Recently we received the following letter and immediately followed up.
“We have developed a Gerotor oil pump that bolts right onto evolution engines,” Bret Barker said, “to give them twin cam style oiling. We have just run it on our test bench atthe shop. We are getting ready to run it on a bike, do our pressure testingetc.”
”We need the vast worldwide Bikernet Testing Specialists to perform complete Bikernet intergalactic testing procedures. I know this will cost us in the seven figure range, but we’re that confident of our Gerotor Pump. Whatta ya say?”
”I would greatly appreciate your help.
Here's the link to the The Merlin Engineering Gerotor Oil pump, manufactured by Walsh Machine site.http//www.walshmachine.com
I await your honest and brutal input….
–Bret Barker
Gerotor pumps are similar to turning on a radio and up pops an old Four Tops tune that takes you immediately back to a weeping brunette with large, young, milky soft… Well, you know. A couple of decades ago a Gerotor pump was developed as a life-saver to poor oil pump pressure problems. I don’t know what happened to them, but I’ll find out. So, the Bikernet Technical Consultation Board met recently and sifted through over 500 products for testing consideration, but the Gerotor continually floated to the surface. We contacted our Texas lab, or Lucky Devil Metal Works. The following are the results of the Devil’s Scientists at work.
–Bandit
Everyone knows it's hotter than hellfire in Texas (like the redhead), so when Bandit told me about a new oil pump coming out, that will keep the pressure up at idle, I knew I had to see one close up and personal. Merlin Engineering has a billet Gerotor pump that will supply an increased volume of oil from idle up to 14,000 rpm (and if you can rev your V-twin that high without it coming apart please call me–I have some questions!).
The pump will also maintain excellent oil pressure under the most severe temperatures, like in Hell for instance so needless to say this all sounded good to me!
After I got Jessica strapped down on the lift, I got my hands in the box and spread it open to discover a nice clean polished oil pump. Okay, let’s clear things up a bit. Jessica is the Bike and the Box is the package the parts came in. Everybody with me now? And I don't remember the Girl’s name but let's not go into that.
Back to business. I grabbed the instructions, to look them over, before getting started. Now that RFR, Bikernet Texas Photographer, is too busy being a hotshot good strip club manager, at night, I needed some help either holding the camera or wrenching. Every now and then I get together with a buddy of mine, Brad, who makes a living as the crew chief for the Mancuso H-D top fuel Race team, as luck would have it he stopped in, and I convinced him to help out.
First things first, it's always a good idea to disconnect the battery before doing anything with your bike that may lead to a misunderstanding between the starter and a body part. Next Brad pulled the rear pipe, the front pipe stayed on since it was not in the way.
The next thing on the list was to remove the old oil pump, the new Merlin Engineering pump comes with a new drive shaft assembly so the cam cover must be removed (or gear case cover as it's called in the manual). I think it's always a sharp idea to have a manual handy for the particulars, like torque specs, you know, useless info like that.
The first thing the manual tells you to do is remove the rocker box assemblies. Well we used a bit of a shortcut here since this Bike has adjustable pushrods. We slipped in under the pushrod tubes and shortened the pushrods to allow us to sneak them out and release the valve spring pressure on the lifters.
Next we actually followed the instructions lined out in the manual and removed the ignition and such to allow the removal of the cam cover, using a handy puller that keeps the cam in place while removing the cam cover. There are some various ones available, most are inexpensive and readily available from just about any parts supplier or local shop. Next, we yanked the guts out of the way and tossed them aside (you need to check your manual for proper instructions here).
With all that crap out of the way we jumped in to remove the oil pump drive gear from the shaft using lock ring pliers as suggested in the manual.
Here’s where we turned to the instructions that came with the new Gerotor oil pump. Starting with installing the new oil pump drive shaft and gears. Once that’s done, it was time to install the new oil pump housing over the drive shaft and tighten the fasteners evenly and make sure the oil pump shaft and gears turn freely.
Once the pump body and the shaft were aligned properly, it was time to use the torque wrench to make it right per the manual.
After installing the Gerotor gears, the inner gear plate and seal we were ready to install the pump cover and torque the fasteners to spec.
Now we installed the barb fittings and rerouted the oil lines, just a tad. It was time to install the rest of the components and button it up with the cam cover, following the service manual.
Merlin Engineering recommends the use of 20/50 and warn that straight 50w or 60w may result in extremely high oil pressure, when the motorcycle is cold, and that a 0 -100 psi oil pressure gauge is highly recommended. We upgraded the one on this bike from a 60psi gauge just to be on the safe side.
After we got the scooter cranked up, we not only noticed higher oil pressure, but it was very responsive to the throttle! This bike was customized for a tall friend of mine and the controls were out of reach for both of us.
We'll have to wait to give it a good thrashing, when it’s back in big Frank’s hands. We'll keep you posted, but so far we were both impressed.
Here are the specs:
Fits all Harley-Davidson Evos 1992-1999
Fits All S&S Evo style Engines
Fits All Rev Tech Evo Engines
oil supply rate: 1.6 times OEM minimum
oil return rate: 4.5 times OEM minimum
oil pressure max cold: 100 psi
oil pressure regulated: 23 psi at 3000 rpm ( @ 180f )
oil pressure at idle: 12 psi@ 1100 rpm ( @180f )
The Merlin Engineering Gerotor Oil pump, manufactured by Walsh Machine
Walsh Machine, LLC.
16890 Church Street
Building # 3
Morgan Hill, CA 95037
408-779-4539
408-779-4342 Fax
Stanley Walsh II, President, Walsh Machine
David Troetchler, Engineer/Owner, Merlin Engineering
–The Devil
