GN250... Running lean.

**degrom** · 13th January 2007, 19:53

My GN250 is running a bit lean... (How do I know?!? Spark plug is White'ish and the engine is hotter than normal)

How can I adjust the carb to be a bit more richer?

I have looked at the workshop manual and they say nothing about it. Is that because it needs to be re-jetted?

Any input on this topic is welcome.

**stanko** · 13th January 2007, 21:43

If it used to run ok then unless you have modified some part of the engine it is unlikley to need rejetting. You could inspect the diaghpram in the top of the carb if it is ruptured it will cause a lean condition. other than that check and clean the pilot jet .

**degrom** · 13th January 2007, 21:55

Originally Posted by stanko

If it used to run ok then unless you have modified some part of the engine it is unlikley to need rejetting. You could inspect the diaghpram in the top of the carb if it is ruptured it will cause a lean condition. other than that check and clean the pilot jet .

I have installed a new exhaust... It's a lot less restrictive than the old one.

I have taken of the Carb and it's in peaces... LOL

I am trying to get the needle loose but I am having no luck. Resone for trying to get it loose is to check if I can move the e-clip down. (Does the GN's carb even have e-clips)

Any idea how to loosen the needle?

**C_A** · 13th January 2007, 22:15

derestricting the exhaust will cause a slight lean out most definitely... i'd saya change in needle/main jet is in order

**degrom** · 13th January 2007, 22:21

Originally Posted by C_A

derestricting the exhaust will cause a slight lean out most definitely... i'd saya change in needle/main jet is in order

Luckily the shop is open on Sunday. I will go and order a new jet tomorrow...

I wonder what it will cost... Don't hope it's to mush.

**xwhatsit** · 13th January 2007, 23:51

Originally Posted by degrom

Luckily the shop is open on Sunday. I will go and order a new jet tomorrow...

I wonder what it will cost... Don't hope it's to mush.

Hmm yeah I'm interested to hear what it would cost, too. I overheard somebody say something ridiculous like 50c each or something? I always thought bike parts were magically ridiculously expensive for even the tiniest simplest parts?

**stanko** · 14th January 2007, 15:38

Main Jets are normally about $15 each. The main jet will only have an effect on 3/4 to full throttle. Is this where you think it is lean? The needle position effects the mixture in the 1/4 to 3/4 throttle range which is probably where you do most of your riding. To adjust the needle position you will need some long circlip pliers. remove the top of the carb and get hold of the diaphram and slide. Looking from the topside down the slide there is a circlip that neds to be removed. the rest is easy. move the E clip on the needle down to go richer. Reassemble paying attention to getting the tab on the diaphram in the locating notch.

**degrom** · 14th January 2007, 16:29

Originally Posted by stanko

Main Jets are normally about $15 each. The main jet will only have an effect on 3/4 to full throttle. Is this where you think it is lean? The needle position effects the mixture in the 1/4 to 3/4 throttle range which is probably where you do most of your riding. To adjust the needle position you will need some long circlip pliers. remove the top of the carb and get hold of the diaphram and slide. Looking from the topside down the slide there is a circlip that neds to be removed. the rest is easy. move the E clip on the needle down to go richer. Reassemble paying attention to getting the tab on the diaphram in the locating notch.

Mate... You are a star!!!

The service manual's tells you nothing about the Needle because they say,if it runs lean there is something else wrong(new exhaust) and you need to fix that.

I will have a look at the needle and see if I can adjust it a bit.

What happens if the needle is set at it's richest?

Should I then get a bigger main jet and set the needle to it's leanest setting?

Thanks for the help!!!

**Crasherfromwayback** · 14th January 2007, 16:39

Bloody hard to get a good reading from 'plugs' now we've gone to this unleaded shite too....

**degrom** · 14th January 2007, 16:45

Originally Posted by Crasherfromwayback

Bloody hard to get a good reading from 'plugs' now we've gone to this unleaded shite too....

LOL... Just Pm'ed you.

If I start the bike and rev it a bit and when at full throttle press the kill switch,then the plug is really white,almost looking like new...

The engine also get very hot and that only in a few minutes riding.

Can't remember it being that hot in the past...