2009 Engine Maintenance

[grayracer513]

So the manual is wrong? Every cylinder head I have seen weap solvent has showed a leak during vacuum and pressure testing the valves and seats. That's unacceptable for racing. We tear down our Yz450's at 3 percent leakage with our Total Seal Gapless Rings. That 3 percent can be the difference btw a podium and a last chance qualifier.

This is from experience working over 40 years for the number 1 race engine shop in the US. Not 40 years in a garage or dealership doing a engine a week.

 

Yes, the manual is wrong if you read it that way, and I'm not going to get into a @#&% measuring contest with you over whether one of us has more experience than the the other building race engines because I'm frankly OK with all of the racing engines I've built over the years, and it doesn't make any difference anyway.  The OP isn't building a race engine, and he probably won't be using a $100 set of rings to do it. 

 

If you think it's beneficial to tell a recreational user that any seepage at all is intolerable and requires him to spend $700 rebuilding his head, fine.  I disagree based only on practical realities.

 

Gray, I am not opposed to a shop doing the test, however I am relatively new to north county San Diego and not sure who would be good to go too. Is a local Yamaha dealer capable of this or would this need to go to a race engine shop.

Also part of me wants to learn how to do the work: 1. because I like to do all of my own work and 2. I am tired of not knowing how to work on a 4 stroke!! They arent going away and I am not going to stop riding. Its a damn shame that bikes have literally become disposable, most friends sell it and get a new one before tackling a job like this.

If you want to go the shop route, I'd give the service dept. at North County Yamaha a call.  The advantage to this route is that they will be able to tell you more about the comparative condition of your engine than you would know yourself because they will have used the leak down tester they have on several similar engines.  Doing it yourself with your own equipment is rewarding in the long run, but the problem in this particular case is that no two leak testers are made the same, and almost any two different brands will show different numbers on the same engine.  It's accurate to say that if any tester were to show an 80% seal and you hear a hissing in the carb that you have a problem, but it's much less clear whether a reading of 97% means that the only thing leaking is the ring ends.

 

The complete solution is to buy your own AND have a shop do one.  You can then use their results to baseline your tester. 

 

Regarding solvent testing used heads.  Say you have one that weeps a bit too much at one or more valves.  If you set the head gasket side down on a bench and try tapping the stems lightly with a punch, just hard enough to make the valve bounce open and shut once or twice, you may find this improves the seal.  This can still mean that the valve face is worn, but at the same time, it can indicate that carbon encroaching on the stem at the end of the valve guide is causing it not to close properly, or that a similar condition is taking place near the valve face on the back of the valve head.  In this case, careful cleaning can get you a few more tens of hours of service.

 

Remember that if they do seep a little, and you want to correct the problem, titanium valves cannot be lapped (even though the good ol' manual says different) under any circumstances.  This is because the only thing that keeps a Ti valve from sinking into the head in 20 hours is the hard coat on the valve face.  The nature of the coating required here is that it must be applied in an extremely thin layer, normally significantly less than .001" thick.  Lapping can compromise the coating enough to severely reduce the service life of the valve. 

 

Inspecting valves is a somewhat more reliable means of deciding whether they should be replaced or not.  Looking at the two in the picture here, the one in the foreground has some life left in it, but the one in the back shows wear (actually quite a bit, too).  When the wear first progresses to the point at which it's critical, it's characterized by a uniform, or nearly so, bright band around the entire face of the valve, without any of the dark spots the front valve shows, and any sort of detectable edge.  By edge, I mean the step you can see where the band of wear meets the darker, untouched metal on the valve face.  Even absent the step, the bright, uniform band means there's very little time left on the valve before the hard coat wears through.

 

Like a lot of things, it's not always possible to look at something used and say, "it will last this much longer", and the only truly safe route to take if there's a question is to replace them.  Bear in mind that the seats also wear, and that wear is much more difficult to inspect visually. 

 

 

 

been told by a local bike fella the wiseco pistons are forged and are a much harder and longer wearing piston as you say , problem is he says because they are harder they tend to wear the bore/cylinder more,

where as the stock pistons being softer piston wears ,hence bore/cylinder lasts much longer

 

As far as the forged wiseco pistons. All aftermarket pistons for the yz450 are forged.

 

Be it known to all that OEM, stone stock, everyday YZF (all sizes) pistons are forged by ART in Japan, and they are as reliable as anything you can use.  If going to a higher compression piston, I don't use Wisecos because they are too noisy, and that to me means an incorrectly shaped skirt that is not going to be conducive to good longevity.  My preference is CP or JE pistons.  Another consideration is whether the piston has one or two compression rings.  This is a choice between the ultimate in performance (one ring) or better longevity (two rings).  Unless you are racing the bike in a discipline in which one horsepower will either win or loose the race for you (flat track, road racing, maybe SM, but not MX, enduro or desert), using single ring pistons is a waste of money.

[savagex]

ok guys I finally got my OTC Leak Tester and I am ready to get started.

 

While I was waiting for my tester to arrive, I checked the valve clearance. Here is what I found and I would like to get your take on what it means and what I should do:

 

TDC

It was difficult to find Top Dead Center. If I lined up the " | " mark, the Cam dots were slightly off, one was a little higher and one was a little lower

 

If I lined up the Cam dots, then the " | " mark was about an 1/8" to the right of the mark on the case.

 

Is this a problem, or a normal tolerance variable?

 

 

Valve Measurements

Because of the previous TDC issue, I took two measurements for the valves.

 

With the " | " mark lined up

Intake

1.    0.076 mm

2.    0.076 mm

3.    0.102 mm

 

Exhaust

1.   0.178 mm

2.   0.178 mm

 

 

With the dots lined up

Intake

1.    0.076 mm

2.    0.076 mm

3.    0.076 mm

 

Exhaust

1.   0.15 mm

2.   0.15 mm

 

 

All of these measurements are out of spec.

 

So what should I do?

Continue with the leakdown test or address the valves?

[NitrousR1]

I would continue with the leak down test first before you re-shim the valves. You can still leak down test It because the valves do have clearance at tdc so you will get a true reading. If one valve had no clearance then the test would show a leak because the valve is not seated with clearance.

The timing marks on the cams not lining up is most likely from cam chain stretch. When you compare the new one to the old one side by side you will be shocked how much they stretch.

One more thing to remember is when looking at the cams you have to think-what if I rotated the cams clockwise, what if counterclockwise. The marks might not be 100 percent dead even when properly timed. But when you consider if you moved the cams one tooth and it will be even worse. It's a process of elimination. Hope this helps

[rhinoracin]

If you do need further assistance with your bike, North County Yamaha does have an excellent service department. I know a lot of riders and racers who only bring their bikes to them for work.

[savagex]

I ran my Leak Down Test here is what happened:

 

I was able to get the input gauge up to 80 psi, with the motor at TDC, the motor gauge was at 77psi, so that is a 3.75% loss

 

When I increased the pressure over 80 the nut that I was holding on the crank would break loose. I tightened it back to 40ft.lbs per the manual and it tried it again and got the same result. Am I doing something wrong? How are you guys getting the pressure to 100 psi and not having that nut break loose?

 

If I am doing the test correctly that would mean I only have around a 4% loss which would be very good, correct?

 

Would you even bother with rings and a new piston?

[Yammer-Hammer]

There shouldn't be, but the reality is that there will be. As far as showing up on a leak down test, maybe it would and maybe it won't, but a head that leaks just enough to wet the margins of the valve can actually go to a total seal under the additional pressure of the air in the cylinder during the test. Speaking as a professional with over 40 years in the trade.

So the manual is wrong? Every cylinder head I have seen weap solvent has showed a leak during vacuum and pressure testing the valves and seats. That's unacceptable for racing. We tear down our Yz450's at 3 percent leakage with our Total Seal Gapless Rings. That 3 percent can be the difference btw a podium and a last chance qualifier.

This is from experience working over 40 years for the number 1 race engine shop in the US. Not 40 years in a garage or dealership doing a engine a week.

The manual also tells you to lap your Ti valves.

[NitrousR1]

It sounds like you have a good seal for your intake and exhaust valves as well as rings.

As far as the nut breaking loose you want the piston at absolute tdc so there is no need to hold the flywheel nut. If it is exactly at tdc the piston will not move when air is forced into the cylinder. It can be tough to find this perfect spot sometimes. However at 80 psi and only 3 percent leakage you are fine.

As far as the piston and rings I always replace based off hours and use, replacing before they fail and cause other damage. So they pass the leak test for now. But how much longer will it last? Who knows, so I just replace pistons on a schedule and not worry about it letting go.

[grayracer513]

When I increased the pressure over 80 the nut that I was holding on the crank would break loose. I tightened it back to 40ft.lbs per the manual and it tried it again and got the same result. Am I doing something wrong? How are you guys getting the pressure to 100 psi and not having that nut break loose?

 

Fudge the crank forward of TDC very slightly.  As it tries to rotate forward, the nut will be tightened, not loosened. 

 

4% is OK in most practical cases.

[savagex]

Fudge the crank forward of TDC very slightly.  As it tries to rotate forward, the nut will be tightened, not loosened. 

 

4% is OK in most practical cases.

 

Gray, do mean where the "H" mark is, or the opposite way?

[grayracer513]

The opposite.

[savagex]

ok I am finally back on this project. I have the top end apart now and checked the valves by pouring solvent in the exhaust and intake ports. Good news, no drips! So i take it that everything is good with the valves? Should I check anything else on the valves while I have it apart?

 

Next steps are to buy

• Piston/rings (12.8:1)  (13:1)  (13.5:1) Which do you guys recommend?
• Gaskets
• Cam Chain
• Shims for valves

Is there anything I should do or have done to the head while its off? Machining, porting etc..

[NitrousR1]

That's good you have no valve leaks. Myself I like to replace the valve stem seals, they could leak in the future. I also like to clean the carbon off the valves while they are out. But the valve stem seals are optional since you don't seem to have any oil burning.

Piston wise I always go for the high compression pistons, usually JE or Vertex. The extra compression will add some low and mid range torque.

Get your new cam chain and you will be good to go

[grayracer513]

Definitely valves seals. Consider new valve springs if the engines has a lot of time on it or you run at high revs a lot. You may need help with compressing the springs for these two things.

I prefer the OEM piston to aftermarket HC pistons for a number of reasons, but the pistons recommended above are good. Add CP to the list.

[savagex]

That's good you have no valve leaks. Myself I like to replace the valve stem seals, they could leak in the future. I also like to clean the carbon off the valves while they are out. But the valve stem seals are optional since you don't seem to have any oil burning.

Piston wise I always go for the high compression pistons, usually JE or Vertex. The extra compression will add some low and mid range torque.

Get your new cam chain and you will be good to go

 

I want to make clear that I didnt take any of the valves and valve components out of the head. I was afraid that I would screw something up by taking them apart. But, if I can dissemble the valve components myself and reinstall with out any special tools ( except for maybe a spring compressor) I will do that and replace the seals.

 

Can you use brake cleaner on the valves to clean the carbon off?

 

I think I may choose a stock piston to save some money.

 

GreyRacer by CP are you referring to the Valve Cotter Pin?

[Gunner354]

I want to make clear that I didnt take any of the valves and valve components out of the head. I was afraid that I would screw something up by taking them apart. But, if I can dissemble the valve components myself and reinstall with out any special tools ( except for maybe a spring compressor) I will do that and replace the seals.

 

Can you use brake cleaner on the valves to clean the carbon off?

 

I think I may choose a stock piston to save some money.

 

GreyRacer by CP are you referring to the Valve Cotter Pin?

Use WD-40 for combustion deposits. You need to let it soak overnight.

[seacraft69]

Cp is another brand of aftermarket piston. I would go with the stock yamaha piston myself.

[NitrousR1]

You are correct all you need to do valve stem seals Is a valve spring compressor.

Gray means cp pistons. They are good quality too.

I like to clean the carbon off the valves and combustion chamber while they are out. Just be careful when cleaning around the valve face and valve seat. Just try to get the majority off.

[savagex]

If I go high compression on the piston, do I need to run race gas? Out here in CA we only have 91 at the pump.

[savagex]

If I go high compression on the piston, do I need to run race gas? Out here in CA we only have 91 at the pump.

[grayracer513]

It depends. You might need more octane than pump 91 if you run near sea level, or in hot weather, or at a low RPM, but otherwise usually not.