Question about 2002 Yamaha YZ 426 F

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How do you put timing chain back on and time cams after head gasket change

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funkychateau

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Most motorcycle cam gears have a mark on one tooth, often just a punch mark, sometimes an "o". Usually this mark should be "straight up" in line with the cylinder when the engine is at top dead center on the compression stroke. Double-check your service manual to be sure for a particular bike.

So here's how you set it. Remove the flywheel cover and rotate the engine so that the piston is at top dead center. There should be a "TDC" or "T" mark on the flywheel, and some sort of corresponding mark or pointer on the engine case to line this up with. To make sure, remove the spark plug and verify with a flashlight that the piston is as high as it can be when the marks are lined up.

Now rotate the cam gear until the punch or "o" mark is at the very top of the engine (in line with the cylinder, if the cylinder is slanted). At this point, neither the intake nor the exhaust valves should be open.

Now connect the cam chain while both the crankshaft and the cam gear are in these reference positions, and you are done!

best regards,

Marty

Posted on Nov 06, 2009

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Will not start ran hot then replaced head gasket with new head set put back togeher would not start. Put new camshaft sensor on where should I start next?


Have it towed to the nearest ASE certified repair shop ! What's missing Tammy ? Is there spark ,Is there fuel pressure ? Did you have to take timing chain off to replace head gaskets ? are the timing marks set right ? Why did you replace cam sensor ? You need to find out what is missing first.

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Does the piston stay conected to conrod when changing head gasket...will the head come past the piston?


Yes they do. You'll probably have to hit the head with a rubber mallet a few times to loosen it up, but then it will just slips off and the pistons stay connected to the rods. You really need a shop manual for this because you'll have to take the cam chains off and then re-set the cam timing when you put it all back together. No big deal if you follow the instructions closely, but if you get it wrong you'll wreck the motor when you go to start it. Also, as long as you've got the motor apart you might consider changing the cam chains depending on how many miles the bike has on it.

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Setting of timing chains


Get Ford timing tool kit, part = otc-6488 (For about $119 USD on eBay)

4 timing chains (3 front including the optional balance shaft chain + 1 back)

2 cam guides (1 front + 1 back)

2 oil tensioners (1 front + 1 back)

1 jackshaft tensioner (1 front)

1 jackshaft guide/cassette (1 front)

1 balance shaft tensioner (1 front) (will probably be ok, so dont replace it)

1 balance shaft guide (1 front) (will probably be ok, so dont replace it)

new sprockets + bolts + gaskets etc.

new spark plugs + throttle body cleaner + lithium grease spray + oil change

head gaskets


some of these parts (the front stuff) can be obtained as a primary timing chain rattle noise kit Part# = 2u3e-6d256-** ab for 4*4 & bb for 2*4.

The kits also have later part numbers for us$ 76 @ http://www.fordpartsonline.com


My parts order (without the balance shaft stuff) was:

$76.04 KIT-TENSIONER TIMING 2u3e-6d256-ab

$47.93 Engine, Camshaft and timing, Timing chain, TIMING CHAIN, Explorer, Mountaineer, Rear - 4.0L SOHC - 4.0L SOHC

$57.36 Engine, Camshaft and timing, Chain guide, CHAIN GUIDE, Explorer, Mountaineer, Jackshaft To Cam - 4.0L SOHC - 4.0L SOHC

$103.22 Engine, Overhaul gasket set, OVERHAUL GASKET SET, Explorer, Mountaineer, Upper (Valve Grind) - 4.0L SOHC - 4.0L SOHC

$28.93 Engine, Camshaft and timing, Tensioner, TENSIONER, Explorer, Mountaineer, Upper - 4.0L SOHC - 4.0L SOHC

Its worth mentioning that this procedure is not enjoyable at all and should be undertaken with at least 8 full days to completion (I recon you could do it in half the time the second time).

It is basically on entire engine re-build with both heads off and the engine out of the vehicle.

It is not possible to do the rear chain or sprocket with the engine in the car as the flywheel needs to come off + at least 1 head, but it is possible to do the front primary chain and or front cam chain with the engine in the car.

You will be a ford exploder and timing expert after you do this - the main reason should be the love of your American built vehicle. Its a solid car - except for the plastic guides!

Disclaimer Note: This is how i successfully did the job, but i am not a ford mechanic and don't hold me responsible if this does not work for you.
Timing Overview

A Small Sprocket on the crank turns a larger (2 to 1 ratio) jackshaft sprocket that is in turn connected front & back to the 2 camshafts.

Thus a 360o turn of the crank will turn both the camshafts 180o.

Firing order is 1-4 2-5 3-6, Right side numbers 1,2,3. Left Side = 4,5,6.

At TDC pistons 1 & 5 are fully raised, thus 1 is about to spark & 5 is evacuated.

The engine will turn freely (no piston to valve contact) with the cams 180o out, it will even run (roughly) with 1 out 180o, any other settings may cause major damage to the valves.

The 2 cam shafts come with timing markings, "yes" real timing marks that anyone can use (even without special tools) to ensure correct timing.

The way to time it is to ensure both the off centre cam shaft slits are level/flat with the head.

With the engine at TDC both the cams need to have the off centre slot in the same position either up and level or down and level.

It is super critical that both the camshafts are 100% in sink with each other, i.e. not a few degrees off, the engine computer can compensate for crank timing but not engineering failure.

Be warned the camshafts can turn easily fast & hard by themselves as a few springs are compressed at TDC, I got my finger jammed and its still healing + if the engine is not at TDC you may damage a valve.

Now heres the hard thing that you will need special tools for - if you need to change the timing, you will need to be able to undo the cam sprocket bolt on both cams & these are done up real tight.

There is a tool that you attach that has 2 pencil thick shafts that fit into the sprocket and prevent it from turning - then you need to put about 90Nm of force on the bolt (remember the rear one if LHT)

For the $money$, its well worth getting yourself the tool kit - it will save you hours in the long run. Search eBay for otc-6488 should be US $119 - then sell them again for say $100.

There is also a tool version of the oil tensioner in the kit that screws right in and puts the correct amount of force on the chain + guide, to enable you to do up the cam bolt with the chain and sprocket in the right spot on the cam.


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Trying to put timing chain back after replacing head gasket on a Nissan N22 motor. Need to find adjustment to loosen timing chain so that i can attach timing gear with chain onto OH cam. can you help on...


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