WR250R Cam Chain help needed

Discussion in 'Thumpers' started by simonpig, Apr 17, 2012.

  1. simonpig

    simonpig droppin' jewels

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    I don't know? I removed the screw and the hex bolt to see what would happen which was nothing really. If I could take the unit apart, I might be able to figure out if the there is blockage in the oil paths, but looks like the unit was designed to be forever locked in the cast.

    #21
  2. markk53

    markk53 jack of all trades...

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    Nice to know the kit functions properly in regards to the cam chain adjustment, now to correct the issue with the nut.

    I don't want to file flats, because there will no longer be any zinc coating on that part and it will rust. The only way I would do that is if I can get some sort of plastic or rubber end cap like a tire stem cap to cover the end in an attempt to avoid rust. There other possibilities though.

    I looked at the pictures, but am not totally sure if I am seeing things as I think I am. I may have a solution I use on the KLX250. I use an allen nut from a Yamaha SR500 exhaust - IF there is any clearance for it. It is 13mm in diameter, I am not sure I see that much clearance there in the pictures so you will have to let me know. I can turn the nut down tight against the end of the bolt and with a dab of blue LocTite on the thread it should stay put. I can also use a shorter bolt since it appears you cut about 10mm off the 110mm bolt. Let me know if there is 13mm of clearance there, otherwise it is plan B.

    If that can't fly, I will look at using an M6-1.00 adjuster bolt with the same jam nut/acorn nut set up since that should clear. The pressure on the bolt is linear, in compression, and in line with the center axis of the bolt so the smaller size will work fine. It will just look small. Not a big deal. Shoot, I think that's the size of the thread on the Tokyo Mods tensioner is even smaller, possibly an M5.

    We will see if the allen nut can work first. You can see it below by the exhaust on the KLX. We went to that because they couldn't access the adjuster that easily when a large diameter aftermarket exhaust is used.

    [​IMG]

    Hopefully there is enough room for the allen nut to turn without hitting the casting. I use the jam nut on the KLX because I prefer to lock the nut against the allen nut, which would not damage the threads at all and the jam nut cost is only about a nickle.

    Get back with me and I can mail out the allen nut if it will work. Otherwise I will get bodies with the smaller thread made for me.
    #22
  3. Jedaha

    Jedaha Adventurer

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    Great Documentation simonpig, I thought it was going to be close re starter motor clearance.
    Great tensioner Markk53, sign me up for one, I'll discuss this with Email.

    Typically how much spare thread would you need for adjustments, I guess your just taking the wear out of the guides, more than the stretch out of the chain. (Unless you have an F model that is.)

    I'm Happy to order one with the allen key end, all I'd ask is don't lock tight it on, I'll lock tight at this end after the fit is successfull. (I don't mind if I have to file the end square with a dab of paint, after tensioned)

    Also I can take my valve cover off (want to check clearances anyway) and observe the timing mark etc, to see if this is risky to do blind. From what I've read, so long as they don't insert a loaded automatic tensioner, things should stay put, my only worry is can it hang lose on the crankshaft end and jump a tooth there. I think there are some little guides down that end to maybe prevent that, not sure.

    I noticed a photo of this that simon took, (a page back) and it looks like it holds tight to the gear teeth at one point and probably won't jump down the bottom.
    (but its a big probably if it does jump)
    #23
  4. simonpig

    simonpig droppin' jewels

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    The current bolt is an M8, yes? The allen nut solution MIGHT work if the adjuster bolt were an M6 and the odds are even better with an M5 bolt as we are gaining clearance from the threads of the adjuster to the starter motor as the bolt gets skinnier (assuming allen nut outside diameter gets smaller with bolt size getting smaller.

    There is essentially almost no clearance from the adjuster thread to the bolt on the housing of starter motor. Its fortuitous that the starter motor sinks in at that location, otherwise, I don't see an type of simple elegant solutions beside the stock tensioner.

    As long as you can find an long allen bolt with same (or smaller) outside diameter of the CURRENT threaded adjuster bolt, it will clear—anything larger in diameter is no good (ala acorn nut). Anything shorter doesn't really help because the clearance issue starts 2–3mm after the jam nut in the pictures I sent.

    Another thought is that if the housing could be half the thickness of the current one that would help gain you some clearance?



    #24
  5. simonpig

    simonpig droppin' jewels

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    You don't need to take the valve cover off to replace the OEM tensioner. The crank end is VERY secure, and the cam gear end will stay put when you remove it. Just pull the stater and install the new tensioner turn in until theres a slight resistance and then fine tuning with the bike running.

    Just make sure you don't forget turn in the adjuster to take up enough slack first before electric starting.

    #25
  6. markk53

    markk53 jack of all trades...

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    Got it covered. I'm going to slot the bolt end so it can be finger tightened with a flat blade screwdriver, then a plastic cap put over the end (tire air valve stem cap) to try to keep the slot from rusting. I know the bolt should NEVER be tightened to the point where the slotted end would not work, so that's the plan at this point.

    Thought of it while on the road coming back from Springfield. Incredible races both the TT and THE MILE. Talked briefly with Henry Wiles, what a great kid. Reflected in his comments and just the look in his eyes when talking about the races. I thanked him for them putting on a good show in the races. He then took a moment to talk with us about the races. We said something about the track (great) and the heat (hot). He commented about feeling a breeze on the front straight and feeling the wind push a bit on the back straight. Then he asked us if we were at the TT and we said yes. He commented about how great the races were and if we enjoyed them. Of course we did then we asked about the tightness of the track and about Peoria. He had total enthusiasm describing it and all. Odd thing, he never once commented about his results at the TT - he won - or his record at Peoria - won seven of the past eight races 04-06 and 08-11 - just the enthusiasm about the tracks and the races. No ego massaging needed, all enthusiasm.
    #26
  7. simonpig

    simonpig droppin' jewels

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    That could provide you enough clearance from starter motor if the bolt were cut to the length of the threshold of the OEM maximum adjustment. The formula being:

    (length OEM adjuster juts into case (51.5 mm) + thickness of your housing + locking bolt height + length of additional thread needed for tire valve stem cap + maybe 1-2 threads to compensate for the depth of your slot)

    With this formula. As soon as the tire valve stem cap cover interfaces with the adjuster bolt, you know you've hit the maximum end of the adjustment for the tensioner and your chain is no longer adjustable.

    #27
  8. markk53

    markk53 jack of all trades...

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    That's the plan. There is no need for any significant leverage factor so a screw slot is easy and a good solution. I will be doing up a few of them and send you one unless you simply want to cut the one you have down a total OAL of 95mm (per below info) and cut a slot in it with a hacksaw or small grinder wheel (Dremel) then swipe an air cap from some car somewhere... :evil It will have to be plastic, because it will be crossthreading, valve stems aren't M8-1.25 and there is nothing out there in that thread that I found readily available. Let me know

    I have the inside engine distance at 51mm plus the body/flange nut/air cap stack up at 34mm plus 10mm adjustment range equalling a total of 95mm. That is pretty much exactly the length of a 90mm hex bolt including the head thickness, which is what I will be using.

    Thanks for the pictures and input so far. :clap

    In a quick afterthought, I may try dipping a bolt in some vinyl tool handle goop, let it set up then unscrew the resulting "cap" and screw it on the slotted bolt. Might work okay and is worth a try.
    #28
  9. simonpig

    simonpig droppin' jewels

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    Would you send me one. Thanks.

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  10. markk53

    markk53 jack of all trades...

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    Will do.

    I looked at a WR while at the shop Saturday. I see the problem. The slotting should work. I don't know if there's enough room for a valve stem cap or not. A dab of fingernail polish or a dab of silicone seal would work to keep from having the sawn slot rusting. It's an esthetics thing, not really functional.
    #30
  11. skierd

    skierd Wannabe Far-Rider

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    I think I'd be interested in trying one of these things as well. Getting a nice clatter from the cam chain side of my motor on most cold start ups now that goes away a few seconds after, thinking the tensioner might have gone after nearly 40k miles. Think its possible to get the MCCT on without removing the starter?
    #31
  12. gloud

    gloud Been here awhile

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    As far as the solution and the end rusting you can get a small zinc coating kit from eastwood . it would only take a few mins with each one to get it coated. Good product.
    #32
  13. markk53

    markk53 jack of all trades...

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    Thanks for the Eastwood tip, I will be doing that. I'm thinking the screw slot is the ticket for this one. It could be done on all of them, but I'm thinking accessability will make it too difficult for some. This one requires the slot though (but saves a $5 Yamaha exhaust nut, keeping the price on it at $30 plus shipping which is a good thing).

    Second one got sent out to Australia. If this solves some WR problems it will become a standard stock item for me. Two on the shelf presently. Email me from here if interested. From what I see the part should be able to be installed without starter removal. The problem was starter interference with the acorn and jam nut I use on the end of the adjuster bolt.
    #33
  14. Jedaha

    Jedaha Adventurer

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    I just had a look at my WR and I think the bottom tensioner allen screw will be a real challenge with the starter motor in place. In one of simonpigs photos on previous page it looks do-able, but I think his starter is still partially removed at that point check your Wr out and you will see the bottom screw is buried pretty well.

    Skierd .. I'm the guy from Australia waiting on the tensioner, so I'll let you know if the starter needs removing. Won't have my tensioner for another week at least due to shipping times.
    BTW. Have your valve shims needed adjusting after 40k miles?
    #34
  15. simonpig

    simonpig droppin' jewels

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    You will need to remove the starter, but it's no biggie. 2 Allen screws and a grounding bolt. It's press fit. Can't remember but i don't think you even need to remove pipe/mid pipe.

    #35
  16. skierd

    skierd Wannabe Far-Rider

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    Jedaha - The intake valves were at their lower limit, and the exhaust valves were slightly too tight when I had the valves done at 25k miles. I'll open it back up around 50k to see how everything's doing probably, might do it if/when I order a MCCT though.

    Simon - thanks for the tip!

    Mark, I'll email you in the morning.
    #36
  17. Jedaha

    Jedaha Adventurer

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    Got my MCCT from Mark today.
    Installed it tonight, assumed Mark had trimmed it to Simons recommendations, but I had to remove it and cut 15mm from the length to make it miss the starter. (Mine was even hitting the recessed bit (just rubbing on it))

    Because there is only 22mm Travel in the auto tensioners piston, so long as there is 22 mm left behind the locknut after tensioning, you should have full adjustment capability, which I have, more than, also I have 11k kms of wear in the guides and chain, so I'd say Mark, you can safely ship the tensioners with the 15mm cut off the length.

    Unfortunately my weird clatter noise is still there, even after adjustment of MCCT. Therefore its safe to say the noise is not the Cam chain clattering, but what is it. (Thanks Mark, you saved me $300 Australian in the diagnosis)

    Could it be something to do with the de-compression mechanism on the cam ??
    Something to do with the starter engagement mechanism??

    It happens when you rev the bike (stationary in neutral), and quickly shut off the throttle, as the revs fall back down, abruptly near the mid to bottom of the revs, there is a weird clatter/ vibration, which you could swear was a rattling chain type of noise. ???????????????????
    Unfortunately I don't have another WRR to compare it to.
    Even my mechanic mate said what the hell is that noise?

    Any Ideas anyone.
    #37
  18. simonpig

    simonpig droppin' jewels

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    Is the noise cause for concern, and is the bike running rough? If you've hit the stock chain tensioner's OEM adjustment range into the engine (~51 mm), then it's either the guides have worn, or the chain is stretched.

    At this point you're going to need to pop the top and check tolerances of the moving mechanical parts to check for wear both visually and maybe with a caliper. Your bike has fewer miles than mine so it would be odd for things to wear this fast, but in my search for answers on the clacking, I did find an instance where someone need to replace their chain at around 15K.

    Beyond valve adjustment check, my guesses are:
    • Worn chain guides
    • Stretched chain
    • Timing is little off (maybe because of stretched chain)

    Let us know what you find.
    #38
  19. Jedaha

    Jedaha Adventurer

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    I thought the noise was cause for concern, thats why I thought it was worth replacing tensioner, as yamaha have apparently changed the design a couple of times since the 98 model. And it did sound like chain clatter.

    I think you misunderstood my post about my adjustment, I have plenty of adjustment left in my manual tensioner. Its probably about 35mm into the engine at the moment, if that.

    I was going to pop the valve cover off and check my valves, but at 11,000ks. I'm pretty sure it will be a waste of time, from what others have found.
    However after what you've just said, I'd be more interested in timing mark alignment, as with my WRF the chain was stretched at 6500k's (Reving harder though.)

    I've only owned the bike for 1,100k's, so I can't really say how or if the noise has progressed.
    I still have the Wr250F (that I can't sell, no-one is buying at the moment) that doesn't have the noise. I know they are very different motors. However.

    Because I can get good tension on the cam chain, I can't see how any of the timing chain mechanics are involved now.

    I spent most of the night looking in the service manual.

    Since this is my first electric start bike, I'm curious how the starter clutch engages/ disengages, and if it could vibrate at a certain rev, looks possible.
    It looks like it sort of free wheels on the back of the generator rotor, until it is actually rotated by the starter motor and engages on the rotor?
    I could imagine how it would be possible for this to shudder at a certain revs.

    Anyway I'll keep you informed, I'll probably take it into the dealer and give them a listen.

    I'm not going to go too overboard on this.
    After all I bought this bike because I was sick of the maintenance on the F, and now I can just ride to the trails and enjoy that just as much.
    #39
  20. markk53

    markk53 jack of all trades...

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    One possibility, but first would it be better to drop 20mm shorter on the bolt or just do 15? This is what I need to know. Will a 20mm shorter bolt work with the screw slot? If so, I will do it. I just don't want to be too short. Email me with notes, it is quicker for me to adapt.

    Now for another possibility. If. by some long shot, the Yamaha decompressor is like that of the KLX650 it is possible there is a spring that has fallen off. I have had that happen twice on my KLX. Once the spring ended up in the sump with no bad effects, the other time it stayed in the head area where I recovered it with a bit of damage to the spring but nothing else. It made a lot of clatter at low rpm.

    I'd take off the cam cover and take a look. Another thing is you could "nose around" with a mechanic's stethoscope to see if you can isolate where the noise is coming from. A long handle screwdriver with the handle against your ear and the tip touching around the engine works too.
    #40