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1st Valve Check Report

By yz-dwg,
in WR400F/426F/450F

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Wasabi

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Indy probably isn't chiming in due to he can't stop laughing about the tight valves = more power comment. Cam profiles are where the power is made not in the lift number. Larger cams with the correct profile can make more power in the RPM range they were designed for, but with the stock cam a valve set in the middle to looser end of the range will hold the compression just a fraction of a second longer producing a more powerful compression stroke and the side benefit is that it gives the valve more time to cool against the seat. This all happens in milliseconds but the cooling of the valve head helps stop it from sinking into the seat due to being overheated , which causes the valve clearance to TIGHTEN and loose power, but this will be called stupid by Wasabi in his next post. WR Dave:busted: :bonk:

No, not stupid at all.

Yes, you can move the power around with your clearance settings. The looser they are to more bottom end (torque) you will have, due to the longer the valves are shut (shortening the profile). If you want more power, set to the tighter end of spec (valve open longer like a more aggressive profile aka. hotcams). You only loose power if the valves stay open during compression (0 lash). :cheers:

Seems like a hard concept for you guys to understand for some reason. ?

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WR_Dave

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You better do some more reading pal.

No Idea what I am talking about? talk to an engine builder if you don't believe me.

Been building engines for 20 years junior !!! Valve clearance spec is just that a specification, if you are on the tight side or the loose side , you are still in spec., BUT if you are trying to gain power through lift in the tight end of the spec you are kidding yourself. I have built several winning race engines over the years and to make the valve train live we usually set the valves a little loose to make up for the fact that at high RPM ( which the WR will run at) the temps ( which the WR will run) and the inertia of the valves will close the clearance up slightly . The loosing valve clearance issue is also a well documented problem on most of the newer bike engines, so unless you enjoy weekly clearance checks , or you would rather ride the bike for a week or two between valve sets, I suggest staying on the looser end of the spec. Most of us can't use the extra .0005 hp that might be gained with a tight valve set. WR Dave.

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Wasabi

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So the facts don't matter, your just picking a fight??? I'm done. WR Dave

No picking fights, you just edited your post after my last post. What I quoted is what you post.....

I think the gains are a bit more than you say too, but that is just being picky.

Look at the gains of a hotcams over a YZ cams:

http://www.hotcamsinc.com/documents/support/40231IN_1158693831348.jpg

*I know that a YZ cam is different to a hotcam, but there is not much difference at all. I know, I got a set in my bike.

Gains from more lift and duration are not insignificant.

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Fullbore4

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Thanks for the fairly comprehensive explanation WRDave and I don't mean to undermine your EXPERIENCE and KNOWLEDGE over that of Indy. Thats what I was looking for.......not some dreamed up belief given by someone that knows less than I do from the get go.

Wasabi I'm sure Yamaha engineers designed the cam for power in a certain rpm profile. You honestly have no business shooting from the hip on what either a "looser" valve or a "tighter" valve clearance will do without extensive testing on a dynomometer, at least, and adequate financial backing also. Yamaha engineers must really get a hoot out of reading crap like this.

Also that hp output for hotcams/yz cam was given on a different thread a few days ago.

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Wasabi

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Thanks for the fairly comprehensive explanation WRDave and I don't mean to undermine your EXPERIENCE and KNOWLEDGE over that of Indy. Thats what I was looking for.......not some dreamed up belief given by someone that knows less than I do from the get go.

What ever.....

Gobble some more mate. Protein is good for your health. :cheers:

Even Dave (regretably) said I was right.

I bet you haven't even torn down your motor yet.....

Wasabi I'm sure Yamaha engineers designed the cam for power in a certain rpm profile. You honestly have no business shooting from the hip on what either a "looser" valve or a "tighter" valve clearance will do without extensive testing on a dynomometer, at least, and adequate financial backing also.

Not shooting from the hip. Why would they have spec limits for?

Talk to the engine builders for the race teams and ask them about valve clearance settings.

I have talked to several engine builders and they all set their valves to the tighter end of specifications.

Not only that, I have tried it out for myself. It works.

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BlueBlood Rider

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I have a lot of engine building experience and there's some credibility on both sides in this argument. The determining factor is what you, as a rider, want to achieve.

In these shim-over-bucket engines, as the valvetrain wears the tolerances get tighter (and the engine quieter). With less clearance to accommodate thermal expansion, a tight valvetrain takes an even greater beating and will wear faster. Adjusting towards the tight end of the spec will yield a miniscule performance gain, but if going for longer service intervals and engine life is what you desire, being at the looser end of the spec is better. As has been pointed out, proper seating of the valve is important for heat transfer to prevent valve face burning and accelerated wear. With the valves set too tight, it can interfere with proper seating, which can also result in compression loss. Too loose and the valve slams shut, also resulting in increased wear. The factory spec takes thermal expansion, potential valve float and machining tolerances into consideration.

Bottom line: If you are building an engine for a race bike that gets torn down regularly and you want every last milligram of power out of it, shim towards the tight side and be prepared to keep a steady eye on your valvetrain specs. If you are a typical rider that wants the longest operating period between servicing and can live without a miniscule amount of power that you probably aren't missing anyway, then shim towards the looser side of the spec and rest comfortably at night.:cheers:

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BlueBlood Rider

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Talk to the engine builders for the race teams and ask them about valve clearance settings.
What works for a race team often has little bearing on what is right for the average rider. Race engines are set up tight not just in valve clearances, but piston rings, cylinder bores and various other tolerances. This is fine if you tear your engine down every other race, but for the vast majority of riders who simply want the longest operating period between teardowns, it is silly to pay much mind to what a race engine builder does. It has little relevance to the way most people ride.:cheers:
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Wasabi

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What works for a race team often has little bearing on what is right for the average rider. Race engines are set up tight not just in valve clearances, but piston rings, cylinder bores and various other tolerances. This is fine if you tear your engine down every other race, but for the vast majority of riders who simply want the longest operating period between teardowns, it is silly to pay much mind to what a race engine builder does. It has little relevance to the way most people ride.?

Yes, but they actually have "experience" in working with these engines, unlike most people here that struggle with a fuel screw adjustment.....

They Know all the tricks of the trade so to speak. They know what will destroy an engine, and know where power is gained and lossed.

Like anything, in spec is in spec, that's why they have upper and lower limits. Stay with in these and you will be fine.

That's what the Yamaha Engineers do Fullbore4, set perameters.....

As for engine life, I wouldn't know which is better, but mine have lasted over 5,000kms with no cupping what so ever, so I will stick to what I am doing as it seems to be working just fine.

Is my engine stock, no.

Do I check and change clearances? I check, but rarely change.

Is it hard to work on these engines? Definatey not.

Did I do all the work myself? Definately.

The only thing I won't touch is my suspension. :cheers:

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BlueBlood Rider

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As for engine life, I wouldn't know which is better, but mine have lasted over 5,000kms with no cupping what so ever, so I will stick to what I am doing as it seems to be working just fine.
The problem is you're making what appear to be absolute statements, as though shimming towards the tight side is perfect for anyone. It isn't. It has its place primarily in a race environment and/or with people who can work on their own bikes and know what they're doing. For the average rider I would recommend they shim loose (but within spec) and enjoy longer intervals between servicing and less risk of premature valvetrain wear.:cheers:
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Wasabi

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I am an engine builder, I know what I'm talking about. And I know your a moron. :bonk:

I am an engine builder.... yada yada yada.

That seems to get thrown around here all the time. Oh look, a few in this thread alone.....

You an engine builder? Pffffft. I wouldn't trust you with my lawnmower!

Do I build my own engines? Yes, have done for years.

Does that make me an engine builder too? I wouldn't think so (it is not my source of income), but most of you seem to think it would.

I guess you are a pro rider too, maybe the next RC??? ?

All I done was stated the fact that if you set your valve clearances to the tighter end of spec, you will make more power.

If you want to be an idiot and make a song and dance about it, fine. A fact is a fact. :cheers:

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04450wrF

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so this is true then?

"in spec is in spec.

the tighter they are, the more power you make!"

just answer YES or NO

so just yes or no....ok?

and why again was Indy not chiming in?

interesting thread, says more about the individuals than the country they represent, dont you think?.... or dont you think?

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bluebike1999

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i agree, very interesting thread.

this is coming from an Australian who doesnt know everything, but i can read and know your never too old to learn,

as in a couple of cases here, after 20 years of building motors without understanding a vital principle of mechanics, you should be happy to have learned something.

its funny, i didnt read anywhere anyone picking a fight, other than some posters ridiculing the person who made the correct statement.....and followed up with "bonehead australian".....the good folks of the US who i dont seem to see here that much anymore, must be so emabrrassed, but hopefully we can all learn and move on.

642, intraspectivity is not just for paranoids.

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