NC30 rev limiting at 12500rpm

[HondaRacingCorp]

Am not all that clued up on the mechanics of bikes, but i have a '91 VFR 400r, and seems to run sweet except for an early rev cut at 12500 (redlines 14500).

Any suggestions as to why this might be happening? It seems to run a tad cooler than my mates NC30 (bout 80 deg as opposed to 90 deg), am wondering if this has an effect?

Any help would be greatly appreciated,

thanks

[avgas]

zxr had one that limited about 2000 rpm lower than red.
was fixed with a derestictor thingy box.
sorry am half asleep

[RC1]

need to get it derestricted cost around $200 i think

[Morcs]

They arent restricted revs wise? its only the speedo?

Anyways, i heard that there is a guy in whenuapai who can derestrict bikes for around $50... will have to find out who he is

[more_fasterer]

Your rev-counter could be out of calibration. Happened to my bike the last time the previous owner crashed it, dunno how or why but the tacho wouldn't move below 4000 and stopped at 12,500. Replaced the tacho and all was sweet.

[FlyingDutchMan]

If it has a speed limiter (more than likely), and its not hooked up to your ignition unit, it'll limit the revs so that you can't exceed the max speed in any gear. So to fix the problem, get the electrical diagram and wire the speed sense wire running to the spark unit to 12v via 3.3k resistor (It may be the Amber/Blue wire from the speedo). $0.20 to do. Don't spend $200 on a speed de-restrictor because it'll be the most over priced resistor you'll ever buy.

A disected speed de-restrictor (for a ~1990 honda cbr250):
http://cbr250.com/cbr250/forum/topic.asp?TOPIC_ID=22334

[HondaRacingCorp]

Thanks for the replys.

The rev's are limited to 12500 even in 1st gear, so how is this got anything to do with the max speed restriction?

If you could explain further that would be good cause i think theres something im not quite getting,

thanks

[Morcs]

maybe something to do with your jets?

im not sure what revs the pilot jets open, but could be around 12500 rpm? if there is something wrong with them or they are blocked then that would explain a lot.

[FlyingDutchMan]

Thanks for the replys.

The rev's are limited to 12500 even in 1st gear, so how is this got anything to do with the max speed restriction?

If you could explain further that would be good cause i think theres something im not quite getting,

thanks

Its because the ignition unit has no idea what gear the bike is in. 14500rpm in top gives you ~215km/h (quick search for the top unrestricted speed), dropping the revs down to 12500 in top gear gives you 185km/h - the Japanese speed limit. Hence the 12,500 regardless what gear.

[HondaRacingCorp]

Hi, thanks i will definately be giving it a go once i find the NC30 wiring diagrams.

I would have thought the speed sense wire would depend on speed not rev's, so still not sure exactly how it works, but worth a shot. cheers