426 Kit

What would be the easiest way to find out if my bike has had a kit installed without taking the head off assuming I can't get in touch with the previous owner?

What kit are you referring to???

I'm wondering if I have a bore kit in my YZ426. The shop I bought it from said they didn't know. I have 52/178 jets which is much higher than everyone elses on the forum that I see. So, its kinda has me wondering why it's running so great given the size jets. That's why i'm wondering if there is a way to check without going to all the trouble of taking the head off. The cylinder said 426cc so unless the guy had it sleaved it can't be right?

Usually a big bore kit requires leaner jetting, not richer. Measure the bore and compare it to the manual.

A 52 pilot is huge. Are you sure it wasn't a 42? It may have a JD jet kit requiring a 178 main jet. Remove the top cover of the carb and the allen bolt on the top side of the slide and see it has a blue or red dot on the needle. If the needle has been painted blue/red that is a JD needle and would explain the main jet size.

Thanks for the info, i'll take a look at it and get back to you. I'm sure it's a 52. It was running lean but I realized the accelerator pump was in upside down ( the guy I bought it from or the dealer did that). :thumbsup: Anyway, i'll check and get back to you, Thanks for the great information!

I checked the needle last night. It said (ODKAR) around the top and the clip was set on #4. What does that mean to all you 426ers out there?

I have no idea what an ODKAR needle is. Try to track down Burned, he is the jetting guru.

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