450 to 426 exhaust cam pics

well i finally got my cam chain replaced and my 450 exhaust cam in... question is... do they look like they're lined up right?

camsfront.jpg

camsrear.jpg

If that exhaust cam was made for a YZ450, rather than a 426, it is installed correctly.

yes sir it was... awesome that's what i was waiting to hear. didn't think there would be harm in double checking with you guys before i buttoned it back up. thanks gray

ok, had to take the bike apart again and replace the front cam chain guide. while putting the cams back in i came back to the question... are they in correct? now i could set them as above but i was thinking that according to the pic of the installation in the sticky on this forum the lobes should be 'flatter' and i set them like this below. which is right? the first way i had them or this 2nd way?

rear:

7c4290f6.jpg

front:

9ff38fa6.jpg

as you can see in these pics the lobes are 'flatter' like the pic in the sticky 450 cam thread but that throws the timing marks on my intake cam way off... what to do?

actually after looking at it again in the last pics it looks like the intake lobe may be pointing downwards a bit much... oh if only the timing marks were any help lol...

Forget what the lobes look like. The marks should look like your first picture.

  1. Line the intake cam up using the stock "I" mark, just like a normal 426
  2. Position the YZ450 exhaust cam so the there are 14 pins of chain between the two marks at 12:00 o'clock on each cam.

That's it. Be sure you double check once tension is applied to the chain.

The pictures in your first post are correct. I already told you that. Don't over-think. :)

ok, so this is where i am now. i unthunk what i was thinking lol and this is as close as i can get... i just can't seem to get the marks to stay exactly where i want them on the intake cam. from the pic it looks spot on but it's actually a little behind. if you look close you can see the one mark is just below the top of the head.

front:

7790bbc6-1.jpg

rear:

bf7c507d-1.jpg

Can someone ex-plane why you can't use a dial indicator on the lobes to set the cams. Thanks

ok, so this is where i am now. i unthunk what i was thinking lol and this is as close as i can get... i just can't seem to get the marks to stay exactly where i want them on the intake cam. from the pic it looks spot on but it's actually a little behind. if you look close you can see the one mark is just below the top of the head.

That's correctly set, just like that. I misspoke earlier when I said the two cams should be separated by 13 pins; that would be for two stock cams. The way you have it now, with the intake timed as stock and the exhaust 14 pins apart from it is correct.

The intake cam is perfectly timed. The marks will only very rarely line up perfectly. The question is whether they can be aligned better by moving one tooth either way. In your case, it's clear that they would not be.

Can someone ex-plane why you can't use a dial indicator on the lobes to set the cams. Thanks
Because in order to do that, you would need the specifics of where the lobe centers are supposed to be located. Do you find that information in your manual?

The timing marks work just fine.

outstanding, lol especially since i buttoned up the engine already. thanks again gray. now i just have to put the carb on, change the oil filter, put in some fresh oil and coolant, throw on the cosmetics and change the tires and see if this thing fires up... keep your fingers crossed :\

You may find the starting drill has changed a bit. Obviously, the decomp lever is out of the picture, but these things may be useful to note:

  • The engine will start best if you bring it up against compression, reset the lever to the top of the stroke, and kick from there. This is exactly the same position you had to work to find by moving the kick crank past compression with the old setup. Trying to start the engine from just any random position is possible, but it's much more likely to start the position I described.
  • Most 426's like to start with the throttle closed, but with the 450 cam, they often like to have the throttle very slightly opened off idle. If you have trouble getting it running, try that.

I will certainly keep that in mind thanks.

I do have another question. I got rid of the decomp cable but left the piece in the head that decompresses the exhaust valve just to keep the hole plugged for now. Is that going to cause any issues? I tried to kind of roll it back a bit if you can picture that, in order to keep it up off the valve as much as possible. I do plan on getting a plug when I get a chance to get to a auto parts store. But for now that should be ok right?

I do have another question. I got rid of the decomp cable but left the piece in the head that decompresses the exhaust valve just to keep the hole plugged for now. Is that going to cause any issues?

It's OK to leave it there if the coil spring stays on it. (item 17 HERE)

yeah i did leave the spring intact. i'll be sure to let you know how things go after i get everything back together. thanks

well i ran into another problem now :) the hole where bolt #13 goes in the diagram you linked to stripped out! it stays in finger tight but i know it's gonna come loose after about 10 minutes with the engine started and vibrating. do the plugs for the decomp require that bolt to hold them in? if so i'm going to have to figure something out and quick. any ideas?

Go to an auto parts store and buy an 18mm freeze plug to block off the hole for the shaft. The original seal will have to be removed, but it doesn't require the bolt to hold it in. That means you're free to tap it oversize replace the bolt with a common 1/4"x20 USS bolt if you don't want to Heli-Coil it.

will do. i guess i'll have to take the valve cover off to make sure i don't get any metal shaving into the valves when i tap it. no biggie though. certainly rather be safe than sorry.

gray while i have your attention, do you think i'll have a problem with my head gasket leaking? i had to lift the cylinder up about a half inch in order to replace the front cam chain guide. it was only up for maybe 15 seconds and the gasket is actually 4 metal gaskets(spacers/shims perhaps?) and they didn't stick to the head surface or anything that could've warped, kinked or otherwise damaged them. i didn't have the foresight to order a new gasket when i ordered the new chain guide. didn't realize i'd have to take the cylinder off.

also the 'freeze plug' you're talking about is a genuine freeze plug and not a core plug correct? or are you in fact referring to a core plug?

also the 'freeze plug' you're talking about is a genuine freeze plug and not a core plug correct? or are you in fact referring to a core plug?

What's the difference? Core plug, freeze plug, cup plug...synonyms.

It is NEVER a good idea to reuse a head gasket. You might or might not get away with it.

well actually there is a difference. the core plugs are meant to be a permanent plug while freeze plugs are designed to pop out if ever your coolant has more water than necessary and when it freezes the plugs pop out to prevent your engine from cracking from the pressure of the ice expanding :)

Trust me, speaking as a professional with over 30 years in the business, they are one and the same.

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