Scrambler's domi and Langer's syndrome

Ssince its appearance in 1988, the Dominator has been my dream bike. But it was not until 1992 that I could afford a used 1988 Dominator, mainly for dual purposes. In Europe, the 1988 Dominator was available with rear disk brake and kickstarter, and in blue, red and black with golden rims, manifolds and handle bars.



The alpes were my favorite region, at that time off-road was still allowed in some areas. Shortly after the picture below was taken, I crashed my Domi and the cowl was totally ruined - so I continuied without it.



Something every endurofan had to do in the 1990s was a trip to Africa. So we did a little one, crossing Africa from Kenia to Namiba. And the domi turned out to be the perfect bike for gravels pads and sand dunes.







The only trouble on this 7000kms was with the oil-pump, although I did not know that at that time. Somewhere in the middle of Africa suddenly the oil was gone from the frame reservoir, a phenomenon well known by every Domi driver. With constantly refilling of oil I was able to finish the tour, but back in Germany the engine died with the usual valve seat and camshaft rattle. I was pretty offended (to say the least) by this behavior, so I rolled the Domi into the barn and didn't look at her for the next couple of years. After my return to Germany (I've spend a few of years in Ohio, but that';s a different story) I started to rebuild my Domi. The engine was taken from a 1991 donor (without kick starter) and I bought a couple of new parts (eg. a complete cowl - consider the costs). Shortly afterwards, I wrecked the domi in an accident; everything except the engine and the frame was damaged. And there was also running oil out of the frame, so there must have been a crack as well. Usually, this would have been the kiss of death for every bike, but I was determined to keep my Domi alive.

So in 2005, I started to rebuild her as a scrambler. Since apparently my Domi doesn't like cowls and prefers to run naked ;-)




To lower the bike, a shorter shock from wilbers was used and in the front fork, shorter internal seat pipes from a NTV650. So this lowered the bike considerably, in order to achieve a classic look.



This was also the main reason for the rear wheel and brake drum of the US-Domi . The most difficult part was the petrol tank. Due to the frame-layout, most other tanks did not fit without mayor changes. I finally figured that tanks from old NSU Max/Fox were suitable. Then some more parts from fifties bikes such as the lamp and lamp holder and there you are.

These are triple clamps (without rubber mounts for the handle bar) from the XL600, since I did not like the look and the feeling of the Domi rubber mounds. Most people think that I gold-plated the handle-bar - but that was stock with 1988 Domis in Europe.



The odometer was taken from a XL185 and fitted exactly into the lamp of an old Zündapp.



It was almost 15 years after my engine died that I found out what killed my Domi (and probably many other). Langer, a guy from our German Dominator forum ("Langer" means the long one http://www.technologyplace.de/nx650/) was sucked up by the oil-checking procedure and developed a tube to check it on sight, even during driving (not recommended ;-)).

With that gadget, he noticed that the oil in the frame reservoir somethimes vanished during driving - a phenomenon well known by brit drivers as wet sumping http://forum.nx250.de/viewtopic.php?t=160. However, according to theory, an intact Honda oil pump should always keep a high oil level in the frame reservoir. As an engineer he was challenged and started to do some experiments with the dismantled oil pump. In the process he discovered that the oil-pump, depending on oil temperature, oil wear and pump wear, may show temporarily internal and external leaks (later called Langer's syndrome ) between the body parts of the pump. For instance, the leaking was stronger with oil that was already 5000km in use, whereas with new oil, there was almost no leaking (which would explain the short changing intervals of 3000kms). In extreme cases (high temperatures, old oil), the pump did not deliver at all, but simply pumping oil from one pump chamber to another.

The mean thing is that after disassembling, the wear of the pump was still within the limits of the factory manual. So no chance at all to recognize a bad pump by measuring the wear. All of a sudden, we had the explanation, why so many Dommies died with cylinder head damage. A clear indication that the oil-pump is the villain is the fact that in Europe (where the domi has been sold until 2000) Honda several times changed it http://forum.nx250.de/viewtopic.php?t=160.



So to avoid Langer'syndrome you have to stick to a few rules and you will happily live ever after with your domi:
Change oil every 3000kms
As soon as the pump shows signs of wear (frame reservoir is suddenly empty AFTER a ride) consider changing it – especially, when you own one without oils seals in the pump
Check oil level often, best after riding at least a few miles; since I was also sucked up with that, I build my own oil sight tube





Cheers, Michael

That is a clever solution to check the oil level. Hope the thousands of technitians at Honda, Yamaha, Suzuki, Kawasaki, BMW, Ducati, etc etc etc etc would have used it looooooong ago.

Now I have to try that on my Tenere.

I do love what you have done with your bike!

Nice trick with the oil level. It should work perfect on a old BSA oil in frame!

Do you have any info on the '95-on oil pump? What is different about it that makes it pump more oil? Are the rotors any thicker or larger? Thanks.

BTW, your dommie build is great. It looks real clean and well thought out, but it sounds like it did not require near as much fabrication as I would have expected. Great job.

Thank you ;-) A 1995 would be a RD08, with the stronger pump. So you're lucky ;-). The rotor of pump A (which pumps the oil into the frame reservoir) is thicker by 50% (8 vs. 12mm), so the performance is also raised by 50%, compared with the old RD02. Note that the RD08 pump has also some reinforcements. Another hint that the problem with the oil pumps has something to do with the pump body. As easily recognizable by the missing kick starter, an estimated 4/5 of the old German RD02 engines had been killed off by Langer’s syndrome. By now, you rarely see a 1988 Domi with the origional kick-starter engine. So it would be really neat to use the stronger pump in an old RD02 engine, but since the pump body is also 4mm thicker, it’s not possible (at least it’s not a plug and play conversion).

Thanks for the detailed information. There was a ThumpetTalk discussion a while back about better oil pumps for the RFVC engines.

So I would guess the RD08 either has a different clutch cover or a different right-side engine case to accommodate the wider oil pump. Do you happen to know which it is? Also, do you happen to know the width of the other rotor in the pump?

Really like the direction you took with your bike. On the Oil Pump, will the new oil pump style oil pump fit another wise stock XL600? We have a same motor and the same problem.

TIA

If I remember correctly, Honda is selling the improved version with oil seals for the XL600 (and old XRs as well) with OEM nr 15100-MN-1771. At http://www.cmsnl.com/honda-xl600_model363/ you can check for your year of manufacture.
(Thats were I got the infos about the Domi oil pumps)

Right, the clutch cover of the RD08 is different, so theoretically, it should be possible to accommodate the wider oil pump with that cover on RD02 housing. One guy adapted a wide pump with the RD02 clutch cover by milling 4mm off the pump, at that point where it is connected with the cover (red arrow). The bush (not in the picture) in there has also to be shortened. By the way, this orifice and the O-ring is crucial for the oil supply to the cylinder head. I guess a couple of Domi/XR/XL drivers killed their engine when changing the clutch and losing the bush/O-ring.
But the stronger pump is not solving the problem, since the infamous cylinder head damages also occur with RD08, only not as often. Langer actually got a RD08 and he suggested a solution to the problem by using a metal joint sealer between the body parts of the pump.

The width of the other rotor is 6mm, as far as I know, this has never been changed.


(can you see this picture? I sometimes got problems with pictures from the Dominator forum - if not, here is the link http://www.forumromanum.de/member/forum/images/profile/12915275174cfb255d19ec0.jpg )

I just bought all the remaining RS600 parts from a guy who bought them from the shop, who bought everything from HRC, when HRC sold out all the Dirt Track stuff.

Bottom line, is I have TWO (2) Brand new, in the original boxes RS600D oil pumps. The scavenger pump is 10.0mm wide and will fit directly into any XR600 or XL600 engine.

If anyone is interested in one, I am selling them, along with a number of other RS600 "SPECIAL" parts. The oil pumps are $500 each. Brand New RS600 Crank Shafts are $1000 each. both 75mm and 80mm strokes available.

PLENTY of RS500, RS600 and RS628 Factory HRC Pistons as well.

E-mail me at nstorm76@aol.com

Thanks,
Ned
May 4, 2012

Last oil service at 2600km on my 1988 NX650.
I drained the oil hot from the engine drain and the front downtube and cleaned the screen in the bottom of the down tube.
I also left it overnight to fully drain, the next morning I refilled the frame with 2 litres but the oil all disappeared into the engine.
After refilling I started it on idle to allow the frame to refill but the frame reservoir doesn't seem to refill.
Did draining overnight with a hot engine allow the oil pump to deprime and subsequently fail to pump oil?
What do I do from here?

awesome...... just an awesome bike!!!!!!

When I do my oil change, I verify the valve clearance and while doing it, I pour 1 liter on oil in the valve cover. I also fill the 2 hole in the filter chamber with oil, to make sure the pump is prime. I also mak sure that oil is flowing to the head by loosening the top banjo bolt of the external oil line.

Call me freak, but I don't want fry the top end!

Great info on the Domi and for the XRL!!!

Thats a good way of ensuring that the head has adequate lubrication on start up.
My problem is that I didn't change the filter so I couldn't prime it that way.
I might drain the engine again and refill the filter housing.
I never had this problem before but I usually don't leave it overnight.

That’s normal with cold and thus thick oil – when starting the cold engine, the oil needs some time to drop back to the bottom of the engine, so the level in the frame reservoir sinks. I made a little video, where you can watch the oil level sinking – the fastest way to get the reservoir filled again is driving for at least a couple of kms.

http://www.youtube.com/watch?v=c2X9KR8W7Og

But it is possible to drain the oil pump during an oil change – if then the oil pump is sucking air, it may not work at all.
Luckily testing and venting the oil pump is easy.
Open the upper hollow bolt of the oil tube just a bit and start the engine – if the oil pump is ok, almost immediately oil will coming out of the bolt (I actually do this after every oil change). If no oil is coming out within 2 seconds, stop the engine. Now you got to put some overpressure to the frame reservoir, best by using a compressor. But a big syringe is doing the job as well. Start the compressor (or press the syringe) and then start the engine – now there should be coming oil out of the bolt. If that is the case, you successfully vented the oil pump

Great info, thanks Scrambler.
It just threw me a bit when I couldn't see any oil in the frame after putting 2 litres in.
I'll give your method a try tonight when I get back from my birthday dinner.

You are welcome ;-) And feel free to let us know if it worked (it usually does)

Update
I opened the 12mm hollow bolt to the head and checked that there was oil coming out of it, fortunately there was.
So I learned a valuable lesson here, and next oil change I will fill the head with oil before I start the engine.
I am going to investigate the oil pump next time as well and maybe think about getting the higher volume one out of the RD08 model and making it fit.
What type of sealant is recommended for the pump body seal?

Good to hear, now usually after riding a few miles, the oil level in the frame should be ok.
That friend of mine was using Hylomar blue, a non-hardening gasket sealer. He also lowered the limits by grinding the pump housing, I don´t know if that can be done with the necessary precision if you are not an engineer ;-). So for me as a normally gifted screw up the best solution is to use a new oil pump every 50.000kms (they are not that expensive in the US), together with new seals in the clutch cover.
Theoretically, it should be possible to use a wide oil pump with the clutch cover of late Dommies in our RD02 engine housing without changes, at least someone claimed so, but I never saw such a combination in the web or in reality.

A little update on my scrambler - for some time I was looking for those nice finned valve covers that were made some 20 years ago for the XR600. cycle wizard is about to reproduce them http://www.cyclewizard.net/shop/finned-valve-covers-xr650l/ but since I was tired of waiting, I found a source in Germany. I know that the cooling effect on the cylinder head might be minimal, but at least they really look cool