crf450 inlet valves

[morg_nz]

so out riding the other weekend i went over a log and stalled the bike - couldnt get it started. wheeled it back to the car and left it in the shed for a few days. went to start it 4 days later adn nothing, except after bout 15kicks the lever was getting stuck bout 1/3 into the stroke.

anyways, long story short took the head off to find that one of the inlet valves had jumped out of the cotter pin and jumped out of the retainer - hence why the kick start couldnt kick move the piston. i have a mate whos a bike mechanic and he said he's never seen anything like it - the cotter pins are not damaged nor is anything else, just the valve stem is munted round the top where its left the cotter pin and been smashed into the head.

no damage has been done to the piston or barrel (luckily!) so i just have to replace the inlet valves (exhaust were replaced bout 15hrs ago) and i should be good to go.

my question is that if i buy stainless inlet valves (such as this set - http://www.motocrossparts.co.nz/moto...ge=1&piece=695) - what are the implications for having stainless valves for the inlet set and titanium for the exhaust? does this cause a problem or is it all good?

any thoughts?

[barty5]

no problem as long as you have the correct springs to match the springs

[morg_nz]

no problem as long as you have the correct springs to match the springs

correct springs to match the valves or correct inlet springs to match outlet springs? would you suggest maybe buying a set of 4 springs then?

[noobi]

Different compound valves, titanium, stainless, unobtainium, are all different weights, and require different strength springs to move. You only need to change the springs on the valves that you change. Ti valves run springs to suit Ti valves, SS valves run springs to suit SS valves.

[barty5]

as noobi said we have the same prob with one we bought although it needs valve guides as well (to be honest it need a whole new/ second hand top end barrel head crank the works ) any way could get you a set of TI valve Prox full set comes with springs to suit etc for 180 plus fr8 if you want norm is 212.49

[scott411]

as said above is right, if you go to stainless valves you need to have the springs to match, i would replace the springs on the inlet valves if you are replacing them as well,

sometimes stuff fails on bikes, interested to know why you changed the exhaust valves only 15 hours ago, were the inlet valves in spec?

[morg_nz]

as said above is right, if you go to stainless valves you need to have the springs to match, i would replace the springs on the inlet valves if you are replacing them as well,

sometimes stuff fails on bikes, interested to know why you changed the exhaust valves only 15 hours ago, were the inlet valves in spec?

previous owner is a bike mechanic and he rebuilt it just before he sold it to me - said that it was only the exhaust that were out, inlet were fine when he did them - odd ay

[motor_mayhem]

With the matching springs, SS will last longer, but your peak revs will reduce due to the weight increase - most likely not a problem unless you are a professsional racer. I replaced the inlet valves on my old RMZ with SS ones and barely noticed a difference.

[scott411]

previous owner is a bike mechanic and he rebuilt it just before he sold it to me - said that it was only the exhaust that were out, inlet were fine when he did them - odd ay

thats the issue with ti valves, they do not really show wear that well, meaning seeing if they are good or bad can be hard if not impossible,