NX250 Restoration

[clemkevin]

On the final photo, you have two places circled. On the upper circle, what should I be considering? I checked that there was .5mm of clearance on the lower one.

Doing fork seals today. These are easy!

[scrambler]

On the upper circle, what should I be considering? I checked that there was .5mm of clearance on the lower one.

Below is the default accelerator pump clearance (about 0.5mm), above how to adjust it. But your ACP seems fine. Still, I suspect there are gremlins in your carb, just wondering where. Hard to tell without pics of your carb or a crystal ball . Is yours a california model? they have a gadget for the tank ventilation, if removed, two holes on the carb must be closed download/file.php?id=19&mode=view

[clemkevin]

Is it 5mm? I thought it was .5mm? Dang, maybe that's my issue.

Should the lower hammer of the accelerator pump linkage (with the adjusting bolt/nut) be touching the choke cylinder? I noticed my choke starts to push on this part of the linkage at full choke, adding some fuel. Should I back this off?

[scrambler]

Is it 5mm? I thought it was .5mm?

my mistake - 0.5mm play is of course correct for the accelerator pump, the choke lever should have at least 5mm play as shown on the pic

NX250_Marlboro_Beschleunigerpumpe (1).jpg

if the play of the choke is too small, loosen the nut of the lever arm and hold it when you tighten it again

[clemkevin]

Thanks for your help Scrambler!

So, I bought the 21/17 wheel set combo, and now it's too tall for my girlfriend! I still want to enjoy this bike, so I'll keep those wheels for me. And I can keep the front as a spare for my XR400. I can keep a DOT tire on one wheel (for the NX) and a more aggressive tire on the XR400.

Instead, I've ordered up a set of tires for the OEM wheels, 70/100-19 and 90/100-16 dirt bike tires. I'm hoping the rear isn't too small.

One thing I've noticed with the CRF230f springs up front, was that they were slightly narrower than the OEM NX250 springs. They seem to make a lot of noise in the forks, I'm assuming they're binding in there. Kind of annoying... Anyone else notice this problem?

I also found an air leak on the intake boot that attaches to the cylinder head, so I had to order up a new O-ring. Am I going to need to drain the water system to remove that boot? I noticed the thermostat is a part of the assembly.

[scrambler]

I also found an air leak on the intake boot that attaches to the cylinder head, so I had to order up a new O-ring. Am I going to need to drain the water system to remove that boot? I noticed the thermostat is a part of the assembly.

I've also tried changing the o-ring without draining the coolant. But it's a mess, because a lot runs out of the hose. So I usually drain it. viewtopic.php?p=18020#p18020
I've never tried the CRF230 fork springs - I always replace the short top springs with spacers viewtopic.php?t=1668.

[clemkevin]

I replaced the O-ring today. I sprayed starter fluid where there had been an air leak in the intake boot o-ring before, and the idle didn't jump. Unfortunately, there is still an air leak somewhere and the bike wants to hang between 3-4000rpm after snapping the throttle. I can get the bike going, but now the bike won't rev past 4000rpm. It misfires and stumbles. Always a new step to figure out. I think I'll pull the spark plug and see what it might be able to tell me.

I was able to ride the bike up my driveway, which is a 2-mile dirt road winding up the side of a hillside. The front feels just a bit too springy with the CRF230 springs. If they were a bit shorter, I think they would be great. But because they need to be compressed to get the fork caps on, the resulting preload just makes it pogo. I think I'll try the XT350 springs next. They were the same diameter as the CRF230 springs, but about 1.5" shorter. I'm sure they're a bit softer, too.

I noticed that with the 5.10x17 rear tire, it feels too high in the rear. I'll wear the tire out, but definitely wouldn't recommend that size for anybody else, even if it does just barely fit with a 45t rear sprocket and +2 links on the chain.

[clemkevin]

So, summer break started (this was my last year as a teacher, taking some time before I start my new career) and I've had time to fiddle with the NX250.

Since my last update, I removed the carb and tried cleaning out some of the passages better. I also have an ultrasonic cleaner coming to me this week, so I can take another crack at it. The bike starts up just fine. Idles just fine. I even took it down the road and it rips! But when I crack the throttle quickly from dead idle it stumbles or dies. IF the bike is leaned over on its sidestand, the revs jump up to 3000-4000. If I'm riding up above 2000-3000 you can abuse the throttle all you want. Totally tolerable for now, but I'll need to fix that eventually.

I have some starter fluid and noticed if I shoot it at the top of the carb, it gets a bit of a jump. I suppose I could replace that upper seal and see if that helps. Does anybody know where I can buy that paper gasket? I'd like to avoid buying the whole seal kit.

Looking for any other suggestions worth trying.

On another note, what are my options for a kickstand swap with this taller 17" rear? The bike is really unstable and leans pretty far. It works for now but I'd love something a bit safer.

[scrambler]

Idles just fine. I even took it down the road and it rips! But when I crack the throttle quickly from dead idle it stumbles or dies. IF the bike is leaned over on its sidestand, the revs jump up to 3000-4000.
I have some starter fluid and noticed if I shoot it at the top of the carb, it gets a bit of a jump. I suppose I could replace that upper seal and see if that helps. Does anybody know where I can buy that paper gasket?

As far as I know, you can't get the topset paper gasket separately anywhere in the US. But I suspect that it's not the gasket, otherwise it would just jerk a little and not cause the severe symptoms you describe. There is probably dirt somewhere in the carb, so ultrasonic cleaning is necessary (or one of the previous owners made some mistake in carb assembly, without pics or a crystal ball it's hard to tell ). But only strong devices have enough power to get the dirt out. And you should only use special cleaners that do not corrode the aluminum.
The idle system seems ok, that the RPM changes could possibly be a problem with the float valve. I would suggest you get the Keyster kit KH-0858N for the NX250 carb - it comes with a new float valve and topset gasket. Also, the set for the NX250 seems to be out of production, so hurry up if you want one.

On another note, what are my options for a kickstand swap with this taller 17" rear? The bike is really unstable and leans pretty far. It works for now but I'd love something a bit safer.

Common problem with a harder shock or larger rear wheel. The only thing that helps is to weld in an extension.

[clemkevin]

Funny thing about the kickstand. I have an NX125 that's currently on the stand for a mechanical issue I haven't figured out yet.

I pulled the kickstand off of it, and it fits. And it may not be the perfect length, but it's longer enough to have been worth finding another on ebay today. Should do the trick.

I rode my bike down to the post office today just to give it a test ride. It's definitely a bit bouncy in the rear with the suzuki shock set at #3 of 7 on the preload clickers. I may have to pull it out and cut more of the ring off to reduce it. Chain was too tight, and with this 5.10 tire, there isn't much room to give it more slack, oops.

For reference, i attached a picture showing an example of the roads in my area. A great place to test ride this nx250.