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Vulcan engineering / motorway 93” PanHead low oil pressure when hot

3K views 31 replies 7 participants last post by  Hoges 
Sorry to hear this & I'm going to be no help at all really, but I too wanted buy one of these motors from Vulcan, but they just never replied to any of my emails when I enquired. In fairness S&S have never replied to any of my enquiries either.

It's really sad that these days of the internet & bearing in mind how easy it should be to reply to emails that companies just can't be bothered to reply, even just to say "yes, we've received your enquiry & we'll get back to you".

Normally I'd say take the motor back to the supplier or go vist them, but considering the distance involved here that's not an easy option.
I hope you do get you issue resolved, but by the sounnds of it & going off your description of your problem, it doesn't sound like an easy/quick fix.

What ignition are you running, not a G5 Morris magneto by any chance ?
These units have a spring mechanism in them that triggers to give a big spark at low revs & they make the engine sound very tappety, if that makes sense.
I have a S&S 93" Panhead with a G5 Morris fitted so I know what I mean !!

Also, what are you using to show the oil pressure, is it just a "normal" oil pressure switch or one of those small oil pressure gauges you can fit to these type engines ?
 
I have both an oil pressure switch & a small pressure gauge on my engine. Is it worth swoping out both your existing parts with replacements just to be sure one of them is not faulty.
If you just have a pressure switch currently, does the low oil pressure light come on ?
What oil pump is on your engine, is it a S&S one ? Could you swop out the oil pump.

Obviously you don't want to be running the motor any more than you have to until you know for sure what the problem is.
 
When I was building my first bobber I ordered an engine from an American shop with a good/high reputation. It took 21 months to arrive !!
In fairness it kind of suited me as I'd almost finished the build by the time it arrived !
They'd bought a brand new S&S P-Series motor, stripped it & powder coated it.
I was assured by other customers of theirs, (got a generic email from the builder apologising for the delay, which he'd obviously sent to all his customers. So, I emailed some of them & those that did reply said not to worry, I would get my engine, it will be good, but he's just bloody slow. Turned out to be good advice, but .... !!).

Having said that I since found out that S&S did a custom service where they would have supplied a gloss black 93" Panhead motor as a "special order".

I'm now build a second bobber & want to use the same motor for this one, but trying to get a reply from S&S when I've asked if they still offer this service has so far proved impossible.
It just seems that in this age of fast communications over the internet, nobody can be arsed to reply when you contact them via email !!
And now, because of covid, everyone is blaming that for any delay, no matter what you have ordered !!
 
I have just been having a read through the service manual my S&S P-Series motor came with, which has a section on "low oil pressure at operating temperature".
These points may help,

It says that most engine mounted oil pressure gauges are not accurate once they are hot & to use an oil pressure switch as the best indication of good oil pressure.

To ensure you have the correct diameter oil lines on your bike, a minimum of 3/8" pipes/hoses should be used with a minimum i/d of 0.350".

To check the tappet screen to check it is not clogged.

After-market oil pump Pressure Relief Spring Cap, some caps have a very deep pocket on the inside causing low spring pressure.

Using too light an oil, minimum should be 20W50.

Check the feed side of the oil pump for damage. Debris that has passed through the oil pump can damage the feed pockets of the pump resulting in low oil pressure.

Check the operation of the pressure relief valve, if it is not closing completely you will get low pressure at idle.

Hope that helps, although the above is taken from the S&S manual these engines are all very similar in operation so I would guess the above points are good for any make of these Harley type motors.
 
According to the Accel gauge on my engine, when it's started & cold, the pressure is around the 40-50psi mark & this drops to around 20psi mark once it's a normal operating temperature.
I fitted the gauge more as a "visual" indicator of oil pressure rather than relying on it being accurate.
 
Off-topic slightly, but I see the Vulcan web site has been very recently updated.
It still has amongst it's offerings the 93" Panhead motor, which I have to say still looks very nice indeed & I'd still really like one for my latest build, but they say it has STD heads, (I though STD failed some time ago ?!) & they list their own oil pump as being fitted as standard.
 
Well today I changed pump back and used 50 weight oil
put a spacer under pressure valve , primed the pump and had return run into a clear bottle to monitor return .
start up pressure 50psi+ Eventually dropped back as before .
ive now moved the return pipes further away from exhaust which helps but still fkin hot so an oil cooler might be best . That or only ridding in snow 😏
I think what I'm about to say is correct in the way that I understand these "Harley" type engine/oil systems work;

The RETURN line from your oil filter to the oil tank is only scavenege oil from the crankcase/sump, not the oil that is circulating in the engine, lubricating it while it's running.
The oil pump is actually two pumps in one body, one part is pumping oil around the engine to the moving parts & the other is scaveneging oil from the sump & returning it to the oil pump via the oil filter.
So, returning oil to the oil tank is not an indication of good or bad engine oil pressure.

When the engine is cold the oil RETURN line & filter will be full, but as the engine runs & heats up this flow will reduce & at some points the oil filter will be very low indeed, maybe only 1/4 full, if that.
Normally you would never see this because the oil filter is not see through & you'd just assume that oil is always coming out of the RETURN to the tank & that the filter would always be full providing the engine is running.
Oil may well always be returing to the tank via the RETURN line, but the quantity will vary & like I say the quantity within the filter does vary rather more dramatically than you would imagine.

Just something to bear in mind.
If I am wrong about this then I'm sure someone with more knowledge will be along to correct me.
 
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