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canoli 5th August 2021 15:34

hydraulic lifter test?
Hi guys

In one of Donny Petersen's Unauthorized Technical Guide books he says you can test a tappet's hydraulic unit before you install it.

1. Fit top lifter piston into bottom cylinder: if it collapses immediately pull it apart, shake the bottom and try again - the ball bearing in the bottom cylinder must be seated.
2. Compress the top into the bottom, don't cover the hole in the bottom. Hold for a count of 10 then release. If the lifter is good the top piston will bounce out of the cylinder when released.

He says if it fails you can try again, this time blocking the hole in the bottom cylinder. If it fails to bounce up after both tests the lifter is defective.

Is this a legit test? I ordered 2 so far, one from Drag Specialties and one from Sifton (V-Twin). The Sifton is better but still fails DP's test. Neither one is airtight when the ball bearing is seated...should it be? According to Donny Petersen it should. I tend to trust him as he's got a mountain of experience. What do you think? Should I install one and hope for the best? Or buy another unit...?

Thanks you guys I really appreciate anything you can tell me...

Hippysmack 5th August 2021 18:21

I haven't read that book.
But I have disassembled the lifters and 91-up, at least, lifters don't have a ball valve.
Full disassembly here in the Sportsterpedia.
It's a disc instead.
But by default, they have to have oil in them to function.
You didn't mention having oil in it.

If you have oil in the body, piston inserted (not fully assembled yet), you can push the piston down equal to the pressure created by fluid level.
Lots of oil in there, you won't push it down much (makes assembly hard to impossible).
However, if then you pull that valve disc cover off, the piston will now bottom out.
Slight amount of oil in there, you can bottom the piston out.

Fully assembled, it's not that hard of a test.
Fill them with oil and you should not be able to push the piston down.
If you can, it's either not yet full of oil or there is something sticking the valve disc open.

You can take a lifter with no oil into a container, stand it up with the oil holes submerged and actuate the piston up and down.
This will fill the body with oil.
If you can't get the piston to stop going up and down, the disc isn't closing fully to the body.

Here is the disc valve location on the bottom.

Here is the disc once you pull that cover off. Disc is against the hole in the main body.

And here is the little spring between the cover and disc.

Iron Mike 5th August 2021 18:45

Sounds like the -53 BT hyd unit test

Hippysmack 5th August 2021 19:06

There is a hydraulic seal between the piston and body also.
The clearance being so small creates that hyd seal.
It's very rare I'd suppose but if you have a certain amount of wear in the walls of the body,
That clearance could widen enough to leak oil between the piston and body.
BUT, again, you will notice upon actuating that the piston will not pump up.

canoli 5th August 2021 19:39

Thank you guys - lots of great info here - yes the lifter I want to replace is from a shovelhead. The roller on the tappet is fine and the bike runs well otherwise, just noticed when replacing the pushrod seals that the front exh lifter is a little sticky.

Petersen says to wash and dry the 3 pieces (piston, piston assembly and the bottom cylinder) before you test it, no mention of filling it first with oil.

I expect you guys are familiar with lifters pre-Evo but I will post a pic if necessary. I'm really curious if he's right.

It seems like the unit, when it's assembled together (and the ball is seated correctly), should be air tight or nearly so. It shouldn't lose pressure in a matter of a few seconds should it?

edit: Here's the text of his test - from DP's Unauthorized..." vol. 5 pg. 230 and the lifter I bought.

Hippysmack 5th August 2021 22:00

Keep in mind air compresses and oil don't.
Sportster lifters (pre-Evo XL) were solid.

BTs went to Evo motors while Sportsters were still running ironheads.

canoli 6th August 2021 01:02

So what do you think about the test? To me it seems a reasonable way to evaluate a brand new lifter I just find it hard to believe 2 lifters from 2 different manufacturers and 2 different vendors are both defective.

Hippysmack 6th August 2021 02:20

I can't find any docs on the internals of those lifters. And I am unfamiliar with them.
I have found that S&S claims their Evo BT lifters have tighter tolerances than OEM.
And that trick about a wire thru the center to collapse the lifter has been spread all across this forum.
But you just can't do that with our lifters. Physics doesn't allow it.
You can fill Evo XL lifters will air and they'll flop like a fish.

I would need to see all your lifter internals completely apart to get an understanding of how they work.
Where is the ball and does operate from the same direction as the disc on mine?
But I do believe this.
If you fill them suckers will oil and actuate the plunger, you'll get an idea of how they are going to operate during normal conditions.
The test verifies that the lifter will build pressure (ball valve will close).
If the piston doesn't bounce (finger away from hole) it's not holding pressure created by pushing down the plunger (ball not seating).
If the piston does bounce, it is holding pressure that bounces it out when you let go of the piston.

I read;
If it bounces, finger off the bottom, it's good.
If it only bounces, finger on the bottom, either ball is off seat or the ball/seat is bad.
If seat is good but doesn't bounce, the clearance is too wide.
Seems like what I originally wrote about Evo Sporty lifters.... just shorter.
Unless the clearance is super tight, I can't see air pressure helping this test.
But I do feel like there is something I'm missing.

canoli 6th August 2021 03:21

Haha I get the feeling I'm missing something too.

Thanks for the reply it's very helpful. These are just your standard-issue shovelhead lifters, OEM# 17920-53, introduced as you can see in 1953.


"trick about a wire thru the center to collapse the lifter"
works perfectly on these. These lifters are a simple design...the wire disturbs the ball, knocks it off its seat, which allows air or oil (or whatever you got in there) to escape, and then the plunger collapses until its spring hits the cylinder. It's your basic check ball setup.

Petersen has decades of experience working on Harleys and I've never read anything that wasn't corroborated by other sources. If something is his own personal taste he says that. My point is this lifter test...I can't see him being wrong about something so simple. OTOH I can't believe I got 2 bad lifters in a row...

I guess as you said I'll fill it with oil and test it that way. It'll spend its life filled with oil so how it responds then will tell me more than what it does "filled" with air.

Thanks again for your replies HS!

Hippysmack 6th August 2021 03:54

I can't find shi nola on the internals so far.
Curiosity done did it to me again....

I don't doubt Donnie's knowledge but I hardly ever believe anything I can't prove.
The test should be repeatable or it's really not useful.
The chances of you having 2 bad new lifters doesn't sound right.
Although these days most quality control departments seem to have started working from home.
(and leaving the parts they are suppose to be inspecting at work)…. woops, I'll just check that box, it'll be OK.

My first impression would be your testing didn't go right.
But a hyd lifter is either gonna pump up or not with oil.
Now that I have wasted many pages here, I'll go back in hole......:geek

Just caught that....
If you have to do the wire trick to collapse the piston, isn't it pumping up already?

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