All I wanted to do was complete an overhaul on the oil system. You know, a good winter maintenance project. Flush the tank, replace all lines, new filter, strip and inspect the pump, new pressure gauge. But this was not to be so simple. Photos and helpful attachments below.

Everything was going so well all the way up to the point that I needed to reinstall the pump. Obviously, I needed to prove none of the gears weren't binding in any way by rotating the pump shaft with my finger, but to achieve that properly you need to remove the Oil Pump Pinion Shaft Gear. (You don't get a good enough feel of what's happening with the pump gears by trying to roll just the pump shaft without having the oil pump drive gear on) This is where the pain and education started.

To remove the Oil Pump Pinion Shaft Gear you need to take off the Pinion Gear and spacer etc which is all held in place by the Pinion Gear Nut, so I think to myself "that's fine, I'll remove the nut" oh no no no, you need a special socket for that. Fine so I ordered said socket (not cheap) and a few of the other perishables that would be required and when it finally arrived, I thought great, let’s go. After heating up the nut to soften any red loctite, as soon as I applied pressure to the ratchet with said special socket, the damn thing slipped straight off and rounded over two opposing corners of the nut and the socket. Oh boy - I hate over-priced cheap metal ****. How the hell can the socket be rounded over too.

So the brain is ticking, what do I do now, I can’t go trying to put a punch on it as that will possible mess up the pinion shaft run-out and I really don't need to be doing that, another option was to try and get some sort grips or modified spanner but with the flange face being so exposed I really didn’t want to damage that. So, the only viable/safest option I could see was to expose the pinion nut that’s recessed in the gear, so that’s what I did, slowly, very slowly it worked a dream.

With the nut now revealed, still I need to get the thing loose, but again, with the flange being so close, my best option was to grind my own socket size with the Dremel on to the nut, being extremely careful not to damage the pinion shaft threads. Eventually we we were able to get the job done with no damage incurred. What a relief hahaha

This is when the real challenge kicked in. Trying to find a Red (24043-90) Pinion Gear for a 1991 Evo with an Andrews EV27 cam gear. So what's the problem?

• Evo’s from 1984-89 = Tapered Pinion Shaft, recessed pinion gear for the nut
• Mid Evo 1990-92 = Parallel Pinion Shaft, recessed pinion gear for the nut
• Late Evo’s 1993 – onwards = Parallel ˝” extended Pinion Shaft, non-recessed pinion gear. Nut sits flush on the non-drive end of the gear

When I say I called suppliers and shops all over the world, I really do mean that. Lots of early Evo pinion gears and lots of late's and even conversion kits but no-one seemed to have a 24043-90.

Even though I had read about the various sized (coloured) pinion gears I had got a bit of tunnel vision on the part number. One day a fella suggested looking for another size and then change the gear on the Cam, and wouldn’t you know it, I eventually found a 24041-90 in France, but they didn’t ship to the UK, thanks to BREXIT. A friend living in France was nice enough to help out there.

The part arrived and I was able then to start doing a dry test fit of the new pinion gear with the Cam gear but unfortunately it was too tight for my liking but I luckily, still had the Gear from my OEM Cam that I had replaced previously, and by the shear grace of the gods, it was a sweet fit.

I’ve attached the guidance I used for matching Cam/Pinion Gears so that hopefully it helps someone out. I’ve loved the journey and the amount of learning I’ve been forced in to, but my main lesson here is to research my future projects in a bit more depth and see what parts are available.

Be good and ride safe lads.

Cookie

 

I love a good learning experience as long as it doesn't cost too much

 

They have 2 different length nuts and that one looks right - its a left hand thread and a special tool to remove it and install it has to be used not right hand thread like everything else

your problem is not the nut but something made of hi carbon steel is falling apart and going through the oiling system — LOOK in side of the breather hole and or the plastic breather valve distorted as the engine was over heated more then just a one time

 

Looks like the pinion shaft has some scoring, too. The breather bore looks bad.

 

His breather bore looks just like mine did after a plastic one died at 32k miles. I put in a new cam @ 160k miles and my breather bore still looks exactly like that. Been running a plastic breather all that time. Breather's critical only on a dry primary, Evo doesn't care.

You're seeing oil and dust glare and on the pinion. Looks like mine with 160K on it but with your eyes looking at it in person, they are smooth..




Wish I could figure out to make these damn photos smaller on here...

 

Easiest way is to resize the image buy using the basic Paint programme. Select and right click on the picture and select "edit", PAINT will open up, see resize, select that and then play around with the PERCENTAGE or PIXELS

 

Yeah its pretty damn bad in there, so heading over to a S&S Reed Breather

 

I use IrfanView but I get your point.

Again, my breather bore looked just like that at 32k, been running a plastic gear since. Now at 160k miles, changed cam, bore still hasn't changed.

I'd wager you'll regret a reed valve on a street bike. Time will tell.

 

Been running an s&s reed valve breather on my 92 since s&s came out with them- never had any issue at all- never think about it.

 

I know just enough to know I stay the hell away from that pinion gear.