carb | Welcome to the Asylum

Hello everyone and welcome to this multi-part lesson on the basics of carburetor cleaning for single cylinder motorcycles. The cadaver we will be resuscitating in this lab is an 02 Honda XR100.

Believe it or not this bike would still run with the choke on even with the dead gas and clogged jets, gotta love a Honda! This will be a general step by step guide to repairing carbs, so I will not be giving you the actual specifications as they vary so much from year to year on some bikes. As I’ve said before you need to obtain the specific information for your exact bike from a reputable source like say a service manual. For this first post let me show you how to remove the carburetor from this bike.

First let me say that it is possible to pull the carb from an XR100 without removing the bodywork, but A; you need to clean or replace the air filter and B; if it’s been sitting long enough to need the carburetor cleaned you need dispose of any fuel in the tank and clean it out before re-starting the bike after you finish the carb.

Now take off the side covers. This picture shows the location of the air filter cover on the XR100

Next look under the rear fender and remove the 2 nuts holding the seat on. Then pull it up and rearward to remove it.

I like to put the nuts and any spacers back on the studs like this so they will not get lost. In fact whenever possible I do this for all nuts and bolts as it keeps them from disappearing.

Now go the the fuel switch, valve or petcock, whichever terminology you use for it and turn off the flow of gas to the carburetor and disconnect the fuel line. Be prepared to cut it off with a knife and replace it if necessary.

Remove the rubber strap that holds down on the rear of the fuel tank and the two bolts at the front of the tank.

It is not required that you remove the shrouds like I did for this photo, I simply removed them so that I could show you the location of the bolts at the front of the gas tank.

After setting the gas tank aside in a safe location it is time to disconnect the throttle cable. On some models it attaches to an arm on the side of the carb but on simpler ones like this it is attached directly to the carb slide. Unscrew the cap as indicated by the screwdriver and pull the slide out.

This next shot is a little fuzzy but it indicates how the throttle cable is retained in the slide, and the following picture shows the slot in the side of the slide that allows you to remove it from the cable.

Now all you have to do is to compress the spring and push the end of the cable out of its hole, past the end of the slide, pull it out through the slot and then through the big hole at the top.

Here’s the removed and disassembled slide, jet needle, and return spring laid out for you to see.

Loosen the clamp holding the rubber hose from the air box to the carb and then remove the bolts attaching it to the engine and pull it out.

Yes I’m using the obstruction wrenches again. Two tools that I feel are must haves for any serious cycle mechanic are obstruction wrenches of decent quality and some extra long screwdrivers of the finest quality money can buy (i.e. Snap On etc.) Inexpensive wrenches are often okay but cheap screwdrivers will drive you bleeping crazy, by stripping out the soft metal heads on Japanese motorcycle screws.

Here’s a shot of the carburetor on the workbench. I like to use the red toolbox tray shown to help me organize the parts as I disassemble the carb, and to keep the parts from disappearing into the wormhole that exists behind my workbench. No part that falls back there is ever seen again, so I try to keep them from rolling of of the back edge. No dear reader I am not going to move the bench to look for them either. In my shop I coexist peacefully with all matter of snakes and spiders both harmless and venomous, and that is their territory and I stay out of it.

Don’t’ forget to protect the engine by plugging the intake hole while the carburetor is off.

I’ll show you the rest later, don’t forget to bookmark this page or to sign up for the email notification of updates on the right side of this page. Cli ck here for part two!

Peace Y’all

The next order of business is to dis-connect the negative cable from the battery as shown here.

Remember any time you are working with any vehicle with a negative ground system (which is practically everything) always dis-connect the negative battery cable first and re-connect it last when you are working on the electrics.
The next 2 pics will show how I use the door panel tool to remove the plastic retainers from the bodywork. First you wedge up the sliding pin in the center enough to get the forks of the tool started under it.

Afterwards you can slide the tool into place as shown and pull the clip right out.
Of course you can just use a couple of screwdrivers or a pair of wire cutters to remove the clips. Don’t forget to look for clips or screws in hidden places like this.

To get the fuel tank out you first need to remove the handle for the fuel switch.

Once you have the tank out be sure to note the position of the various vent hoses and take note of the routing. If you pinch them closed during re-assembly your four wheeler may not run correctly, or may stall going up hill.

Once all the plastic is off it’s time to get down to the nitty-gritty. Now remove the foot pegs. This will save you lots of needless foul language and bleeding. Plus on some models you can’t get the engine out with them in the way.

Remove the foot brake and shifter after you get the pegs off and then drain the oil so it won’t be sloshing out all over the place when you lift the engine. It’ll take some weight off too.

Do take a little time now to put some penetrating oil on all of the exhaust system nuts and bolt that you can reach and let them soak a few minutes.

Then remove the plastic covers from the sides of the engine and the muffler & header as well. While I was doing this the head of one of the screws stripped out so I got out my extractor set to remove it. Normally I am a fan of inexpensive tools especially for the hobbyist but there are 2 things that I recommend that you buy the absolute best in the world even if you have to save up for it. The first is a good set of screw extractors and the other is a Phillips screwdriver set.

85% of the time I don’t even have to use the extractor because the left handed drill bit will walk the broken screw right out.
Back to our engine now it’s time to remove the carburetor and then unhook all of the other cables going into the engine. Leave the throttle and choke cables attached to the carburetor unless you plan to remove it to work on it also,

Be sure to loosen the clamps over the drive shaft boot!
The last item to get to is the reverse lock out cable located at the bottom rear of the engine under this little metal cover.

Now unbolt the 2 motor mounts on either side, carefully remove the spacers and slide the engine forward and tilt it as need to make the frame look like this.

Finally here’s a shot of the engine sitting on the workbench waiting to be completely disassembled… starting tomorrow.
Peace Y’all