Got my 450 cam

Finally got my 450 Ex. cam today woohoo. Prolly take a couple days to install since I dont have long to work on the bike before the yamaha shop closes where I can pick up the shims. Does anyone have any secrets or problems that I might run in to? This will be my first time in a big 4 stroke motor so I'm sure anything can help. I have already printed off alot of info that I think I will need.

I read as much of the thread as my eyes could take, printed out the vital info, and read it over and over. When I got around to doing the job it all made sense. When you finish it, tell everyone how much you love it! :applause:

One "trick" you can use to make the job easier is to zip-tie the cam chain to your intake cam before you pull the exhaust cam out so that you don't have to re-time it. The trouble is that timing the intake requires the exhaust to be in place so the chain can draw up tight on the front side. Since the 450 cam is marked wrong for the 426 head, you have to time the exhaust cam by counting pins (14) between the two 12:00 marks, based on the properly timed intake cam. (remember, you're doing something different than re-timing the stock cams from WR to YZ or vice-versa. Don't confuse the instructions for one with the other. 14 pins will time the cam correctly as a YZ) Doing it like this helps keep the intake where it belongs and shortens the process.

Here's a picture from another member. A little fuzzy, but right.

I read as much of the thread as my eyes could take, printed out the vital info, and read it over and over. When I got around to doing the job it all made sense. When you finish it, tell everyone how much you love it! :applause:

Besides making the bike easier to start . . . any other advantages to swapping to 450 cam?

Ok I got into my motor today. The 2 outside intake valves were at max .15, I think i should leave these right? The center was at a .07 and has a 190 shim so a 185 should put me back in the good right? With the 450 cam in place I checked clearances there an i got a .16 on both, can this be right? I thought the gap would be bigger. On those valves the chain side had a 181 shim and the right side with a 184. So to correct these a 175 and a 180 should do it?

Also in some of the info. I got it said not to line up the H but the I. The only mark I saw was the H unless the I is the line right beside it? Even then i had to pass that mark up rotating counter clockwise for the marks on the cams to line up correctly

Besides making the bike easier to start . . . any other advantages to swapping to 450 cam?
The guys who have run them in 426's say that they give the bike consierably stronger low and middle range without loosing anything on top. This flattens the power curve, lessens the sudden "hit" at the lower middle, and makes the bike both stronger and more rideable.
Ok I got into my motor today...
First off, if you don't have a manual, download one:

Next, yes, the I is only a couple of degrees clockwise from the H. If you have any doubts as to whether it's right, you should check how well the I mark matches TDC by removing the spark plug and probing for the piston with a long philips screwdriver. If the two don't match, you could have sheared a flywheel key. Remember that only your intake will line up like a stocker. If it seems not to have lined up right, imagine it another tooth one way or other. It probably won't line up perfectly, but if you look at it, moving it a full tooth should make it somewhat worse. If the cam has not rotated far enough forward to move into line at TDC, and looks to be a half tooth or more off, think about how long it's been since the timing chain was replaced.

On your intakes, leave the outers and put the 185 in the center.

On the exhausts, you changed the cam, so the clearances could be anything. Since they are both .16mm, work from there. You don't say whether your bike is an '00, or a later one; it makes a difference. The '01/'02 engine with Ti valves calls for .20-.25mm at the exhaust valves, so you are off by .04-.09. The 175 and 180 you suggest will just do it for you. The '00 had stainless valves, however, and calls for .25-.30mm instead, so you would need to go to a 180 and a 185 in that case. Always double check after making your corrections.

Dirttrack 25

I did the 450 cam swap in my 2002 YZ426 10-11 months ago and it was very easy to complete and I had never even checked my valves. Make sure you use a torque wrench that measures in inch pounds NOT foot-pounds to torque the four bolts that hold the cam caps. After you check your valves with the new cam you will need to go to your dealer to buy/order the correct shims to give you the right clearance. If your valve clearance readings seem odd or way out of spec. make sure that you are using or reading the gauge in mm. and not inches. The other benefit that I enjoy about the cam is that I can now “bump start” my bike should I stall it on a down hill section, I could not do that with the stock cam. Good luck and enjoy the cam swap. :applause:

Im pretty sure the flywheel key isnt sheered because it ran fine. When I put it all back together I'll time it with the I lined up. Hopefully that works. Ill be back tomarrow evening with the result.

Well I got everything put back together now. Started pretty good but im not sure that everything is timed right. It still takes a swift kick if your at TDC when you start. Everything was lined up when I closed it but could it have slipped the chain when i tried to kick? I only got a little 5 min. ride in the dark and at 36 degrees, but from what i could tell it felt like the bottom was good, mid felt kinda weak, but it didnt seem like wouldrev out like usuall but that could be from 1 it was lean since its cold? or maybe 2 cuz i was freezin and wasnt twistin like usuall

The auto-decompresor doesn't relieve all the compression, it just reduces it by holding one exhaust valve open for part of the compression stroke. That way, it has enough compression that it can actually start and run, but little enough that it can be cranked through the compression stroke. Whereas your original setup had about 180-220 pounds cranking compression, you should now have closer to 120. With healthy rings and valves, getting it over the top will still require a positive effort, but no drill, no precise positioning of the engine, etc., just kick it like it was a 300cc two stroke.

Gray, you are a virtual Yamaha Encyclopedia!

Alright sounds good to me then. I left the manual on anyways because i didnt have a plug. So if i need it its there. Ill give a better ride report when its a little warmer. Thanks for the help guys

We ran our 250F with the decomp shaft as the bore plug for quite a while ( it was that way when I bought it) until Junior made a small handful of TT style plugs in metal shop. Leave the little wind up return spring on the shaft/lever and ditch the cable and bar lever.

The only disadvantage to using the original shaft is that it gets in the way of reshimming the right exhaust valve. You can also cut off the half-round end that overhangs the valve lifter and the lever on the outside for a "cheater" bore plug.

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