1989 Honda NX 650 Oil Pump Rebuild Help!

Good day Thumpers! 

I hope everyone had a nice Valentine's Day. 
I have run into a quandary that has me perplexed: while rebuilding my the oil pump on my 1989 Honda NX650 (California, USA model. XR650 & XR650L similar), I failed to note exactly which way the rotors go, when being reinstalled.  :banghead:
The problem is that the Honda repair manual states to put the B rotor with the punch mark facing "in." ok. That seems to make sense. It then goes on to say to put the A rotor (the thicker one) with the punch mark facing "out." 
All would be ok, except: 1. that does not match with the photos I took during disassembly-see photo (although I may have not been as accurate on those). 2. it also does not match with the scratches on the rotors. Those seem to suggest having the rotor  punch mark facing inwards, just like the other one. 
So, to follow the Honda gods and their manual, or the evidence? 
And now for the zen question: does it really matter which way the rotor is installed? 
Any advice greatly appreciated. 
Thank you, 
A Rotor During disassby.JPG
A Rotor Punch Mark (lower left).JPG

I take it you can`t find a new pump..instead of playing with an old one??????????


I`d rely on your pictures and wear marks and assemble it the way it was.......


But i`d exhaust every possible avenue trying to get a new pump first..


I wonder if a late model XRL pump would fit,,i seriously doubt there would be fitment issues..



Hello Brian, 


Thanks for the thought. Yeah, I've been trying for over a year to find a new pump to no avail. They're not made anymore, and from what I've read on forums, the new pumps have either higher capacities or are build differently and do not fit in the older bikes. 


The good news is the pump I have measures way below all the limits in the Honda manual, so it's in great shape. I also have figured out the rotor quandry. 



As you can see in the photo, the left side of the rotor (the edge with the punch mark) is chamfered more than the other one. Since this is the side intended to go into the housing (and up against a corner), it makes sense it would leave more clearing. This is the opposite of the way it came out, but it appears the manual was correct, and the original builder assembled it wrong at the factory.  :jawdrop:

Rotor Close.JPG

Or.... the engine has been apart since it left Mr. Honda's factory.

I'd seriously doubt there's any difference between any oil pump from the RFVC NX650,,650L,, XL600,,XR600,,XR500,,GB500 GB400. I have read that some are supposed

to pump more oil..the design and fitting is no doubt the same.




HT's thread on pumps above..I'm prepared to be wrong..

Edited by Horri

I think you are correct Horri.....i really think they are interchangeable...they may pump more but that is not an issue on these bikes,,the more the better..as long as it`s the same height laying flat against each other so they flow through the clutch cover it will fit........only way to know is to have both...i`d get a new one for the XRL and see if it was me...



Sounds plausible and would definitely be cool.  :thinking:  It'd be much easier, if one of the parts 'fiches' would have a 'compatible with' or 'superseded by' and the other pump. I'll look into it. 

I'm happy to announce the pump primed and is working great! Thanks for your suggestions! As the old pump measured well within tolerances, I stuck by it. 

Now, just a tune to go, and it's a rideable summer!  :ride:

Btw, any of you guys heard these engines don't run well on K&N air filters? The tuner won't even touch it, unless I swap back to stock... 

Crikey ,,what sort of tuner is he,,Dyno only I expect..Plainly he has no figures on what a bike should run like without his machine and figures for

an original setup..I'd call him fairly useless tbh..No I know nothing of how a 650L /NX650 should/would run with a K and N filter.


Btw, any of you guys heard these engines don't run well on K&N air filters?


I wouldn't even give my old one to anyone; unless I really hated them. I purified it with fire (just kidding, I gave it a live burial).


More flow for the same size filter (surface area) = less filtration.


Cotton gauze, filters out crap (cow chips), bugs, rocks and the occasional squirrel, only. Anything labeled as "race" or giving general HP increases as proof of quality, should be approached with much caution for real world use.


In case you haven't heard, K&N filters are not good at, filtering.


The stock filter is best at filtering and foam is best if there is a chance of it getting wet. Save the cotton gauze for the first-aid kit.

Edited by Onederer

Good thoughts. It sounds as though this guy is of the same opinion. It wasn't a huge investment to get the filter, so I'll do what he says and then ask again, when I'm at the shop.

I like idea of the K&N and that I wouldn't have to buy filters anymore (parts are getting rare around here), but ultimately, I want to do what's best for the bike. 

I'll post again, once I'm back from the shop with a report. 

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