1958 35 HP Big Twin Model 25034 Electric Start

[twier]

I'm stumped...nothing new here folks.

New to me Big Twin spins like crazy with no plugs in or just one plug in (either one). But with both plugs in it struggles, maybe one revolution per second. It did however, turn over fast enough briefly (just one time) with both plugs in.

Facts:
It had the same symptoms when I first bought it but would only would only crank with both plugs out
compression is 110/120
6 month old battery fully charged (12.6 volts) This cranks my 115 merc just fine
new water pump, and I lubricated it with some dish soap when I put it in
new starter motor
I lubed the cylinders pretty well with fogging oil so they should not be dry
using car jumper cables directly to starter and ground so no solenoid issues
it has compression relief valves that appear to work but only with the rope start
tranny is in neutral
I have not tried to actually start it. I'm just trying to get it to turnover properly, so no gas is hooked up and spark plugs not plugged into magneto

Any ideas?

Thanks

 

[oldboat1]

Plugs out,and recoil starter mechanism removed, are you able to spin the flywheel smoothly -- no restrictions? Don't know if you did some work on the magneto, but coils can bind against the flywheel if installed slightly off their mounting bosses.

 

[F_R]

So, you say it is a new starter, otherwise I would have pointed a finger at that. If it isn't a battery problem, and it isn't a starter problem, and it isn't a cables problem, and it isn't a motor problem, then I don't know what it is. All I can suggest is put it all together the way it is supposed to be, then do some voltage drop tests. If you don't know how to do that, now is a good time to learn.

You say you are grounding it with a jumper cable. Otherwise, I would suggest a possible resistance problem where the cable attaches to the side of the motor. The knob/screw that secures it is the ground connection. Yes, a proper voltage drop test will indicate that also.

 

[oldboat1]

^^with that in mind, try twisting the motor plug back and forth a bit -- same with the wires. If you hear some crunching, there is some corrosion. Also apply a good dose of electrical spray at the plug, in the holes -- do some scraping with a small phillips screwdriver. Take a look at the male connectors -- spray them and use a little sandpaper on them.

 

[twier]

oldboat1,
It is easy enough to turn the flywheel (plugs out, recoil off) by hand but the resistance is variable as the pistons go up and down? I assume this is normal? I did replace coils, points, condensers. I have pulled the flywheel since then but did not see any rubbing. I will pull it again tomorrow.

F_R,
I will figure out the voltage test drop procedure. My best guess now is the jumper cables ( I've tried two different sets) are not making good enough contact with the starter. I am hooking the neg to the bracket that holds the starter in place and the pos to the wiring bolt on the starter itsself. Lots of sparks when that touches.

 

[F_R]

At their best, jumper cables rarely make a good connection. At their worst, they are sometimes those el cheapo $6 skinny aluminum cables with thick insulation to make them look big. That kind is nearly worthless. Good jumper cables are expensive. That's why somebody stole mine.

 

[twier]

Gents thank you much,

I cleaned up the ground cable and then bought the battery cables and switch I will need down the road anyway and it turns over no problem. On to the carb kit, then some new gas and the moment of truth!

 

[F_R]

Thanks twier for reporting back. There are probably a couple dozen other guys reading this out there and shrugging off the suggestion that it might be the cables or connections. Listen up, you guys.