Jets

[canadian-dirtbik3r]

Im planning on ordering some jets and have come to the conclusion that i am running lean. So what jets would richen my jetting? For the pilot jet im pretty sure i have a 58 in but i still have to check and the sizes go 52, 55, 58*, 60, 62 which jets would richen? A higher number or a lower number? If what ever one how many sizes should i buy? The next 2 richer or perhaps 3 and try them all? And now the main jet which is again im not exactly sure but the stock jet is a 172 and the other jets that i would need to try would be 168 170 172* 175 178 and which way would be richening it out? a 170- or a 175+? I almost got this jetting thing down any help would be great.

 

[wornknobby]

the higher the number the richer your bike will be.

go the next 3 sizes if you can, this way you can tune the bike in better then if you only had the 2. their only like 5 bucks anyway.

 

[canadian-dirtbik3r]

Ok so if i am running lean i should go with buying a 60, 62, and 65 pilot jets and 175, 178, and 180 main jets if i feel they both are off?

 

[yo its matt!]

the larger the number on the jet , the larger the hole, the more fuel it will flow, your pilot jet really only effects less than 1/4 throttle, and you main is mostly 3/4 to full throttle , so anything in the mid range you should try tuning with your needle,most needles have at least 5 positions, the lower you move the needle down the leaner the bike will be, fine tuning can be accomplished with different needle profiles and nozzles but you have to have your jetting as close as possible before you really need to buy those so you can tell exactly what you are trying to achieve.

 

[canadian-dirtbik3r]

Yah i was planning on tuning my needle and air screw first then moving onto the pilot then main.

 

[BigRedAF]

Why after 14 years have you decided that your bike is lean?
Are you talking about the 91 CR125?

If it has always ran fine untill now I'm thinking dry side crank seal might be sucking air and causing you to run lean.

Try to get stock numbers and needle posistion before you randomly change anything.

Bigger numbers equals more fuel, in on the air screw equals more fuel on that bike.

If you can adjust idle quality to peak RPM with the air screw and your between 1.0 and 2.5 turns out from full in then your pilot jet is fine.

 

[BigRedAF]

More than 2.5 turns out to get proper idle then use smaller pilot.

Less than 1.0 turns out to get proper idle then use larger pilot.

Ideal air screw setting is about 1.5 turns out with proper pilot jet, that leaves room for adjustment when temp changes.

Sorry if this seems to easy but you wern't sure about the sizes so I assume you might need the info.

 

[canadian-dirtbik3r]

I got most of the concepts down and ive only had this bike like 5-6 months and havent jetted yet. But first im going to adjust the air screw then the needle height but i dono how to test the dry side crank seal for a leak ?

 

[BigRedAF]

You would have to pressurize the cylinder, pretty tough if you don't have any of the required equipment.

You can pull off the ignition cover and see if you have any oil residue. If the seal sucks air on the intake stroke it can push oil and fuel out on the compresson stroke as well and that is a bad thing.

 

[BigRedAF]

You would have to pressurize the cylinder, pretty tough if you don't have any of the required equipment.

You can pull off the ignition cover and see if you have any oil residue. If the seal sucks air on the intake stroke it can push oil and fuel out on the compression stroke as well and that is a bad thing. :yikes: