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Thread: Yamaha NXC125 20,000km

  1. #121
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    3,866
    I'm going to try my RG50 radiator. It is slightly larger than the uncovered area so should be near ideal with the radiator cap and the pipes being in more or less the right places and angles.

  2. #122
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    Carb falling off problem sorted. With the taller cylinder the head and carb were 6mm or so further forward. At a reasonable amount of suspension compression the carb was pivoting forward with the engine and the hard part of the throttle cable where it fastens to the carb was hitting the enclosure I've made for the carb under the seat. I've rotated the curved hard part to the side more and it seems OK now. Only problem now is that the enclosure lid won't fit on now because the cable sticks up too far.

    I phoned Mikuni Oz(https://www.mikunioz.com/?v=787739c35a69) yesterday at midday to enquire about a new filter. The only guy there was sounding a bit stressed and said he had about 80 orders to get out before he went home for his holidays and that it would most likely be sent on 7 January when the shop reopened. I wasn't worried about that and went ahead with the order anyway. Early afternoon and I get a message from the couriers saying I had a package on the way. Another example of the fantastic service from MikuniOz.

  3. #123
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    RG50 radiator fitted and about 1/2 covered with duct tape. Even with the warm weather and the odd traffic light it still doesn't warm up properly. Generally it sits around 60deg. I'm still taking it easy and running it in. I changed out the oil today with more of the same lower grade stuff. I'll run a couple more tanks of petrol through it then put in better oil.

    It really doesn't like 50kph. It's just too slow and the carb is barely cracked open making it difficult to control. Even 60Kph is a big improvement.

    The filter arrived on Friday. Unfortunately it won't fit very well. It was suggested that I return it and they would send the right one but I pointed out that I was in NZ so not so easy with courier satchels etc. Tom from Mikunioz has been replying to my emails despite being on holiday. Turns out he is in Taupo and he suggested I drop it off and he will sort it out. Then it sounds like they don't have a filter for the 50mm carb spigot, but there is a way.

    It's running reasonably well. It gets to 80kph with hardly any throttle real quick, and even 100kph is quick. It still does wheelstands though so far only down my drive.

  4. #124
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    Few more rides and it seems that a radiator 100mm X 25mm would be spot on. Unless stopped for a few minutes it doesn't overheat. In fact it doesn't overheat at all, it just gets a bit warmer. That's with the radiator out the front anyway.
    Had a longish sting at a steady 80kph and no sign of warming up, just sitting on a steady 60-70deg.

  5. #125
    Join Date
    20th January 2010 - 14:41
    Bike
    husaberg
    Location
    The Wild Wild West
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    10,143
    Quote Originally Posted by speedpro View Post
    Few more rides and it seems that a radiator 100mm X 25mm would be spot on. Unless stopped for a few minutes it doesn't overheat. In fact it doesn't overheat at all, it just gets a bit warmer. That's with the radiator out the front anyway.
    Had a longish sting at a steady 80kph and no sign of warming up, just sitting on a steady 60-70deg.
    Is any heater cores fom cars that small? you could likely get away with few of these. Be easier to package

    https://cometkartsales.com/WildKart-...Exchanger.html

    Click image for larger version. 

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    looks like people use these for tig welder coolers
    https://www.mindfactory.de/product_i...m_1128745.html

    https://klozey.com/products/80mm-str...industrial-row

    techy types water cooler computers with tiny rads
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  6. #126
    Join Date
    5th January 2007 - 14:58
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    motocompo
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    Buttfuck nowhere
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    4,898
    A barrel alone will take very little cooling.
    Most of the heat in a four stroke engine is produced in the head & that's the part that needs cooling most to prevent detonation.
    Here's an example of an engine that I'm familiar with that has a water cooled head & air cooled barrels, which would be the usual route for a air/liquid cooled engine.
    https://en.m.wikipedia.org/wiki/Rotax_912
    How difficult would it be to water jacket the head as well?
    The amount of cooling you require for this application currently, demonstrates how little heat is produced in the barrel compared to the head.

  7. #127
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    Got about 1000km on the new engine. Changed the oil for good stuff and gave it a bit more of a handfull. It may be better than before. The rod length is about 6mm longer but I doubt that would be obvious when riding. Bore, stroke, & cam are all the same. The head is all new with a smaller exhaust port & valves but slightly larger intakes. Whatever, on the motorway cruising with the speedo off the clock is effortless.

  8. #128
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    It's getting a good thrashing now. Been along the motorway for a good distance with the speedo needle buried in the bottom of the gauge without a problem, except for one little one.

    I pulled off the motorway and the revs weren't coming up like they should with throttle. Stopped in a driveway and gave it a bit of a rev and it seemed OK but when I went to leave it was labouring and was vibrating. The vibration went away with a bit of speed and the engine revs came up as the scooter gained speed. I was thinking I might have melted rollers in the variator so just rode it home carefully.

    Took the transmission cover off when I got home and it looked OK except the belt wasn't in the low ratio position but rather it was at about 3rd gear position. I pulled off the front pulley and found that one roller had managed to jam itself sideways and was stopping the variator from moving to a low ratio. It was probably holding one pulley face at an angle causing the vibration of the transmission on the belt.

    I had been planning to fit a new belt anyway so went and replaced all the rollers and the belt. I have slightly lighter rollers in it now so it should be doing a few more revs everywhere which from the dyno will make it more interesting but will stress things a bit more on those extended motorway thrashes.

    The water temp was solid on about 60 on the motorway and only rises when I get stuck in bad traffic. The guy I bought the bits off, Chris from Race Concepts Scooters(RC Scooters) maintains I don't need the fan to supply air to the head and has suggested an oil temp in the head around 100-120 works well. I have the fan controller still fitted and currently only monitor the water temp but it has a 2nd sensor for oil so I'm going to screw that into the exhaust tappet cover where the oil pools a bit. I'm running Hobao billet valve cover heatsinks one of which already has a threaded hole for a temp sensor.

    The back tyre has worn out. It didn't last that long.

  9. #129
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    I've put a proper back tyre on it now and it handles a lot better.
    It does rev a bit more but I hardly notice it after a few rides. Giving it a handful at 60K sees it really get going now. Taking off from the lights got a bit erratic with it not always taking throttle. There was also a reluctance to take full throttle on the motorway. I had a bit of a look at fuel, checked the float bowl and the idle fuel adjustment but it was all good. The plug looked OK but I noticed black stuff down the outside which might have come from the tool. I put a fresh plug in anyway and checked inside the plug cap and found more of the black grime. After cleaning it all out went for a test ride and it's back to it's old snappy self but with the extra revs is just a little bit zippier away from the lights. Down a side street off Rosebank Rd testing starts was a bit of fun. It'd wheelie without too much effort and even come back up after you put it down, probably catching the bounce. On the dyno it definitely liked smaller rollers, making more power everywhere with the extra revs. I had it booked in for a WOF on Saturday but that didn't go ahead of course.

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