Hey Guys,

I've got the mighty MC21 up and running!

I've done 3 rounds of racing and a hand full of test days but I still have one little problem.

In a straight line the bike gets up and boogies just like it should but on the track where I've been riding there a a couple of sweeping corners.

When I try to keep up the revs mid corner by easing on the throttle the bike splutters ( kind of just crackles and pops ).

After the corner when I get hard on the gas the bike resitates and they kicks into life!

I really want to get this little problem ironed out becasue I've really noticed it at the last to rounds that have been....WET

Any help would be great! I've got a new Tyga tail section and some nice paint planned before the next round so it'd be good to roll up ready to rock!!!!

Is the intake or exhaust modified in any way? If so, did you rejet to suit?

To me it sounds like a carburettion (sp?) issue, so if you have modified any of that stuff, you'll have to tinker with the jetting.

If it's stock standard, I would guess that your carbies need a clean, and double check the routing of fuel lines, and make sure you have mounted the carbies and airbox correctly and not impeding airflow.

Good advice available on this website, outside of the forum section.........http://www.nsr-world.com/tuning/250-tuning/carburation%20index/jetting/
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Thanks Guys! I'll have a big read up of that page!

I have done the wire splice on the bike and have done the holes in the air box ( Which make an awesome noise!!)

Ok Team,

I took the top off the carbs tonight to find that my carbs don't have adjustable needles.

The needles have J81E which I saw is the stock needle.

haven't talking to a few people I think I need to lean the bke out a bit in the lower revs so which needle do I need?? ??? ??

I'm 85% sure that the bike has the right size main in it after checking and double checking the plug as advised!!!

You don't lean the mixture for given RPM, you adjust it for a given throttle position.
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Andy.
NSR-WORLD.COM

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Sorry what I meant to say was lower throttle position have than lower revs!

As you'll read above the problem I have is between 1/2 and 3/4 throttle!

Where do you think woulb be the best place to start Andy???

I understand that the needle taper has the greatest effect on this kind of position and after reading that WHOLE page I'm thinking I need a "C" needle! Do I just rock into Honda and ask for a C needle???

I had a look on the parts manual but it's a bit hard to make out whats going on in that picture!!!

IMHO it sounds to me as if it's more to do with transitioning from one fueling system to another. By chance are you still running power jets? One of the reasons for blanking the power jets is that it can be difficult to tune with both factors at play. As there are lots of wide open spaces in Oz, I toyed with retaining the PJ's to provide extra fueling on long straights, and allow me to run smaller mains. I ran smaller mains and PJ's with c needles and had a similar issue to what you are describing. In the end I have returned to bigger mains, no PJ's and B needles. it runs a little rich in the middle, but gives me more confidence at wot, and there are no stutters.

shmokica sounds like good advice! Yes I am still running PJ's! I'm not quite sure how you go about blanking off the PJ's!

I'm not sure if I want to go down that raod but I would be interetsed to know how to go about it!

It would be good to keep the PJ's and get rid of this spluttler.

Did you have tis sort of problem with your PJ set up??

The best source of this info is in the carb tuning section, under the tuning section link to the right <- . If you blank of the PJ's you'll most likely need larger main jets. In fact I'd suggest that just putting the holes in the airbox and doing the wire splice may mean that the bike could already be running lean. If you want to start playing around with the jetting, you'll need to get some more jets. The best advice I can give you is to find a good two stroke tuner in your area, and get the bike sorted by an expert the first time around. Once you have some good base settings you'll be able to make small changes yourself. Cheers.

Hey,

So would anyone have the part numbe for the "C" needle???

If no body chimes in before tomorrow morning I'll grab the part numbers, as the sheds down the back yard.