Leaking Valves

No disrepect meant to Grayracer but every engine builder I know (including myself) seats the rings in the cylinder dry. If you are not confident in doing it that way then at least use non synthetic oil for break in.

See, this always happens. No disrespect to you, either, but I haven't built an engine dry in, ever, which covers from 1964 to the present, and I'm not about to start. My son's '06 leak tested at a 97% seal 10 minutes after it was started.

As far as break in on synthetics, you should probably tell Chevrolet, Mercedes, Porsche, Cadillac, and others that this is a bad idea. They'll void the warranty on some of their stuff if it doesn't run on the specified synthetic for the entire term. Break in is a critical time in an engine's life, and lubrication is more important during this time, not less.

Both these discussions have already been had several times, and I'd rather it didn't side track yet another thread.

Thanks for the cylinder advice Charlie, but I have a race to get to on Sunday and time is of the essence! Combustion chamber is about 99% clean it is the valves and inner working of the head that is filthy with carbon.

I live right outside of Oly. You?

Ha ha no worries. Just trying to help. I live just east of Monroe in Sultan. Good luck at your race.

See, this always happens. No disrespect to you, either, but I haven't built an engine dry in, ever, which covers from 1964 to the present, and I'm not about to start. My son's '06 leak tested at a 97% seal 10 minutes after it was started.

As far as break in on synthetics, you should probably tell Chevrolet, Mercedes, Porsche, Cadillac, and others that this is a bad idea. They'll void the warranty on some of their stuff if it doesn't run on the specified synthetic for the entire term. Break in is a critical time in an engine's life, and lubrication is more important during this time, not less.

Both these discussions have already been had several times, and I'd rather it didn't side track yet another thread.

Thats fine 10 minutes after it was started but where was it at 20 hours at 40 hours?

I have spent my entire life building engines and I tried engine break in many different "recommended" ways. I have found that running the rings in dry on the MX bikes has resulted in higher ring seal for longer durations than just running the rings in with none synthetic oil. As for the manufacturers you mentioned they make passenger cars not motocross engines. Ask someone from PR2 how they suggest seating rings in a 2 or four stroke MX engine.

I guess I also dont know why this would "side track" a thread. I am not giving anyone bad advice just a different approach.

Different strokes for different folks!

Gray, there is ONE hairline vertical scratch on the cylinder after honing it, and toward the top of it there are ridges from the rings that you can feel...not scratched, but wavy. Is it toast as well? I want to do this right as I will likely keep the bike another year. That and I don't want to sell someone else my problems.

Gray, there is ONE hairline vertical scratch on the cylinder after honing it, and toward the top of it there are ridges from the rings that you can feel...not scratched, but wavy. Is it toast as well? I want to do this right as I will likely keep the bike another year. That and I don't want to sell someone else my problems.

If you can feel them, you should re-do the cylinder. The scratch will carry oil past the rings, and ring ridges are dangerous in a high RPM engine, as the rings will essentially collide with them at the top of the stroke.

Remember that the tolerable wear limit is only .002" of bore diameter, or .0015" on any one point. Nikasil is outrageously hard, but it's also very thin. I'd rather not take a chance.

Thanks again!

Thats fine 10 minutes after it was started but where was it at 20 hours at 40 hours?

About 98%, actually. When I did his top end, I also ran a leak down test on the assembled engine before it was run, just to collect some info. At that point, rings straight out of the box, it sealed 93%. After cycling the engine through 20 revolutions with a wrench on the crank, it tested at 95%, with the oil as described above.

The point of dry building rings is supposed to be that the compression rings have to be seated to seal at very high efficiency before they develop a coating of combustion blow by deposits that will prevent them from sealing correctly. The only influence this will have on longevity is that if the rings seal quickly, they will seal for a long time because the lack of leakage will reduce the contaminants that might otherwise be deposited over time and reduce their efficiency. The fact is that modern piston rings fit to a properly finished round bore seal almost immediately regardless of how they are assembled, and for more than 99% of people, there simply is way too much made of the whole process beyond the question of bore condition. There may be some advantage for racing engines where the ability to extract every tenth of a horsepower possible, but in my experience, there's no provable benefit to dry building in terms of longevity, and no performance advantage in the vast majority of cases.

Even if the rings are built dry, cylinder will stay dry on start up for what, 40 or 50 revolutions? If you really think the rings need that much time dry, you can dead spin it before starting it without running the risk of scuffing the piston skirt. In the case of a two-stroke the question is even sillier, since if the engine fires, it has oil on the rings because it comes with the fuel anyway, so again, why bother, and why take the risk? (BTW, the fuel; is the primary compression ring lubricant in a 4T as well)

As for other reputable builders, more than you think are using dry moly lubes on the rings. Technically, this means they are dry, yes, but they aren't being run without lubricant, and the only thing being avoided is actual oil on the ring faces. Ron Hamp (the first builder I'm aware of who legitimately got 60+ hp from a 5 valve YZ450) does it that way.

The whole myth about synthetic oils during break in is based on the entirely false beliefs that too much lubrication will prevent moving parts from wearing into each other correctly, and that synthetic oils are somehow "slipperier" than petroleum oils. The function of lube oil is to prevent ANY metal-to-metal contact of mating parts from occurring, and precisely because the surfaces of new parts have not worn to a matching finish with each other, the integrity of the lubrication provided during this time is actually more important than it is later on when things have achieved a nice polish. Synthetics in general are simply more able to maintain that integrity under a greater number of adverse conditions for a longer period. The only downside to using synthetics for break in is the expense of discarding the used oil at an unusually short interval.

As far as disparaging the vehicles mentioned as "passenger cars", Corvettes, Camaros SS and Z28 models, MB's, and Porsches, among others that fall into the group built with, shipped with, and required to run synthetics are hardly in the category of an Olds station wagon from the '70's. In fact, now that the norm has become asking a 3 liter engine to do the work of a 5.7L at 50 degrees higher operating temperatures, and do so for at least 200,000 miles, it would seem the longevity question applies much more to these vehicles than to an off-road motorcycle.

In any case, I build my stuff as I described, and I will continue to do so because it works, and works with a success rate as near 100% as can be imagined. Anyone who wants to is free to go about it any other way they choose.

Ok Gray, so while I had the head off I checked my valves and all but one needed some minor adjustment. So since I had the head cleaned at a machine shop I decided to go ahead and do one last solvent test out of curiosity. Well with the intake cam cap torqued down, it was very hard to move the cam and the center intake valve was not passing the leak down test. Is this normal?

Edited by FinchFan394

About 98%, actually. When I did his top end, I also ran a leak down test on the assembled engine before it was run, just to collect some info. At that point, rings straight out of the box, it sealed 93%. After cycling the engine through 20 revolutions with a wrench on the crank, it tested at 95%, with the oil as described above.

The point of dry building rings is supposed to be that the compression rings have to be seated to seal at very high efficiency before they develop a coating of combustion blow by deposits that will prevent them from sealing correctly. The only influence this will have on longevity is that if the rings seal quickly, they will seal for a long time because the lack of leakage will reduce the contaminants that might otherwise be deposited over time and reduce their efficiency. The fact is that modern piston rings fit to a properly finished round bore seal almost immediately regardless of how they are assembled, and for more than 99% of people, there simply is way too much made of the whole process beyond the question of bore condition. There may be some advantage for racing engines where the ability to extract every tenth of a horsepower possible, but in my experience, there's no provable benefit to dry building in terms of longevity, and no performance advantage in the vast majority of cases.

I do mostly build mod engines and I have been able to prove that doing the dry ring seating does increase the length of time the rings seal effieciently by almost double the time of doing break in with oil. Its not a matter of gaining more power but retaining the maximum amount of power that is there from the begining of the build for as long as possible.

Even if the rings are built dry, cylinder will stay dry on start up for what, 40 or 50 revolutions? If you really think the rings need that much time dry, you can dead spin it before starting it without running the risk of scuffing the piston skirt. In the case of a two-stroke the question is even sillier, since if the engine fires, it has oil on the rings because it comes with the fuel anyway, so again, why bother, and why take the risk? (BTW, the fuel; is the primary compression ring lubricant in a 4T as well)

There is a very good reason for running the rings in dry on a 4-stroke. Yes you could try to crank the engine over by hand before starting it but then you have to try to hold the timing chain in one hand and keep it from binding up on the crank gear while trying to turn the engine over with the other hand.

On the two strokes perhaps you misunderstand the process there. I (and nobody I know) assembles a 2-stroke and trys to dry seat the rings by putting the rings in the dry cylinder and starting the bike. On a two stroke its done on the bench by hand or drill without the head installed. Once the engine has been cycled about 100 times the cylinder is then lubricated with what ever premix is to be run.

As for other reputable builders, more than you think are using dry moly lubes on the rings. Technically, this means they are dry, yes, but they aren't being run without lubricant, and the only thing being avoided is actual oil on the ring faces. Ron Hamp (the first builder I'm aware of who legitimately got 60+ hp from a 5 valve YZ450) does it that way.

I dont think there was any arguement there. As I said before different people choose different methods for engine break in and I have a lot of respect for Ron.

The whole myth about synthetic oils during break in is based on the entirely false beliefs that too much lubrication will prevent moving parts from wearing into each other correctly, and that synthetic oils are somehow "slipperier" than petroleum oils. The function of lube oil is to prevent ANY metal-to-metal contact of mating parts from occurring, and precisely because the surfaces of new parts have not worn to a matching finish with each other, the integrity of the lubrication provided during this time is actually more important than it is later on when things have achieved a nice polish. Synthetics in general are simply more able to maintain that integrity under a greater number of adverse conditions for a longer period. The only downside to using synthetics for break in is the expense of discarding the used oil at an unusually short interval.

That also depends on the characteristics of the synthetic oil. Some are designed to bond to the metal to reduce friction. In that case during break in the rings would not get a chance to seat before being coated.

As far as disparaging the vehicles mentioned as "passenger cars", Corvettes, Camaros SS and Z28 models, MB's, and Porsches, among others that fall into the group built with, shipped with, and required to run synthetics are hardly in the category of an Olds station wagon from the '70's. In fact, now that the norm has become asking a 3 liter engine to do the work of a 5.7L at 50 degrees higher operating temperatures, and do so for at least 200,000 miles, it would seem the longevity question applies much more to these vehicles than to an off-road motorcycle.

They are still not the same even though they have come a long way technologicly. A modern MX engine is better compared to a single cylinder formula 1 engine than a passenger or luxury car.

In any case, I build my stuff as I described, and I will continue to do so because it works, and works with a success rate as near 100% as can be imagined. As do I and with mine the same. Anyone who wants to is free to go about it any other way they choose. And on this I think we both agree.

As I said before there are some different ways of doing things with the same end result. I never disagreed with the way you do things I just gave my input too. That being said I digress. :thumbsup:

In my experience, and meaning no offense in saying so, "been able to prove" quite often turns out to be something closer to, "I'm reasonably certain", and/or "proven to my own satisfaction". While I've conducted a number of tests of different kinds that "proved" things to me (usually for reasons I can explain), I don't think that the method would have always passed full scientific muster. A lot of times the only thing we prove is that you can repeatably get a certain result in a certain way. But just proving that A works doesn't necessarily establish that B won't. Careful and skilled work can usually produce good results by more than one means.

If a two-stroke should be dead run, then a four-stroke should be, too. The timing chain's not that hard to remove. Then again, you can put the head on.

The point you made regarding polar bonding friction reducers in oil is valid, but the same concern exists with premium petroleum oils, particularly some C grades that have a lot of low friction additives. This isn't normally an issue with JASO T90 (the MA/MA2 standard) compliant oils regardless of whether they're synthetic or not, though.

The fact that it's become typical for "passenger" cars and light trucks to go 200K probably says at least as much about manufacturing and metallurgy as it does about motor oil or maintenance, but the feat shouldn't be downplayed entirely. My truck has logged about 39,000 horsepower/hours per liter in that time if it averaged 50 horsepower per hour. Assuming a 450 with a 50 hour engine life at a whopping 50 HP/hr average, that's only 5600 HP/hr per liter. The comparison to F1 engines is popular, but it's a bit of a reach. Yes, a highly modified YZ450 that produces 57 HP does turn out 126 hp/L, 2.5 times more than my truck, but not so much more than a Mitsubishi Lancer. In '06, F1 engines were producing over 300 hp/L. So, yes, it's true that modern MX bikes are more like F1 engines than a Chevy 350, but they aren't really quite that much like them.

Good discussion, though. :cheers:

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