NC21 seems restricted ????? Help

[backon2wheels]

Hi, i have a problem with my vfr400 nc21 i recently got off an Uncle after been aid up over 5 years. The problem been its goes well ( except the flat spots in mid range) in the 1st three gears then hits a brick wall at 100mph ( on private and ) it has the kph-mph converter on it and i've also removed the disc/plate in the speedo but it does still feel electrical the way it seems to stop at the same speed all the time. I've now got the carbs off and found both left hand side carbs have the 110 main jets in and right have the 112 in so i'll clean them up and put right, also does any one think i should go up a size all round as i've fitted an race end can but other than that standard all round. I look forward to hearing if any body else has had a similar problem.
CHEERS

[Neosophist]

The NC21 was never electronically restricted.

The dial in the speedo just illuminated the 'speed' light on the dash to inform you that your doing over 80km/h.

Not ran a bike with the system disconnected so not sure what happens there (keep meaning to try that)


Check / set the valve clearances fist.

Sort the jets / emulsion tubes and float heights next, 112's in the rear, 110's in the front (make sure if you have emulsion tubes with more holes in that they go in the rears)

Try your pilot screws a 2 1/4 turns out if you have a race can, shouldn't need an upsise of jets unless you mess with the collectorbox or the airbox.

Raising the needles with a 0.5mm shim might help your mid-range flat spot.

The only restriction you might find is that there are metal restrictor washers inbetween the carb rubbers / engine (uk restriction to 33bhp) have you checked for these?

[backon2wheels]

Hi, cheers for that. Keep getting different info on the carbs, i know the nc24 and nc30 have the 4 and 5 holed emulsion pipes but some say the NC21 has all 5 holed ones as mine has ? If it should have the 4 holed ones i'll get 2 ?. No restrictor washers in but as i said both 112 were in the two right hand side carbs and 110 were in the left two !. Not tried pilot screws yet but i do have a race can on so would it need 2 3/4 ? Also people have put on this site about vacuum pipes been a problem?

[Neosophist]

If it's got all 5 holed ones thats fine, you can't mix them up.

Putting the main jets in the right places is the first port of call, along with making sure your valve clearnaces are right.

Once these are done you can balance the carbs for a smoother idle.

the NC21 is happiest about 2 turns out, usually upto half a turn either way for fine tuning.. in your case i'd go with the 2 1/4 I initally suggested to take into account the race can and see how you go from there.