Tag Archives: carb repair

Harley Keihin Carb clean

Posted on by Motopsycho

Another bike left to die


This patient is a 2000 Harley Davidson FXST Softail standard. I realize this isn’t really vintage but it is 19 years old. Picked up not running, coated with a quarter of an inch of dust, 2 flat tires, and a tank full of stale gas it is in dire need of some attention before it’s too late. After making sure it had compression and spark I was ready to tear into the Harley Keihin carb.

Harley Keihin Carb on 2000 Twin Cam Softtail

First thing was to remove the air cleaner than go to the other side of the bike to loosen the enrichment(or choke) knob so you remove it cable and all with the carburetor. After this pop the carburetor out of its spigot.

Harley Keihin Carb on 2000 Twin Cam Softtail

Once you have the carb loose unhook the fuel line and throttle cables.

Harley Keihin Carb

Take the Harley Keihin carb to a work bench where you have plenty of room to spread out the parts as it is disassembled.

Harley Keihin Carb

Harley Keihin Carb

Make note of the numbers on the carburetor as they might come in handy when you need to get parts. Then pull the enrichment plunger out and set it aside.

Harley Keihin Carb

Take the accelerator pump housing, diaphragm & spring off the bottom of the float bowl.

Harley Keihin Carb accelerator pump

If the previous mechanic would have used a top shelf screwdriver like this Vessel Impacta shown here I wouldn’t have had to replace so many of the screws.

Harley Keihin Carb float bowl screw
Yes these are JIS screw

With the float bowl off inspect everything well and make note of what parts are where.

Harley Keihin Carb inside float bowl

There was a little damage on the mixture screw tower from the plug being removed. Normally there’s a cap over this that you have to drill a hole in & use a wood screw to pop it out. If you live in an emissions inspection state the cap has to be replaced with a new one. If I lived in an emissions inspection state this carb body would have to be replaced.

Harley Keihin Carb pilot mixture screw
someones been in here before

first remove the float & float valve, followed by the main jet & emulsion tube.

Harley Keihin Carb

then take out the pilot (idle) jet.

Harley Keihin Carb idle jet

Next up is the idle mixture screw, first screw it all the way in slowly & count how many turns it takes to bottom out, and make a note of it. Then remove the screw completely.

Harley Keihin Carb mixture screw

There are four parts to the mixture screw assembly on a Harley Keihin carb. 1. the screw itself 2. the spring 3. a small washer & 4 the o-ring. Chances are that the o-ring & washer will remain in the carburetor body & you’ll have to use a small pick to carefully fish them out.

Harley Keihin Carb pilot mixture screw parts

Moving on to the top cover remove it,

Harley Keihin Carb top removal

and then set it & the spring off to one side.

Harley Keihin Carb CV diaphragm

Pull the slide out, inspect the needle (metering rod) for wear & check the diaphragm for holes.

Harley Keihin Carb

I always push the needle jet that the metering rod passes through out of the body so I can inspect it too. Since I clean carbs in a heated ultrasonic cleaner if I don’t push it out and keep track of it, it’ll probably fall out any & I’ll have to go fishing for it.

Harley Keihin Carb

Here’s a shot of the float chamber with all of the removable parts out.

Harley Keihin Carb

Since this is only a repair job & not a restoration this carburetor only got a cleaning, no vaporblasting. This body was in nice shape & looks decent with only cleaning. If you’re working on a crusty old pile of junk and want your parts to look good again please see my vaporbasting page.

The next few pictures show this carburetor’s parts laid out in the order that that they go back in. Make sure you carefully inspect all parts and replace any that are not usable especially the rubber pieces.

Re-install all of the internal parts,

Harley Keihin Carb jets, float mixture screw & enrichner

and the mixture screw being sure to set it as it was before. If you think it was wrong verify the setting with a good service manual.

Harley Keihin Carb pilot mixture screw assembly

Then set the float height.

Harley Keihin Carb float height

Harley Keihin Carb

Carefully line up the accelerator pump rod through it’s hole in the float bowl & reinstall the bowl. Don’t forget to put the bellows on as shown before the float bowl.

Harley Keihin Carb accel pump linkage

The rest of the accelerator pump arts should be reassembled to the carb now.

Harley Keihin Carb

The last couple of steps are reassembling the needle to the slide making sure to put any spacers that may be present back where they were to start with and then putting the slide back in the body, with the spring & then re-installing the cap.

Harley Keihin Carburetor

Once this is all done it’s time to put the carburetor back on the bike, fire it up and make any needed adjustments. I hope you have found this pictorial overview of a Harley Keihin carb helpful & interesting.

Harley Keihin Carb ready to install

Peace Y’all ‘Psycho

Dirtbike Carburetor 101 Part Two!

Posted on by Motopsycho

Welcome back everyone,

At the end of the last class we ended with the carb sitting on the bench and the intake port in the head plugged to keep out dirt & small critters. Now let’s pull off the vent hoses and turn it upside down on the bench like this.

Take note of the pilot mixture adjustment screw that I have labeled here for you. I will be giving you a tip about it later in the lesson so be ready to refer back to this picture if you need to. Please remember these are not in the same place on all carburetors. I have seen them on the top and on the side depending upon the make and model. Some late model machines have them hidden under aluminum caps to keep you from tampering with them, but if you have a real problem you can remove the caps to repair it. Just be sure to replace them especially if you have to pass emissions inspections in your state. As usual I recommend you consult your handy dandy service manual for your motorcycle just to be on the safe side, because some carbs have more than one aluminum plug and you don’t want to remove the wrong one. Trust me I know….

Of course this bike has none of those annoying issues so let’s go ahead and take the screws out of the float bowl and look inside.

EWWW!

Now I am a fairly environmentally conscious guy, I grow organic veggies, the shop that I work in is powered by solar electricity, drive reasonably efficient vehicles etc. but you will never convince me in a million years that today’s gasoline is good for the environment. Once the lead was removed there really was not that much left to improve. There is no way  fuel that will rapidly break down into this toxic and corrosive sludge as fast as the fuel made in this day and time, can possibly be good for the environment. Just think of what it is doing to your vehicles as they sit in the driveway right now.

Let me get out of rant mode and get on with the lesson; here’s a shot of it with the float removed. You should be able to push the pin out to one side with a small punch and lift the float and float needle (float valve) out of the bottom of the carb.

So when someone tells you the float is sticking this is what they are talking about. Sticking floats are usually caused by either a piece of trash getting under the point of the float valve, or if the motor has been sitting by gasoline evaporating, and gluing it into place with a coat of gunk like you see here.

In this next shot I have removed the jets and the mixture adjustment screw. Even if you have a service manual handy, before removing the mixture screw, turn it all the way in slowly and count how many turns it takes to go all the way in. Write the number down somewhere, and then remove the screw along with the spring the washer and the o-ring that are in the hole under it.

You’ll probably have to dig for the o-ring using a piece of wire or a small pick like I did above.

At this point all of the metal parts are ready for a good long soak in the parts washer or carburetor cleaner until tomorrow. In fact the longer the better. Gather up some supplies.

If you have an air compressor and a parts washer you may not need the spray carb cleaner. If you don’t have a compressor it is mandatory even with a parts washer or a dip bucket of carburetor cleaner. For this bike I did pick up a carburetor overhaul kit. If your o-rings are all still in good shape and you can get all of your jets spotless you may not need it, but it is often difficult to clean the idle jet good enough to work again even with all of the right tools. If it’s my own bike, and I am broke that week, I might chance it, cause hey it’s part of the price I pay for this hobby. If it is your bike, you are getting new parts, because if it does not work, then I would be working on it for free and that would just piss me off. You would probably be upset at me too.

Here’s a teaser shot of everything laid out on the bench after cleaning, be sure to come back for the next lesson!

exploded view!

Click here to continue this lesson!

Dirt Bike Carburetor 101 Part 1 (how to clean a single cylinder motorcycle or atv carb)

Posted on by Motopsycho

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.

“barn fresh” 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. Click here for part two!

Peace Y’all