main jet question

bike is 2007 rmz 250, elevation around 6500 the kit I bought came with the main jet as a 170, the jet that was in the carb previously is a 162. I'm just wondering should I keep the 162 or put the 170 in also would changing from 162-170 even change anything? Thanks

Kehien jets or some other brand?

Different needle?

Other mods?


Once those questions are answered, a guess can be proffered as to the effect of the 170. However, assuming it is a Kehien jet, the bike is stock and no other changes, it would probably be very rich at wot, esp. in the lower gears when not under extreme load.

some other brand. I have a diff needle that came with the kit. The kit only included seals and all the jets. My manual says 170 is the stock jet. Which has me wondering why there was a 162 in it. just rebuilt top end, currently waiting on the accel diaphragm when I opened up the carb the diaphragm was in pieces. bike is stock.

Also what is this o ring mod deal if you familiar with it?

Non-stock brand jets are not comprable to OEM. You can only compare them to ones made by the same company. This is one of the many reasons the only jet kits to buy are the James Dean ones.


Oring mod is at the top of the page, pinned for ease of locating.

Alright then I'm going to put it in and ride thanks, also the needle was a notch lean I'm just going to put it back to stock with the 170. And I read the post about the oring I was asking if it's really noticeable heading to.the store might pick up some orings

Hey William I went riding today and the bike cuts all power when I get to high rpms. For instance in the air and before landing and holding it full throttle there's nothing until I land then it picks back up

Sounds like you are hitting the limiter.

That's actually the problem the bike wouldn't hit the limiter it would just cut out completely as if I was holding down the kill switch. I put the old 162 main back in and took it down the street seemed like it fixed the issue can't really tell unless I hit the track. I am still having the problem with cracking throttle anything past 1/4 and it'll just shut off. If I roll on its fine and pulls super hard. I was thinking about bringing the needle back up to the 3rd notch as it was before. Manual says 4th notch. But yeah any input is great this jetting stuff is really complicated. Oh and also with the accelerator pump I brought the screw to 2 turns out like recommended in the manual and it's terrible I had to bring it back out to like 3. Thanks a ton

You have another problem probably. Unless the jetting was stupid lean (which you are not) the scenario would not happen. More likely you have an electrical issue, perhaps as minimal as a bad connection.  Realize too, the AP and what it does is not the same as the needle. Do not tweak anything unless you have a good understanding, you can make a bad situation worse and I have seen many people adjust the carb beyonfd thier ability to get it back and require a real pro shop to fis what the owner 'fixed'.



To eliminate jetting as a problem. return it to stock. I have seen people mess with the jetting so much as to make it completely out of wack.

Alright I'll probably bring the needle back to what it was before, my spark plug is fairly old I will have to order one online since nowhere Carries them and the local substitutes will literally non run at all just non stop popping.

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