EC250 RPM vs Main jet

[Jakobi]

Question for all those in the know. How many RPM should the gasser rev to roughly? I've done a few little test runs with different mains and while none of them make the revs break up, there are significant differences in the revs that I can achieve. All tests performed with a 40 pilot and N3EW#2.

185 - 8999rpm
180 - 9200rpm
178 - 9450rpm

Now obviously the 178 felt much more agressive and pulled harder through the top, but the bike also started to feel a bit lean around half throttle. The 185 felt much richer throughout and much more sedate in nature.

I really should have pulled a plug chop at the 178 to evaluate. I wonder if I could go a half clip richer on the needle, and drop the main another size to pick up more over rev.

Thoughs??

 

[Jakobi]

Did another run with N3EW#2 180. The bike is definitely lean on the needle confirmed with a half throttle plug chop. Too light for my liking. The big main was also making it feel rich and fluffy off idle and towards WOT.

I want to try a 175 but will probably go back to 40 N3CW#3 178 and try and get a WOT chop done over the weekend.

 

[GMP]

Jake,

I was told a long time ago by a knoweledgeable dealer that the rev limit in the CDI is 10k RPM. This info supposodly came from the factory. I have not verified it as I never had a tach. It does seem reasonable. I just set my bikes up for best feel with a little pad for safety.

You really need to try a JD Red, it fixes the lean mid taper of the N3 series and will allow a leaner(slightly, its still a fat tip) main. Thats why I was not to enthused about working with the N3 series in this new '12, the NE series makes more sense as an alternative.

 

[Jakobi]

The 300 used to hit 9800rpm using a 172 main but I'm not sure if I'm comfy jumping straight to that with the 250, especially at this time of the year. I'll roll with the 178 for now until I can confirm otherwise. The JD actually specifies to run a richer main than I would with the N3 needle, but may be a buffer zone too.

Speaking of JD Red, I will have one in my possession next week so will be able to give sone feedback then.

Cheers

 

[skid jackson]

what elevation are you at ... I'm running a 175 at sea level

 

[Jakobi]

Lots of variables as to right or wrong main though. I'm at 300-1000M, usually 20-35C, with 50-100% humidity. It is winter now though so humidity is significantly down. Temps are at the lower end of the spectrum. Been about 11C over night but warms up by 0900hrs when we are on the bike.

Needle taper profile, float height, port timing, fuel brand/octane, oil ratio, and compression ratio probably all have some effect on the fuel requirements of any given engine also so to compare one main to another isn't really the be all or end all.

At the end of the day it'll need a good plug chop to confirm whats right/wrong. I've set it up with a 175 to start which is one step leaner than my previous best and will see how it feels. If it feels lean I'll go back to a 178. Most the day will be spent in singles and off the main anyway.

Still interested in hearing from anyone who uses a tacho/trailtech vapour what kind of max rpm they are recording.