Posts
6161
Joined
1/31/2018
Location
Mansfield, OH
US
Edited Date/Time
2/12/2018 5:28am
Building a 09 kx250f. Put a new wiseco piston in, new head, new prox valve kits, new stage 1 hotcams, new cam chain.
Having a problem with the intake valves hitting the piston when i try to turn it over. Ive redone the cam timing about 4 times over and am pretty sure its right. All valve clearances are in spec.
Ive done this so many times on my 450 and some friends bikes but cant figure this one out. Any ideas?
Ive attached pictures of where the crank is, where the cam markings are, where the motor stops turning, and the service manual.
Having a problem with the intake valves hitting the piston when i try to turn it over. Ive redone the cam timing about 4 times over and am pretty sure its right. All valve clearances are in spec.
Ive done this so many times on my 450 and some friends bikes but cant figure this one out. Any ideas?
Ive attached pictures of where the crank is, where the cam markings are, where the motor stops turning, and the service manual.
back in 09 i did a crank in a kx250f i used a 08 cank i thought it was the same it wasnt and i had the same poblem you have so i moved the intake cam a couple teeth and the bike ran fine come to find out the 09 crank had the keyway fo the flywheel in a differnt place, so i ended up putting the rite crank in
did you buy it used? whats it got for a crank
maybe check and make sure the flywheel key is still there
The Shop
My intake clearance is .15 on one and .13 on the other. Within the service manuals spec. Hotcams card says .15 for clearance. Is the .02mm going to matter? Thats all i can think of
With the dots aligned properly, like shown in your 1st pic, the exhaust cam lobes should be pointed at about 10 o’clock and the intake cam lobes should be pointed at about 2 O’clock. Like it is shown in KB’s post on the 450.
Another way to check the gear alignment, is by confirming the circular hole in the cam gear is inline with the camshaft’s lobes.
The cam gear can spin on the shaft on these models, it’s happened to mine before. They should index the cam gear onto the shaft but they don’t. You can tack weld the gear in place like I have done.
Also, i rotated the intake cam to make it more flat(opposite but same angle as exhaust cam lobe) and that did not help the situation.
Paw Paw
When you put in the valve kit...Did you do it or a good shop? Was the piston to valve clearances checked?
Paw Paw
Also if hotcams messed up on the cam gear timing, ill have to have them replace it.
Or i need to double up on base/head gaskets.
Pit Row
After work ill throw a stock cam in and just make sure i dont have a piston/valve clearance issue. Once that checks out ill get hotcams to replace my cam with a good one.
The flywheel has 3 marks in 3 different locations for some reason. Obviously i mixed them up. I used a long screwdriver in the spark plug hole to find tdc, lined up the closest mark to the ignition cover, timed the cams and the motor turns over.
Post a reply to: Intake valves hitting piston