hack saw I could barely see a wisp of light brown

WTF? hack saw?

WTF X 2. Just a visual test of the end of the plug. Some guys just wipe off (small wire brush) and use the same plug.

the "chop" in "plug chop" refers to the throttle not the actual plug

pull it out and look at it, simply put...

if the ground strap looks like the color of cardboard you are good, if it looks lighter you are lean, if it looks dark / wet / oily you are rich.

I did quite a bit of research on this and the most effective way to do the plug chop is to cut away the threads so you can get a good look at the base of the ceramic. There should be a 2mm brown ring at the base if you have it properly jetted. You can try to look down the plug at the base but from what I've read this is rather difficult. For instance I couldn't see any color at all until I cut away the threads. Then I could see the slight brown ring at the base.

here is two of the pages I read on it. I know that some folks just look down the plug but I wanted to be very thorough

http://www.dfn.com/benkaren/plugchop.html

http://www.mopedarmy.com/wiki/Plug_chop

well I tried the 95 jet and it blogged down like crazy when I gave it some throttle. Then I tried the 90 jet, same damn thing. How can an 85 jet be way too lean and a 90 be way to0 rich? I'm seriously confused here. I can go back to the 85 jet but that seems foolish. Is it possible that I bumped something on the carb thats causing it to blog down like this? Do I now need to give it some air, should I drill holes in the air box, I have no idea what to do at this point

HELP!

UPDATE: I called my shop and they suggested I clean the plug so I did and nothing, its bogging down like crazy and it gets worse the more throttle I give it. At full throttle I'm going 5-10 mph. Not sure what I did but I must of screwed something up when I switched back to the 85 jet cause it was running strong on the 85 jet.

Did you adjust your air to fuel ratio when you changed the jetting?

Ray Knobs wrote:Did you adjust your air to fuel ratio when you changed the jetting?

no I just changed the main jet that came with the kit. When I first installed the kit I used the 85 jet and it ran awesome but a bit lean. Today I installed the 95 jet and it bogged like hell, then 90 jet same thing, finally I put in the 85 jet anagin and its still bogging like hell. I just tried adjusting the idle but that did nothing. It still boggs down when you give it gas

Find the little air/fuel screw, you need a screw driver to adjust it.

I don't remember how much of the carb you take apart to get at the jets but is there a chance you got the float stuck?

Ray Knobs wrote:Find the little air/fuel screw, you need a screw driver to adjust it.

I don't remember how much of the carb you take apart to get at the jets but is there a chance you got the float stuck?

I suppose there is a chance the float is stuck. You have to take off the lower portion of the carb (I believe this is called the float bowl to get to the main jet.

How do you know its stuck and what do you do to get it unstuck?

UPDATE: Well I took the bottom part of the carb off again and the float didn't look stuck so I put it back together again, put 3 oz of seafoam in the tank and let the scooter sit for about an hour while I took my wife to work. Just got home and started her up, I couldn't get her up to full speed but shes not bogging down at full throttle anymore like she was. Hell if I know what was wrong but it seems to have been fixed. I think what might have happened is that she might have gotten flooded when I put the 95 jet on and needed some time to just sit and dry out. Anyway, I'll have to wait until tomorrow for a top speed run just to make sure everything is good.

Once again, thanks for all the help folks. Hopefully someday I'll be good enough at this stuff to pay it forward

when you cut the plug apart like that you are looking for the smoke ring it should be no smaller then 2mm if you are jeted right

so if that whisp of color you see at the bottem is less then 2 mm you are lean if its greater then 2mm you are rich or good

if you fell like tearing your scoot apart you can even look at piston wash to see if you are rich or lean

but before you take the head off let the scoot cool down so you dont warp the head

jmkjr72 wrote:when you cut the plug apart like that you are looking for the smoke ring it should be no smaller then 2mm if you are jeted right

so if that whisp of color you see at the bottem is less then 2 mm you are lean if its greater then 2mm you are rich or good

if you fell like tearing your scoot apart you can even look at piston wash to see if you are rich or lean

but before you take the head off let the scoot cool down so you dont warp the head

I have another question then. I am lean at 85 but the 90 jet is way too rich (at least I think it was, maybe I just srewed something up at that point). Do they make the in between sizes 86,87,88,89?

Ray Knobs wrote:http://www.jetsrus.com/

thanks for the link Ray, you wouldn't happen to know which jets the buddy50 uses would you? from the scooterworks website I see that they have the Buddy 50 listed as taking a Keihin PB style jet but there are two different versions on the jetsrus website a PB16 and a PB18. Then for each of those two choices you have the choice of OEM or GENUINE. Not sure which kind I'd need. is there a way to measure one of the jets that came with my stage 1 kit so I'd know what to order?

So here is a picture of the plug that I ran for the test for the 85 jet. As you can see the brown line is no where near 2mm. Unfortunatley from what my dealer tells me the 90 jet will not work without drilling holes in the airbox which I don't think I'm ready to start screwing with the air at this point. I'm gonna order an 88 jet since that looks like the only size I can get a hold of between 85 and 90 and see what happens. If thats still too big I might try to order a few more 85 jets and drill my own custom sized jets. There are instructions on how to do this on 49ccscoot.com

It stands to reason if you want to ad more fuel you'll need to ad more air.

Ray Knobs wrote:It stands to reason if you want to ad more fuel you'll need to ad more air.

o.k. so I'm new to this whole thing. I thought that if you were lean it was because you had too much air and not enough fuel which seems to be my case at this point. Am I correct to try the 88 jet or do I really need to start screwing with the air side of things at this point. I'm a bit leary to do so cause I've heard nightmare stories about folks who started scewing with thier airboxes.

yes you are correct to try a jet larger then the 85 and smaller then the 90

i dont know what carb they run on the buddy but you need to make sure you get the right ones for your carb as jets are reated diffrent by the diffrent cars

just becuse it fits and says its an 88 doesnt mean tha that its inbetween the and besides the hole size you have to worry about the seat angle being the same too

i would get the genuine jets that is the jet that the carb manufacture makes some times oem jets come in limited sizes

jmkjr72 wrote:yes you are correct to try a jet larger then the 85 and smaller then the 90

i dont know what carb they run on the buddy but you need to make sure you get the right ones for your carb as jets are reated diffrent by the diffrent cars

just becuse it fits and says its an 88 doesnt mean tha that its inbetween the and besides the hole size you have to worry about the seat angle being the same too

i would get the genuine jets that is the jet that the carb manufacture makes some times oem jets come in limited sizes

yeah, I noticed that the jets scooterworks sells go by 5's so it jumps from 85 to 90. I'll have to call them or go up to my delaer and ask what jets I need to order. The original jet that was in the scooter was marked m75, and the jets that came with the stage 1 kit were marked k85, k90, and k95. I do know that the Keihin PB style jet is what I need and it does come in an 88 so all I really need to do is double check that the jets from the site that Ray posted will fit.

EDIT: just measured the jets that came with the stage 1 kit. these jets should fit the Buddy 50 and they are the same brand and type as come with the stage 1 kit so should be a good fit between the 85 and 90 jet

http://www.jetsrus.com/a_jets_by_carbur ... 38-xxx.htm