History: 30 years ago I bought a 72' Datsun B110 car from a junk yard to use for parts to fix another car. Then I scrapped everything except the engine, 4 speed stick trans., propeller shaft and rear end. Then in 1993 I went into the windmill business and needed a boom truck to take down and erect windmills. I bought an old 1967 International 2 ton truck and built a 36' boom and mounted on the truck chassis. I decided to use a small engine, instead of the PTO off the trunk tranny, to run an 8000 lb. winch and also have it drive a 2 gpm hydraulic pump to raise the boom and for outriggers. So I mounted the 1200 cc engine with 4 spd tranny, shortened the drive shaft to adapt to the pinion shaft, which I removed from the rear end and mounted that to drive the winch. I took a small radiator from an Opal car and mounted it sideways so that I could mount the hydraulic pump right off the front crankshaft pulley. I put in a new carburetor kit, plugs, points and condenser. The engine shares the truck gas tank and battery. It fired right off and ran good. The engine only runs at idle or fast idle most of the time when in use except at times if I'm pulling pipe out of the well I run it half throttle. About 6 yrs. later the engine wouldn't idle very well, even after adj. the idle adj. screw. Went to put in another carb kit and noticed the bowl cover gasket wasn't indented equally on all sealing surfaces. Took a flat file and smoothed up the surfaces both upper and lower bowl assy. Installed new carb kit and ran fine. About 6 yrs later had to repeat the process again.

New problem: Now several weeks ago it won't run at all even with choke fully closed except unloaded, unless I hold my fingers over the carb opening and allow only a very small amount of air to create more vacuum. To get enough gas to start requires several pumps with accelerator pump and at least 1/3 throttle and fingers over the opening. Manifold vacuum is around 20". Used carb cleaner all around manifold to head gasket. Plus all around carb gaskets with no increase in speed. Squirting carb cleaner into intake increases engine speed but then back to barely running. Seems to me there is not enough vacuum in the venturi to pull the gas through the emulsion tubes. I wasn't able to remove the tubes for inspection and cleaning. Gas in sight bowl is right on the dot. The engine never has to reach full power so the power valve and secondary's are never engaged. I have a mechanic friend who has done quite a few carburetors and put it back together and he didn't find anything wrong either. Is there a way to remove the emulsion tubes?

Dave..

Yes the emulsion tubes come right out



Carburetor Repair

Sounds like the idle circuit is blocked.

Hi windmill Dave,

Would you be able to upload or email a picture of the engine and mechanical assembly that you use?

We have a thread about other uses for the a-series engines and it'd be great if you could send us a photograph.

Other applications for the A-Series

Regarding your carburettor problem, I am told these are of good quality and performance.

Chinese made carburettor

Chinese made Carburettor seller 2

No, the idle circuit is not blocked.
Yes, I will get photos of the boom truck and engine arrangement. I'm proud of the way I assembled everything and the way it works. I'm going to see if I can get the emulsion tubes out.

Finally getting back to the carb problem. I disassembled the carb again and tried to remove the emulsion tubes but no luck. I used a tat needle ground down to get inside the tube and pull up but neither pri. or sec. will budge. So looks like I'm in for a new carb. Damn. Been looking at some vendors on ebay that sell the Chinese carbs. I haven't had a chance to move my truck outside for the pics you guys wanted of the 1200 engine. But maybe this week.

Dave..

With the cold weather I haven't had much chance to work on this. I did find another used carb. but would like to know what would be the jet sizes for a stock A1200 engine. Want to make sure while I have it apart. Primary/secondary slow jets? Primary/Secondary main air bleed? Primary/Secondary main jets? Thanks.

The jetting is only correct for a 1200 carb.

Most DCH-306 have larger venturis so technically require larger jets when used on a 1200. But in practice they usually work OK with factory jetting.

See Carburetor Specifications and Jets.

my primary main jet is 97 my secondary main jet is 145.
The emulsion tubes should come out easily. My carb sat for 15 years, it does not seem as good as it used to be but it works.
You gave an excellent description of it in your post, sounds too lean. It is more common for jets to clog than the much larger passages, but nothing is impossible. I have had to remove lead plugs and drill out clogged passages on Webbers
Not hard to do. Fishing line shot weights can be used to plug the access holes again.

Thanks guys. I found a used carb on ebay, same model as mine for $30. I carefully disassembled it and compared the jet sizes, air bleeds etc. against what should be in there for a standard 1972 production A12 engine. All jets and bleeds matched against the chart you provided. Cleaned and blew out all passages. The accelerator pump check ball was missing and the choke unloader unit diaphragm was ruptured so used my old one that was good. While turned upside-down the primary emulsion tube fell out. Good deal. All holes were clean. The secondary tube wouldn't come out so figured it was OK. The secondary part of the carb is never used anyway as I never run the engine RPM high enough for it to open Installed a new carb kit and is now all reassembled. Waiting for zero degree weather to go away before I install on the engine and check it out. I don't use my windmill boom truck during the winter so it's parked in the non heated part of my building. I am using a electric fuel pump that I originally installed 14 years ago. It keeps the fuel level in the sight glass right on the center dot. I checked the fuel pressure at the carb inlet anyway after starting to have problems to see what it was doing and it was 2-3 psi.