525 Exc Head Removal

OK, '03 525 exc -greatest bike ever! better than my '72 Bultaco Matador!!

it was overheating and steamin' - you know what i'm talkin about, and then went BWAAAAAAAAaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah and then silence - it had to have sucked a valve.

OK, so how do I get the head off? I can't get the cam chain off the gear to slip the cam out and pull the head.

I have:

taken the tensioner off

backed out the gear bolts but couldn't spin the gear to pull it off

tried pulling the gear side bearing off the shaft

no luck.


What's the trick?:D

nevermind found my answer on dirt rider.:D

KTM Four-Stroke Top End Rebuild

This month we take you on a tour of the KTM Racing Four-Stroke (RFS) motor, specifically the top end. KTM's Tom Moen has rebuilt a few and knows the ins and outs to make this job as painless as possible. Relatively simple in design, it has only one fly complicating its design ointment: an endless cam chain that wraps in and out of holes to prevent it from coming apart without breaking the chain. And it requires a special KTM tool too (part No. 590.29.020.000, $138.49); pricey for all but the tool aficionado.

1. Remove the seat, tank, sidepanels and any skid plate you may have, and take the headpipe off the bike.


2. Empty the oil through the drain plug and pull off the ignition sidecover. This will let you turn over the motor more easily and allow you to get out the last of the motor oil.

3. Empty the coolant using the lower drain hole on the front of the cylinder.

4. Remove the radiators; first the left side then the right side, with the hoses still attached to the right radiator.




5. On to the carb. Disconnect the TPS wire before you loosen the clamps. The trick is to push the carb back into the airbox boot and remove from the right side, so you don't have to undo the throttle cables.

6. Remove the spark plug cap and blow out the hole with air (you don't need to remove the spark plug). Take off the gas-tank mounts from the frame. Remove the decompression cable by loosening the 8mm adjuster and lifting out the cable.

7. The external oil line comes off by removing the two banjo bolts with a 12mm wrench. Remember, the longer bolt is from the centercase and the shorter one goes in the head.

8. Next remove the valve-adjustment covers and water-pump cover bolts using an 8mm.




9a. Taking the cam-chain tensioner out—first, take the spring cap nut off the back and remove the spring to get the tension off the adjuster. Then undo the two 8mm bolts and carefully pull out the tensioner.

9b. Examine this tensioner very carefully as it will indicate cam chain life. Basically, if there isn't much adjustment remaining (two clicks left is as bad as you'd ever want to find this), the chain should be replaced. And if the cam chain is this loose, it can retard cam timing 4 degrees.


10. Take off the rocker-arm cover, and make sure to mark all of the bolts as they are different lengths. If you get messed up, the KTM owner's manual shows which one goes where.

11. Set the bike to TDC on the compression stroke, so the cam lobes are down. Now is the time to break the cam chain with the special KTM tool. Be very careful not to drop the chain pin into the motor. If you are not going to replace the cam chain, remove the whole link so you don't have to do it upon reassembly. Also, check the cam bearings and always replace the water-pump O-rings and seals.

12. Loosen the three 6mm (8mm head) bolts—one in the front, one in the back and one on the left side—then the four 13mm bolts. There are washers on all four larger bolts and one on the smaller bolt by the water pump. Finally, remove the head.




13. Remove the cylinder and take the piston off the rod, again, being careful not to drop anything into the case.

14. Check the ring end gap and piston clearance with the chart as a guideline (on next page). Now would be a good time to disassemble the head to check the state of the valves. Look especially for any intake valve cupping.

15. For the cam and water-pump assembly, its gasket support and housing has a seal inside where you can use a big socket to stabilize the housing and punch out the seal, because you can't clamp on the seal housing. To press in the new seal, you can use a vise with a protector.

16. Clean up the valves and head, using a wire wheel on the valves and a Scotch-Brite pad and a razor blade on the head. You can use a felt tip pen to check the valves' sealing. Do not lap the valves as it will take off any coating.

Well thanks for the info norcaltroy... I hope never to have to rebuild the top end of my motor...


Sorry, I didn't see this early.

Dave Hopkins also has a write-up floating around here that's very good. He's also a great one to send you head to should need work.

But I digress. You found it out, but you have to seperate the cam chain to take the head off. Which of course means you'll need to have a link to put it back together. Some people use the Motion Pro tool to swedge the new link. Other use 2 hammers and beat the link into submission. Still others go with the pricey KTM tool (my choice).

If you need any more help don't hesitate to ask. There are some of the best RFS motor builders around here and they're more than willing to lend some advice.

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