Notices
Gas Engines Questions or comments about gas engines can be posted here

Carb rebuild…..the extra steps

Old 01-16-2016, 03:47 PM
  #1  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Carb rebuild…..the extra steps

I've done several carb rebuilds and it's no big deal. Usually a rebuild consists of replacing the diaphragms and gaskets on both sides and cleaning or replacing the fuel screen. You may also want to remove and clean/inspect the high and low speed needles and the metering needle. I usually do that if I find gunk on the filter screen.

Now, here is the reason for this thread. Have any of you, as a matter of a rebuild, gone so far as to remove the welch plug covering the low speed fuel metering chamber. That is the large silver dome cap on the metering side. Or, have you also removed the smaller screen and circular clip covering the high speed metering chamber. I would think the only reason for doing this is if you suspected blockage in the chamber or ports. The only other chamber is the needle fuel feed and I don't think that is serviceable.

I keep both K10WAT and K20WAT rebuild kits on hand. The welch plug, circular clip, and small screen is usually in these kits. However, I have never used them nor do I recall anyone posting about them. It looks like it is a PITA to do those two chambers.

Opinions please.

Indiomike

Last edited by Indiomike; 01-16-2016 at 09:49 PM.
Indiomike is offline  
Old 01-16-2016, 04:06 PM
  #2  
CK1
My Feedback: (60)
 
CK1's Avatar
 
Join Date: Apr 2002
Posts: 1,363
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

mike , I usually don't mess with the metering chambers unless there is an issue that replacing the diaphragms and inlet screen didn't cure . Rarely some debris will end up in those passages but 99% of the time you don't need to go there. I'm sure others will chime in and have different moa's but why spend unnecessary time on a carb unless it really needs it
CK1 is online now  
Old 01-16-2016, 06:37 PM
  #3  
kmeyers
 
kmeyers's Avatar
 
Join Date: Jan 2004
Location: lake in the Hills, IL
Posts: 785
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I've a opinion, your parts are wrong the pump side flapper valves and pump diaphragm go against the carb body. The metering side the gasket goes against the carb body and the diaphragm goes against the cover with four screws.
read my sig.
kmeyers is offline  
Old 01-16-2016, 07:24 PM
  #4  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by kmeyers View Post
I've a opinion, your parts are wrong the pump side flapper valves and pump diaphragm go against the carb body. The metering side the gasket goes against the carb body and the diaphragm goes against the cover with four screws.
read my sig.
+1, this is the correct order.
Truckracer is online now  
Old 01-16-2016, 08:58 PM
  #5  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

OOPS, brain f…t

I got that backwards. Sorry.

The metering side has the diaphragm on top of the gasket whereas the pumping side has the flappers underneath the gasket.
Indiomike is offline  
Old 01-16-2016, 09:29 PM
  #6  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Man, I'm not thinking well today. The main thing I'm interested in is whether anyone routinely removes/cleans/replaces the metering chamber parts when doing a normal overhaul. I don't think so because I rarely read about those items (welch plug and small screen with the circular clip). I guess it makes sense that if doing the normal rebuild things don't make the carb run right, one would then consider blockage in this area and proceed with going in there.

Now where did I put my bottle of Crown Royal.
Indiomike is offline  
Old 01-16-2016, 10:06 PM
  #7  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I deleted the paragraph I had mixed up so that nobody would get confused, especially me

The side with one big screw is the pump side. The correct order is cover, then gasket, and then flap diaphragm which lays against the carb body. The metering side has four screws and the correct order is cover, then diaphragm, and then gasket which is against the carb body.

Sorry for the confusion.

Indiomike
Indiomike is offline  
Old 01-17-2016, 05:34 AM
  #8  
ahicks
My Feedback: (2)
 
Join Date: Aug 2008
Location: Waterford, Mi/Citrus Springs, Fl
Posts: 3,726
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Mike, I haven't had to remove those welch plugs yet either. Don't intend to either, as long as the needles respond as expected.
ahicks is online now  
Old 01-17-2016, 09:40 AM
  #9  
kmeyers
 
kmeyers's Avatar
 
Join Date: Jan 2004
Location: lake in the Hills, IL
Posts: 785
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I don't do more then a clean, new screen, remove needles, flush out passages and change diaphragms myself.
kmeyers is offline  
Old 01-17-2016, 11:10 AM
  #10  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

As long as the carb feeds fuel as desired and the needles adjust in the normal range, there is no real reason to remove the welch plugs. In fact, my bet is the average person may cause more harm than good by removing them.

Most of the carbs we use on engines up through 60 CC are the Walbro WT or a WT clone. Most of these carbs use the capillary screen (the small screen(s) retained by a "C" ring) as a high speed check valve. Unless the carb is full of corrosion or really clogged with crap, it is easy enough to back flush this and blow it out with air. An exception might be a carb who's owner decided to remove the large screen in the pump chamber letting excess crap in that could clog the capillary screen. In this case it might be a better idea to just replace the carb rather than trying to repair or clean the small screen.

On larger carbs such as the SDC, WJ, WB, etc. they often use a pressed into place HS brass check valve assembly that uses a rubber valve and spring as a check valve. The rubber part can be damaged by some carb cleaners, bad fuel, etc. and removal of the welch plug is required to replace the valve. This is probably more than most owners would want to undertake so once again, carb replacement is probably a good idea if the check valve goes bad.

By the way, I have ruined a HS check valve before by using strong, spray can carb cleaners. These cleaners can be very aggressive to rubber parts and can destroy them in short order. As a result, I only use spray solvents such as brake cleaner, or rubber / plastic safe carb cleaners for the task. Read the labels before use as the cleaners will usually say whether rubber parts have to be removed before use. Many people don't know there can be tiny rubber bits buried in their carb though and damage can result.
Truckracer is online now  
Old 01-17-2016, 04:58 PM
  #11  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Up until now I have been using regular spray carb cleaner and blasting the spray into every orifice when I suspect there may be debris or clogging of some kind. Reading your responses gives me the thought that something like electrical spray cleaner might be the better choice. Would you agree? Something not quite as harsh as regular carb cleaner.
Indiomike is offline  
Old 01-17-2016, 05:07 PM
  #12  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I've used the electrical spray in great quantity when I had access to it (free) at my work. But since that supply went away (retired), I use cheap brake clean that I get at the auto parts store. It isn't harsh like some of the carb cleaners and it does the job quite well. Some carb cleaners will dissolve rubber parts. As I said in the previous post, most of the sprays adequately warn whether they are safe for use around rubber and plastic parts.
Truckracer is online now  
Old 01-17-2016, 05:19 PM
  #13  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I just went out into the garage to get my can of carb and choke cleaner. I read all the fine print on the side of the can. It does not say anything about avoiding any rubber contact. It was bought at a car parts store. Brand is K&W Technician Grade carburetor and choke cleaner. I guess it is okay to use but I also have on hand a spray can of electrical contact cleaner. I think there is a one way valve which is a rubber plate that is located in a recessed area between the welch plug oriifice and the C ring orifice. As far as I know that plate is not serviceable.
Indiomike is offline  
Old 01-18-2016, 12:09 AM
  #14  
CK1
My Feedback: (60)
 
CK1's Avatar
 
Join Date: Apr 2002
Posts: 1,363
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Most of the carb / brake cleaners sold at parts stores in CA has had all of the volatile stuff removed from it so that can be sold in CA ,
Thank you EPA. So the cleaners now are not as strong and don't clean as well as they have in the past. Having said that I still would not use them near rubber components without testing first ,regardless of what the label does or doesn't say .
CK1 is online now  
Old 01-18-2016, 09:47 AM
  #15  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by CK1 View Post
Most of the carb / brake cleaners sold at parts stores in CA has had all of the volatile stuff removed from it so that can be sold in CA ,
Thank you EPA. So the cleaners now are not as strong and don't clean as well as they have in the past. Having said that I still would not use them near rubber components without testing first ,regardless of what the label does or doesn't say .
And as California does, so does the rest of the country after a few years. I wouldn't have thought about their less volatile requirements until I read your post.
Truckracer is online now  
Old 01-21-2016, 07:38 AM
  #16  
av8tor1977
My Feedback: (6)
 
av8tor1977's Avatar
 
Join Date: May 2003
Location: Tucson, AZ
Posts: 7,213
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

That's how our wonderful EPA lowers its workload. They just find all the chemicals in the world that work well, and outlaw them. No real world justification needed. Bye bye R-12, good cleaners and strippers, paints, solvents, etc., etc. ad nauseum. The other day my brother and I searched for a good, old fashioned style "hot tank" to thoroughly clean a really cruddy car engine block, and couldn't find one in the entire city of Tucson, Az.

AV8TOR
av8tor1977 is offline  
Old 01-21-2016, 09:12 AM
  #17  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Could you even find a really good machine shop? Other than a few race car shops, good automotive machine shops are harder to find every day. Mostly because automotive shops rebuild fewer and fewer engines these days. Because with the high price of labor and the increased complexity of engines, it is easier and cheaper to just replace than to rebuild.
Truckracer is online now  
Old 01-24-2016, 09:55 AM
  #18  
Indiomike
Thread Starter
My Feedback: (5)
 
Indiomike's Avatar
 
Join Date: Feb 2008
Location: Indio, CA
Posts: 376
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

It sure looks that way. Almost anything electrical is simply replaced rather than repaired. Not long ago I had a radiator leak in an old truck. When I took it to a repair shop they said it was cheaper to replace than to re-core. I hope that line of thinking is never picked up in the medical profession.
Indiomike is offline  
Old 01-24-2016, 10:14 AM
  #19  
Truckracer
My Feedback: (19)
 
Join Date: Apr 2004
Location: Des Moines, IA
Posts: 4,958
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Modern consumer radiators with their crimped, glued and plastic construction can be impossible to repair by any traditional means. On the plus side, they're pretty darn reliable.

I use to buy race car radiators that had the tubes epoxied to the end plates that were in turn, TIG welded to the tanks. All aluminum construction, it could be twisted to ungodly shapes then pressed back into shape and it wouldn't leak. Unless the epoxy area was damaged, everything else was repairable by TIG welding. They weren't that expensive which was surprising.
Truckracer is online now  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.