Rejuvenating our 1973 850 Sport Spider

I removed the plugs, so I didn't have to fight the compression, and then I squirted a little Marvel Mystery Oil in each cylinder again before attempting to turn the engine over manually by raising one of the rear wheels, putting it in first gear and turning the wheel with my foot. It is turning over freely! No weird interference noises or resistance.

 
AND...I hit my first hurdle. Since I have the engine spinning now and because it had been sitting for so long (it had sat for at least 25yrs without running before I got it), a friend suggested that I also check the compression on all cylinders,

Compressions were:
Cyl 1 - 92 p.s.i.
Cyl 2 - 98 p.s.i.
Cyl 3 - 50 p.s.i.
Cyl 3_50psi.jpg

Cyl 4 - 90 p.s.i.
Cyl 4_90psi.jpg

Well, looks like I'm going to have the opportunity to get very familiar with this motor :)
At least its a breeze to remove (and I had practice when stripping down the parts-car 850 Spider I picked up right after I acquired this one).
 
I've ordered up a bunch of parts (new plugs, air and fuel filter, belts, radiator hoses, engine and transmission mount rubber, the rubber brake hoses at the corners, rebuild kits for the rear brake cylinders, inner/outer axle boots, etc.), so I'll be getting to that soon.

One question I have: my 850 has dual brake fluid reservoirs (same size, side-by-side, with an interconnection hose between them just below the fill caps), but MWB has a single reservoir identified. I guess I'm wondering if I can replace the dual-bottles with the single one?
 
I've ordered up a bunch of parts (new plugs, air and fuel filter, belts, radiator hoses, engine and transmission mount rubber, the rubber brake hoses at the corners, rebuild kits for the rear brake cylinders, inner/outer axle boots, etc.), so I'll be getting to that soon.

One question I have: my 850 has dual brake fluid reservoirs (same size, side-by-side, with an interconnection hose between them just below the fill caps), but MWB has a single reservoir identified. I guess I'm wondering if I can replace the dual-bottles with the single one?
I believe they still use two only those are bigger than stock. They are just sold separately.
 
OK, I'll have a look when it arrives. I may need to order a 2nd one, then. The one in the MWB image does not have a fitting for a hose to interconnect the reservoirs, though.
 
AND...I hit my first hurdle. Since I have the engine spinning now and because it had been sitting for so long (it had sat for at least 25yrs without running before I got it), a friend suggested that I also check the compression on all cylinders,

Compressions were:
Cyl 1 - 92 p.s.i.
Cyl 2 - 98 p.s.i.
Cyl 3 - 50 p.s.i.
View attachment 62601

Cyl 4 - 90 p.s.i.
View attachment 62602

Well, looks like I'm going to have the opportunity to get very familiar with this motor :)
At least its a breeze to remove (and I had practice when stripping down the parts-car 850 Spider I picked up right after I acquired this one).
After all this time a valve could be sticking or unfortunately burnt if it was run with tight clearances. That you have compression at all is a good sign. It is an odd outlier pressure given how consistent the other cylinders are. Try the compression test again but add a small amount of oil in the cylinders to see if it is the rings or a valve.
 
The one in the MWB image does not have a fitting for a hose to interconnect the reservoirs, though.
It doesn't have an interconnect fitting because it's for the early 850 with the smaller single-circuit master cylinder. For use on an 850 with the later dual-circuit m/c, you'll need to use 2 reservoirs & just keep an eye on fluid levels in each one.

This same non-interconnect type plastic reservoir was also used on the old Fiat 500's, which is a major reason it's been remanufactured & is widely available.
 
After all this time a valve could be sticking or unfortunately burnt if it was run with tight clearances. That you have compression at all is a good sign. It is an odd outlier pressure given how consistent the other cylinders are. Try the compression test again but add a small amount of oil in the cylinders to see if it is the rings or a valve.
This. I had zero compression on a cylinder due to the pushrod falling off just enough to jam the rocker.
 
Well, I located the Air Filter lid clip that I need - it only took buying a parts car to get it ;)
20221203_165448.jpg

The weird thing is that the parts car is missing 2 of the 3 original air cleaner housing clips, too. Some substitutes were rigged into place for the missing ones. So, it seems like the pins for these can shake loose over time and the clips get lost? Is that what others have experienced? If so, is there a recommendation for what to use for the pins for the clips, instead? One thought I had was maybe a really small clevis pin, so that the clip of the pin prevents it from falling out.

I did put our 73 back on the lift, as I had to use its wheels/tires to roll the parts Spider onto the trailer.
20221203_200040.jpg

I noticed a hole in the exhaust on the 73 (and signs of a mouse nest inside), so I'll have to swap in the best of the spare exhausts I have as part of getting it running.
 
I removed the plugs, so I didn't have to fight the compression, and then I squirted a little Marvel Mystery Oil in each cylinder again before attempting to turn the engine over manually by raising one of the rear wheels, putting it in first gear and turning the wheel with my foot. It is turning over freely! No weird interference noises or resistance.

This is clever - I’m gonna try it this way!
 
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