Question about 1979 Harley Davidson XLS 1000

1 Answer

Low oil pressure at rocker box

My 79 xls has low? pressure at the rocker box when hot. cold with 50w hd oil has 40 psi then when warm(after 5 min running) drops to 0. at 3500 rpm hot has approximatley 1 psi. is this normal or should i look for worn rocker bushings or weak pump? anyone please help cause i haven't had a clear answer from anyone!! thanx

Posted by on

  • 4 more comments 
  • 79ironhead May 02, 2009

    my oil is circulating and have oil to both rocker boxes when cranking. i haven't had problems with wet sumping. i did put 2 guages on, 1 at pump and 1 at rear rocker box, and started cold. about 38-40 degrees. upon startup had 100+ at pump(pegged my guage) and 45 at rockers. engine at 1800rpms. warm after running 5-7 minutes had 1-4 at pump and 0-1 at rocker with 50 w oil and new filter. i also have vacuum in the oil tank when running. when i pull out the dipstick the engine drops in rpm, about 75-125 rpms, and runs uneven. it doesn't smoke and isn't oily in the pipes. when revved warm to 3500rpms pressure at pump is 6-10 and at the rocker is 0-3. is there anything i can check or is it just that way?

  • 79ironhead May 02, 2009

    this was all with the air filter off the bike

  • 79ironhead May 05, 2009

    all tests were done with air filter installed and does have breather hose from cam cover by generator to air cleaner. carb is kehin(?) original. and engine is bored 0.020" over and has about 10k on upper rebuild. 29k on bike. also have dual open 2" drag pipes for exhaust. went on little ride sunday(2nd) and had 0 pressure at rockers at 65mph and engine at 3100rpms. had no noise or problems but am worried about no pressure.

  • Mel Jacobson
    Mel Jacobson May 11, 2010

    I dont know what the problem is ... but no ..... your pressure should never drop below 5 ,, I'd start by checking all yer lines for blockage.... check and make sure the oil is circulating to the tank.. let me know

  • Anonymous Mar 22, 2014

    oil spitting out of rocker box pushrod tube hole

  • Anonymous Mar 23, 2014

    Pressure is good at idle but drops to 0 when ridding? Thanks!

×

1 Answer

  • Level 1:

    An expert who has achieved level 1.

    Corporal:

    An expert that has over 10 points.

    Mayor:

    An expert whose answer got voted for 2 times.

    Problem Solver:

    An expert who has answered 5 questions.

  • Contributor
  • 16 Answers

The Ironhead Sportys have a tendency to do this when the Gerotor Gear Set is worn. These are the thin set of drive gears in the oil pump. HD Part # 26492-75. Do you have a problem WET SUMPING? This is when the oil drains from the reservoir into the crank case if the bike sits for a period of time and when you attempt to start it pukes oil from the breather tube. If so you need to check these gears. Gerotor Gear Sets inner/outer clearance should be .000 the shaft should have a clearance of .0005 and the feed gear height in the pump should be .011. Normal operating pressure when hot should be 4 psi at idle and 10-20 psi at 3500 rpm. The pumps generally have issues before the rocker bushings.

Posted on May 01, 2009

  • 1 more comment 
  • smitty368 May 02, 2009

    There are 3 lines connected to the oil tank. One connects to the lower left inside under the battery box (near the drain plug) and is the feed line connecting to the rear of the pump, the second line connects to the upper left inside just above the battery box and is the return line connecting to the front of the pump, filter output or oil cooler return (depending on your setup), the third is connected to the top right under the seat and is a vent line that connects to the right side crank case just in front of the main sprocket (you have to remove the sprocket cover to get a good look at it). There is a forth line in this though, on the front of your cam cover (right side) you have either a down tube for venting or a breather hose connected to the back plate of your carburetor. I mention both as some early “79” models had the "78" style down tube. If you look at the generator bump on the front of the cam cover you will see the "flats" for both, the down tube would connected to the 6 o'clock position flat and goes to ground and the breather hose would connect to the 9/10 o'clock position a connects to the carb. If you have the down tube there shouldn't be a noticeable vacuum in the oil tank, if you have the breather tube the carb creates a vacuum through the hose to the crank case and to the oil tank through the vent line. The vacuum will vary depending on how clean your air filter is. The dirtier the filter the more air it will draw through the Crank Case & Open Oil Tank. You might consider removing your air filter, replace the filter cover, start the bike and see if there is a significant change. If so change the filter. If you are running a K&N style oil dressed filter this also increases the resistance the filter creates increasing the draw through the oil tank when opened. With a dirty filter or oil dressed filter the reason the bike’s rpm changes is when you open the oil tank while running you change it from a “sealed” system to an open system effecting the way the bike is breathing and with the increased air flow the air/fuel mixture will be enriched causing the rpm change. The vacuum is not a real issue, but be sure to check your filter.



    As to oil, I live in Cleveland and run 60w oil year round. If you are in a warmer climate than Cleveland consider moving up to 60w. I also add 6 - 8 oz of Lucas Heavy Duty Oil Stabilizer to prevent dry starts and help with oil viscosity break down. The Lucas doesn’t help with wet sumping when the Gerotor gears get worn though.


    Sorry about the length of this post, I’m just trying to be complete.

  • smitty368 May 03, 2009

    What carb does your bike have? Is your bike using the breather hose attached to the air filter backing plate? What type exhaust do you have the 2 into 1 or dual single?

  • smitty368 May 10, 2009

    All seems correct with the carb set-up, hoses and pipes so my concerns go back to the gerotor gears in the pump. Try an oil change to the 60w with a few oz of the Lucas. If that fixes the problem then the gear are most likely worn but not worn out. If it doesn't fix the problem then the chances are the only cheap fix is to rebuild the pump. But this is still cheaper than the heads.

    Good Luck

×

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Me again, my truck when i start it up in the morning oil pressure is good but the 15 min. ride to work pressure drops down to around 5-10, but i dont lose any power still runs strong


5-10 psi at idle with a warm to hot engine is not unusual with a well used engine but is low enough to ring alarm bells if that is the reading at speed. The manufacturer will issue specifications for an oil pressure test but as a general rule the test would be made at around 2000 rpm and the oil pressure should be around the oil pressure relief valve lift-off pressure which commonly is about 40-45 psi but could be higher or slightly lower.

Oil pressure has little relationship with engine power as long as it still has some...

If the oil pressure is low the cause might be simple or it might be complex and expensive, but whichever it turns out to be, rectification should not be delayed even for a day...

Jan 02, 2017 | Cars & Trucks

1 Answer

Front AC cold but Rear AC very hot


Not likely, but Is Hot water flowing to heater coil in back? How hot is "very hot" Is it a refrigerant line? If a refrigirant line, Very Hot means it is hot gas from the compressor that "should be going to the condenser coil usually in front of the radiator. It's almost impossible for that Hot refrigerant gas to go to the cooling coil in the back unless you had some repairs done and they weren't certified. My guess is the radiator hot water is not being controlled properly, due to bad valve or control system components.

Jun 07, 2015 | 2009 Saturn Outlook XR

1 Answer

CADILLAC 2005 CTS-C LS6 ON THE CHEVY 350 WHATS THE COVER FOR THAT LOOKS LIKE A OIL COOLER LINES CONNECTIONS HAS 2 X10MM BOLTS HOLING IT ON BUT CANT FIND ANY LINES OR STOCK OIL COOLER TO ANY INFO


There are 2 possibilities; The pressure relief valve in the oil pump is defective and as the oil warms up and thins down there is a loss of pressure. There is wear in one or more bearing on the crank/camshaft doing basically the same scenario. How do you know its too hot? Are you assuming because it says so it must be correct? Get a cooking thermometer and sample the oil for some idea of temp. Is the oil pressure switch defective? If its possible to access the switch easily can you rig a manual oil gauge to it to double check the pressure is what it says?

Oct 09, 2014 | Cars & Trucks

3 Answers

Oil light on after engine warm-up on idle


this means a mechanical gauge test is required to check actual pressure warm idling if low below 20 psi then the oil pressure pump relief is stuck open or engine bearing are worn

May 15, 2014 | 2005 Opel Astra 1.4

1 Answer

1999 Z-71 with high mileage (224,000) I lose oil pressure as the engine warms up. Cold start I run 40-50 PSI but after it warms up it drops to around 20-25 as long as your foot is in the pedal. When I...


I dont want to be the one to bring you bad news, but you most likly have engine wear. Bearing clearances, oil pump clearances all are getting out or tollarences. you can improve this by using 15/40 mptor oil , or heaver, but that is a patch. for a long shot change the oil presure sending unit or better yet use a mechanical gauge to verify the true pressure

Jun 11, 2011 | 1999 Chevrolet Silverado 1500

1 Answer

Hi there, my 2002 Dodge Intrepid's oil light just came on (and STAYED on, no flickering) yesterday when we had a -20 degree day. I didn't warm up the car very good before taking off (maybe 30-40 seconds)....


The thing to do is to remove the oil pressure sender and put a mechanical oil pressure gauge onto the fitting. Start the car (if it will start) and watch the mechanical gauge. If there is no oil pressure or very low oil pressure (less than 5 psi minimum), immediately stop the engine. Engine damage is sure to result with oil pressure that low. The cause of the low pressure will have to be diagnosed and corrected before running the engine again. Causes of low pressure could be worn engine bearings or a worn out oil pump. There could also be a restriction in the oil system such as a clogged filter or clogged oil pump pick up screen in the oil pan. The oil itself, if it is dirty and full of moisture will become like mayonnaise in the bottom of the pan at such cold temperatures and the oil pump will not be able to pick it up.

I know this won't be easy to do in -20 degree weather. But your car should be towed home or to a shop and not run again until this oil pressure check can be done. I'm hoping damage has not already occurred.

Feb 10, 2011 | 2002 Dodge Intrepid

3 Answers

I have a 79 ford f-150 with a 351w modified engine. when i first start the engine it has approx. 65 psi oil pressure. as the engine warms up the pressure slowly drops off to around 12 psi.the oil is clear...


First off its not a 351W modified. you are confusing two different blocks. its either a 351 windsor or a 351m (modified) and if it is the modified its not that bad. these engines are notorious for having low oil pressure. at idle they can be anywhere between 10 and 40. as long as you gain 10 psi per 1000 rpm its fine. and a pump doesnt drop off as it gets warm. it either works or it doesnt, oil pressure dropping off is a bottom end bearing problem

May 20, 2010 | 1981 Ford F 150

1 Answer

1999 firebird 3.8L low oil pressure at idle only when hot


your oil pump does that on purpose - more noticeable with a dented oilpan as pressure is slightly increased. nothing to do until it goes (if it goes) unless you want to throw parts at your car anyways.

Aug 24, 2009 | 2000 Pontiac Firebird

1 Answer

Sudden High and Low Oil Pressures


yes it might work if u flush it, give it a try

May 27, 2009 | 2000 Dodge Ram 1500 Truck

1 Answer

Oil Pressure Suddenly Reading in High and Low Ranges


either the oil pressure sender is defective or the pressure relief ball valve in the oil pump is sticking, my money would be on the oil pump pressure relief valve ball sticking.

May 27, 2009 | 1998 Dodge Intrepid

Not finding what you are looking for?
1979 Harley Davidson XLS 1000 Logo

475 people viewed this question

Ask a Question

Usually answered in minutes!

Top Harley Davidson Experts

Arnie Burke
Arnie Burke

Level 3 Expert

4514 Answers

Gills Lango

Level 2 Expert

195 Answers

Mike

Level 3 Expert

4336 Answers

Are you a Harley Davidson Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...