How to know if the bike is running lean?

[Capz85]

Isn't the n1ef needle the one everybody says to throw away?

You said you had some other jets, why don't you see how it runs at the weekend, either richen it up on the needle or go up on the jet sizes and see how it feels, try a 45 and 178

[GGRider01]

Originally Posted by Munch

How do I go about richening it?

Pay attention to how the bike is responding to throttle. You have the pilot, needle, and main jet to play with. The main is the easiest of all because all you have to do is dump the throttle wide open. The others take some persistence to sort out.

Bigger numbers = richer jets. Always go in one step increments. 170-172-175-178-180 for main jets.

Your bike is a 250 if I recall, so you're even leaner than I first though. The smaller lung can't pull fuel through the jets as readily as a 300, and it's even worse on the 125s.. I'd start at a 180 main, 45 pilot, and fine tune from there.

Get the bike nice and hot before deeming your jetting good or bad.

Eventually you should get rid of that N1EF. Junk needle only good at sub freezing temperatures.

[Munch]

Ok I will get rid of the needle, what one should I replace it with? Maybe I can get one locally.

I am checking out the jetting database on the forum and I have a few examples of people who are at similar temperature and elevation to me:
http://www.gasgasrider.org/forum/sho...&postcount=209
http://www.gasgasrider.org/forum/sho...&postcount=188
http://www.gasgasrider.org/forum/sho...C250#post13712

Looking at the above maybe I should consider changing my main to a 178 and leave the pilot at the 42?
Unfortunately I didn't get a 178, I have 170, 172, 175, 180, 185. Suggestions?

I am super nervous about seizing the bike because it's too lean, with my previous bike it came working and I have put over 150hrs on it (2 pistons) and no problems so I don't have any experience with jetting at all.

Also something that was pointed out to me while I was getting advice was how thick of a reed spacer(?) I have on the bike, the pic below is around the thickness, mine may even be a little thicker. Would this effect the jetting and explain the low main jet?
https://www.economycycle.com/wp-cont...12/spacers.JPG

[Capz85]

You can order needles from jim aim motorcycles online they arrive pretty quick

[GGRider01]

Just throw the 180 in. If you deem it too rich then get the 178. A lot of people are content with the n1ef so it's hardly an urgent change. It's a very rich needle anyway, so it's safe to leave it.

I know when I got my first 2 stroke I spent days reading forum posts I'd pulled up with Google and my head felt like it was going to rot and fall off. Point is don't over think it.

That reed spacer isn't going to have a measurable change.

[Munch]

Ok cool so I am going to ride it on Sunday, get it warm and see how it's running. Once I confirm all is good and no problems I will switch over to the 180 main and see how it's going and report back.

If I put the 180 in and it makes it a worse ride, would it be ok to revert back to the 172 do you think? Or am I likely to cause damage?

I am coming from a kx 125 so I won't be riding the bike hard.

[Jakobi]

Originally Posted by Munch

Ok cool so I am going to ride it on Sunday, get it warm and see how it's running. Once I confirm all is good and no problems I will switch over to the 180 main and see how it's going and report back.

If I put the 180 in and it makes it a worse ride, would it be ok to revert back to the 172 do you think? Or am I likely to cause damage?

I am coming from a kx 125 so I won't be riding the bike hard.

I am in hot humid tropical environment at some elevation.. a 172 main is lean on my 250's and they use the newer model carb that has better efficiency. Old one, without knowing your conditions. I'd be looking at starting at 180 easily.

[barossi73]

The plug has some use,but the key is its relative to how the bike was ridden last/rider style.a lot of puttering will darken,look rich/a wot run right before pulling plug will show a greyer/hot/drier leaner looking plug.
Pay attention to where the problem areas are-pilot=0-1/8 with a small affect to 1/4.main=3/4 to wot.needle type/clip=everything in between.
With that needle the best youl likely get is ok 0-1/8,blubber 1/8-1/4,then whack,clean mid hit to wot.
The blubber just before the hit makes it difficult in tight technical stuff.if you ride wot/fast the mid to top hit is fine,but when you roll on/off it may burble then hit.changing needle type will help get a smoother transition

[Munch]

Can you guys recommend some needles I can try?

[Munch]

Originally Posted by Jakobi

I am in hot humid tropical environment at some elevation.. a 172 main is lean on my 250's and they use the newer model carb that has better efficiency. Old one, without knowing your conditions. I'd be looking at starting at 180 easily.

I'm really sorry but I am finding it hard to get some clear instructions from the posts in this thread.

I am currently running 172 which seems to work fine, power is there through the gears, powerband hits. However running 172 is likely to be far to lean so I should switch to the 180 main. What should I do if I switch to the 180 and it has some running problems like bogging/spluttering?

Edit: Also in regards to the needle I am searching places like ebay for "LTR" but not coming up with any results, from the jetting database I noticed a few people were running the LTR needle.