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Message started by MnSpring on 07/20/14 at 18:18:48

Title: Oil Pump
Post by MnSpring on 07/20/14 at 18:18:48

A Question, on the ‘Oil Pump’ in the LS650/S40.

Fairly documented that it needs, 1000 + RPM on start up.
And it is often stated, it is ‘weak’.

A, “few years ago”, when I was playing with my 1929 1/2 Model ‘A’.
(the 1928 & 1929, were different than the 1930 & 1931’s
But, their was a, ’transitional ’ model, it was dubbed the, ‘1929 & 1/2’)
(Which I bought at a local farm Auction, before I even had a DL, for 100.00. Picked a Lotta Rocks, Fixed a Lotta of fences, and hoed a LOT of corn out of the beans, that summer)
A local station/repair shop, with some, ‘old’ guys in it. Told me about a easy fix, to the, Model, ‘A’s Oil Pump.

For some reason, they took kindly to a punk, who bought more rear tires, for a 62 Buick, than they thought was ’normal’.

Anyway, it was a easy fix, just a little grinding, to make the parts fit together tighter, thus increasing the Oil Flow.

Now the question: Many, VERY, Knowledgeable, “Gear Heads”,
(and that is a, VERY, kindly remark), here.

Has anyone ‘played’ with the Oil Pump, to make it more efficient, than the OEM one?

Title: Re: Oil Pump
Post by Dave on 07/20/14 at 18:29:15

Not sure the oil pump is weak....the bike just wasn't made to pump a lot of oil at a slow idle. The lower end is all bearings and needs no oil pressure but needs oil flow at very low pressure. The only area that needs oil pressure is the cam bearings......and they do just fine as long as you keep the idle speed up. The crankcase has some small passages that provide a restriction to the oil flowing to the bottom end, so that oil is forced to the upper end. If you set the idle too low and the pump therefore has a low flow...then too much of the oil can flow to the bottom end, and not enough goes up top.

Title: Re: Oil Pump
Post by verslagen1 on 07/20/14 at 18:44:28

yep, don't think the pump is weak, it's just geared for a wide rpm range.
it gets up to 50 psi at speed. Keep the idle up where it's supposed to and it's fine. otherwise you'll need to design a 2 speed oil pump.

Title: Re: Oil Pump
Post by Kris01 on 07/20/14 at 20:47:44

I've never heard the 50 psi mentioned around here, only 10 psi. Are you saying idle pressure is around 10 psi and climbs to 50 at speed?

Title: Re: Oil Pump
Post by verslagen1 on 07/20/14 at 20:49:24

I think it starts at 5 and builds to 50+

who told you 10?

Title: Re: Oil Pump
Post by Kris01 on 07/20/14 at 21:00:27

I may be wrong but I think I read on this forum multiple times that it runs at around 10 psi. Not sure if the RPMs were ever mentioned.

Title: Re: Oil Pump
Post by Serowbot on 07/20/14 at 22:14:23

Gotta' figure it can build enough pressure to blow the sidecase if you install the oil filter backwards...

It's mostly the popularity of that slow Harley "potato potato" lope, that causes the problem...
Funny thing is,... Harley sites warn against having that low idle, too...

If you're willing to sacrifice your engine for a slow idle sound... it's the price you pay...
Not a mechanical problem,... it's an IQ problem...
I blame Hollywood... ;D...

Title: Re: Oil Pump
Post by WD on 07/21/14 at 00:04:10

4F594E534B5E53483C0 wrote:

But you can "fix" the Harley pump with an upgrade from S&S. High volume or high pressure versions are available from the 1930s UL/VL through current production Twinkie (Twin Cam) big twins... You can even upgrade Henderson, Excelsior and Indian big twin and 4 cylinder pumps through their Flathead Power subsidiary...

In addition, you can get cylinders, heads and external oil lines that will interchange fairly readily amongst the generator case OHV big twins.

The Savage, be it the restrictive oil system or the weak sister electrical components, you are stuck with them (for now). I'm working on a stator/rotor upgrade, but I'm NOT going to tackle the oil pump. My 98 had a catastrophic electrical failure, but the engine is pretty much cherry inside according to a bore scope.