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1984 J70TLCRD is testing my patience.

Z

Zack70

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I was given a 1984 Johnson 3 cyl. outboard, 70 HP model J70TLCRD. I was told it had been rebuilt, but hadn't been run since the rebuild, a few years ago.(the motor has been painted, and the compression has improved since I've got it sort of running) I replaced one ignition coil, and have spark on all 3 cyl. now. Cleaned the carbs, replaced the internal gaskets, did not replace needle valves or floats. Floats are level. Compression on cylinders from top to bottom are 100, 102, and 110. Test done dry with carbs held open.
It starts with difficulty, then runs rough, surges, backfires at idle. The carb jets are not adjustable. Anyone have any advise?
 
Thanks for your comment, and I was thinking that. But the compression at the beginning has improved considerably since I've gotten it getting it to run. So I'm thinking that the rings may have not seated properly yet as it's never been run since the rebuild. I had a moment of hope because for perhaps 15 seconds it purred, then went back to belching, and snorting.
 
The outside flat edge of the flywheel key must be installed vertically, inline with the engine, straight up and down... NOT in line with the crankshaft taper! It must be torqued to factory specifications (105 foot pounds) otherwise it will shear and cause damage to the flywheel and crankshaft tapers.
 
Well, that's the first flywheel I've removed. It put up a good fight... but I won. The key is fine, and installed correctly.I was hoping it was sheared. But the pickups are really dirty, rusty looking. Doubt that it's the problem, but it's a good opportunity to clean them up. Not sure of the best way to do that, so if you have advice, please fill me in. I am new to 2 stroke motors, but my gut feeling makes me question the timing. Is that a possibility?
Thank you for your idea to check the key.
 
No I didn't because I have no idea what link and sync refers to. Is it a process to sync the carbs together? I can slide a drill bit into the the idle orifice tomorrow, and let you know its size. Thanks.
 
NO do not put a drill bit in the orifice there is a number on it that will tell you the size. Get a manual preferably a factory one that will tell you how to link and sync it
 
The number on the idle orifice is 89, with the tail of the 9 pointing to the hole. It could be 68. After I pulled the flywheel off I noticed the nylon ball connection to the timer base looked rough. So it is split, and I have to find one before I can go any further. But I'm really curious to know why you asked for the orifice number.
I found an old manual that covers this motor at a local collectables store, read the link, and sync procedure. It will make more sense when I'm beside the motor.
 
If you look straight at the carb on top of of the throat you will see a screw take that out and behind there is the low speed orifice. Make sure that is all clean I asked which # because I wated to know which one you cleaned. The one you want is #27 on the pic I also think faztbullet is right about the compression

convert
 
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All of the jets are clean...(3 on each carb). Yes, I'm concerned about the compression. I'll do a wet test today. I should check the reed valves as well. Thanks for the help.
 
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