Time for a new top end?

04 CRF 450, 80 hrs run on MX tracks and some playriding, very well maintained, valves in spec. "C" rider, Tires in great shape and right for surface ridden.

Seems to me that I used to be able to loft the front wheel to manual over small kickers or entering whoops, with just leaning back a little in second thru fourth. Now it takes being in the thickest part of the band and a good yank in only 2nd or 3rd. Still has a good mid-range kick but it seems to be milder than before. Low end feels sluggish. Should I get a compression test to tell if I need new top end? Or should I inspect cylinder and piston because it may just need rings? Or if it looks pretty good in there, maybe I need a Hot Cam Stage One or a higher compression piston (that doesn't need race gas)? Help! :bonk::thumbsup:

From what I have read on here from the gurus... you need to freshen it up. You definatly need new rings and should replace the piston as well since it is nothing more than a "ring holder". :thumbsup:

How does it feel when kicking it over? Very light? The power going away and a light feeling when kicking over were indicators to me to check my valves. The right intake was at 0 although I had not yet experienced any starting problems. I went with Kibblewhite valves and springs and had the valve seats redone. Since I was in there at 45 hours, I also put in a J&E 12.5:1 piston and new rings. The old ring end gap was a .012, which is well within the limit of .018.

maybe a dumb ? but how is your clutch?has it ever been replaced

A leakdown test will clue you in on where the problem(s) are; worn valves/seats, smoked rings, etc.

you are just so used to the power----80 hrs seems a little low compared to most on here :thumbsup:

maybe a dumb ? but how is your clutch?has it ever been replaced

No, actually a great question. Does a notched basket effect the power that much?

Cold it feels great but it drags a lot (hard to push if clutch pulled but in gear when properly adjusted). Needs to be adjusted once ran for more than about ten minutes. It has never been replaced.

Sounds like I need a leak down test and also inspect the basket and plates as well.

Buy a gasket kit, tear it apart and mic things out if they ck out fine put it back together, if not replace the bad parts

check to see if it has good compression and if it doesnt tear it apart re ring it and put a gaskit kit on it and check if you have any burnt valves that will make you lose hp because your either spiting fuel back into the carb our your spitting fuel into the exaust so your could be rich or lean rich would be your power loss

With 80hrs on the bike he shouldn't go near it until he has fresh rings in his hand. His are clapped out. Burned has some great posts that will have me paying way more attention to my ring-holder :thumbsup:

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