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flat spot
Jul 21, 2014 21:04:49 GMT 1
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Post by gazbeemer on Jul 21, 2014 21:04:49 GMT 1
Hi again guys. Any help would be appreciated. So here goes. Bike is a rd125lc mk1. Has a micron power small can exhaust with a standard 12A00 carb. Starts and runs great with a very healthy power band but has a really bad flat spot for a couple thousand revs just before the power band. I know its a two stroke with a micron chamber so its meant to be ridden in the power band all the time but there must be some way of having some kind of mid range. Its just really flat. Has normal power for the first couple thousand then a bad flat spot for the next 1500 to 2000 rpm then all hell breaks loose. Lol. Cheers in advance gary
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Post by rob99 on Jul 21, 2014 21:08:02 GMT 1
Airbox or open filter
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Post by bertiemollie on Jul 21, 2014 21:13:43 GMT 1
What you have described sounds exactly like the power delivery of a small can micron.
If you prefer mid range you would probably be better off with an Allspeed or 10W pipe.
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flat spot
Jul 21, 2014 21:53:02 GMT 1
via mobile
Post by gazbeemer on Jul 21, 2014 21:53:02 GMT 1
Running standard airbox with genuine foam filter. When u twist the throttle back in the flat spot u can hear the suction roar but no power to go with it.cant get rid of the micron it looks so good. Lol.
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Post by rob99 on Jul 21, 2014 22:39:34 GMT 1
Something you will have to live with I'm afraid lol a small price to pay for such fun I've going to work on mine great fun
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Post by looey on Jul 21, 2014 22:44:58 GMT 1
In my experience, if you want any power at all before the powerband, then it's a standard pipe with the correct setup you need.
I have virtually every type of RD125LC pipe here for mine (12A, 10W, Allspeeds, Microns (large and small can of both), Nikon etc.) and there's bugger all going on before the power band on any except the standard pipes.
I've settled on a later detachable end can type Micron but with a straight through aftermarket end can which gives the best I can get whilst retaining all the power you'll get upto 10,500 rpm.
If yours is particularly bad (maybe spluttery ??) in the mid-range just before the power band, then it maybe a needle clip position change you need to iron that out ?.
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flat spot
Jul 22, 2014 7:46:57 GMT 1
via mobile
Post by gazbeemer on Jul 22, 2014 7:46:57 GMT 1
I have a bit of splutter during the flat spot nothing major but the odd misfire so could try needle clip position. Which way should I go. Up or down. Even if it eases it slightly would be a help
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flat spot
Jul 22, 2014 8:36:44 GMT 1
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Post by rob99 on Jul 22, 2014 8:36:44 GMT 1
Try it both ways a bit of trial and erra
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Post by looey on Jul 22, 2014 14:25:52 GMT 1
I have a bit of splutter during the flat spot nothing major but the odd misfire so could try needle clip position. Which way should I go. Up or down. Even if it eases it slightly would be a help If it's spluttering, then it would appear that it's running rich there. To lean it out, you need the needle to be lower into the jet, so move the clip on the needle one position nearer the end (i.e.further away from the pointy end). Be careful though, if you lean a 2-stroke out too much in the mid-range and then cruise on part throttle in the power band, they will be using the clip position as part of the fuel delivery process, which if lean can lead to obvious consequences  . You could try it one clip richer first to confirm that it makes it worse. Does it splutter more or less if you give it more throttle at that point ?. |
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Post by mudguts on Jul 22, 2014 18:00:22 GMT 1
Got a allspeed on mine, ran quite well until the hot weather got here now it runs terrible in the midrange, the hot weather richens the mixture as the air is less dense,
i jetted and set mine up for 17c air temp, what i would call normal english weather. matching throttle opening with rev build helps, give it too much then big splutter.
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flat spot
Jul 27, 2014 1:19:28 GMT 1
via mobile
Post by gazbeemer on Jul 27, 2014 1:19:28 GMT 1
Just a query but what way does what on air screw. Richer or leaner in or out etc. Just the standard mikuni vm round slide carb fitted
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flat spot
Jul 27, 2014 8:00:04 GMT 1
via mobile
Post by rob99 on Jul 27, 2014 8:00:04 GMT 1
I would ASSUME that if you screw it in the apperture will get smaller and make it weak and if you screw it out the apperture gets bigger making the mixture more rich....
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Post by mudguts on Jul 27, 2014 9:17:53 GMT 1
screw in richer, screw out leaner, but this only effects up to 1/4 throttle, im using 1 1/4 out for winter 1 1/2 out summer seems best, book says 1 3/4 out
but ive a allspeed, one size bigger main Mk3 rd, and leadar nozzel standard filter, you can get the air screw setting by, go for ride warm engine,
stop at side of road and screw the airscrew in and out till revs pick up the most, then back in 1/4 turn. keep testing on the same bit of road,
wont be long to you find the sweet spot.
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