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Long winded 70 gas question

H

henry g

New User
Recently purchased a 70 gas tractor. Tractor smokes,needs ringing but runs fine. The timing was set very late, so I adjusted it to sparking at TDC. Now the tractor runs even better, BUT it knocks when you accelerate the engine. It does not knock at low idle or high idle, but only when you crack the throttle and accelerate. I don"t think I gave it too much timing, but wanted opinions. Also I checked the clutch driver, it was tight. I removed the adjusting nut on the crank, the flywheel does not appear loose and the splines look fine. Searching for answers and opinions. Thanks
 
Make sure the advance is working in the dist. and use a timing light to set the timing to the specs. running wide open throttle. Then idle it back and make sure the advance backs it off.
I won't even guess at the specs. as that's what books are for. But I don't think TDC was to be correct for those ?
 

I can not speak to the accuracy of all of the numbers, but tune up specifications for your '70 can be found here:

http://www.yesterdaystractors.com/atrp/specs/jd.htm

It would seem that starting with these values would put the tractor reasonably close.

intake and exhaust valve clearance at .020 hot.
points at .022.
timing mark on the flywheel (10 deg. ATDC).
new autolite plugs at .030.
 
I can tell you that advancing the timing is not proper. Most of the gas engines fire after top dead center to allow sufficient burn time. The advance of your distributor is critical. When running properly the engine will sound like it's laboring slightly, then when the advance moves up it comes alive.
 
WE set timing ,valves,points at 22. just an easy no. to remember. Timing is wide open throttle. Make sure the distributer advance is working .This pertains to all waterloo built tractors .
 
Check to see that some Hack has not drilled the rocker tube to supply oil to the intake rockers. This would explain the smoking AND the detonating. Very worn rings & cylinders typically still do not cause smoke on these tractors.
 
I need to correct my timing degrees. The 70 gas was set at 15 degrees wide open. been awhile, I'm getting old and grey.
 
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