Cleaning Internal Carb Parts - the Brass Ones

How to keep your little baby running smoothly.

Cleaning Internal Carb Parts - the Brass Ones

Postby Bronco638 » Sun Jan 06, 2013 10:19 am

I had an opportunity to give my carbs a really good cleaning this weekend. I encountered a situation where simple inspection did not reveal any issues but they clearly were there. After switching from pump gas to Sunoco race gas, for the winter, my rear carb began to leak.

At first it was tired and old float bowl gaskets. I ordered a set of o-rings (from inmate John Hilmer). Before install, he suggested I ensure the float bowls were flat. To do this, he recommends 320 grit wet/dry sandpaper and a surface plate. I happened to have some 3/8" thick aluminum plates which sufficed. Sand the top float bowl surfaces until you can see you are removing material all the way around the float bowl mating surface. Clean off any residual grit (I used carb cleaner). Make sure the o-ring channel is completely clean of old gasket and any gasket adhesive. I used carb cleaner and a dental pick for this. Any good auto parts store should sell 'hook' picks which can be used in the same manner. Install the o-ring in the channel by starting at a convenient spot (I used one of the corners) and work your way around in one direction, holding onto the 'start' point. Once you get all of the way around, the o-ring should sit in the channel without any adhesive or having to hold the o-ring in-place.

Now is the time to remove the brass parts from the carb for 'special' treatment. Remove the floats and float valves. You will need a small flat-bladed screw driver, a 7mm wrench, 10mm deep socket and 1/4" drive ratchet. Use the screw driver to remove the main and pilot jets. Use the box end of the 7mm wrench to remove the emulsion tubes (the main jets screw into these). Use the 10mm socket and ratchet to remove the float valve bodies. Make sure you identify the small aluminum crush washers under the valve bodies, set these aside in a safe place. There are small screens on the underside of the float valve bodies. If they stay in the carb body, use the hook pick to pull them out (carefully) and snap them back onto the float valve bodies.

Bottom the fuel mixture screws, counting the number of turns until they bottom (you do not need to bottom them hard, once they stop turning, that's good enough). The number should be about 2 turns (mine were 2.25). Now, back them all of the way out and remove them. In addition to the screw, there should be a small spring, a metal washer and an o-ring. Sometimes the washer and o-ring gets stuck in the bore. Remove them with a straightened paper-clip with a small hook fashioned at the tip.

If you're going to give the carb body a good cleaning (and you might as well), you need to remove the slides because the diaphragms cannot stand up to carb cleaner (they will dissolve!). You can also clean the needles along with the brass parts. Remove the four screws that hold the diaphragm cap in-place (place a finger over the cap because there's a spring on the other side). With all four screws removed, slowly pop the cap off and remove the spring with the cap. Carefully unseat the diaphragm from the channel and remove the slide. Inside the slide is a retainer for the needle. Use a small Phillips head screw driver to turn the retainer 90º counter-clockwise. The retainer should now slide out (on the tip of the screwdriver, if you're careful). If you turn the slide over, the needle should fall out. Be careful, there's a spacing washer between the needle and the slide. Don't lose it (set it aside where you kept the cush washers). If the diaphragms need cleaning, use warm water and perhaps a little soap. No Chemicals!

Gather the brass carb parts (jets, emulsion tubes, float valve bodies and pilot screws) along with the needles and put them in a metal soup can (w/o the label). Mix up a solution that's 1/4 Pine-Sol and 3/4 water. Place over heat and boil the parts for an hour. Use a vent fan if you're doing this in the house. It will keep the odors to a minimum (not that it smells bad but the smell of Pine-Sol will be easy to detect).

After an hour, let the solution cool until you can pick up the can in your bare hands. Dump the solution (which should be less than half of its original volume) without dumping the parts (I like the soup cans because they have a nice lip to keep parts in the can). Rinse with water and dry with compressed air. Do not be surprised if some of the parts are now a different color (I had an emulsion tube change to a copper color). Re-assemble the carbs. Take care when installing the needle retainers in the slides. They are plastic and should snap into the locked position easily. If they resist, re-orient them 180º and try again. Don't forget the spacer under the needle. When installing the diaphragm cap, be sure to orient the relief in the cap so that it's over the corresponding vent in the carb body (there's a little loop in the diaphragm to go around the small vent tube). Don't forget the crush washer under the float valve bodies. You do not need to really crank down on the emulsion tubes or the jets. When they snug up, that's good. Reset the pilot screws from bottom. Install the float valves and floats. Check the float height. Install the float bowls and insure the new o-rings are properly seated. Now is the time to install new carb-to-head boots. They have a proper orientation and are marked "carb side" and "up" (up meaning toward the sky). Consider switching the boot clamps so they're accessed from the left side of the bike (more room on that side and you don't have to fight with coolant hoses). Also consider switching from the Phillips head screws to Allen head cap screws (in stainless). You can use a ball end Allen wrench for easier tightening from various angles.

Also consider having the carbs balanced and resetting the idle drop.

Let me know if I made any errors or if I left anything out (I'm sure I did). As you can tell, this is not a comprehensive procedure but meant to be used in conjunction with the shop manual. When in doubt, ask and I'll do my best to answer (or another inmate with more knowledge will, I'm sure).
2002 Honda XR250R
2002 Honda Reflex
1993 Aprilia 280R Climber
User avatar
Bronco638
Moderator
 
Posts: 665
Joined: Tue Jun 05, 2012 8:01 am
Location: Chicago-land

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby John Hilmer » Sun Jan 06, 2013 10:42 am

Dave,

Another nice write-up on a subject that I'm sure will get used.

John
Lord help me to be the man my Labrador thought I was.
It's never too late to have a happy childhood ...
John Hilmer
Moderator
 
Posts: 1980
Joined: Tue Jun 05, 2012 7:29 am
Location: Scotts Valley, Ca.

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby ranathane » Sun Jan 06, 2013 11:01 am

Very nice Dave! As I have apparently have a fuel issue to the front cylinder on the 89 (doesn't seem to have any fuel until I twist the throttle a bit) I was going to do a full teardown of the carbs soon. This will make that much easier as the manual if kinda deficient.
Ralph Daugherty
AMA Member 2892740
User avatar
ranathane
Site Admin
 
Posts: 300
Joined: Mon Jun 04, 2012 4:36 pm
Location: Orlando,FL and greater US

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby Bronco638 » Sun Jan 06, 2013 2:44 pm

ranathane wrote:Very nice Dave! As I have apparently have a fuel issue to the front cylinder on the 89 (doesn't seem to have any fuel until I twist the throttle a bit) I was going to do a full teardown of the carbs soon. This will make that much easier as the manual if kinda deficient.

Considering the number of times I've had the carbs on and off the VTR, over the last month, I would now consider myself an "EXPERT". So, feel free to ask lots of questions. I should know EVERYTHING. :D

p.s. - John was a huge help and I still expect him to offer his thoughts.
2002 Honda XR250R
2002 Honda Reflex
1993 Aprilia 280R Climber
User avatar
Bronco638
Moderator
 
Posts: 665
Joined: Tue Jun 05, 2012 8:01 am
Location: Chicago-land

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby John Hilmer » Sun Jan 06, 2013 3:34 pm

Dave & All,

I don't know if you actually used some spray carb cleaner as I suggested to clean the passages in the carb bodies or not, but it is a prudent thing to do. You just have to make sure that the diaphragms, slides, pilot jet "O"Rings and all other synthetic parts are well away when you use this stuff. It will kill those parts faster than you can sneeze.

Squirrelman is the real expert and I hope that he'll chime in to add his thoughts. He may have some valuable input that could be incorporated into your thread that I think should become an all encompassing tutorial.

Actually he may well be working on doing his own write-up.

John
Lord help me to be the man my Labrador thought I was.
It's never too late to have a happy childhood ...
John Hilmer
Moderator
 
Posts: 1980
Joined: Tue Jun 05, 2012 7:29 am
Location: Scotts Valley, Ca.

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby Sir Real Ed » Wed Jan 09, 2013 6:26 am

Excellent information. Thanks.
Sir Real Ed
 
Posts: 57
Joined: Fri Dec 28, 2012 8:29 pm
Location: Forest, VA

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby squirrelman » Wed Jan 09, 2013 5:17 pm

Good writeup, Bronc ! ;)

Choke enrichment won't work right unless you've probed the long brass pickup tube with a steel wire (.010") to a depth of about 65mm. The tubes are almost always partially or totally blocked with crud that neither air nor carb spray will clear.

Additionally all the small side holes in idle jets and emulsion tubes need wire-probing to knock off deposits there.
Attachments
IMG_1088.JPG
User avatar
squirrelman
 
Posts: 965
Joined: Wed Jul 18, 2012 1:57 pm
Location: Buffalo, NY USA

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby John Hilmer » Wed Jan 09, 2013 5:43 pm

Squirrelman,

This is what I hoped for; I forgot about the fuel enrichment passage and the valves themselves. These have to move freely and can't be overlooked.

John
Lord help me to be the man my Labrador thought I was.
It's never too late to have a happy childhood ...
John Hilmer
Moderator
 
Posts: 1980
Joined: Tue Jun 05, 2012 7:29 am
Location: Scotts Valley, Ca.

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby Bronco638 » Thu Jan 10, 2013 8:26 am

I was hoping to use some of my "thin" safety wire to ensure that the pilot jets were clear but the wire thickness was too big (diameter). Is there anything special about the steel wire you use (other than the fact that it's .010)?

I was hoping that the Pine-Sol boil would remove any deposits from the emulsion tubes. I check the side holes, in mine, and they all appeared to be clean/clear. The bike starts and idles pretty nicely, not that it didn't before. What ever was on the float valve body was certainly dissolved. The float valve seals now.
2002 Honda XR250R
2002 Honda Reflex
1993 Aprilia 280R Climber
User avatar
Bronco638
Moderator
 
Posts: 665
Joined: Tue Jun 05, 2012 8:01 am
Location: Chicago-land

Re: Cleaning Internal Carb Parts - the Brass Ones

Postby squirrelman » Thu Jan 10, 2013 4:19 pm

I've heard that a guitar steel string works well to clear holes, don't know which note.

On the emulsion tubes the holes may seem clear, but after running a wire through one sample hole, you'll see the difference clearly !! :roll:

Just like the idle jet, you might see light through the holes, but that doesn't mean they're 100% clear. Not until you've wire-probed do you know. Invisible deposits build up that you can't see because they're invisible ! :geek:
User avatar
squirrelman
 
Posts: 965
Joined: Wed Jul 18, 2012 1:57 pm
Location: Buffalo, NY USA

Next

Return to Maintenance/Minor Repairs

Who is online

Users browsing this forum: No registered users and 1 guest

cron