NX250 Restoration

[clemkevin]

It's quite a story how I got this bike. I posted about my NX125 on ADVrider and somebody commented about how sad they were about letting their NX250 sit in a shop in a desert 10 years. I suggested they give it to me, so they did for $500. Not only that, they had a 600 mile drive planned and they dropped it off with me about 500 miles into their drive.

So as soon as I got it, I knew I wanted it to be as trail-ready and my NX125, which my girlfriend has been riding. (I love that bike by the way. I live up a twisty, scary ranch road on the Lost Coast in California. It's been a great commuter.) So I immediately purchased 21" and 17" wheels for the bike. I couldn't justify the 18" with the lack of good trail tires in such a limited tire size. I also found a pair of husqvarna footpegs my landlord left in the shop on the property he said I could use, which fit PERFECTLY. I also have CRF230 fork springs ready to go; though I may upgrade the forks in the future. I have Transalp forks, but I'm also really tempted to get XR250R forks.

As far as the current status of the bike goes, It's currently stripped down as I needed to clean the carb, reroute cables, add 1-1/8" bars with handguards. It's almost ready to start, except....electrical issues.

The bike has a new battery (charged), starter solenoid, cleaned the starter button contacts, but I'm getting no voltage on the starter side of the starter relay. When I push the starter button, the headlight dims, but no power goes to the starter. Not sure what is stopping this, and without a high quality harness diagram, it's hard to know without good electrical intuition (that I do not have).

So, here I am asking for help to get this sucker running ASAP, as my girlfriend and I have a trip planned to Moab in a month and I want to put as many miles on this sucker as I can before the trip.

[scrambler]

When I push the starter button, the headlight dims,

It's always like this, the light switch directs all the juice to the starter when you press the starter button. If the starter relay doesn't even click, check plug connections (red and yellow-red cable). Is the main fuse (20A, on the relay) OK? If I understood correctly, a new starter relay was installed - cheap ones come from China and don't necessarily have to work. So I would try the old relay, to check if you don't at least hear a click with it.

NX250 wiring diagramm eng starter.jpg

By the way, carburetor - there are two small O-rings that are easy to overlook, one on the mixture control screw https://nx650.nx250.de/albums/userpics/ ... hraube.jpg , the other on the jet of accelerator pump https://nx650.nx250.de/albums/userpics/ ... mmer_3.jpg (pics from viewtopic.php?p=14562#p14562 ).



The diagram is for European models, the only difference is the light switch. But it makes no difference on this issue.

[clemkevin]

So, I think I've come to find the source of the issue. I can jump blue/white and yellow/red and get the starter to jump, but when you press the button in, it connects black/white to yellow/red. Black/white is cold. Based on the harness diagram, it looks like that wire comes from the CDI. What to do next?

[scrambler]

when you press the button in, it connects black/white to yellow/red.

thats ok and blackwhite / blackred should be connected

NX250_wiring_switch.jpg

Black/white is cold. Based on the harness diagram, it looks like that wire comes from the CDI. What to do next?

Check the clutch switch (greenred cable) connections of the ignition switch and the CDI. Is there a shindengen label on it? Chinese CDIs are known for doing all kind of weird stuff.

NX250 CDI wiring.jpg

[scrambler]

by the way: if the switch should be defective - NX250 kill switches are difficult to get. I see you have a Transalp - it has a standard Honda kill switch (like XR650L or NX650) that adapts to the NX250 wiring harness viewtopic.php?p=14922#p14922

[clemkevin]

Woohoo, I got it! It was the upper switch. I just had to figure out how to take the assembly apart. It wasn't obvious the first time I played with it, so I overlooked it.

Now the bike is idling okay. But the intake box is making an audible sound like it's aspirating, and when I chop the throttle the bike wants to die. Only smooth inputs let me raise the rpm.

How many turns should I set the idle air control valve?

[scrambler]

Now the bike is idling okay. But the intake box is making an audible sound like it's aspirating, and when I chop the throttle the bike wants to die. Only smooth inputs let me raise the rpm.

sounds like there is an air leak somewhere (O-rings of the accelerator pump / intake manifold or carb cover gasket)

How many turns should I set the idle air control valve?

1 1/2 turns out.

[clemkevin]

Nice, thanks! I saw on ADVrider people quoting 2-1/8 turns.

I wondered if there might be an air leak. The sound is coming out of the airbox, but nowhere else. What is typically a culprit of this issue? It seems the intake manifold would be the worst case scenario. Does the o-ring go, or does the whole rubber unit start to leak? I didn't replace the upper gasket, but I supposed I can find a replacement. Are there any available online individually?

[scrambler]

I wondered if there might be an air leak. The sound is coming out of the airbox, but nowhere else.

sometimes the intake tube is shortened or the resonator is removed. https://www.cmsnl.com/honda-nx250-domin ... BihGsKZND8

What is typically a culprit of this issue? It seems the intake manifold would be the worst case scenario. Does the o-ring go, or does the whole rubber unit start to leak?

The O-ring of the intake manifold has the dimensions 37.4x2.4 mm. But it never actually leaks unless you remove the intake manifold. I don't know what was done to the carb, whether the jets are clean and not clogged, and whether the accelerator pump and mixture control screw o-rings are ok and in place.

I didn't replace the upper gasket, but I supposed I can find a replacement. Are there any available online individually?

Honda does not sell the orings separately. The honda gasket set (OEM 16010-kw3-014) is probably no longer available in the USA? But all necessary seals are included in the Keyster set, except for that little bellows on the accelerator pump.

NX250_carb_ seals.jpg

[clemkevin]

I did check the accelerator pump o-ring. It's old and pretty flattened, but seemed like it could still hold a seal. The only replacement o-rings I have on hand are slightly thicker and I'm worried about them restricting flow once they're tightened down.

The carburetor got a thorough bath, cleaning, and jets were replaced. The pilot screw o-ring was replaced as well.

I supposed I'll start it up later and shoot some starter fluid at areas of concern.