06 YZ250F won't kick start after new pipe

[markbxr400]

My son installed a Yoshimira RS2 pipe with spark arrestor on his 06 YZ250F. We installed the JD main jet and needle, and it runs very well once it's started, however we have to push start the bike now (actually pull it with another bike several hundred feet). It will not start cold with the kick starter. Once warm, he can kick start it all day, so it's just a cold starting problem. It has the stock pilot jet and leak jet. Only thing we've changed is the main. Any ideas?

Thank you,

Mark

[Mr. Epeen]

how does the bike idle once started? you may want to clean the pilot jet. also have you checked the valves lately? they may be getting tight.

[markbxr400]

We had adjusted the valves about 10 hours prior and had them spot on. It would start fine before he swapped pipes. I had pulled the pilot jet to go get sizes on either side of it. Wasn't able to get a different size from the dealer, but did clean the original (it was actually vey clean when I pulled it out).

Any other idaes? Would this pipe tend to cause the bike to pull more, or less fuel on startup (eg., if I were to try and change the pilot jet, should I try larger or smaller)?

Thanks again,

Mark

[markbxr400]

Oh, and regarding how the bike runs - at first it had a very bad bog, but we kept dropping the needle on the JD jet until we got it leaned back out.

Thanks.

[otge306]

I have an 06 YZ250f and last year I installed the it Yoshimira RS2 Stainless Steel on my bike. I am not running the spark arrestor insert

I have no problems however I am running a 45 pilot and this pipe really rocks

I was lucky enough to try a White Bros, FMF Powerbomb and a buddy of mine has the same bike with a Megabomb. The Yosh pipe has really good bottom decent mid and pulls on top good. I just put Hot Cams stage 1 in. Holy cow lower mid on up pulls awesome. Very lowend is the same which is fine

Hope changing the pilot helps you

[av]

Try leaning out the pilot circuit by turning your fuel screw clockwise until it starts easier. Most of the bikes that I have seen with hard starting problems tend to be running too rich in the pilot circuit. You have lowered your needle to lean out the mid, maybe your pilot circuit is still too rich. Did you make your MJ bigger or smaller? You want to jet your bike just slightly rich to get the best throttle response, being lean on the pilot circuit will also make it start easier from my experience - as long as your needle and MJ are just slightly on the rich side you'll be fine.

[markbxr400]

Thanks - I'll try going with a leaner pilot jet (Ibelieve stock is a 42, so maybe a 40). I'll also go back and recheck the valves and put in another new plug.

One thing I have noticed is gas running out of the float bowl overflow, I am assuming from the million kicks to try to start it, but I'll also pull the float and the make sure it's seating properly. It definitely seems that it is getting way too much gas when kicking it. Sometimes we can drain the float bowl and get it to start. When we pull start it, it also seems like it has to clear the engine of excess fuel.

[SUnruh]

fuel running out of the overflow is from a stuck float.

has ZERO do to with kicking.

you put in the RED needle right?

hopefully on clip 4 or 3?

[davidl9999]

+1 on correcting the float bowl flooding problem.

Once that's corrected and the bike is running, set the pilot circuit this way:

https://www.thumpertalk.com/forum/showthread.php?t=327405

I wouldn't change pilot jets without the fuelscrew setting telling me that I need to do that.