Hi All,

3rd post of mine. Previous help has been amazing, so hoping you can help with my current issue that I have been wrestling with for the past month or so.
Doing some freshening up work on the bike(MC21SE 1993); carb clean(new kit), adjusted the floats to 12mm, RC valve adjustment + some general servicing.
Got the bike back together, started fine, warmed her up. Took her down the road for a test. RC adjustment seemed to do wonders for my mid range, no flat spots and great pull.
However, hitting about 9k the power staggered, seemed to have hit a wall..... Few more rides and same thing, but I noticed if I maintain WOT the revs will very slowly creep past the 9k mark...????
Could this be something to do with the float? too much fuel; float hight set to low?
Plugs look slightly black. Plugs are about a week old.
Aside from the wire splice, which I did this weekend, bike is stock.
Thanks for your time in advance, any other info needed just let me know.
Cheers
Kal

Not sure about NSR but on my RG if it hits the wall like that it's rich.

I think since this discussion involves jetting is only for the members area?

That was my thought Dmitry. Adjusted the air screw, seemed to help a little; still some stammering at 9k. Thought the air screw only applied to low-mid range though?
Have not stepped into the jetting realm, carb is stock jetting.

Pilot screw mostly affects idle however there is a small change through the entire range.

Your symptoms described my bike. I finally ended up swapping out my RC servo and cables with a spare and adjusted them, and she revs up smoothly.

Dana

And make sure that your battery is 12 volts at least or else this too will hamper you .

so any mods to the bike? If you change airbox, exhaust or the like then you need to rejet. Check the tuning section on how to read your state of tune.

When you adjusted the rc valve, did you also give it a good clean?

No mods aside from the wire splice which was done today. Had the problem for about a month.
Gave the servo and pulleys a good de-grease, lots of gunk.
When i adjusted the RCs it took quite a bit to line them up. Any sign that the servo is on the way out? Apart from the obvious: no go.

How new/good is the battery?A bad battery can cause all sorts of symptoms.

what about your battery voltage? Measure both when the bike is off & at idle.

When you say degreased your valves, did you reassemble dry or use a lube of some sort? Did you check your cable tension? How/why did you degrease the servo? It's a sealed unit so shouldn't get any gunk.

Have you checked continuity in the loom? Got the connector plugged in?

Have you actually checked that the RC valve is opening fully at high rpm?

No disassembly of the servo. Only degreased the pivot points then a quick spray with crc. Battery seems to be holding charge. checked a few other posts and battery voltage is comparable.
Not sure how to check RC valve is opening fully at high rpm. help?
next step will be to check the loom.
my thoughts are still leaning towards rich mixture.
Had another look today: fuel tap out(little bit of debris on the mesh), plugs are changed, checked voltage.
Took it for a ride: still has a little stammer at 9-10k, but there is a flat spot now(new) at around 4-6.5k then boom, band kicks in like a horse. from idle to 6.5k, exhaust has a high pitched popping sound(not a back fire).????
Sorry for my lack of knowledge guys. passionate about this bike, but its a love/hate relationship.

kalnz44 wrote:No mods aside from the wire splice which was done today. Had the problem for about a month.
Gave the servo and pulleys a good de-grease, lots of gunk.
When i adjusted the RCs it took quite a bit to line them up. Any sign that the servo is on the way out? Apart from the obvious: no go.

Actually my servo would sound like it was moving when I inserted the key, but upon actually looking at it with the tank propped and engine running, me thinks it wasn't moving all the way. In fact, when I took off the cable pulley, it had some spots that felt like the gears inside wear stripped. Sure enough, I gently twisted the newer servo and there weren't any "free play" spots.

(I had also double checked to see that the RC valves were able to turn freely back and forth, and they were.)

Dana
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2016 Husqvarna 701SM
2021 Husqvarna FS450 supermoto
2014 Honda CRF250R supermoto
1995 NSR250r MC28

In your first post you said plugs were slightly black, are they wet and black or just black? If they are black and wet, then they are rich fouling and you need to make sure you carbs are setup correctly (so that means clean jets, emulsion tubes, air screws everything setup right).

But could a electrical missfire contibute to black plugs beacause it is not burning the fuel