Will the exhaust fit between 250f and 450f

I would like to know if 2006 yz250f exhaust slip-on bolts on to 2007 yz450f

No it will not. The header on the 07 450 is too large in diameter. A 250F slip on will bolt up to an 06 YZ450F, but the performance will not necessarily be the best.

... the performance will not necessarily be the best.
The noise is likely to be a bit out of range, too.


How about fitting 08 250f`s slip-on to 07 450f?


How about fitting 08 250f`s slip-on to 07 450f?

Nope, the dameter of the 250F header has been the same for 06-08. In 06 the 450 had the same diameter header, but in 07-08 the header was made a larger diameter. The angle of 450's was also changed between 06 and 07 so the 06 header will not fit perfectly on the 07, but maybe if you played with it enough you could make it fit.

If it is an aftermarket slip on, the situation may be different. FMF slip-ons are made to fit 06-08 YZ450F's, they come with a spacer you can use ito make the joint smaller to fit it on the 06. The FMF 250F midpipe is the same, and also comes with the spacer. In this case an FMF slip on (and maybe other companies as well, I'm not sure) will bolt right up to an 07 450. In fact, FMF shows the same part number for some of their pipes between the 06-08 250F and 450.

When it all ready came to aftermarket things fitting with wider variety of years then OEM things - is it true that wiseco HC piston is the same for 03-07? I was thinking it should be different between 03-05 and 06-07. Please confirm that.

the yz450f pistons didnt change. after all, it is 450cc's. so the 03 will fit an 07. BUT THE GASKETS ARE DIFFERENT. i just learned that.

i ordered a gasket kit from the TT store (my mechanic couldnt get em, they were ALL backordered...from everywhere) and it was for an 03-06 and they sent it and it was completely the wrong gasket. but its listed as an 03-06...i just ordered it from the dealer. which is what i should have done in the first place

the yz450f pistons didnt change. after all, it is 450cc's. so the 03 will fit an 07.
The OEM pistons did change, however, the change was always in the crown shape to enhance flow and adjust compression. The same ring set is used from 2001 to date. The bore size hasn't changed.

One thing about Wisecos: There have been 4 cases reported here that I can remember of wrist pins breaking and destroying an engine. All 4 were Wiseco pistons and pins. Draw your own conclusions.

i just installed a wiesco, herd some metal to metal noise...my bike goes pop pop pop CLUNK and black smoke came out....what do you think happened?

drop a valve?

What ever it was, I feel sorry for you. Maybe you made a mistake with timing chain and camshafts!?

BTW, I think I am going JE 12,8:1, instead of Wiseco (possible pin problems) or CP (too expensive).

i dont think the wiescos have pin problems. ive used them for a while. i actually used a shim that was a tad too tight.

i used the lowest tolerence feeler gauge and it was way loose. then i put the next size shim in and the smallest tollerence feeler gauge barely fit in there....

but no worries.

i ride a 4-banger, and it takes some sacrifice to stay off the crappy 2 strokes (and be up front) lol

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