Can I use my stock needles and just replace my main jets?

[SchaffDogg]

Or is the complete kit necessary? i have two washers under my needles now, but I've removed my snorkel and added a slip on. it feels like its running lean and i know i need to jet. i was thinking of using the jetting database to make an educated guess on what sizes might work best and replacing the main jets with keihin jets and making adjustments from there. I've searched for a long time and can't seem to come up with much good info on jetting. and a lot of the info i find is contradictory. there are a bunch of different brands with different numbers for the sizes, stage 1,2,3 kits... individual jets?? can someone please help clarify this for me? or maybe a really good link with reading material? I really appreciate it thank you!

[Singh2jz]

Yes, I believe you can keep the stock needles and just add washers.

You can just buy the individual jets. The aftermarket needles are usually why the jet kits cost as much as they do.

When do you feel the bike is running lean?

Lets also wait for more experienced riders to answer lol..

[Lazarus]

IIRC the stage 1,2,3 kits are to correspond to your mods (stage 3 being the most amount of mods including pod filters, full exhaust, maybe some headwork, etc and stage 1 being the least amount, say maybe just removing the snorkel. Don't quote me on that buy I'm pretty sure that's what they mean.

Check the factory pro website for reading material. I've never heard bad things about their kits or instructions on how to jet.
http://factorypro.com/tech/tech_tuni...m_engines.html

[SchaffDogg]

Thanks for the input guys. So it sounds like I can just replace my main jets. Anyone do this? And is there a real big advantage to the aftermarket needles?

Also is Kehin the best brand to get? And also I've heard there are different styles of jets too, what is the best to use?

I've read the only difference between the stage 2 and 3 kits is one size bigger jet, is that true?

You guys are the best thank you!

[Ghostt]

You can just change the jets, without the needles. Aftermarket needles offer you the ability to change there settings.

Why do you feel the need to change your jets? Have you done modifications to warrant this?

[jkv45]

With the proper Main Jet and shimmed needles you should be able to get it running fine.

Make sure you have the idle mixture caps removed so you can set the screws at 2.5 turns out, which is richer than the stock setting and smooths out the transition off-idle. The needle picks up from there. Raising the needle with a washer or 2 richens the midrange and usually helps it pull smoother to WOT.

Aftermarket needles are adjustable, and usually have a different taper than the originals. That can give improvements, but if it transitions fine all the way from idle to WOT (as it's set now) I wouldn't worry about it.

[SchaffDogg]

Originally Posted by Ghostt

You can just change the jets, without the needles. Aftermarket needles offer you the ability to change there settings.

Why do you feel the need to change your jets? Have you done modifications to warrant this?

I removed the snorkel and it felt like it was struggling in the midrange so I've added 2 washers under my needles and it really came to life. After that I added a slip on exhaust and the top end seems better but almost like it lost some midrange grunt. I'm going to add another washer this weekend but I think I'm going to re jet as well. What do you think?

[SchaffDogg]

Originally Posted by jkv45

With the proper Main Jet and shimmed needles you should be able to get it running fine.

Make sure you have the idle mixture caps removed so you can set the screws at 2.5 turns out, which is richer than the stock setting and smooths out the transition off-idle. The needle picks up from there. Raising the needle with a washer or 2 richens the midrange and usually helps it pull smoother to WOT.

Aftermarket needles are adjustable, and usually have a different taper than the originals. That can give improvements, but if it transitions fine all the way from idle to WOT (as it's set now) I wouldn't worry about it.

Awesome! That's what I was hoping g to hear, any suggestions on main jets? Brand, etc.. should I change the pilot jets too? Thank you!

[Ghostt]

Pilot jets/idle mixture screws only effect the closed to 1/4 open range of the throttle, after that is the main jets/needles job. Fine tune the idle mixture screws first.

I've always used the manufacturer jets, no aftermarket.

When playing around with jets, I do it one step/change at a time, so I know what does or doesn't work. Don't make a bunch of changes at once, it makes it harder to know what did what.


Jets are cheap, so pick up a few different ones, so you can try them out, and see their effects.

Consult the jetting database odds are someone else has done their homework and posted their results.

And finally, if your playing around with jets it a best guess scenario, without an exhaust gas analyzer.

Good luck.

[SchaffDogg]

Originally Posted by Ghostt

Pilot jets/idle mixture screws only effect the closed to 1/4 open range of the throttle, after that is the main jets/needles job. Fine tune the idle mixture screws first.

I've always used the manufacturer jets, no aftermarket.

When playing around with jets, I do it one step/change at a time, so I know what does or doesn't work. Don't make a bunch of changes at once, it makes it harder to know what did what.


Jets are cheap, so pick up a few different ones, so you can try them out, and see their effects.

Consult the jetting database odds are someone else has done their homework and posted their results.

And finally, if your playing around with jets it a best guess scenario, without an exhaust gas analyzer.

Good luck.

OK awesome stuff thanks for all the info! So where would I get factory jets in different sizes?

[Ghostt]

Originally Posted by SchaffDogg

OK awesome stuff thanks for all the info! So where would I get factory jets in different sizes?

Try @ducatiman first, after that a motorcycle shop/dealership.

Remember that jet sizes are not standard, so stick with the manufacturer of your carburetor.

[ducatiman]

for full selection use jetsrus.com they have a make and model breakdown

[jkv45]

If you have a local dealer or performance shop, you may be able to get your jets there. Bring an original one with you, and only use OEM jets. Dynojet has it's own numbering system, which makes it a pain. Be sure you are looking at OEM jet numbers when you are deciding on what to try and not Dynojet numbers.

If you do some research you should be able to get pretty close on the first shot, but there are some variables (altitude, temp, type of gas) that may be different.

[bruce71198]

The profile or tapper of the aftermarket needle is superior to the stock one and will benefit even a box stock engine.

[SchaffDogg]

Ok, might as well do it right since I'll be in there. would you recommend factory pro or dynojet? And I know there are different stage kits. Right now I have the snorkel removed and a slip on, at Sea level in California 50-100 degrees. I also plan on getting pods soon so would I need a stage 3for that? Also what is the difference between the stages?

[jkv45]

I hate the fact that Dynojet has it's own numbering system, so I would definitely go with Factory Pro.

[SchaffDogg]

Ok thanks, so factory pro uses the same numbers as Kehin? And what's the difference between the stagees? And are the kits universal? Or do I have to search one for the 250 specifically? Thanks guys!

[bruce71198]

I have always used DJ The standard kit should have everything you need including jets to get your bike tuned without to much drama.