NX250 Thread -- official ADV owners manual

Discussion in 'Thumpers' started by valvecrusher, Mar 17, 2008.

  1. muddyrabbit

    muddyrabbit Lost Boy

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    Well, Jill found the answer, since we're not really interested in ripping the airbox out, if anyone wants a very nice GSXR rear shock let me know. $30 shipped.
  2. fikse

    fikse All-season-rider

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    Like this one? :-)
  3. xckarlos

    xckarlos n00b

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    I think Germany is the best place to look for an nx 250. I am from Szczecin (in Poland for all the other nxers) and I got one for my girlfriend last year. I know most of the bikes that come up on mobile.de are in west of Germany, but if you are patient you will eventually find a bike near our border. We got ours for 1350 euro, it's a 1994 bike with 16000kms on the clock.
  4. Keisler

    Keisler n00b

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    Roger that, Fikse. Also need the rest of parts. Hoping to find used readily here, but I can break down and buy new.

    Thanks for the lead! :thumb
  5. Keisler

    Keisler n00b

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    Hi Pavlo,

    There are three NX250 dominators for sale on ebay Germany. Two look like '90 models. The third is a. Series 2, '94 model. That would be the machine to get all other things being equal.

    I was writing you a reply last night but fell asleep while typing, so you probably missed on of them already.

    Good luck and let us know. I will crate mine up and ship it if you cannot find one.
  6. Sambucas

    Sambucas travelin.tk

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    Just a short question: How to know when your cam chain is worn and needs to be replaced?

    In a later post I will ask the long version of this question, including the stuff that happenend to my NX250 engine...

    Thanks for the answers already! :)
  7. muddyrabbit

    muddyrabbit Lost Boy

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    You either have enough experience to know, or you ask someone, or you get a chain wear gauge. Is you chain tension adjustment maxed out?
  8. tntmo

    tntmo Oops, I did it again.

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    I have a crankshaft waiting to be removed soon and two bent exhaust valves that probably matches items in your possession.

    The chain wasn't worn to the point where I figured there would be a problem, the tensioner still had plenty of tension on the chain. I think the chain wasn't worn, but rather the tensioner failed.
  9. scrambler66

    scrambler66 Been here awhile

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    A worn cam chain will rattle softly at first, after a few 10000km, the rattling will become stronger. If the tensioner failed, it will make a lot more of unpleasant noise - was that the case, just before the engine died?

    There was an interesting post from mass out, I've tried this, since my engine was rattling the last 28000 km or so - now the rattling is gone, but I guess I really should change the cam chain now :D

    There is something I have to add to Mass out’s consideration. When the rattling became really loud, I tried his fix described below. But at my Nixie it was not possible to turn the adjuster while the engine was running. With the screwdriver at the adjuster I could feel that the adjuster was pushed back and forth by the cam chain while running, so that’s where all the noise came from. Only after shutting the engine off it was possible to turn the adjuster and fix it as described by mass out. BTW: the tensioner was only 28.000 km “old”, I changed it when the rattling began at 70.000km.

  10. Mass Out

    Mass Out n00b

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    Hello,

    When I first started work on my 1989 NX250, it was making a lot of ugly metallic sounding noise. This noise was not the same as what you would hear with excessive intake/exhaust valve clearance.

    I think it is very important for us to do what is necessary to educate our ears as to what different out of spec or failing internal engine components sound like. The sound of excessive valve clearance should have a clear and regular tempo that increases with engine RPM. Timing chain issues, on the other hand, should not have this regular tempo sound characteristic, For me it was an ugly, chaotic, metallic noise.
    Excessive valve clearance: Relatively (compared to a slack timing chain) pleasant sounding with even tempo.
    Slack timing chain: Dissonant, nerve rattling, metallic, ugly sound.

    I would like to comment on scrambler66's post # 5349.
    Provided you use the correct tools (I listed the tools I used in my previous post), you can definitely access the tensioner's internal adjustment screw with the engine running. Doing this will give you a great education on the sound of a slack timing chain. It also teaches you how much tension the timing chain needs to run relatively silently. It was more than I thought it would be.

    Finally, when insisting on using a somewhat worn and stretched timing chain (not recommended), you will have to seriously consider modifying the tensioner, as even a new tensioner will probably not work well on a timing chain in this state of wear.

    Take care.....
  11. fikse

    fikse All-season-rider

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  12. Sambucas

    Sambucas travelin.tk

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    Thanks muddyrabbit, tntmo, scrambler66 and Mass Out for your replies! :)

    Indeed it sounds like we have the same problem as you have experienced and know about.

    So our engine died suddenly while driving 60-70kph with about 5000rpm, after a loud tick and then a series of ticking sounds coming from the engine. It then wouldn't start anymore, even though spark and fuel were fine.

    After taking of the valve cover, to check the timing, we noticed that one of the links of the cam chain was broken. (later we found another link broken, so 2 links broken in total on this cam chain!) Also the cam chain couldn't be bended easily, as if all the links had seized up a little in some weird way. A new cam chain is very 'fluid'.

    [​IMG]

    [​IMG]

    More close inspection revealed the crankshaft timing chain gear was stripped of about 5-6 teeth. (And tntmo is right by stating that this is a stupid design!) Also the cam chain guide (piece of aluminium attached to the oil pump assembly) below the crankshaft timing chain gear had grooves in it and was broken. And the timing was off (2 teeth on the inlet side and 3 teeth on the exhaust side), so my inlet valves are bent.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    The strange thing is that when I compare the cam chain with the broken links with a brand-new cam chain, the length is identical (although it is not 'fluid', like mentioned before), so I presume that the cam chain is not to blame, but that we became a victim of the dreaded cam chain tensioner problem. (which I knew about before, I just didn't consider it critical enough to do something about it. (apply the cam chain tensioner fix.))

    [​IMG]

    Now I have a complete replacement engine (engine 2), to replace the first broken engine (engine 1). While engine 1 only had 45.000km, this engine 2 has 85.000km. Looking at the cam chain, it doesn't look like having 85.000km, so my guess is that it has been replaced at least once and so maybe this chain has 30.000km (?). I am not sure about the tensioner, but I will look to apply the tensioner fix, as recommended in this forum. (altough I don't fully understand the fix yet, but I will try it and get back to you if it doesn't work out.)

    But looking at the timing of the cam shafts, I notice that the cam shafts marks are not perfectly aligned with the cylinder head. They are a bit tilted towards the back of the engine, towards the cam chain tensioner. My thinking is that the cam chain might be a bit longer (worn) and the tensioner therefore more extended and therefore the cam shafts marks a bit more tilted towards the tensioner.

    [​IMG]

    Am I right in my thinking and is this cam chain worn and do I need to replace it???

    Basically I have 2 options:
    - Leave this cam chain and applying only the tensioner fix.
    - Replace this cam chain with a brand-new cam chain and applying the tensioner fix. The problem is that dismounting the old cam chain and placing the new chain (one piece) is not totally without risk. (removing clutch, crankshaft output gear and oil pump...)

    Thanks for your advice! :)

    Greetings from Ethiopia!

    Dave and Marly
    www.travelin.tk

    Ps. This is such a RISKY issue on this bike, somehow we should inform anyone on this forum right away to check for this issue and apply the right fixes! I suggest that we put it on the FRONT page, in a not-to-miss way? Or even create a separate section in this forum, just about this VERY important subject? (ruining your engine, because you are not aware of this, is NOT fun!)
  13. Sambucas

    Sambucas travelin.tk

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    Just another short question:

    The replacement engine has a bit tight valve clearance. The clearance should be 0.23 +- 0.03 mm and on this engine it is about 0.15 mm.

    The problem is I don't have shims and they are not available in Ethiopia. My plan is to drive to Nairobi, Kenia, which is about 2000 rough kilometers with this valve clearance. In Nairobi I should be able to find shims to adjust the valve clearance properly.

    Would it be very harmful for the engine to drive 2000 km with a valve clearance of only 0.15mm???

    I suspect it should be OK, but I am not sure...

    Thanks again for your help!

    Dave and Marly
  14. fikse

    fikse All-season-rider

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    Sambucas,
    I wish I could contribute to your challenges, but Im new to this bike/engine (and far from an mecanic), so I just want to give my support by saying: Best of luck, and :thumb for your trip :-)

    PS: I also have some challenge to understand the tensioner fix. And I'll guess Im not the only and last one wanting to do this. If you do have the opportunity, it would be lovely with some photos from when you apply that fix :clap
  15. Sambucas

    Sambucas travelin.tk

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    Hi guys,

    So I have just tried the tensioner fix as first described by Local Machine and later more refined by Mass Out.

    I think it should look like this:

    [​IMG]

    So where you normally have the short bolt and washer, just to cover the hole where you can tighten the tensioner with the screw, you now put a longer bolt (30mm) with a nut. Then put the tensioner to the right tension and tighten the bolt manually (so with LITTLE force). Then the bolt is hand-tight, you hold the bolt with a spanner and tighten the nut really well, to fix everything up.

    In the picture you can see how the spring in the tensioner is now unloaded, because the end of the spring doesn't touch the wall of it's groove anymore.

    Thanks to Local Machine and Mass Out for figuring out and publishing this fix! :clap

    (Ps. Here is a link to a document containing the descriptions for this fix from these guys)

    Any comments welcome off course!

    Dave
  16. Sambucas

    Sambucas travelin.tk

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    One more question...

    If I would like to replace my cam chain, I need to remove my clutch (been there, done that) and the primary drive gear.

    The manual states that I need a 'gear holder' to hold the gears when I remove the primary drive gear lock nut.

    I don't have a gear holder, what can I use instead???

    Just a piece of soft wood between the gears?

    The last time I remove this nut, my cylinder head was off, so I put a piece of wood between the piston and the frame, but now I don't have the cylinder head off and I don't wish to take it off.

    Thanks for any advice! :)
  17. tntmo

    tntmo Oops, I did it again.

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    A small wooden dowel might work, I usually use a piece of aluminum between the gears. I've also heard of people using a penny.

    As for your other post of riding on tight valve clearance....it probably won't hurt anything. Probably. Usually tight valves will make a motorcycle more difficult to start. If the clearance gets worse, you may overheat and burn a valve. With the numbers you listed, I would feel confident to get to your destination. What about robbing some valve shims from the broken motor? Might be able to mix and match some to make it work.
  18. scrambler66

    scrambler66 Been here awhile

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    Maybe the problem is not the cam chain, but the wear of the guide A and the cam chain tensioner (see below). If those wear out, it would probably have the same effect as a lengthened cam chain – the rod of the tensioner (even if it’s a new one) will push forward to the point, where the tensioner lifter is not able to apply enough pressure to the cam chain. If that is the case, changing the cam chain and the tensioner lifter will not solve the problem. When I finally overhaul my 100.000km engine I will take a close look at those parts and will replace them anyway. And I will measure the length of the old cam chain and compare it to the new one.

    Ok, but that wouldn’t help you with your two options to choose :D. But if I were you … if engine 2 is running without any inappropriate noises, I wouldn’t touch it – I totally agree with you that replacing the cam chain is a risky operation – that’s why I tried Mass out fix - and it worked fine so far for the last 2000km. And given the considerations above, it probably wouldn’t help anyway - a guy from our German NX250 forum also changed the cam chain because of the noise, but found out that afterwards the noise continued – I have to ask him if he noticed any wear of the guide and the tensioner.

    Anyway, this wearing out issue is apparently a slow process (mine was increasingly rattling the last 28.000km to a point where I couldn't ignore it any longer) so I suspect that the sudden breakdown of your first engine has probably nothing to do with it. Did you check the lifter operation as described in the manual (see below)?

    [​IMG]
  19. Sambucas

    Sambucas travelin.tk

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    Thanks for your answer, Scambler!

    To answer your first question of a few posts back: Yes, the engine was making strange noises, already for a long time:

    http://advrider.com/forums/showpost.php?p=14385022&postcount=3648

    http://advrider.com/forums/showpost.php?p=14428303&postcount=3659

    But the most common answer was that it was nothing to worry about, although a few people mentioned the cam chain.

    http://advrider.com/forums/showpost.php?p=14436596&postcount=3665

    I didn't have enough practical mechanic experience to understand the sound was the cam chain (if it was that sound).

    Now I know...

    The cam chain tensioner / lifter works according to the manual. I actually played around with 2 different tensioners before we started this travel, so see if I could make the sound go away. But it was all with the same half-worn chain, so same result, obviously.

    My cam chain guides seem to be OK and not too worn, except for the damage that the broken cam chain link did, now they are scrap. But they didn't seem to be so worn out as to lengthen the cam chain.

    I will run the replacement engine with the current cam chain and see how it sounds and then decide to change the cam chain or not.
  20. fikse

    fikse All-season-rider

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    Im also into suspension, both front and rear. Most probably I will go for Hyperpro all way. Most expensive, but also seems to be first class. In meantime, when raising funds (flirt my wife for some months...) I'll go for an ultracheap ($40) yellow SV650 and Hyperpro progressive in front. I talked with a Hyperpro dealer, who wrote excactly this: "It is just regular SAE40 fork oil, with a air gap of 150mm on this bike".
    So, SAE40 is a new one (for me), and air gap is 107mm as standard... That's a new twist in making better suspension! Maybe this 40-oil and 150 gap is something worth to try even on OE springs? :wink:
    Regarding oil brand/supplier, I have yet to see any neutral / objectively review. Personally I'll stick to well-known brands, who get's good results in motor-oil reviews. Until anyone convince me there is something brilliant better product than what i.e. Castrol/Valvoline does :thumbup