North East Buggy Association - View topic - Modifying your buggy: REJET Mod! - NEBA is an association for North East Buggy Members. - Free Message Board Hosting by FreePowerBoards.com

This is my first installment of a few parts series to help others with installing get-up-and-go goodies in their buggies! For starters, you will need a baseline to start out at... Stock, or partically modified already, you will need to get a watch, and find a long run/climb/trail to get a baseline run on. Test your buggy to make sure it is running right, and all is well. Then you can mod and instead of just feeling the difference, you can see a difference on the clock and in the dirt!!

The most common order of most mods people do in ANY GY6 Buggy (150cc), are usually a set of ROLLERS, A high performance (hp) AIR FILTER, and a YELLOW (1500lb) CLUTCH SPRING. These simple mods will open up the breathing of the buggy, get a little more power in the top end, and get the buggy moving faster at the bottom end... After those mods, people usually drill out the exhaust (punching), and re-jet the carburator so that the engine runs correctly, mixing enough fuel to match the air going in the engine, as well as leaving the engine...

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SO... Here were MY mods prior to today....

Stock Howhitt 150cc
128 Jet in 32mm carb
K&N filter
30mm billet intake manifold
9 gram rollers
1500lb spring
gutted exhaust
modded suspension
ITP mud lite rear tires 22X11X10

Well, with all those cool mods, it still wasnt enough... My jetting was off, I was running lean, and the Dune actually ran worse on the short balsts...ie, hill climbs and drag racing... BUT...I hit 38 mph easily on a long run....

So- To make up some lost ground on the short runs and hill climbs, I figured I HAD to get the jetting correct, and even better, I had to get a new belt, as my stock belt was slipping real bad, and it was hurting the clutch...

I bought this stuff during the NEBA Buggy Bash...

step by step, I did this, and tested each mod to show loss/gain...all gain by the way.... hehehe....

STEP 1.... Run what you brung. Using a Magellan explorist 100 palm navigator, I was able to get a signal within 12 feet accuracy...pretty good! With that... I drove to the bottom of my street after warming up the buggy... I live on a steep, long hill climb... I took three runs up the hill with the navigation, and recorded top speed and time it took to reach the top.

First runs yielded a top speed of 21.5 mph, and about 46 second to the top + or minus 1 sec for error.

very first thing I did to make sure a re-jet was totally necessary was to read the spark plug... Color tells it all!!! White-Lean (not enough fuel), Black-Rich (too much fuel), and that leaves shades of grey!!! lol... This pic tells it all:

I was completely correct in my assumption, thereby necessitating the re-jet as the first mod.

How do you re-jet? SIMPLE!!! #1: shut off fuel supply to carb at petcock or inline shut off... if you do not have one, drain fuel tank, or crimp fuel line to keep fuel out of carb... # 2: unscrew the intake and the manifold hose clamps on the carb. simply remove the carb from the manifold (gently) or sometimes you can just twist the carb counter clockwise to have the bottom facing the passenger side... either way, this is what you should have:

and the manifold left on-- make sure to clean the area but first put papertowel in the manifold to keep debris out!

NEXT...you unscrew the screw at the very bottom of the carb, most of the time found in the center... this is the "fuel Bowl Drain"..... it will drain out the gasoline left in the carburator...so make sure you have a drip pan or catch can under teh buggy to catch the fuel...

NEXT!!! after the dripping subsides, you simply unscrew the 3-4 screws holing the Fuel Bowl to the carburator... Take special care when removing the bowl, as there is a rubber gasket attached to seal the carb, and you DO NOT want to break this!!! The fuel floats are found in here, and most of the time they are plastic and can break easily, so you do not want to bang on the carb to loosen the Bowl... This is what it should look like with the bowl off:

OK...now you locate the MAIN JET...This is it:

Simply unscrew this jet with a thin, flat head screwdriver... and install your new, oversized jet... For my testing, I went from a 128 jet to 137.5...

Now, you carefully line up the fuel bowl and screws, tighten them evenly, and make sure you tighten the fuel drain back up... Then simply re-install the carb back to it's original position, and tighten all clamps tight...open the fuel supply back up, let the carb fill for a minute or so, and start your buggy.... use carb cleaner to spray the engine while it is running to check for leaks... buggy will bog down or shut off if you have a leak... spray one spot at a time, and if the motor doesnt slow down, you are free to run it and see how it performs!

My second run set with the new 137.5 Main Jet yeilded: 23.6 mph and 43.2 seconds to reach top of street... A gain of 2.1 mph top speed and 2-3 seconds faster!!! Yeah!!! Just adding more fuel was already a huge gain!

Next mod to follow in new post!!!!!

John Very Happy

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