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Thread: Yamaha NXC125 20,000km

  1. #1
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    Yamaha NXC125 20,000km

    As the title implies the scooter is coming up on 20K. I've checked the tappets to find them all a little loose and set them to about .003". Strangely it seems to have knocked a bit of performance off, most noticeably up the hill from Stanley St to the NW motorway. I'm gonna set them loose again to see what happens. I need an airfilter and the owners manual says the belt should be changed. Oil changes have been done.
    Does anyone have advice on whether the belt really needs to be changed, or rollers? Is there an improved variator or other parts rather than stock Yamaha bits? I commute Henderson to Glen Innes every day. The only real performance improvement I'd like is to get away from the lights a bit quicker.
    I haven't needed to do anything to the scooter since I bought it which is pretty good I reckon considering it regularly gets held full throttle from one end of the North Western to the other.

  2. #2
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    It would be wise to change the drivebelt if it's already done 20,000km, I doubt it will last another 5000. A snapped belt is a pain in the ass and will lock the scoot rear wheel up which is always fun, especially not good on the motorway with rush hour traffic up yer date.
    Do the variator rollers at the same time, if you want better jump from the lights, go 1-2 grams lighter from standard, but you may notice a drop in top speed. You may find your original rollers have flat spotted a bit by 20K anyway, so new ones will prob feel fresher on the acceleration.

  3. #3
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    Pulled it apart in the weekend to have a look. Half the rollers have flat spots but otherwise everything looks good. So, belt, rollers, and air filter is all that is going to be changed.
    I did note there is a line of slightly scorched rubber on the pulleys in the high speed position so I figure these full throttle trips on the NW motorway may be pushing it a bit.

  4. #4
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    While your mucking around in there and if your inclined, pull the clutch bell off and rub off any glazing around it and the clutch friction plates.
    "Your talent determines what you can do. Your motivation determines how much you are willing to do. Your attitude determines how well you do it."
    -Lou Holtz



  5. #5
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    12th February 2004 - 10:29
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    I did look at that but there isn't any obvious glazing and the clutch takes up nice and firm when you gas it up.
    Looks like the rollers may be a few weeks away. If anyone in Waitakere or East Auckland has a couple of spare 20x12 9g or 8g rollers I could use you can have the new ones when they arrive. The scooter definitely has a problem where the engine revs get dragged down on hills and into winds because the variator obviously isn't working properly with the flat spotted rollers.

  6. #6
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    12th February 2004 - 10:29
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    I've still got the scooter off the road waiting for parts. It took 1.5hours to get home tonight in the car.

  7. #7
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    Woohoo, back on the road. Fitted a full set of 8.5g rollers, standard are 9g. So far seems like a very good mod. Scooter is a bit nippier in trafic with that couple more revs on. Will probably drop a full set of 9g rollers in on the weekend just for comparison. It has a small rattle coming from the variator region still but I couldn't see any problems when it was apart. Will have to take a few back road trips to work til I get a few miles on to give the belt a chance to bed in.

  8. #8
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    12th February 2004 - 10:29
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    What a great day getting to and from. Why do people continue to use cars?

    Zipping along in the bus lanes, cutting to the front at lights, and probably used $1 worth of petrol, and parked 10' from the front door of work. The magic of commuting on a scooter.

  9. #9
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    The rattle seems to be worse and associated with the drivebelt jumping around. I've got it all apart again including the torque thingo and it all looks good, plenty of grease and free moving with no obvious notches where it could hang up. It also still has that problem where the revs get dragged down on hills more than I remember it did when new. The only "possible" problem I can see is what looks like a pattern of cracks on the outside cone of the variator. There is no matching pattern on the other side of the cone and I can't feel anything even when the cone is stressed. There is no indication of movement on the edge. I'm going to try the old belt just for comparison.

    Thoughts and ideas are welcomed.

  10. #10
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    You may have to fatten up the mixture with a jet change.

    I imagine going up long hills that the fuel pump that runs on vacunm on most scooter would be low due to the throttle being wide open and the float bowl fuel level too low for good performance

  11. #11
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    It's a thought but the motor is standard and I'm sure Yamaha would have checked that. The revs are pulled down as the scooter slows on a hill. With the torque thingo it should rev more and I'm sure it used to. I knew a guy who used to have one so I'll try for a test ride on his for comparison.

    I fitted the old belt but there was no discernable difference so it's all back together for the Friday commute.

  12. #12
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    check out Dr Pulleys sliders on You Tube

  13. #13
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    The rattle is bad enough now that I started it this morning but turned it off and took the car to work. It comes apart this weekend. It sounds pretty much the same from both sides and is coming from the bottom end. There is more end float on the crankshaft than I would expect but as it's a roller bearing crank that may be just fine.

    As I've got more miles on the new belt it seems to handle the hills a bit better. Maybe it just needed to be worn in a bit to allow the pulleys to move freely under load. The revs aren't being dragged down so much.

    Depending on the problem I'll be replacing parts. I've found a very well priced Taiwanese supplier of oversize cylinders and pistons, stroker crankshafts, and heads with bigger valves, plus a selection of camshafts. They go right out to 288cc. I'm figuring 200cc would be a good size for what I use it for.

  14. #14
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    Stripped it down without dismantling the motor. Removed all the variator etc and ran it with just the engine. The noise was still there. A very careful check of the oil which has only recently been changed showed a small amount of shiny flecks so it looks like the bearings are going away. I've ordered a new crank and while I was at it also ordered a new cylinder with larger bore. Standard bore and stroke is 52.4 X 57.9. The rebuilt motor will be 58.5 X 61.4 and 165cc. I would have gone for a bigger bore but that would require me boring the cases so it will have to wait. It's only about US$175 so pretty reasonable.

  15. #15
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    sounds good hope the compression ratio is on the planet

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