Carburetor rebuild
Sep 1, 2009 | 05:03 PM
#2
best wright up I have seen on the net ...
http://www.bluebassdesign.com/boonin/carb_faq/
good luck !!
.
http://www.bluebassdesign.com/boonin/carb_faq/
good luck !!
.
Mar 13, 2010 | 03:33 AM
#6
Registered User
Joined: May 2009
Posts: 79
Likes: 0
From: Flagstaff, AZ
I've had good luck rebuilding. Of course nobody likes to admit that the carburetor itself does not usually require rebuilding. I am not an expert in the land of old Toyotas so if anybody has a different thought or can point out an error in my methodology here please correct me. 
Here is my advice:
1) Buy two of those cheapie drip pans from the parts store. They usually run like 3 bucks. That way you can do your initial cleaning in pan #1 which can become quite soiled. As your parts get cleaner switch them to pan #2 and do your final clean/wipe operations. Having good lint free shop rags can be handy here.
2) Buy one of those automotive "tooth brush" sets . They usually come cheaply in kits of 3 each - nylon, brass, and stainless. Only use the stainless on parts that are really fouled and avoid brass pieces with the stainless brush. As with the drain pan you should consider keeping one of your brushes as "final clean" and one as "soiled".
3) Treat the process as if it were surgery. Do it where there is a lot of light. Treat it like a bomb tech- little spring loaded pieces could jump out at you at any point.
But seriously you do want to be careful to account for everything you take apart.
4) Buy plenty of carb cleaner. Don't be bashful about using it. I've heard good things about some of the carb parts "dip" cans but have never found them to be necessary on anything I've worked on yet. You can go through 3 or 4 cans easily. Believe it or not I've taken a liking to Autozone Valucraft carb cleaner but everybody has a preference. When I was young I used to use 2+2 Gumcutter but that product seems to be only east coast and of course it comes at a premium.
5) Remember that sometimes an old carb can leak air badly around its throttle shaft seal. As far as I am aware on the Aisin 2bbl on our trucks this cannot be replaced. Air leaks at the throttle shaft can cause vacuum fluctuations and of course can cause the engine to injest dirty air. If you feel the throttle shaft has a major leak than rebuilding simply may not solve your issue.
6) Many recommend the NAPA brand carb kits. Unfortunately the smog tags are mising from a lot of carbs for various reasons. From first hand experience with the 1980 federal emissions pickup, the GP Sorensen brand rebuild kit sold at Autozone seems to work fine. Do not be alarmed when you don't use all the parts in the kit though - it is intended as a universal kit. Generally the most important parts it will come with are the gaskets, orings, accelerator pump piston, needle and seat and of course the base gaskets. I believe they come with new jets too but see my next piece of advice.
7) Aftermarket rebuild kits can vary greatly in quality. Look for anything that might present a problem to the smooth operation of your carburator - roughly machined components and the like. I have found some variance sometimes in cheaper rebuild kits in jet size. Maybe you want to experiment with this and maybe you don't but here i what you do: get an open ended spark plug feeler set, or a machinist's drill bit set and find the diameter of the jet in question. Compare it to what is already installed in the carburetor. If they vary much - say .002" than consider simply cleaning the original jets thoroughly (i.e. thread a few of the bristles of your brass brush up through the jet hole and work out any corrosion or deposits).
8) Remember that carburetors are simple devices that rely on two simple factors - reliable fuel flow and clean air flow. Dirt, dust, or crud in any form is the enemy here. Anything that has sharp edges, any gaskets that don't mate cleanly, and any thing that is scored or scratched can be a haazard to the function of the carburetor.
I am far from a Toyota carburetor expert. In fact carburetors were mostly off the road by the time I started working on cars. This is what has worked for me in the past though. A generally meticulous, scientific attitude goes a long way in successfully rebuilding a carburetor.
That being said, there are several major problems that I have seen commonly in a carburetor. Specific to my Toyota experience:
1) The AAP diaphragm is ruptured.
2) The accelerator plunger is worn out
3) The aforementioned thorttle shaft leakage
4) Improperly set float level
5) Fuel cut solenoid sticks
The above problems can mostly be fixed without carburetor disassembly.
I hope this helps. Just a few points to consider. You should also read the instructions that come with the kit and probably get the opinion of the factory shop manual, or at least a Chilton or Haynes manual.
Here is my advice:1) Buy two of those cheapie drip pans from the parts store. They usually run like 3 bucks. That way you can do your initial cleaning in pan #1 which can become quite soiled. As your parts get cleaner switch them to pan #2 and do your final clean/wipe operations. Having good lint free shop rags can be handy here.
2) Buy one of those automotive "tooth brush" sets . They usually come cheaply in kits of 3 each - nylon, brass, and stainless. Only use the stainless on parts that are really fouled and avoid brass pieces with the stainless brush. As with the drain pan you should consider keeping one of your brushes as "final clean" and one as "soiled".
3) Treat the process as if it were surgery. Do it where there is a lot of light. Treat it like a bomb tech- little spring loaded pieces could jump out at you at any point.
But seriously you do want to be careful to account for everything you take apart.4) Buy plenty of carb cleaner. Don't be bashful about using it. I've heard good things about some of the carb parts "dip" cans but have never found them to be necessary on anything I've worked on yet. You can go through 3 or 4 cans easily. Believe it or not I've taken a liking to Autozone Valucraft carb cleaner but everybody has a preference. When I was young I used to use 2+2 Gumcutter but that product seems to be only east coast and of course it comes at a premium.
5) Remember that sometimes an old carb can leak air badly around its throttle shaft seal. As far as I am aware on the Aisin 2bbl on our trucks this cannot be replaced. Air leaks at the throttle shaft can cause vacuum fluctuations and of course can cause the engine to injest dirty air. If you feel the throttle shaft has a major leak than rebuilding simply may not solve your issue.
6) Many recommend the NAPA brand carb kits. Unfortunately the smog tags are mising from a lot of carbs for various reasons. From first hand experience with the 1980 federal emissions pickup, the GP Sorensen brand rebuild kit sold at Autozone seems to work fine. Do not be alarmed when you don't use all the parts in the kit though - it is intended as a universal kit. Generally the most important parts it will come with are the gaskets, orings, accelerator pump piston, needle and seat and of course the base gaskets. I believe they come with new jets too but see my next piece of advice.
7) Aftermarket rebuild kits can vary greatly in quality. Look for anything that might present a problem to the smooth operation of your carburator - roughly machined components and the like. I have found some variance sometimes in cheaper rebuild kits in jet size. Maybe you want to experiment with this and maybe you don't but here i what you do: get an open ended spark plug feeler set, or a machinist's drill bit set and find the diameter of the jet in question. Compare it to what is already installed in the carburetor. If they vary much - say .002" than consider simply cleaning the original jets thoroughly (i.e. thread a few of the bristles of your brass brush up through the jet hole and work out any corrosion or deposits).
8) Remember that carburetors are simple devices that rely on two simple factors - reliable fuel flow and clean air flow. Dirt, dust, or crud in any form is the enemy here. Anything that has sharp edges, any gaskets that don't mate cleanly, and any thing that is scored or scratched can be a haazard to the function of the carburetor.
I am far from a Toyota carburetor expert. In fact carburetors were mostly off the road by the time I started working on cars. This is what has worked for me in the past though. A generally meticulous, scientific attitude goes a long way in successfully rebuilding a carburetor.
That being said, there are several major problems that I have seen commonly in a carburetor. Specific to my Toyota experience:
1) The AAP diaphragm is ruptured.
2) The accelerator plunger is worn out
3) The aforementioned thorttle shaft leakage
4) Improperly set float level
5) Fuel cut solenoid sticks
The above problems can mostly be fixed without carburetor disassembly.
I hope this helps. Just a few points to consider. You should also read the instructions that come with the kit and probably get the opinion of the factory shop manual, or at least a Chilton or Haynes manual.
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