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craigfedd

valve clearance for 2005 crf450

9 posts in this topic

as per faq;

Valve Settings

Seems like there is some opinion here, but it looks like running the closer than the book will extend the valve face by setting the valves into the pockets a tad easier.

.004" on the intakes

.008 on the exhausts

Now the decompressor can do a couple different things here. If you were to run the decompressor at .014 in addition to the .008, youre net is only .022 instead of the recomended .024. You can add the missing .002 to the secondary measurment or simply run it slightly tighter overall. The result will be opening the decompressor just slighty earlier than normal which will reduce the kicking effort just slightly. Guys with High compression pistons may find the bike is less finicky to start.

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just curious why do u say tighter is better on the valves.. i know loose isn't better..

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just curious why do u say tighter is better on the valves.. i know loose isn't better..

once again a search finds info per rhc

this is for you tech heads . Valve seating velocity this is the speed that your intake valve is impacting the seat .in genral you will see velocity in the 25 inches per second to 35"per sec range these are for maximum rpms . here is an example this is a very similar cam that im using to the stock crf cam.with your valve lash set @.006 " and your bike reving to 10500 rpm your seating velocity is 26.9 inches per sec. @.009"lash the same rpm your seating velocies are 32.49 inches per sec. and @11200 where your crf hits its rev limiter', with .009"lash your velocity is 34.657 inches per sec.this is genral rule of thumb 25"for a endurance engine that will have to make along race 30" for say a sprint car engine requireing lots of maintenance and 35"for a drag car that you hope runs for 7 secounds.the point im trying to make here is when installing new valves in your crf try setting them on the tight side of the spec it will lower your seating velocity and make your valves last longer . also when your engine is hot they gain lash raising the velocity. i supose that an engine running very hot and being set up cold on the loose side could exibit valve problems.Ron

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just checked mine on my 07 crf450r supermotard and @46.3hr.s the valves are right @ .004in and .008 exhaust right where i set them after the 5 hour romp-athon when new......good stuff!!!

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How should the Feeler gauge feel when slid into place? I was told that spec for a 2005 crf 450r should be at .005! The gauge for that clearance was snug,but the .004 fit smoother with a little drag!! Any ideas?

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