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Question Posted By: THUMPERRRR on 9-26-2010

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Make of Bike: harley
Model of Bike fxe
Year of Bike 1977
Engine Size 95ci
Other info on Bike low oil pressure
What's your question? low oil pressure
Details: Looking for causes of low oil pressure after about 5 miles of riding. Starts with 35#s at warm up, drops to the expected 3-4#s and then about 5 miles goes to 0 and intermettient pressure light flickering. Also looking for good reputable pumps that wouldnt require drilling the case. History: No unusual top end noise and motor runs tight. 500 miles on a fresh build: cylinders honed, re-ringed pistons, headwork done (all by reputal engine shop). I did change from a drop in filter to remote. tried mult filters with and with out pressure valves. no change in behavior. Its within the last 100 miles the bike started dropping oil pressure after bike warms up (5 miles) on a fresh motor rebuild (about 500 on it). Its just a flickering on the light. put a gauge on the tappet location just to waste $25 bucks. gauge goes from 35#s cold to 2-3#'s after warm up, then starts to drop to 0-1. Light will flicker on and off, typically stays off during road speed. Longer i ride, the less acceration registers gains on the pressure gauge. Running Amsoil 20-50 wt. I have tried new pressure sensor, isolated electrical from sensor to light,new bypass spring, new tappet screen & spring, new check valve (wasn't sumping but its an easy elimination). Return line shows good flow on start up but have not checked the return when motor is hot. any thoughts would be appreciated since next step is a pump which is looking to be some coin.

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  1. Thumperr, Thanks for getting it posted for me. having is much luck there as with the bike! By: beau on: 9-26-2010

  2. I've read this whole thread at Hawg's. At this point, I think checking the return flow when the engine's finally warmed up may give you an insight into this. Here's why: I have a feeling that when the engine warms up and the oil becomes less viscous, it's leaking through the bushings from the pressure side of the pump into the scavenge side of the pump. After all, that pump is around 34 years old and I doubt if anyone's rebuilt it. You mention replacing the bypass spring. If the spring were the culprit it would have raised the pressure, but if oil is seeping through the pump bushings to the scavenger side...replacing the spring will do nothing since there's no pressure to regulate. Now, if you remove the return line at the tank, fire it up cold, use a timer and let it flow about a half quart, exactly, check the time it takes to do that...then shut it off, replace the hose, replace the oil, start it up, let it get good and hot...then repeat the procedure; if you find you get more oil in the same amount of time, you might pull the pump and mic the shafts and bushings for excess wear. I'd also think about going back to straight 50W, Shovels don't care much for multi-viscosity oils, Amsoil or not.

    That's all I got. Good luck. By: 47Knuckle-Dragger on: 9-26-2010

  3. Damn Knuck, I decided to try your advice and switch from Amsoil 20-50 to a straight 50w non synthetic. Holy shit, gained twice the pressure on start up and seems to maintain a 30# read after it heats. Have yet to go for a mileage run but i am becoming a believer. Thanks..may have saved me alot of unnecessary BS! By: beau on: 9-27-2010

  4. "When you eliminate the impossible, whatever remains, however improbable, must be the truth." -Sherlock Holmes

    By: 47Knuckle-Dragger on: 9-27-2010

  5. knucks right. Another thing is be sure to use an oil made for air cooled motors. aviation oils for continental or lycoming motors. might want to look at diesel motor oil as they run a bit hotter than gas motors, By: MarkGoff on: 10-3-2010

  6. well straight weight got some more miles before it acted up, but didnt solve it. Tearing into eplacing the pump. Thanks all for the input. By: beau on: 10-4-2010

  7. There are a few things you can do to try that may improve your oil pressure, though harley oil pumps are designed more for volume than for pressure. A quick and dirty fix to raise your pressure is to put a 5/16" ball bearing on top of the spring in the relief port (the tall tower). Just a couple notes about oil for your motor: 1. pre-evo engines have much looser tolerances than late model (84&up) engines and do not like multi-grade oils. 2. If the motor is fresh use 50wt. DO NOT USE AUTOMOTIVE OILS IN ANY HARLEY AS THEY ARE MISSING CRITICAL ADDITIVES THAT CUSHION AND AID IN LUBRICATING THE ROLLER BEARINGS IN YOUR ENGINE! Any of the aftermarket M/C oils for harleys will work. 3. Use only oil filters for harleys. Those for autos have the wrong pressure relief (way too high) valve. 4. Oil coolers are generally not necessary until continuous daily temps are above 80 deg. Oil needs to be at 145 and most harley oils work best at or above 175deg. 5. Oil press at 145deg should be 5psi at idle and 10 to 35psi at 2000 to 2500 rpm measured at the tappet screen plug. 6. If you have to get in the pump check the feed and return gear height above body, min. .003" to max .004". In worn pumps I have seen this at .000" and once -.002" pressure will suffer a lot if gear and/or body are worn this much. If ht is low check gear faces and pump bore at bottom for wear. Pump body can be surfaced to raise gear. Also use a high quality rebuild kit w/springs,clips, keys, check ball, gaskets and seals (if your pump has seals lip goes to body) also check pump bores esp. return side for scoring or gouging on bore walls. Make sure tappet screen and spring are in good shape and clean regularly at each oil change. 7. Lastly if your oil pressure is still low but more than a couple of pounds at idle, check volume at filter by removing filter or line in to it for a reasonable flow hot and if you have good flow, check your guage for accuracy. Use one that is 0to60psi or 0to45psi for this check as the higher the pressure guage the less the low accuracy. Good Luck and I hope this helps you solve your problem. Later, Wolfman51pan By: Guest on: 11-5-2010

  8. One other thing check the fixed shaft in your pump and if loose, pump should be replaced. Also when running oil coolers always use a thermostat to let oil come up to temp and mount as close to pump as you can to reduce line restriction. Your return side runs at about 3 to 5 psi. Later, Wolfman By: Guest on: 11-5-2010

  9. If oil pump gear is missing some teeth it will give you this problem By: grizzly08 on: 11-9-2010

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