FZ1 Holeshot Stage 1 Kit, part II: Jet Kit Install

December 31, 2014

Day 2 of the project was the actual carburetor work:  installing new jets, checking float levels, adjusting mixture screws, and installing carb shims.  As complicated as it sounds, with the exception of nervously drilling out the mixture screw plugs the kit install was much easier than removing the carbs from the bike.

Installing New Main Jets

The first step is to turn the carbs upside down and open the float bowls to get to the floats and main jets.  The instructions recommend to do this one bowl at a time, although this is not possible given the new jet sizes.

Note: This should be done in an extremely clean, dust-free environment.  A spec of dust can clog jets or float needles and render the bike inoperative.

Each float bowl has a cover with 4 screws holding it on.  The screws are extremely difficult to remove.  I ended up whacking all of them with an impact screwdriver, and ruined a couple screws.  Fortunately the Holeshot kit provides replacement hex bolts which are used to secure the covers after new jets are installed.

Floats and jets

The main jets are the largest of the round slotted brass fittings sticking up between the pink floats.

FZ1 carburetors are odd in that the main jet sizes are not all the same.  In #1 and #4 (outer) the stock size is 132.5 and #2 and #3 (inner) the stock size is 130.

The Holeshot kit calls for a 130 jet in #1 and #4, and 127.5 in #2 and #3.  However the kit does not include 130 jets, so the 130s from #2 and #3 end up being swapped into carbs #1 and #4.  Then the 127.5 jets from the kit go in #2 and #3.

Actual jet replacement is easy, just hold the base with an 8mm open end wrench and unscrew the jet with a large flat screwdriver.

At this point it's a good idea to check the float levels.  Pat's Ivan's Jet Kit install page has some guidelines for how to measure and set float levels, and Holeshot sells a nice float gauge which I bought, that makes this easier. Suffice to say I've never adjusted float levels from their stock positions when installing a Stage 1 kit, and one can spend quite a long time bending float tabs random amounts trying to get the levels perfect.  I did measure the levels and found them to be within a mm of spec, and decided not to mess with it.  That way lies madness.

After the jet swapping is done the covers should be put back and the screws replaced with the hex bolts from the Holeshot kit.

Mixture Screw Adjustment

This is the hardest part of the kit. There are brass plugs covering the mixture screws that must be drilled out and removed.  The kit includes a drill bit and self-tapping screw to help with removal of the plugs.

The brass plugs can be seen in the first photo, they are the brownish-colored circular metal disks with a tiny hole in the middle.

The hazard here is that if one drills too far one can drill through the mixture screw underneath the brass plug, thus ruining it. The best way to avoid this is to create a drill stop by cutting a ball-point pen in half and then sliding the pen half over the drill bit.  That way the drill bit can only go a small distance.  Did I do that?  No.  Stupid, stupid.

There is a lot of brass dust created that is best vacuumed up with a shop vac after drilling.  It is hazardous to get any debris near the carburetors.

So 3 of the 4 plugs came out perfectly and I managed to drill into the mixture screw in carb #3 almost enough to ruin it.  Fortunately there was just enough of the screw left to turn it delicately with a jeweler's screwdriver.  The base setting is 3.5 turns out from bottom.  Turn the screw in all the way (clockwise) until it doesn't turn anymore, then back out 3.5 turns.

Brass plugs drilled out

Shims

The next step is to turn the carburetors right-side up and unscrew the black caps on top to install shims, one cap at a time.

The caps are spring-loaded and there is a tiny o-ring and spacer that can fly out, so they need to be removed carefully.  Take note of the position of the o-ring and spacer.

Cap removed, showing spring and o-ring

Underneath the cap is a delicate rubber diaphragm that needs to be gently peeled off the carb, while removing the plastic needle cap in the center of the diaphragm.  There is a tiny spring that can go flying.

The base setting is 3 shims (they look like steel washers), which get slid over the pointy end of the needle.  Then reinstall the needle and diaphragm and move on to the next carb.

Needle with shims:

After the shims are done the carbs are ready to be reinstalled in the bike.

Air Box Mod

This can be done anytime before the tank goes back on.

The air box has a rubber cover which gets discarded, except for tabs on the right and left side that fit over posts on the frame.  The rubber tabs are needed to secure the tops of the plastic side panels.  This is another one of those steps that can't be undone.  So I very tentatively cut up my air box cover with a scissors.

A 1" hole saw is needed to drill a hole in the air box lid.  The drill bit in my hole saw became detached somehow and I had a heck of a time getting the hole saw not to drift all over the place.  But eventually I got the hole drilled in the center of the lid.

After drilling through the air box lid it's a good idea to clean up the air box hole with sandpaper to prevent plastic shavings from entering the air box.

1" air box mod

So ended day 2 after 5 hours or so.  Up next, carb reinstallation.