NX250 Thread -- official ADV owners manual

muzcuk · Jul 9, 2013

polarized said: ↑

I believe you are talking about the resonator for the air box.

I think it changes the sound of induction, not really sure though.
Click to expand...

Yes, it somewhat reduces intake noise. It is not indispensible, but it would be hard to modify for an expansion tank as it is connected to the intake manifold. It would be a pain to seal and it would cause catastrophic failure (water in cylinder) if the seal ever fails.

I have ziptied a 50 ml flask to my radiator which acts as a halfway proper expansion tank. It regularly overflows, though, I guess something in the range of 100-200 ml would be better.

Also, running without an expansion tank is not out of question. First time water expands, some of it pours out, when it contracts, some of the radiator remains empty. But after all, when water expands again, it fills the radiator. I don't see the problem in this, unless most of the water is somehow removed from the system. A lot of KTMs run like this.

Someone please correct me if I am wrong?

Jac Cambo · Jul 9, 2013

Thanks for that.

I think the difference between my KTM EXC and my NX is that the EXC is designed to be able to tolerate being far hotter than the NX.

On that I use a baby bottle as an expansion tank, cause coolant is both expensive and smelly when vaporising on a hot engine.

The NX system, imo, is supposed to be somewhat pressurised, where the ktm is not.

I could use a baby bottle on the NX, but will probably hunt down a replacement bottle.

muzcuk · Jul 9, 2013

Pressurized? No. What kind of pressure would the puny expansion tank provide anyways?

Free of air? Maybe. I remember someone saying that the radiator is supposed to be bled of air.

Though I can't imagine how that would be a problem with the pump that far below the radiator.

What is wrong with the expanding-water-filling-the radiator argument? So long as all internal volume is filled with water, should it not perform the same?

When I open my radiator with a cold engine, water level is far below 'full'. As the engine heats up I see bubbles rising in my expansion tank, so I assume the water inside is expanding and displacing the air in the radiator. When really hot, bubbling stops, so I assume the radiator is now full with water.

What do you think is wrong with this picture? Is the cooling system really supposed to be air-free? And why?

PTC · Jul 9, 2013

muzcuk said: ↑

Pressurized? No. What kind of pressure would the puny expansion tank provide anyways?

Free of air? Maybe. I remember someone saying that the radiator is supposed to be bled of air.

Though I can't imagine how that would be a problem with the pump that far below the radiator.

What is wrong with the expanding-water-filling-the radiator argument? So long as all internal volume is filled with water, should it not perform the same?

When I open my radiator with a cold engine, water level is far below 'full'. As the engine heats up I see bubbles rising in my expansion tank, so I assume the water inside is expanding and displacing the air in the radiator. When really hot, bubbling stops, so I assume the radiator is now full with water.

What do you think is wrong with this picture? Is the cooling system really supposed to be air-free? And why?
Click to expand...

Pressurized yes at about 11 psi. When the coolant reaches the caps pressure,
Which is 1.1 bar the. The caps spring/seal moves up and the coolant fills the
Overflow resivour . As the engine cools the coolant is pulled from the resivour
Back Into the radiator. Therefore eliminating the need for topping off the coolant that would be lost without a resivour . A proper system should have no air in it.
Air will get way hotter than the coolant ever would and it will increase the systems pressure by being Compressed. (You can't compress water/coolant)
Air can also cause a system bind by getting stuck and not allowing the coolant to
Circulate. By pressurizing the system the coolant also is more resistant to heat.
I always fill very slowly with the front of the machine uphill. Once "full"
Then run the bike and squeeze both hoses alternating squeezes (to remove a y air)and top off as needed. Go for a good ride and check the resivour and add to the res. to the mark. Use distilled water only as it does not have the minerals found in tap water. The minerals will greatly decrease the cooling ability and damage your pump and radiator . So pressure... Yes. Air no.

Jac Cambo · Jul 9, 2013

Good post PTC, thank you.

muzcuk - firstly, I don't put water in my bike. I fill it with coolant.

Secondly, if it overflows; the job of the expansion tank is to catch said overflow/ and not piss it onto my clothes. I've now got close to 60'000km on my daily NX, and this is a new problem.

It is a pressurized system, but thank you for the info on the resonance thingy.

Basically, imu, a pressurised system will overflow to the expansion bottle - but on cooling will cause the lost fluid to be drawn back to the rad/cooling system through a vacum effect.Essentially this removes the hassle of constantly monitoring coolant levels.

And I live in the tropics and commute in absolutely killer heat, so this is more important to me than if I were living in a colder country.

muzcuk · Jul 10, 2013

Thanks for the info. So I will upgrade to a decent reservoir, baby bottle sounds good. Its easier to ziptie shit on when you don't have any fairings to get in the way. :)

By the way I use distilled water. Coolant is preferable for colder temps where there is risk of frost, afaik, but what do I know.. But anyways, here is a true story for you, happened to me today :

You rebuild a nx, tune the carb, starts instantly, runs perfectly.
A few months later suddenly you start having trouble starting it.
When it starts it runs fine.
No, its not the CDI.
You change the oil, nothing suspicious.
One day when cranking you realize it spits a little water from the exhaust just before starting.
There is also some fluid seeping from the lower cylinder seal. Probably water.
Add my weird coolant habits to this, what do you get?

What I want to understand is this: If it is the lower seal (transmission-cylinder interface), I should have found water in the oil. If it is the upper seal (cylinder head-cylinder interface), why is the stuff seeping out from below..? And does this have anything to do with the air in my cooling system?

I will outright confess that I re-used the (metallic) head gasket but it was only because the one I ordered from ebay was like 2 mm thick and made of something entirely unlike the original.

Should probably get in there and replace both, right? Anything else to try before that?

By the way, Kampuchea, I saw your videos before. The traffic looks somewhat like İstanbul, so I sorta know what you feel riding through under the sun. Wish I had a gopro to show you around. Cheers.

Local Machine · Jul 10, 2013

If any of you guys wanna remove the expansion coolant tank you'll hafta go "waterless".
Evans produces a waterless coolant fluid, silicone based, that dont boil like water and most important, it dont expand like water does.
Its not cheap and the whole water circuit must be free of any water or moisture beforehand but it works some pretty serious magic.
Once you pour it inside the radiator, it lasts a lifetime
Code:
http://www.evanscooling.com/products/coolants/
http://www.evanscoolants.co.uk/
Thats what all them monster drag racer vehicles use nowadays.
These guys dont even bother to fit any kind of radiators on there rocket ships.
Pretty xpensive tho, buck a gallon plus the cost of the de-humidifier fluid.

Now as far as the lower weepin cylinder gasket, chances are that the four cylinder bolts need re-toqueing (thats the best case scenario of course)

muzcuk · Jul 10, 2013

Man, how I wish I could buy stuff like that in Turkey. You are worried about 50-bucks-a-gallon for coolant? Enter Turkey where gasoline costs $8 per gallon and cheapest engine oil is $15 per liter (~$60 per gallon). Add minimum wage of $500/month for flavor and cherish your first world privileges.

As for re-doing the cylinder bolts, as far as I remember 2 of them were directly under the cams, so that would require removing the cams and re-doing the cam chain. If I am going that deep I might as well do the gaskets, I guess.

Think I can remove the cylinder with the engine on the frame?

Jac Cambo · Jul 10, 2013

muzcuk said: ↑

Think I can remove the cylinder with the engine on the frame?
Click to expand...

Yes, absolutely.

Did valves and camchain on mine last December - and pulled the cylinder and piston for inspection at the same time with the engine in and the bike on a stand.

muzcuk · Jul 12, 2013

Hey guys,

Turns out servicehonda asks $87 shipping for $25 gaskets. I cannot source them locally neither.

Any volunteers to help me out here? Just get them from wherever, stick them in a bubble envelope and send them to me USPS priority, no tracking. Should cost around $10. I will send you the money through paypal and throw in an extra $10 for your inconvenience. PM me if you are interested.

Part numbers 12251-KW3-003 and 12191-KBK-611 , costs $18 and $5 from servicehonda.

I will try to open her up and re-torque the cylinder bolts this weekend, see if it helps. I am worried that the water will erode the cylinder while I am waiting for the gaskets. Bike actually runs fine after you get it to start. This is my daily commuter.

mito-nx · Jul 12, 2013

I have a set of new piston rings.
One has "R" and one has "RN" writen on it.
Can someone tell me which one is the top one?

mito-nx · Jul 13, 2013

Okay, found it.
R is the top one with the rounded edges.
RN is the second one wich has a square shape.

Jac Cambo · Jul 13, 2013

Muzcul - forget about servicehonda to Turkey. Why not try ebay Germany - much closer and has to be far cheaper on shipping.

I was adjusting the valves on mine the other day when it was noticed my oil was coffee coloured:eek1.

Water pump seals, fixed them for $10. Luckily no damage done, must have just happened a day before I went adjusting valves.

scrambler66 · Jul 13, 2013

Jacl-Kampuchea said: ↑

Muzcul - forget about servicehonda to Turkey. Why not try ebay Germany - much closer and has to be far cheaper on shipping.
Click to expand...

rrrrrrright, if you want German parts, eat dis http://www.ebay.de/itm/121892-Motor...torrad_Kraftradteile&hash=item5ae1e14e73#shId

(complete engine gasket set for 41€ plus 29€ shipping to Turkey)

muzcuk · Jul 15, 2013

Hey guys,

Following Local Machine's advice, I re-torqued the bolts over the weekend and it helped a lot. They were seriously loose, and I don't know why. If they get loose again I am locktite-ing the crap out of them. (also replacing gaskets for peace-of mind)

The oil was milky as fuck and I wish I was blind not to see my brand new piston bathing in it. But I know this happened within a week because the oil I drained last week was perfectly healthy.

As for the ebay gaskets, I already have a set like that. Be careful about those, guys, the head gasket that came with my 'set' is a 2 mm thick piece of shit that is made of 3 layers (cork-metal-cork). I am sure it would cause more trouble than its worth if I would ever put it in the engine. I would expect reduced compression and near-impossible removal compared to the original metal gasket. So that's what you get with a 40$ kit. You have been warned.

About servicehonda, they used to be reasonable. I did get my piston and rings and several other pieces from them with reasonable shipping. I usually order from wemoto.com in UK, they deduce tax for international orders and offer very reasonable shipping. But in this case the gaskets are non-stock and would take several weeks for them to acquire (I know from experience).

So I fixed the bike and changed the oil on Saturday and went for a ride in the woods. My starter engine died the moment I got out of the woods. Turns out I've worn through a set of brushes last week while cranking the shit out of her.

Little bastard sure is getting expensive to maintain. :)

muzcuk · Jul 15, 2013

By the way, I installed a slightly bigger (~100 ml) expansion tank and it fills when the engine runs, but does not drain when its cool. So the water expands allright but it does not get sucked back into the radiator.

What would you make of this?

PTC · Jul 15, 2013

Make sure the overflow hose reaches the bottom of the tank, is cut at an angle
And the tank is sealed and vented. Aside from that maybe kinked hose,or faulty
Radiator cap? Tank placed too low? Good luck & sorry she keeps breaking on you.

crobox · Jul 16, 2013

Ad in Flea Market section for some used NX250 plastics.

HERE

Also got other surplus parts, PM me if you need any of it.

Thanks

scrambler66 · Jul 18, 2013

thirstybuck said: ↑

I KNOW that I set the timing properly when I put everything together initially and when I checked everything out today the intake cam was off a tooth. (!) That might explain the lack of power I had coming back.
Click to expand...

  I actually never checked the alignment of the cam timing marks when checking the valve play. But as it turns out now, the intake cam was off two teeth, the outtake cam one tooth. I do not know how long my Nixie was running with this setup, but it could have been a long time. Because I also noticed a lack of power for some time. Interesting enough, a second NX250 I looked at last week had the same offset, and after correcting it, it was running much stronger. So it seems to be a not that uncommon problem.

tntmo · Jul 18, 2013

If your cam timing has changed like that, you may want to check the cam chain tensioner. It's a weak point in the system. If it fails, your cam chain will slip on the lower cam drive sprocket. This sprocket is machined into the crankshaft, and if the teeth get chewed up you need to replace the crank.

Ask me how I know.

Log in or Join

NX250 Thread -- official ADV owners manual

muzcuk Adventurer

Jac Cambo Booze Merchant

muzcuk Adventurer

PTC Turd polisher

Jac Cambo Booze Merchant

muzcuk Adventurer

Local Machine Been here awhile

muzcuk Adventurer

Jac Cambo Booze Merchant

muzcuk Adventurer

mito-nx Dutch Humor

mito-nx Dutch Humor

Jac Cambo Booze Merchant

scrambler66 Been here awhile

muzcuk Adventurer

muzcuk Adventurer

PTC Turd polisher

crobox Been here awhile

scrambler66 Been here awhile

tntmo Oops, I did it again.

Log in or Join

Useful Searches

NX250 Thread -- official ADV owners manual

muzcuk Adventurer

Jac Cambo Booze Merchant

muzcuk Adventurer

PTC Turd polisher

Jac Cambo Booze Merchant

muzcuk Adventurer

Local Machine Been here awhile

muzcuk Adventurer

Jac Cambo Booze Merchant

muzcuk Adventurer

mito-nx Dutch Humor

mito-nx Dutch Humor

Jac Cambo Booze Merchant

scrambler66 Been here awhile

muzcuk Adventurer

muzcuk Adventurer

PTC Turd polisher

crobox Been here awhile

scrambler66 Been here awhile

tntmo Oops, I did it again.