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Posts: 833
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I have many projects going on right now. One of them is a 1984 Honda BIG RED that I bought. This thing needs some work but I got it at a good price. I plan on restoring this classic and need to get it right mechanically first before I even think about the cosmetic stuff. The atc runs but only on choke. I plan on starting to make sure there are no air restrictions and fuel restrictions. Next I will move on to checking the valve clearances and engine compression. Then I will move on to the carb – cleaning it and tuning it as long as the engine is in good shape. The guy I bought it from bought a $30.00 carb from ebay for it. I am interested to check out if these reproduction carbs are any good. Stay tuned to see how this one pans out.

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Oh yeah. BIG RED on the lift!

Back on to the Big Red again the issue is that it only runs on choke and not very good. Before I look at the carb I want to make some overall checks of the engine. If there is a major issue with the engine or if the engine is worn out it won’t be able to be tuned properly. You will just waste a lot of time trying to get it to run right. So I will start with a compression test. Before the compression test I will check the valve clearances. This is important because if the valves could have no clearance to a point where the valve never fully closes. This will affect the compression since it will have a “leak” at all times. To start the job I take out the spark plug to make turning the engine over easily. Next I removed the seat, gas line and gas tank.  Next I took out the inspection plug on the left side and the rocker covers. Turn over the motor until you see the “T” mark on the flywheel through the inspection plug. This indicates top dead center or “TDC” on the compression stroke. Then I used feeler gauges to check the clearance between the rocker and the valve. They needed adjustment which is easy to do. Just loosen the locknut then adjust the screw using a screwdriver to the proper clearance (.002” for both the intake and the exhaust) and tighten the locknut. Make sure you recheck the clearance after turning the motor over a couple of times. Next it is time to move onto the compression test.

First tings first. Get out the service manual for procedures and specs
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Next take off seat , gas tank, gas line, rocker covers, and inspection plug for flywheel. The inspection plug was tight so I had to use a screwdriver wrench combo to break it loose.

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Rotate engine until the "T" mark is centered in the inspection hole. I couldn't get a good pic.

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Use a feeler gauge to check clearance between rocker and valve.

Using a screwdriver and wrench to adjust to the specified valve clearance.

I did a compression test on the big red. The compression spec is about 150psi. I got 125 psi for the initial reading. I then put two squirts of motor oil in the cylinder through the spark plug hole and checked it again. This time I got around 160 psi. The higher reading is due to the oil sealing up a leak. This motor could have worn piston rings or a leaking head gasket or leaking valves. During the compression test I could hear air leaking. From the looks of the cylinder which has oil stains near the head gasket I think the head gasket is bad. A leakdown tester would help me diagnose this better but either way the motor needs to come out. I will take the motor apart to correct the issue and get this big red running correctly again. I will post the progress of the disassembly, inspection, and reassembly.


initial reading

Couple of squirts of oil in the cylinder

Higher reading after oil was put into cylinder

Notice the oil stains on the left side of the cylinder. This is where I think the head gasket is leaking.


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Reply with quote  #2 
What tool do you use to adjust exhaust valve? Not a lot of room to work while it’s in frame.

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Posts: 833
Reply with quote  #3 
Thanks for the question. I agree it is pretty tight. I use an offset screwdriver to get in there. See pic below. You can buy these on line or at most auto parts stores.


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