Because in 1993 we went to our preferred area, the French Maritime Alps, twice.
In the Alps, the standard tires were completely unsuitable in the mud; there were no AX41 at the time. While browsing through the spare parts lists, I noticed that the XL350 and NX250 have the same brake shoes - so I got a XL350 rear wheel (which wasn't that easy back then without the web or even Ebay) and tried it out - it fits without any changes and the first 17 inch conversion was born. More info about different rims see NX250 wheel swap viewtopic.php?t=864 . In order to reduce the seat height that had increased due to the larger wheel, a shorter WP shock viewtopic.php?p=22722#p22722 was installed .
when a few friends offered to take us on a short trip to Africa from Kenya to Namibia in 1994, we jumped on board straight away. The NX250 survived the Africa tour (travel report can be found here https://nx250.de/afrika-1994.html) without any problems.
Unfortunately my NX650 didn't survive Africa quite so well - cylinder head damage. That's why 1995 I started driving the NX250 myself and was immediately impressed by its handiness.And because my family-building phase began at the same time, the time of big motorcycle tours was over for the time being - but the NX250 has been used as an everyday and winter vehicle ever since. It is ideal for this thanks to the low-maintenance engine. In 1996 she got a 21 inch front wheel and an enduro headlight from the XT350. The paintwork is based on the 1993 version - I didn't know any better back then
. After just two winters, the first manifold was rusted through and so was the exhaust - the latter could be welded again.
In 2007 the 80,000km mark was broken. Apart from a timing chain tensioner, a CDI (what else
, a clutch cable and an gas cable, nothing ever had to be repaired until then. Oil consumption still around 0.1 / 1000, despite 7000 km through Africa and although it was mostly driven at full throttle. Chain sets were due every 12,000 to 15,000 km, which was annoying because of the expensive swing arm grinder, which usually had to be replaced at the same time. Because replacing the manifold every two winters was annoying in the long run, it was flame-sprayed aluminum viewtopic.php?p=4154#p4154.
In 2009 the 90,000km mark was reached. In the meantime my NX had survived two more winters, the main silencer had rusted through again, this time it was unweldable. But the aluminum flame-sprayed manifold, which no longer gives the Gilb a chance, has proven itself. Later I also had the silencer flame sprayed. At the beginning of 2011 it looked as if the endurance test would have to be stopped at km 97,700 - the scary rattling that came from the engine was more reminiscent of a BMW with a completely exhausted valve train and the aluminum shavings in the oil filter also warned of the need for immediate action . Since the NX does not have any rattling rocker arms, the cause was immediately clear - the timing chain had stretched to such an extent that the timing chain tensioner could no longer do its job. Then I stumbled upon a tip from the ADV forum: the tensioner can be fixed with a longer Allen screw and the chain is tensioned correctly again viewtopic.php?t=2534 . After oil consumption rose to 0.3 liters after 80,000 km, I tried synthetic 10W40 for the first time in a long time at 98,000 km, which reduced consumption slightly again.
On June 2, 2012 the time had finally come - 100,000km with an unopened engine were achieved! Unfortunately, I don't have to take the usual 99,999 speedometer picture because it has had a KLX speedometer on it for 10 years.
At 102.000 km I changed the timing chain, but after a few hundred km the engine started to make rattling sounds again. At this time I was testing a prototype digital CDI with more advance ignition – apparently this put too much stress on the already worn out conrod bearings. If I had overhauled the engine at this point, it would have saved me a lot of money. But I was kind of in denial (I thought the rattling was due to poor quality of the new cham chain) and it was at the beginning of the winter. And I urgently needed the NX because I didn’t want to corrode any other of my bikes. On a drive back home in October 2013 the rattling became suddenly frightening - but I was on a highway, which is not a good place to shove your bike along. I tried to reach the next exit ramp, which was only 2 km away. That was the second big mistake, since it turned out that the lower connecting rod bearing disintegrated, causing the piston knocking on the valves.
After a few hundred meters the engine finally gave up (for the first time ever) because the piston finally had beaten up two valve, and with no compression left in the cylinder I had to shove (for the third time in 15 years, once I had a broken chain link due to poor maintenance and the other time a cheap Chinese CDI failed) the NX to the next exit. Which is a special treat on a German highway when cars passing you only inches (actually most highways have breakdown lanes, this one didn`t) away with 180km/h and more …
oct 2013 - shortly before desaster
During disassembling the engine, I noticed only very few signs of wear. The gears were still in good condition, except for one damaged by a needle of the disintegrated rod bearing. The oil pump was ruined by brass flakes of the rod bearing. Surprisingly, the cams did not show any signs of damage or wear. A bit more damage was done to the valves – two of them were screwed by the piston (so I guess I could call myself valvecrusher as well
). The only other wear of the cylinder head were two worn out valve guides. The piston and piston rings were still within the limits given by the manual (after 105.000km!), however the piston skirt showed that the piston was just about to seizure (likely due to the ruined oil pump). note that the upper two valve pockets show signs were the piston hit the valves
Amazingly, the cylinder was still like new, even the cross grinding was still visible – this nicasil coating really does a good job. Besides a new crankshaft, I only had to replace the sealing of the water pump and of course all engine bearings.
So after this experience I would recommend the following.
If the Nixie starts to rattle take a look at the oil filter first. If the metal flakes in there are silver colored, it’s the timing chain grinding at the cylinder head => change the timing chain (usually necessary around 80.000-100.000 km) .
If the shavings in the oil filter are golden colored, it’s brass from the lower conrod bearing. Don’t drive any further and get yourself a new conrod. Unfortunately, OEM connecting rods were never sold separately – and a test of a chinese conrod endet in a catastrophy viewtopic.php?t=2379&hilit=conrod
When the engine was stripped down for a rebuild it turns out there was a long piece of swarf stuck in one of the metal oil pipes that feeds the camshafts....this must have been lodged in there from the factory and I only discovered it when drying various parts with an air line 
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