Thanks for taking a look at my post.

I recently noticed a decent sized pool of 2T oil under my '91 MC21, having traced it back around the bike I would say the 2T oil reservoirs and connecting pipes are all dry...there is a small drip around the oil pump and the oil pump seems damp, I will inspect and replace as nec...but my main concern is the exhaust valve and the RC valve around the front cyl are pretty well soaked.

Seems obvious to me that I need to remove inpsect/clean/replace the RC valves as necessary but I just wondered if this is a common issue or has been seen by owners before? Fingers crossed one of you is going to tell me something is just sticking and a good clean will do it!!

I am a new owner and in full deep clean and refurb mode since the bike has stood for about 8 years.

Any help, pointers greatly appreciated...roll on the great British spring weather!!

When you say "a decent sized pool of 2T oil under my '91 MC21", just how much are we talking about? Not that there should be any under the bike! Is there any oil left in the reservoir/remote? Or is it all on the garage floor?!

Have you checked the transmission oil? This one probably sounds weird, but the 2T pump shaft seal can become unseated allowing the 2T reservoir to drain into the transmission. It's not common, but it does happen more than it should. If you take the cap off and oil immediately flows out of the filler neck, then you've found the problem.

Any oil around the outside of the RC Valves could indicate the RC shaft seal(s) are worn and leaking, and possibly a rich mixture and/or badly adjusted oil pump.
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Andy wrote:When you say "a decent sized pool of 2T oil under my '91 MC21", just how much are we talking about? Not that there should be any under the bike! Is there any oil left in the reservoir/remote? Or is it all on the garage floor?!

Have you checked the transmission oil? This one probably sounds weird, but the 2T pump shaft seal can become unseated allowing the 2T reservoir to drain into the transmission. It's not common, but it does happen more than it should. If you take the cap off and oil immediately flows out of the filler neck, then you've found the problem.

Any oil around the outside of the RC Valves could indicate the RC shaft seal(s) are worn and leaking, and possibly a rich mixture and/or badly adjusted oil pump.

Hi Andy, Thanks for jumping in on this one.
A decent pool is perhaps half a teacup or a good three finger slug of your favourite spirit depending on your preference.
Both reservoirs are full, roughly as full as I left them anyway and the oil on the bench is Rock green.

In order to check the bike ran OK I kicked it up and hand forced the 2T pump wide open just to provide a bit or extra oil for the initial minute or so...but the bike has not been run and has just sat on the bench whilst working on the swingers etc. (err just noticed the typo here, I think the confuser spell corrected me...sofor the record I meant "whilst working on the SWINGARM etc)

I will have a look at the gearbox oil as it needs to come out anyway...might be interesting what I find in that lot! And given the oil pump is wet I need to have that apart and check it out.

The odd bit is the exhaust collet and RC valve...I just can't figure where it has come from.

Still it's all part of the fun!!

Cheers
Max

Damn those pesky confusers!

Well there aren't too many places it can come from. If the 2T remote reservoir is full, and the plumbing is all dry, the only thing left is the pump. Maybe the O-ring(s) under the pump aren't doing their job? (Later MC21 and all MC28s have two O-rings.)

Is the transmission breather hose intact? Is the end wet? Are you sure it's not transmission oil that's been pumped out?
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Andy wrote:Damn those pesky confusers!

Well there aren't too many places it can come from. If the 2T remote reservoir is full, and the plumbing is all dry, the only thing left is the pump. Maybe the O-ring(s) under the pump aren't doing their job? (Later MC21 and all MC28s have two O-rings.)

Is the transmission breather hose intact? Is the end wet? Are you sure it's not transmission oil that's been pumped out?

I'll have another good look around in the morning. Its been sat on the bench a good 2 months without breathing a beat so....If I remember right the oil pump is lower down (in gravity terms) than the rc and exhaust outlet.
Prob a combination of two issues, over oiling on initial start up (for safety sake) spitting out of the exhaust outlet and leaving the RC coated... and an oil leak from the pump onto the bench.

Will keep you updated and thanks for all the effort 👍

It's difficult to come up with ideas when you can't see for yourself what's going on. I'm just trying to think of possible scenarios. At the end of the day, there's only two places it can originate from. The 2T reservoir(s) or the transmission... or a family member/friend with a warped sense of humour!

I would've thought it's unlikely that holding the 2T pump pulley wide open for a minute on idle would be enough to create a pool of oil under the bike. Best plan is probably to get in there with carb/brake cleaner and thoroughly clean away any oil residue and start it back up to see if you can trace the culprit.
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Andy wrote:It's difficult to come up with ideas when you can't see for yourself what's going on. I'm just trying to think of possible scenarios. At the end of the day, there's only two places it can originate from. The 2T reservoir(s) or the transmission... or a family member/friend with a warped sense of humour!

I would've thought it's unlikely that holding the 2T pump pulley wide open for a minute on idle would be enough to create a pool of oil under the bike. Best plan is probably to get in there with carb/brake cleaner and thoroughly clean away any oil residue and start it back up to see if you can trace the culprit.

Hi Andy

I thought I would update you on this now that I have spent some more time on the bike.
I found a snapped exhaust header stud which is causing the oil wetting around the RC valve and there is definitely a leak on the oil pump somewhere (not investigated yet as working on the barrel etc)
So a combination of two issues making the right side of the engine soggy and miserable!

Thanks for your input and effort 👍

Doh! I guess I should've asked what colour the oil was! Hindsight is a great thing!
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Anyone have any tips on what to look out for when servicing the oil pump? Not sure where it is leaking from yet but seems to have soaked the top of the crankcases...

Cheers
Max

Andy wrote:Doh! I guess I should've asked what colour the oil was! Hindsight is a great thing!

Hi Andy,
Just checking in before I go and make a stupid mistake...the thrust washer on the bottom of the oil pump drive shaft seems to have stayed in the crankcase recess when removing the shaft for inspection, its hard to see but I'm fairly confident it is in there. Although the washer seems to float about a fair bit left and right, is that correct?
When I refit the oil pump shaft it seems to locate easily enough but there is play left to right on the shaft (I guess this play is taken up when fitting the oil pump over the top)?

Still not finally located the leak so I want to reassemble correctly and see what happens..

Cheers for any input.

Max

Yeah, the shaft is often unnervingly wobbly, and the steel thrust washer just floats in the recess -- just make doubly sure it's there! It's only there to stop the steel shaft wearing against the soft alloy, but crucial!

Fit the shaft to the pump first, then then pump assembly into the crankcase.
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Hi Andy, washer present and correct but can I ask a newb question... I can't seem to find part 10 in my assembly at all, the little O-ring? (pic enc)
Where does this sit?

Cheers
Max

That picture is a little misleading. If you have an earlier MC21, there is no little O-ring; it's only found on the later models, where there's an additional crank bearing feed on the bottom of the pump.
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Aha! Thats why I can't see it then! Thought I was going bonkers...correction thought I was going more bonkers!

Do you supply clear manifold oil line through the market place? Not sure I trust these original ones much.

If you want clear oil lines, I'd maybe try to get some from the local RC car model shop. Never done it myself, as I've never encountered a problem with the OEM lines, but that's probably where I'd start.

You could always flush the OEM lines with some carb cleaner to check there are no blockages or restrictions, and then even prime them with 2T if you're so inclined.
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