Just checked details again, given you've been running a 165 main with the N1EF you'll probably have no issues with a 175 main with the N3, or probably even down as low as a 170... based off your current main being OK.

The H diameter might be a bit rich still though, and especially with a 40 pilot. 38 may be closer.

Waiting on the NEDJ should get you closer quicker, I think.

Thanks Jakobi. You are a legend.

I'll give it a couple more days for the NEDJ to arrive then use the N3CH if it doesn't. I have mains in 172 and 170, pilots in 42 and 40 so should be able to find something that will be an improvement on the N1EF for the weekend and swap for the NEDJ when it arrives - sods law says this will be the day after the race. I doubt I will be spending much time on WOT, if any, so if the main is a size off optimum I should be OK.

Well the NEDJ arrived before the enduro and I fitted it on #2 with the 42 and 170 but quickly swapped back again. It started fine and the initial throttle opening was crisper but beyond 1/4 throttle the engine would quickly foul the plug and stop running. I didn't have time to play with it but I suspect it wants the needle dropping to the 1st clip and a smaller main.

It seems that my bike needs a leaner jetting. I still have to set the squish, which is probably a bit wide, so I don't know whether this is the reason.

I think I might have just identified my problem. The original owner was insistent that the bike used to run beautifully with the current jetting so I started wondering whether there might be another problem.

It has a new piston, the dents blown out of the exhaust and silencer repacked so that was all ruled out.
I got a bit more analytical about how the bike was running - bogging at low revs but clearing higher up, regardless of throttle opening, suggesting it could be something other than jetting.
I had an idea, did a bit of googling which supported it, then pulled the reeds. Bingo! 2 of the petals are chipped along the edge - just enough to affect the seal and allow a little leakage back to the carb at low air velocity.

Nice work! That'll do it for sure.. and you'll never out jet a mechanical issue!

Swapped the reeds and running better. Still rich and blubbering below 1/4 throttle but the lack of power at lower revs due to air leaking back past the reeds has gone.

Dropped in the NEDJ#2 and 42 pilot today and it pulls a lot cleaner. Still a hint of hesitation just as the throttle is opened but only given it a quick beat up the road and back so far. Centre and earth electrode much cleaner but still looks sooty on the outer ring. Out for a run tomorrow so I'll see how she runs and check the plug when I get back.

Since you fixed the problem try putting your settings back to where they were in the first place and try it. Previous owner claimed it ran great, right? I have an N1EF needle with a #7 slide in my 05 ec250 and have no problems down low. No bobble and pulls like a 4 stroke. Hope you get it ripping good!

Been a while but haven't been able to get out much due to other commitments.

The NEDJ#2 was working well with 165 main and 42 pj with fuel consumption improved and pulling much cleaner than before.

I was able to wind the idle screw out a turn which allowed the air screw to come into play - previously it had no effect as so much air was coming past the slide.

So I was pretty happy with it until I went for a ride up in the mountains (around 1000m, 30C) at the weekend. The bike was almost unrideable with very little pull until the power valves opened. On hill climbs (long steep fire breaks) the I was struggling to keep the bike on the pipe in 2nd when it should have been able to fly up in 3rd or more. On technical climbs it was even worse as once it came off the pipe it wouldn't even pull up in 1st and I was unable to get up stuff that should have been well within my capability.

Back down the hill and normal service is resumed so it was nothing more than a bit of altitude sickness. I have dropped the needle to the #1 today which has removed the last bit of hesitation as the engine comes on pipe but that is close to sea level. No idea whether this will be enough back up in the mountains.

I am wondering whether the NEDJ needle is more sensitive to altitude changes than the stock needle - is that possible? I also think I will need to get a leaner needle than the NEDJ for riding up in the mountains (up to 2000m) since I am already on #1. I don't know whether I just need to get a needle which is a clip or 2 leaner or change the diameter or taper, and what about the main? Advice please...

In my current stock I have the NEDJ, the stock needle and N3CH which I haven't tried yet.

TIA

Was it getting rich at altitude? or was the added load from climbing causing it to lean out and lack torque? These engines do make more 'grunt' with a bit more fuel. I have tried going leaner many times and you get a very responsive snappy power delivery which feels great under low loads and on fire trails, but once you get in the hills it falls flat.

It might not be the problem you have though, but keep an open mind to it.

If you haven't had the squish reduced, that's where I'd be looking. Makes the engine much more consistent and resistant to changes in temp, humidity and elevation.

I don't think it was leaning out from added load while climbing as it was also suffering on the roads.

I do think you are right about the squish though. One of the first things I did was replace the piston since this had never been done and was at around 350 hours. I removed 2 base gaskets but was unable to measure them as they tore when I lifted the barrel. On reassembly I used what I thought was similar thickness gaskets and chose the thickness to set the piston level with the bottom of the exhaust port on BDC. If I have used thicker gaskets I will have opened up the already wide stock squish band. This has got to be a priority.