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Old 03-13-2007, 09:03 PM
basanch73's Avatar
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Default YZ426 Cam Chain Replacement Guide

Steps for Replacement of My Cam Chain on my '01 YZ426F

Initial Tips: Ensure you have a clean area or table to place out all the parts. A old white sheet on a rollaway worked fine. Also, a large drip pan below the bike kept fallen screws from running off and hiding on me. Most importantly, do not tighten cam cap 8mm nuts without a torque wrench. 86In lbs is a must (No more, No less)! You definitely donít want to ruin the whole process by stripping out the aluminum threads within the cylinder head.

Special tools needed: Left Hand Thread 27mm Flywheel remover tool; set of torx (Star looking) bits; (10-100Ft lb) and (10-250In lb) torque wrenches; & Lots of Patience!

Parts Needed: New Cam Chain; Oil; Flywheel cover gasket and Valve cover gasket. The gaskets could be reused depending on condition. Itís your call. Optional: Oil Filter, if you donít have a reusable steel one and possibly valve shims.

REMOVAL

1. Remove seat, tank and shrouds.
2. Drain oil.
3. Clean all loose debris around frame area above the valve cover and blow out any debris in plug area with compressed air.
4. Remove Spark Plug and Breather Tubes.
5. Carefully remove valve cover and seal.
6. Remove Timing and Crank plugs on flywheel cover.
7. With the bike in Neutral, turn the motor over by ratchet and socket on the crank nut until the "I" mark lines up with the top and bottom notch on the timing plug hole. You want to get the bike to Top Dead Center (TDC) on the compression stroke to relieve all spring tension to all the valves by having them all closed at the same time. At TDC Compression, the "I" mark should line up and the exhaust and intake cam lobes will all be facing outward from each other. Additionally, there will be three dots on each of the cam gears that should be at 9, 12 & 3 O'clock with the 3 o'clock dot on the exhaust cam and the 9 o'clock dot on the intake cam pointing at each other when the crank ("I" mark) is positioned at TDC Compression. (As an added note of faith, I inserted a long #1 flathead screwdriver in the plug hole to notice the flat point where it neither goes up or down, which verifies true TDC of the piston.)



8. At this point mark the caps directly behind the cam gears with a scribe or other sharp object to the 12 o'clock dot positions. Do the same for the crank. (I quickly found out that pencil and marker quickly rubs off with oily hands) It is highly recommended to take pictures for reference later. I also wrote down that there were 7 links between the 12 oíclock dot and tooth on each cam as reference.


9. At this point it would be wise to check your valve clearance. You might as well adjust your shims if need be at this point.
10. Now that you've got the crank and cam marks referenced, turn the rear wheel to where you can put a long pry bar or screwdriver thru the sprocket, wheel and brake and place the bike in gear. Then, temporarily remove the shift lever to get the side cover off.
11. Remove the Flywheel cover, but be sure to lay out the 8mm bolts in order that they were removed, such as poking them into cardboard or something. Not all of them are of the same length.
12. With the cover off, bike in gear and wheel now kept from rotating, you can remove the nut on the crankshaft. The crank and cam gears will move, but with your references you can rotate them back into the TDC Compression position again with the help of the kick starter while holding in the decompression lever (if you still have one).
13. With a left hand thread 27mm flywheel puller tool, remove the flywheel.

14. Place a reference mark on the pick-up plate and the center of the torx screws that retain it to ensure exact placement upon reinstallation and to not alter the timing in any way. Making a reference mark on this plate to the position of the crank is wise as well. (Again Digital Picís help)
15. Remove the two Torx screws on the pick-up plate and carefully secure it off to the left somewhere away from the crank.

16. With the cams and crank all lined up at TDC Compression, remove the chain tensioner, but be sure to remove the center 10mm screw to it before the two 8mm retaining bolts. (I did not have to remove the Carb to do this) You can go ahead and check it at this point for proper operation as pointed out in the manual. If you donít have one, just insert a small flat head screw driver and turn in clockwise while holding pressure inward on the plunger until it stops and does not release. Then turn it back slightly to see if the plunger moves back out freely.
17. Remove the two bolts that retain the lower portion of the chain guide on the right. You canít remove it completely, but it allows it to move out of the way of the chain.

18. Now you can carefully remove the 8mm bolts to the cam retainers/caps. Be sure to retain the half moon shaped retaining ring that seats into the bearing and cap. I left mine in place since they didnít move from the cap.
19. Place a long flathead screwdriver or like item thru the chain and across the top of the motor to keep it from falling in. You can also use cord or zipty to hold it up.
20. Remove the exhaust and intake cams.
21. Now for the pain in the butt part. The chain can now be removed fairly easy from the right side of the crank gear, but I had to put lots of pressure on the left chain guide and roll the chain off carefully with a small flathead screwdriver. You just have to be real patient and careful not to scratch the crank shaft or guide.
22. Optional: With the chain off you can place it stretched out side by side to your new chain to see how much stretch and wear you actually had as reference of how long you can expect to go before replacing it again. My chain was stock from 2001 (recreational riding only, no races) and lasted 6 years with minimal stretch (Lucky I Guess!). My only indication of needing to change it was a slight rattling noise from the left side of the engine noticed only as a came off the throttle with the clutch in, which was when the chain would have the least tension on it. Once I gave it throttle in gear, the noise went away with the tension re-added.



INSTALLATION

1. Take the NEW chain and oil it. Once done drop it down thru the top of the motor and suspend it again, leaving enough excess below to work it back onto the crank gear.


2. With the chain on at the bottom, you can now route it over the exhaust cam and the intake cam carefully to ensure that the cams and crank are still in the same TDC Compression positions previously marked.
3. Secure, but donít torque the cam retaining caps onto the cams, ensuring the half ring bearing cap retainers are properly in place in their grooves when installing.
4. Reattach the bolts to chain guide at the bottom.
5. Install the chain tensioner. It must be wound up and then released after the 8mm attaching bolts are installed. Once you have tension on the chain, you can install the 10mm bolt to it.
6. Install the pick up plate to the reference marks.
7. Re-verify that the cams and crank are still in their proper position TDC compression with the chain having tension on it now. If everything is correct, go ahead and torque the 8mm bolts to the cam retaining caps.
8. Prior to installing flywheel, ensure itís cleaned thoroughly. There was a ton of old metal shaving sludge that built up over the years. This will take a bit of time, but it makes no sense in reintroducing it into your motor. After itís all clean to include the woodruff key groove, dab some clean oil on the inside hole and groove.
9. Install Flywheel, washer and nut to crank. Youíll have to revisit step 10 of Installation to retain the crank from moving to torque the nut.
10. Install cover, but hold off on installing the timing and crank plug.
11. Install shift lever to proper position and properly torque its retaining nut. Thereís nothing like loosing that in the mud or sand.
12. With the valve cover still off and side cover plugs still off, re-verify all of the camís dot positions along with the ďIĒ timing mark for the crank are set at TDC Compression with the cam lobes outward.
13. Install valve cover and seal.
14. Install breather tubes and spark plug.
15. Reconnect plug wire, tank, shrouds and seat.
16. Before you fill oil to proper level, do one last check of parts table and look the bike over thoroughly. No sense in wasting some expensive oil, because youíve forgotten the crank washer like I did. Thanks to the built in oil filter check valve and lack of actually kicking it over, I only lost a few ounces. Fortunately, you can fix this by just removing the crank plug.
17. Optional: If youíve waited to do this during you normal oil change interval, you might as well replace your oil filter or clean it if itís reusable at this point.
18. If everything looks good, fill the bike to the proper oil level and fire it up!

Note: The chain slap noise I had when backed off from the throttle had completely disappeared with the new chain in place.

ENJOY and GOOD LUCK!

Brian
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  #2  
Old 03-13-2007, 09:17 PM
crfjedi393's Avatar
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Default Re: YZ426 Cam Chain Replacement Guide

Oh man! Nice post! Thanks for going to all the trouble with the pics and all.
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Old 03-13-2007, 09:33 PM
Semper Fidelis
 
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Usflag Re: YZ426 Cam Chain Replacement Guide

Brian,
That is an excellent job and great narrative/pictures. This one will be in the 4 stroke knowledge base shortly.

Bill
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Old 03-14-2007, 01:21 AM
Thumper426's Avatar
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Default Re: YZ426 Cam Chain Replacement Guide

awesome post, I am about to swap cam chain guides and tensioner, if that doesn't make my occasional rattle go away.. new chain is next. Not a bad rattle, just on occasion it will sound like it has a lil slack. Figured swap cheap and easy first, the bike is a 2000 on all OE parts so might as well.

Definately will keep this one in my mind for when it's time to swap chains. I am startled to see the compression cable in the picture. I thought all 426's came with 450 exhaust cams by now! hehehe..

Granted.. the lever did limit who could ride the bike. "If you can start it.. you can ride it"
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Old 03-14-2007, 11:43 AM
basanch73's Avatar
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Default Re: YZ426 Cam Chain Replacement Guide

Yeah, Yeah . I still have a decompression lever. My son has the Cam MOD, but just ask my son who starts up quicker. If you know how to use it, you'll start quicker since your guaranteed to kick it over at TDC every time. Heck, I've got it down so good now that I'll hold it and the clutch in at the same time and start and go in first. I must admit though, that I have to pick up a DrD Hotstart. I'm not that good, to hold both levers and the hotstart on the carb and kick at the same time. That's just not gonna happen.

Oh, if you happen to swap your guides, please post a picture of the chain surface side and the time on them. I'm curious to the wear it shows. Knowing mine were stock, I was amazed that they were still flexible and absent of any significant wear.

Well, I'm glad that I could be of service and share the help. I've definately received enough of it from all of you at ATM. I failed to take pics of my recent rebuild of my forks, but I'll do another narrative on that here shortly if anyone needs it. It was definately easier than the chain replacement, but found some skipped steps within the manual that I had to figure out on my own.

Later,

Brian

Quote:
Originally Posted by Thumper426 View Post
awesome post, I am about to swap cam chain guides and tensioner, if that doesn't make my occasional rattle go away.. new chain is next. Not a bad rattle, just on occasion it will sound like it has a lil slack. Figured swap cheap and easy first, the bike is a 2000 on all OE parts so might as well.

Definately will keep this one in my mind for when it's time to swap chains. I am startled to see the compression cable in the picture. I thought all 426's came with 450 exhaust cams by now! hehehe..

Granted.. the lever did limit who could ride the bike. "If you can start it.. you can ride it"
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  #6  
Old 03-14-2007, 12:28 PM
Thumper426's Avatar
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Default Re: YZ426 Cam Chain Replacement Guide

I will definately post up a thread about guide swap complete with pics when I get to it. I used to start the bike just dandy with the comp lever, and I know what you mean about working both levers at once. I went for quite a while pre-cam mod until I got into some larger rooted, rutted hills, then it was both levers while trying to hang onto the brakes while sligind down greasy hill sides. That got old to me, gave in and swapped cams. Then spent who knows how long tweaking on the carb and got it to pretty much start first kick most every time. Occasionally if I really bury it into something and load it up it takes a lil to clear it out, but I rarely ever use the hot start now. Took forever to get it to that point though! LOL

Awesome bikes, I like seeing a pair of them sitting together waiting to hunt 450's! hehehehhe
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Old 03-14-2007, 11:13 PM
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Default Re: YZ426 Cam Chain Replacement Guide

Oh yea DAD i can beat u startin it anyday haha, yes it is true he starts before me EVERYTIME. and it is a pain in the butt to start it without the decompression lever. Nice to see my bike in the backround lookin all pretty and stuff. oh yeah i see u dont give me props in your thread for helpin u post them pics haha ahh its alright tho.
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