nc 21 not going over 60mph!!!

[castrol101]

My 24 had a speed light and that was 88, they come on 100kmh...but it still did 120mph no probs.
Is it fast all the way to 60 (i.e. as fast as a v4 should be) and then suddenly stops accelerating? that would indicate a speed restrictor, which bikes of that age don't normally have, but i spose some1 may have put one on. or is it pretty slow and you can't get it past 60, it may be power restricted (i.e. 33hp washers) and then maybe not firing on all 4...as even at 33hp it should be able to do at least 90-100.

[ktb]

yeah it revs out in neutral
i thought it might be the carbs i'll have to get it looked at in a garage because i dont know where to start to look!

[ktb]

its fast up until 60 then just stops it rides absolutely fine lovely but just wont go over 60 mph!
any suggestions on where i should start?

[wullvfr]

try the carbs,time consuming but it will eliminate them as the culprit.tbh if the bike runs fine up until 60 then it seems the carbs are ok as there is no spluttering or misfiring.but check them anyway,there may be obvious signs of something being iffy,and possibly any form of restriction.



william

[Neosophist]

somethings up anyway

there 60bhp as standard, same as the other NCxx 400's.

They don't have a speed restrictor in as standard, same as the NC24 they have a speed light that comes on at 52.5mph (which was the max speed you could go in Japan at the the time) but other than light up it does nothing.

It should do 130mph in 6th at the redline if it's running properly.

60mph is very odd though. It's not a VFR400K is it?

[ktb]

no its a vfr400rg nc 21 '86 got the year wrong! the speed that the light comes on sounds bout right it must be restricted in some way cuz its a pretty specific speed 60mph? i need it to commute up and down the M5 and i cant be dealing with 60mph!

[wullvfr]

even for a 33bhp restricted bike 60mph is a bit low............


very strange!!!!



william

[Neosophist]

even for a 33bhp restricted bike 60mph is a bit low............


very strange!!!!



william

bhp alone isnt' a good indication or way to gauge of of how fast the bike should / could go. As ie the CBR125 only makes 12bhp and will go 75mph, but you also have 33bhp cruisers that will go 75mph. and 33bhp bikes that will go a lot faster.

As for the original poster.It could by any number of things affecting your bike. It is odd that it always stops at the same speed tho, that would indicate some kind of restriction, unless it is down to 33bhp restrictors there are no other 60mph mods I know of.

Work your way around the bike and do a full check over it, it should only take the best part of an afternoon.

-Remove the fuel tank and airbox, check that you a. have an airfilter. b. it's clean.
-Remove the carbs from the V and check there are no restrictor washers in there limiting the air-flow. Remove if necessary.
-While the carbs are off remove the bottoms and give them a good clean out and blow some compressed air through all of the jets.
-Check pilot settings on carbs and rebalance them

Give it a try :-)

Anything else is likely to be electronic..

where abouts are you? If your local and dont' have the gear I dont' mind balancing your carbs / giving you a hand getting it sorted out.

[wullvfr]

contradicting everything i say neo man!!!!!

what im saying is,as my grandpas bike was restricted to 33bhp but still managed 80mph plus,and that was a bike that was not as powerful,so surely the bikein question would manage more than 60 mph.



william

[beardsroad]

Have you checked your fuel tap as the diapham was split in mine and it wouldnt go above 80mph its worth a look.