Jockey Journal Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
117 Posts
Discussion Starter · #1 ·
Just rebuilt an SU for an 80" Shovel, the only mods to the engine are an Andrews J Cam and solid lifters. The SU seems to be working well, I do notice a pronounced "ticking" from the dome when I cruise at a constant throttle.

My question is, how do determine which weight spring to use in the dome? The one installed now fully lifts the piston at 3/4 throttle but as I said, I can hear it when I hold the throttle steady at speed.
 

·
Registered
Joined
·
1,326 Posts
The stronger the spring used the slower it makes power as its winding up - will feel as if your towing a load
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #3 ·
Experimented a bit and found a softer spring seems to work better all around. What would be the effect of the spring being too soft? I suspect it would run rich off idle?
 

·
Registered
Joined
·
803 Posts
There’s some good info here:

 

·
Moderator
Joined
·
4,037 Posts
There was a light spring and a heavy spring available at least, which could be paired up, as well. Damping oil viscosity and volume plays a big part in things. The ticking is normal; that's the slide moving up and down as it is supposed to.
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #7 ·
There was a light spring and a heavy spring available at least, which could be paired up, as well. Damping oil viscosity and volume plays a big part in things. The ticking is normal; that's the slide moving up and down as it is supposed to.
Ya, 2 springs I could deal with but I've seen at least 3 variations plus a dozen different needles. I'm suspecting there is a black art to this, but so far so good. Just put the softer spring in. The ticking is significantly quieter than before. Idle is smooth and doesn't hesitate or bog down when I get on it. Will have to check the plugs after a get a few more miles on it.
 
1 - 7 of 7 Posts
Top