hi guys, im new as you can see and would like to say what an outstanding and informative site you have, if i could ask afew questions about my project. i run a 250 sprint kart and im fitting up a mc21 with mc18 barrels and billet heads onto a crg chassis, what i need to know is the following.
how much of the wiring do i need to run for the igniton? can i dump the magneto or do i need that for the ignition? do i need to run the gear position sensor as well as the tps?
i only need the basics for a kart and ill also be running on alky as the class is open plus 38mm carbs.
any sudgestions would be great, cheer steve

Two minor probs, but can be overcome.
1:The NSR electrics from 1989 and later ran a throttle position sensor.
I took the one on my Aprilia RS250 and epoxied it to run at WOT only because I run 38mm carbs, resulting in a rather unrideable power delivery. I have since Mickey Moused it back in. Massive improvement in power delivery

2:Dumping the power generating circuit means that you will have to run a battery. More weight, but less drag on the crank(=more power going to gearbox/tyres).
And you get to choose where the battery goes in.
Ask people about Total Loss electrics for more info.

The other-and better option, is to use NSR HRC F3 electrics (rare as hens teeth) or HRC RS250 electrics from 1989 to '92 (A little more common...)
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The Chopster

many thanks for the reply and didnt think it was going to be easy. one thing i thought was to use a ignition setup off a 250 rotax. they run a motoplat igniton which doesnt need all the other bits but i dont know what the ignition curve is.
when you said with the mods you did the power delivary was aggresive that might not be as bad in a kart, cheers steve

If you print off a copy of the wiring diagram, and delete all the lines to and from the lights, you'll find you can strip the loom down quite a lot.

You do need the gear position wires, and the TPS if you want a decent power curve.

The standard NSR battery is really small and won't last too long when you consider it will also be driving the powervalves, so if you do go total loss, use a bigger battery from something like a CBR400.

Personally, I doubt the charging gear saps more than 1hp, so is it really worth removing?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Or run the charging system, and a Bat-Pac battery eliminator (Capacitor).
Still means a bit of drag, but no heavy battery. The Bat Pac weighs about as much as a packet of cigarettes.
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The Chopster

f it were me then I'd run the thing total loss. The stock NSR battery will run for at least half an hour, so I doubt you'll have problems there unless you're endurance racing.

If you go total loss then you can lighten the flywheel by turning the outside diameter a little, and also remove the magnets from the inside. Would be pretty good in a shifter Kart I reckon.

MC21 PGMIII would be a good choice, or an F3 PGMII. The F3 PGM offers more advance fom standard setting, but if you're going with Meth then you'll be needing a whole lot more I expect.

Block the GPS sensor hole and wire it up for third gear. I'm running the TPS at WOT on my 300 (38mm carbs) and it runs without trouble. Don't just turn the TPS up to what appears to be WOT though, you'll need to measure the resistance accross it first while it's still fitted to the carbs, and then reset to this measurement with the TPS off the carbs. Alternitively you could wire up a 5K potentiometer in place of the TPS and have a fiddle while you're on the hop.

The harness can be stripped pretty bare for race mode, especiually in total loss spec.

many thanks for the help guys, a days racing is about an hour in total so ill keep the system as is as i dont wont to be changing batteries eveytime i run it. when i brought this engine it didnt come with carbs so ill have to find a tps. if i dont run a battery i gather the stepper motor for the power valves will still work?

run a bat-pac and it will...
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The Chopster

hi guys, im well on the way to finishing the kart but i have a few questions,

2, also is if dont run the power jets, will this effect the pgm-3?
3, how big a differance will it make if i didnt run the power valves?

the reason for all this is its very tight for room as this is all in a sprint kart not a super kart.

ive also fitted a pair of 38mm carbs and a pair of jha pipes, i was going to remote mount the gear position pot so i can select the curve i need based on conditions, eg: use 6th if its wet.
im also running without a battery and going straight from the voltage reg
look forward to your wisdom

cheers steve

First off, be careful not running a battery. The battery helps dampen any voltage spikes that may occur and also keeps voltage right up there. Just this passed weekend I experimented with a "battery eliminator" of my own and the results were pretty good. I ran it on an MC21 and it worked fine.

You may find your "battery-less" setup difficult to start and the RC valve will function slowly at lower rpm. Not good.

I still think that you should go with the total loss setup. It's hp for nothing. Just costs you a little in time keeping the battery charged. Or fit an RS250 (NF5) ignition.

When you say not to run the power jets, are you referring to the air solenoids? They control airflow (via MAJ) to emulsion tubes. You're running big carbs, so just disconnect them. It'll make no difference.

Don't worry about wiring in the GPS to select different maps. Just hard wire it to 3rd gear and forget about it. The most important thing is that you do the wire splice (Or/Bu to 12V). If you need to alter ignition timing then make up some offset woodruff keys, or get yourself a selection of flywheels. MC21 is most advanced, then 18 then 28. Then go out and play.

Sounds like a awesome idea. Whilst this isn't exactly on topic, are you allowed to run twin engine configuration ? Like 2 max's, or twin leopards ? That would net you the same HP as a NSR250 donk.

Have you though of running butterfly carbs off a leopard ? Would be handy to be able to adj the fuel mixture on the run. They support 32hp each on a 125 revving to 15k, so a pair should accomodate a tweaked NSR.

Anyway, goodluck with it
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Winning isn't everything, but loosing isn't anything

thankyou very much for the great advise, ill look at running a 12v cap? then i can leave the heavy battery off.
how much would it hurt it if i didnt run the power valves?
ive been told ill have no bottem end at all, then again it is a kart and not in the bike,
any ideas would be great,
again thanks
cheers steve

id run the valves in open position, remove the intake bottles, set the tps to 1st and set the ignition to advanced.

ill sacrifice the hp/torque down low in the revs but will make it alot simpler to setup/tune and remove most of the wiring, you could then have a wider choice of carbs to stick on it.

i just found a carb from a 620cc UAV that crashed in a feild next to wer my mate lives was thinking this would be good for a kart engine or sumthing as its 42mm butterfly carb thing that has no float bowl just a valve thing that activates under a slight vacume. :S
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Honda nc23 CBR400 AERO 1986, 1990 honda NC23 Tri-Arm, 1987VFR400 NC24 Rothmans Rep, NSR250 MC16 1987, CL250s 1983. Moto guzzi zigolo 110cc 1958. Fantic 50cc 1972. Suzuki Cobra Race bike 500cc 2t 1975 , GP125 1975. Triumph T110 1954. BSA Thunderbird 1955. Ariel VB 600 1952, 1990 MuZ 125 etz.

To ride an NSR with the PV wired fully open is (for me anyway) very hard. You have to remember that with the stock system the valve isnt fully open until almost 12,000rpm.

Its a very slow and progressive movement.

You will be amazed just how much middle you loose as well as bottom by doing this. Far better, if you must, is to set the valve 3/4 open. This at least give you back some of the midrange with very little loss to peak power.
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If I have to take the carbs off once more...

would be good to set it to where you need the power id attach the cables to a lever so i can trim the valve timing on the fly.

ive got a 1 wheel drive gokart that i am trying to put a 17bhp cd200 twin engine in at the moment.
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Honda nc23 CBR400 AERO 1986, 1990 honda NC23 Tri-Arm, 1987VFR400 NC24 Rothmans Rep, NSR250 MC16 1987, CL250s 1983. Moto guzzi zigolo 110cc 1958. Fantic 50cc 1972. Suzuki Cobra Race bike 500cc 2t 1975 , GP125 1975. Triumph T110 1954. BSA Thunderbird 1955. Ariel VB 600 1952, 1990 MuZ 125 etz.