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View Full Version : Aisan DD38/38 Carburetor Rebuild


RicardoJM
11-07-2010, 12:00 PM
Red72FJ40 (Pete) started a carb thread (http://www.risingsun4x4club.org/forum2/showthread.php?t=13593) and via the forum, we were able to determine that his accelerator pump was not working as it should. After some e-mail/pm exchange we decided to do a rebuild of the carb. Pete ordered a Keyster kit from cruiseroutfitters.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete04.jpg

It took a while for our schedules to align and few weeks ago I met Pete and picked up the carb. Pete's FJ40 is a 1972 and is running an F engine.
http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete05.jpg

Prior to removing the carb we checked the timing, vacuum and compression. As we were warming the truck up for the diagnostics, it idles smooth and does not smoke at all. The engine is a bit dirty and oily, but not any worse than other old F engines. Overall, the engine really appears to be in good "run it" shape.

The timing was spot on the BB and vacuum was just over 14 and under 15 with very little waver. Longmont is a bit lower altitude than Denver. The FSM for an F engine indicates that compression between 128 to 150. Adjusted for 5,000 feet altitude (http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-2.htm) ; an F engine with compression between 110 and 129 is within spec. The compression numbers on Petes engine ranged from 122 to 129, nice and tight.

RicardoJM
11-07-2010, 12:03 PM
The carb is DD38/38 Aisan with a 1972 build date. It has been worked on at some time in the past. This will the fourth Aisan carb rebuild that I have done and as with all the others, photos and notes are important to keep things straight. Here are some photos of the carb before tearing it down.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete01.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete02.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete03.jpg


In the second photo above, you can see the throttle positioner linkage has been previously removed. I was concerned about this, but after some doing some research, I have come to understand the carb will be ok with out it. Coolerman has some detailed photos (http://www.globalsoftware-inc.com/coolerman/fj40/23.htm) (Fig. 5 and Fig. 9) of his DD38/38 before and after having it rebuild by JimC. This thread (http://forum.ih8mud.com/40-55-series-tech/161617-f-carb-question-throttle-positioner.html) has additional insight on what the TP does.

Another concern was the brass nozel that funnels the fuel spray into the primary barrel. On this carb, the brass nozzel appears to have been cut off. Upon cleaning it out, it works just fine.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete06.jpg

The next concern was the amount of white grit pebbles that had worked their way into the fuel inlet. They were all throughut the screen, inlet and the finer particles made their way into the float bowl.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete07.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete08.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete09.jpg

In short order the carb was torndown and ready for cleaning.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete10.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete11.jpg

RicardoJM
11-07-2010, 12:05 PM
The cleaning and rebuild were uneventfull. Coming out of the carb dip, everything was very clean and new looking.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete12.jpg

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete13.jpg

The carb kit came with replacement jets for everything but the seconary slow jet. This is the second time that I have used this exact kit and each time it came with only one slow jet.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete14.jpg


On this carb I did not change the float adjustment to the specification (4.1 mm) from the FSM. Fact is the float level was perfect when we removed the carb from the truck and on all my other rebuilds where I have adjusted the float to specification - it has ended up with the fuel level being too high and needed to be re-adjusted. In Pete's carb, the fuel level was spot on.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete15.jpg

The new power valve, jets and clean fuel bowl look much better than before.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete16.jpg

The jets sizes are:

Primary Slow Jet - 50
Secondary Slow Jet - 80
Power Valve - 60
Primary - 114
Secondary - 180

RicardoJM
11-07-2010, 12:06 PM
Yesterday morning we installed the carb. It looks a bit too clean for the rest of the engine bay.

http://www.risingsun4x4club.org/uploads/ricardojm/petescarb/w_pete17.jpg

I did not bench test the accelerator pump at home and the brass discharge nozzle was plugged. In short order we pulled the air horn and got it cleaned up. The engine fired right up; full choke and two pumps.

We were having issues dialing in the idle and vacuum adjustements. The adjustements were not having the effect they should. The idle was not consistent, bumping around between 500 and 700 and missing. The vacuum was very low, around 10. The slow idle adjustment would kill the engine.

We went about double checking items. We swapped out the coil to distributor wire and found not change. We checked the power to the idle cutoff solenoid and solenoid operation - they were just fine. We sprayed starter fluid around the carb, manifold and vacuum connections and could not find any vacuum leaks. I was certain we had a vaccum issue, but really stumped that we could not find it. It turns out that our issue was with a vacuum connection to the distributor. Pete's truck has a vacuum retard distributor and the vacuum connection was direct to manifold vaccum. Once we removed this connection and capped it at the manifold - our lean drop adjustments worked just like they should. Vaccum is steady between 13 and 14.

Overall, we are very pleased with the results. We took the truck out for a test drive and it is running nice.

nattybumppo
11-07-2010, 03:44 PM
I see a good retirement business for you, Ricardo...

Rzeppa
11-07-2010, 11:09 PM
Thanks for sharing your new expertise Ricardo!

Red72FJ40
11-08-2010, 09:01 AM
Big SHOUT OUT to Ricardo. You rock, man. Thanks for all your help and expertise, and for posting this thread for others. I took the Cruiser for a cruise yesterday, and it runs great!

Thanks again.

Pete

Old40Dog
11-08-2010, 09:17 AM
i See A Good Retirement Business For You, Ricardo...

X2

corsair23
11-08-2010, 02:00 PM
Ricardo,

Just let me know when you want to tackle/learn Weber carbs :D

RicardoJM
11-08-2010, 02:12 PM
Big SHOUT OUT to Ricardo. You rock, man. Thanks for all your help and expertise, and for posting this thread for others. I took the Cruiser for a cruise yesterday, and it runs great!

Thanks again.

Pete

I really enjoyed being able to give hand. Many here have helped me along and it is nice to be able to pass some of it along. I'm looking forward to you getting to a club meeting and/or run when your schedule allows.

Ricardo,

Just let me know when you want to tackle/learn Weber carbs :D

I have a 32/36 DGAV and the Weber carb manual. I'm still having to hunt down a bracket for the accelerator cable and air filter - but I do intend to put it in my truck and give it a whirl. It might not be a replacement for my Aisan, but I am curious enough to give it a try.

subzali
11-08-2010, 03:16 PM
Ricardo,

Just let me know when you want to tackle/learn Weber carbs :D

Or maybe you should put an Aisan carb on your FJ40 so you'll stop having problems :homer: :p:

rover67
11-08-2010, 03:28 PM
Or maybe you should put an Aisan carb on your FJ40 so you'll stop having problems :homer: :p:

or we can tune his weber..

corsair23
11-08-2010, 03:55 PM
Don't sidetrack Ricardo's excellent thread boys...even if I did start the sidetracking :hill:

My plan is to tune/rebuild the Weber in my 40 first and go from there. It has only been the way it has for 5 years now so it isn't like I'm in a big hurry :D

RicardoJM
11-09-2010, 08:03 AM
or we can tune his weber..

Don't sidetrack Ricardo's excellent thread boys...even if I did start the sidetracking :hill:

My plan is to tune/rebuild the Weber in my 40 first and go from there. It has only been the way it has for 5 years now so it isn't like I'm in a big hurry :D

This is a sound approach. Many that run weber carbs and are very happy with them.

Jacket
11-09-2010, 10:12 AM
Nice work Ricardo. Funny thing about those old carbs - rebuilding them seems foreboding to the novice, but once you do one it kinda becomes fun and you want to do it more and more.