Fine tuning a SU for a 1340 Shovelhead

[Fetch]

Rebuilt a Rivera Eliminator II for my Shovel. Pretty happy with it, starts easy, runs well at all speeds.

Got a question regarding the available springs and piston dome noise ( is there a relationship?).

At idle the carb is pretty quiet, but when the rpms come up it ticks and sounds like an old fashion sewing machine.

Normal or do I need to make some adjustment?

[Hoghead]

What damper oil do you use? Here in the UK most run 20wt (in car applications), but I hear Rivera recommend WD40. I've seen a few posts claiming carb noise as a consequence of this.

[Fetch]

I've been using WD40. Any chance you can direct me to those posts? Been searching for a few days and have not found much on SU Carb. noise.

[ncmc47]

Way back when. I used 3in1 oil in the dash pots of my MG.

[rockman96]

I've always just used WD40... If you use an actual oil don't use too much, you can affect the damping action of the piston.

You'll love the SU on your motor, they're great carbs! And the noise is pretty normal.

[Fetch]

I've always just used WD40... If you use an actual oil don't use too much, you can affect the damping action of the piston.

I think your right. I watched an hour long video on tuning SU's last night. He spent a good bit of time on oil weights and dampening effects. Apparently I have a condition known as a "dancing slide"

And your right, the SU seems perfect for a Shovelhead. Just need to get past this final issue.

[Hoghead]

I've been using WD40. Any chance you can direct me to those posts? Been searching for a few days and have not found much on SU Carb. noise.

Tada!

https://www.jockeyjournal.com/threads/su-carb-on-my-pan.178954/

http://www.jockeyjournal.com/forum/showthread.php?t=102457

[Fetch]

Thanks Hoghead, 2 threads I had not seen before. Lots of contradictory information but gleaned some important info.. This is what I've learned to be SU Truth,

A dancing piston (slide) is corrected via the Dampner, through oil viscosity and volume.

In the case of the Rivera Eliminators, that oil is WD40 and it requires a certain volume which varies according engine's displacement and cam duration.

Mine requires the tube to be filled to about an inch above the base. At that point the slide "dances" a slight bit at idle but immediately smooths out as the rpms rise.

I've entered a new phase of "I love my old shovel"

It's like I've entered into a new realm of mechanical wizardry!

[Hubbard]

If you ever need parts try Moss motors. This carb or some version of it came on practically everything that burned gas in england. Rolls Royce, MG, Triumph cars,etc.