Have I understood shovelhead oil system correctly? - The Jockey Journal Board

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Old 09-01-2019, 02:57 PM   #1
Winnebago
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Default Have I understood shovelhead oil system correctly?

Trying to figure out smoking shovel, will update my other thread, but wanted to ask if I have understood how the oil moves around correctly -

I have S&S cone cases, with an evo up to 91 oil pump. The FSM seems to say that oil pressure goes to rockers first (with a split off to lifters) and when these are oily the back pressure lifts the bypass valve and then oil goes to the big end. Is this correct?

If it is, does that mean that oil pressure to the rockers would decrease slightly when the bypass valve opens?

Over on the HD forum, a member called 'twizted biker' has made several posts over the years about soldering up the rocker oil feel line and drilling out to .060 to stop over oiling the rockers, and I've found a very vague mention of the same trick in S&S pdf oil pump instructions. He (twizted) says that this is an old and common mod, but I cant find any other mention of it online, does anyone here have an opinion?

My oil pump was well used, if a PO had fitted a heavier spring to the bypass plunger, would that mean my top end could be over oiled at idle?

My bike smokes at idle, when I rev it up (even just to a fast idle) the smoke goes away, and returns after a few seconds wait after returning to idle. My theory is that the bypass valve is not open at idle, so all the oil pressure is going to the rockers, filling the boxes and allowing the high manifold vacuum at idle to pull it down the guides, but revving it opens the bypass valve reducing oil flow at the rockers, which then take a few seconds to refill when the bike is back at idle. Surely it would smoke immediately if it was just worn guides? (the valves guides and rocker bushes are all within FSM specs)

If all of the above is correct/plausible, is this what twizted bikers fix is addressing? does the smaller oil line fitting bore act to open the bypass valve earlier (eg at a lower rpm?)

Sorry for the long post.
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Old 09-01-2019, 04:07 PM   #2
BJ Shock
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Default Re: Have I understood shovelhead oil system correctly?

Do you have valve stem seals installed?
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Old 09-01-2019, 04:13 PM   #3
Winnebago
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Default Re: Have I understood shovelhead oil system correctly?

no, but they were only fitted (originally) to later bikes. I know valves seals are good, but it shouldn't need them, theres obviously something else going on.
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Old 09-04-2019, 07:38 PM   #4
mlotti
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Default Re: Have I understood shovelhead oil system correctly?

The bypass, the big plunger with spring is called a bypass for a reason..It by passes oil when the pump has pressurized the system. soooo it doesn't open until the motor has all gotten oiled. they used to and still do plug the overhead oiling and size it down because the oil was building up and could be forced down the guide and cause smoking. this was a cure for some other underlying cause...bad rings...crankcase breather issues etc etc. All things being correct, the factory engineers had an oiling system that worked proper. if your smoking at idle something is not correct...fix it..
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Old 09-06-2019, 03:33 PM   #5
BJ Shock
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Default Re: Have I understood shovelhead oil system correctly?

Quote:
Originally Posted by Winnebago View Post
no, but they were only fitted (originally) to later bikes. I know valves seals are good, but it shouldn't need them, theres obviously something else going on.
I saw your other thread,
You found some seals in there?
In the past we have shortened the seal to gain clearance..
Good luck.
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