Hello
I have a problem with my Mc18II, the right exhaust tip looks very oily compared to the left one, also the spark plug of the vertical cylinder looks like functioning with more oil than the horizontal one.
Bike runs perfectly and survives a 2.500km trip in one week without problems, is at the last kms when I,m aware of that issue. Previously both exhaust and spark plugs runs equal. Thinking I had toasted the oil pump.
I have read in this forum it,s impossible to repair the pump and probably switch to premix, at least to the moment I,m able to find a new one
Anyone has this issue or is normal when pumps fail?
What changes in jetting are advisable for premix, bike is stock and for road use
Thanks from north Spain

Hello "asturtarmac", and welcome to NSR-WORLD.COM

The 2T oil pumps are generally very reliable, and in almost 30 years of NSRs, I've personally never seen one fail on just one side. The most common "failure" of the oil pump is the drive shaft oil seal unseating from it's housing, and allowing all the 2T to drain into the transmission*, but even this isn't common. That is not to say however, that the pump cannot fail -- just that it's not common.

You probably know already, but just to be sure, the exhausts on the R5/6K "cross over", so the RHS tailpipe actually corresponds to the LHS/upper cylinder/carb.

To see one side start oiling up while the other remains "normal" would suggest a carburetion or ignition problem, rather than an oil pump problem.

I would start off by pulling the airbox, cleaning the air filter, and checking you don't have any debris partially blocking a jet. Also check the condition of the spark plugs, caps, and HT leads.

Please take the time to check the fault-finder in Chapter 1/Page 26 of our Honda Approved English Service Manual in the Members Content area of the site.

Please note, we do not allow jetting discussion (other that stock settings) in the public forums, as every scenario and condition is different. What works for someone may not work for someone else, and could have (and has in the past indeed had) catastrophic consequences. You can find the stock information here: NSR-WORLD Technical

*As a side note, I always recommend topping off the 2T oil tank before ever ride, that way if the oil pump drive shaft oil seal has unseated and alllowed all the oil to drain into the transmission, you will discover the issue before starting the motor.
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Andy.
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Thank you very much Andy
I have the bike fully serviced before the trip and have the oil pump seal replaced and fixed with hermetic to the oil pump housing, it,s leaking to the gearbox and this problem solved
Yesterday I checked spark plugs, carburettion-air screw, etc, all seems to be ok, next is to check coils, ignition cables and pick-ups. Then check oil pump delivery with graduated vessel and clear tubing
I know the matter of jetting can be problematic here and will try on my own whith larger jets if my pump don,t work
I,m thinking about the possibility of center crankshaft seal leaking from one cilynder to the other? but engine starts perfectly cold-hot and runs ok troughout all regimes
I will take advantage of this post to thank all the people publishing here and the administrators of the site, it,s very useful to newbies on this bikes like me

Yes, check the "easy" things first! It could well be the centre crank seal, but it could also be something as simple as a broken/worn reed on the intake. Normally, when it's the centre seal, the bike will usually be hard to start, and often run badly at lower RPM. If it was the RHS pipe on an MC21 or MC28, it could be the RHS crank seal leaking additional transmission oil into the cylinder, but that would generally produce white smoke from the exhaust, but as it's MC18, the exhausts are routed differntly, and if it was the left crank seal, you'd almost certainly be drawing air and running lean.

Please keep us updated with your findings, as every shared experience helps the wider community.
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Andy.
NSR-WORLD.COM

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Problem solved, carburettor n° 2 air solenoid valve was not sealing and lean the mix on horizontal cylinder...Changed the o-rings and some silicon grease on the tip rubber seal of the piston inside the valves. I wasn,t able to find that little rubber seal new. Attached pics of the seals into the valves, it would be a good mainteinance thing to look for.
Oil pump delivery is the same in both outlets, about 5ml-10 min with pulley fully open and engine idling.
Probably I had some water from clean the bike into the right exhaust and that looks like excess oil in it.
Thanks

Excellent news, and thank you for coming back with your solution.

I don't see any photos attached, but if you want to PM me I am happy to upload some to the NSR-WORLD server and add them to your post.
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Andy.
NSR-WORLD.COM

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Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

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Hi asturtarmac

I’d also be interested in seeing the picture as well as I cannot visualise the fault with my limited knowledge