Leak down Test

[spray25]

Isn't crankcase pressure also caused by the pistons pumping up and down? Without proper venting the crankcase would act very much like a cylinder. As the pistons move down they would cause compression within the crankcase. If this were not the case then NO motor would have vents, yet I can't remember ever seeing a 4 stroke that didn't have a vent of some sort.

Rings being upside down is possible, but I would hope that Yamaha would not make that mistake on this many sleds. I guess anything is possible.

 

[LazyBastard]

We know for a fact that increasing the crankcase pressure DOES cause it to consume oil.. when? On the INTAKE stroke. Vacuum above and pressure below, the pressure in the case dumps past the rings upward, taking some oil along for the ride.

We also know that there is no such thing as a perfect ring. No matter what, SOME leaking will happen past the rings into the case, which will cause pressure in the case.

 

[nhrxrider]

The pistons moving up and down will cause agitation of the crankcase pressure...marginally increasing and decreasing it, from the pistons moving up and down. A single cylinder engine is effected far more than our 4 cyl. engines, because we have 2 pistons rising as 2 are dropping, cancelling each other out. There is still some pressure change, but not really like a pump. As I mentioned, venting is required because of the pressure that is lost past the rings even on a new, low mileage engine...there is indeed some very minor pressure loss past the rings on any engine. I don't agree about the crankcase pressure blowing past the rings on the intake stroke. Although the rings work somewhat like a check valve, sealing combustion chamber pressure better than crankcase pressure, they would still do a very good job of sealing the very small amount of crankcase pressure that is created. Maybe after I pull my head and check the cylinders, I'll reassemble the engine and install a gauge to monitor crankcase pressure. I'll have to find a gauge that reads very low pressures...I doubt crankcase pressure is more than a couple PSI. I find it interesting that my friends who race cars (circle track) only need to run a simple vent system of filters on the valve covers, and they don't go through oil even after a day of racing at constant speeds of 4500+ RPM (usually quite a bit faster than that).

Of all the problems my sled has had, I think this oil problem is the most annoying. While my 2-stroke friends have to fill up their injection tank every few tanks of fuel, I have to add a quart of oil every other fuel fillup, sometimes more often than that. Thats especially annoying now that I'm running Amsoil...I have to carry a quart for a day ride, and a couple quarts or more for a weekend of riding. aaarrrggg.

Jim

 

[spray25]

We may have to aggree to disagree for now. There is a DEFINATE crankcase pressure problem. The complete oil consumption problem? I don't know. A contributor? Yes.

If there was no crankcase pressure issue people would not have oil blowing out their vents and/or into their air box.

Interesting comparison to your freind's race cars but 4500 rpm is a LONG way from 10,000. Also if high power high rpm race motors don't have these problems then why do many of them run elaborate evac systems with oil traps and vacuum pumps? Look at Drag cars instead of circle burners.

From what I understand Jason added his new crankcase vent system and no longer burns oil. That certain leads one to beleive that there is a corilation

 

[jtssrx]

From what I understand Jason added his new crankcase vent system and no longer burns oil

I never said it prevented you from buring oil. What I said was it decreases the possibility of buring oil. The crank case need to breath more. this box allows your to do so. It also has teh ability to catch passed oil and return it to the crank case instead of buring it through the carbs.

 

[spray25]

So you are still using oil then?

 

[spray25]

Jason,

Help me understand what you are saying....

"In the next Couple Weeks we will be releasing a Crank Case Breather Box. The purpose of the box is to accommodate and increase the crank case venting of the RX-1. The other purpose of the box is to eliminate the burning of passed oil. The Box will drain any passed oil back into the motor. That will eliminate the possibility for oil consumption thought the air box.

This is a must have product for all RX-1's, Not just turbo units. Any pressure in the crank case causes a parasitic loss at the crank. That causes lost ponies. So this isn’t just a oil problem fix. It should translate into extra HP. By adding extra venting, you will decrease crank case pressure. "

So are you saying that your box eliminates the burning of oil that is forced into the airbox, but there is another area of the motor burning oil?

When you say "passed oil" where is it passing from?

Reading the above I hope you can see why I am confused and was thinking you were no longer burning oil.

 

[jtssrx]

If you do a leak down and you have a ring problem you will still burn oil and that needs to be fixed. This Breather box kit will prevent the issue from resurfacing.

We believe the RX-1 deosn't have enough crank Case venting. Increasing the venting should eliminate this from becoming an issue. No one burns oil in the first 500 to 1000 miles from what I've seen. I'm of the opinion a lack of venting is casueing these things to have probelms as you put miles on them.

 

[rxwarrior]

Oil Burning

This may sound way out there, but when I change the oil and filter on my Warrior and fire it back up the dipstick will read about 1 qt. low. This is after letting it set for about 15 minutes after shutdown. If I add the extra qt (now it is 1 qt over full but the level on the dipstick is on full) it will burn it out quickly and then stay at the same place on the dipstick for the next 2500 miles. Is it possible that some of these machines are getting overfilled?

 

[nhrxrider]

Spray,
I think we are agreeing, just coming in from different directions. I don't disagree that there is a venting problem, I'm just saying that there shouldn't be that much pressure there, and I don't think its the CAUSE of the oil burning...I think its a symptom. Getting back to the rings, if they aren't sealing well enough, there will be excessive crankcase pressure because of the combustion leak. If the rings aren't sealing well enough, and the crankcase pressure is getting past the upper rings, then why can't the crankcase pressure get past them also during the intake stroke?

I guess i should correct what I previously said, since it sounds like I'm saying just the opposite as I did in my last post...but before I was referring to a clean, fresh engine...now I'm theorizing on a used engine with the oil burning already present.

This would also explain the oil in the airbox issue Yamaha knows about and has the update for (cutting the slit in the hose...whatever thats supposed to do). The oil would be blowby from excessive combustion pressure in the crankcase, again pointing to a cylinder/ring problem.

Now I'm getting really cranked up to pull that head...I may have to go do that next week if I have time.

For the RPM differences between cars and sleds...I have gon through oil while doing mild trail riding with my wife, running not much more than 5000 RPM all day with easy take-offs and no high speed runs at all. And drag racing isn't a good comaprison...they are running 5000 HP for 4-5 seconds at a time. I'm talking about running a high revving 4 cyl. (mini-stock) for a long race at constant high revs. I think its as close a comparison as I can get for a stock RX.

No matter what, we do all seem to agree that there is a probloem. Street bikes with similar engines can have 50,000+ miles without a problem...I was on a Hurricane list for a while, and riders have 100,000+ miles on their 1000 Hondas with no oil burning. Although our engines get a bit more abuse, we still shouldn't be going through oil at 2000 miles or less.

Jim

 

[lakercr]

NHRX - I'm tearing down one of our motors right now - if you want some pics of what it looks like send me an email and I'll forward them to you. The engine coming apart uses about 1 qt. every 5-600 miles.

 

[jtssrx]

I don't disagree that there is a venting problem, I'm just saying that there shouldn't be that much pressure there, and I don't think its the CAUSE of the oil burning

It is causing the problem. Crank case pressure will cause blow by. On fresh motor this wont happen. As a motor breaks in the seal of rings become less and less. The pressure not only blows the oil by but weakens the rings.

If you properly vent your crank case this shoudln't be an issue.

 

[spray25]

Re: Oil Burning

This may sound way out there, but when I change the oil and filter on my Warrior and fire it back up the dipstick will read about 1 qt. low. This is after letting it set for about 15 minutes after shutdown. If I add the extra qt (now it is 1 qt over full but the level on the dipstick is on full) it will burn it out quickly and then stay at the same place on the dipstick for the next 2500 miles. Is it possible that some of these machines are getting overfilled?

Yes it is VERY possible.

My turbo takes it's oil from the motor therefore it has lines going all the way back to the turbo in the rear from the motor in the front.

When I added this new oil system (used to be a seprate tank) I filled it according to what yamaha says it holds plus about 1/2 quart figuring that is what the lines and turbo would need. I started it and let it run for a minute then turned it off and checked teh oil. It was low. I repeated this proccess until it read full. I do not remember how much oil I put in total, but I remember being suprised at how much it took.

It was probably over filled. The morning after a long high rpm ride I started my sled let it warm up, then turned it off and checked the oil. It was on the E line. I added a quart and went on my way.

Maybe the upper and lower lines on the dipstick need to be a "hot" and "cool" oil level similar to a coolant resevoir.

 

[Srxspec]

As a motor breaks in the seal of rings become less and less

J, as the motor breaks in it should slowly gain compression & have less leak down because it should create a better seal if it is broken in properly. After about 150-200 miles each RX-1 that we've broken in has stayed the same compression & leak down for well over 1500 miles now with no oil usage. I don't think it's a crank case vent issue, I believe it lies else where in the engine. If it was a crank case venting issue you would see alot more owners having problems. I think the crank case venting adds to the problem once it starts occuring, but I don't believe it's the cause of it all.

 

[nhrxrider]

Thanks srxspec, thats exactly what I'm trying to say. I also agree about the rings...its common knowledge that a brand new motor needs to be run and broken in to properly seat the rings so they match the exact shape of the cylinder. After that they should provide a good seal for the life of the engine. You have a good point about the venting issue...although all RXs seem to have oil usage to some extent, it seems to vary in severity, and if it was a vent issue, it should be fairly consistent sled to sled.

Jim