Nytro engine knocking..

[Off Trail Mike]

If rollover's were oil changes, Dimebag would be going through more oil than gasoline! LOL

The difference is that during an oil change, a thin film of oil will remain on your bearing surfaces long enough to rebuild oil pressure. In a rollover, the film is there initially too, but quickly gets sqeezed out on successive crank rotations as oil pressure goes away. Also you have to remember that almost one litre of oil remains in the Nytro during an oil change (not a complete oil change) leaving quite a bit of oil to help rebuild pressure quickly.

If you were really worrried about a loss of pressure after an oil change, you could also remove your plugs and crank over the engine with a cordless drill and a socket on the clutch bolt. It will build pressure within just a few cranks. Big job, yes, but very cheap insurance.

Do you really need it? Probably not. Dime's turbo'd sled still got past 12K even with his gentle riding style! .....not bad.

OTM

 

[HYFLYR]

Otm said it great. When you do an oil change is makes a couple noises for a brief seconds then clears up. If you fill through the head with oil like instructed in the service manual the length of that noise is even less if at all. Also the motor once started after an oil change is only at 1500 rpm and generally not that warm and the oil being fairly dense due to its room temperature. Now when you roll it out in the field and the oil is at its thinnest and the motor is at 8800 rpm is where the damage takes place. Does this make sense? I can further elaborate if need be but that's the general understanding.

 

[yamaha06]

No that's great I understand, thanks a lot guys!

 

[Dimebag]

Guys, If i where you i would check the operation of your roll over valves.
Mine is stuck for the second time this season. The first time i had to replace it, this time I managed to get it loose by using warm soapy water and some wd40. I also had to tap on the solenoid to make the piston come loose.

I talked to Bill, and he recommended to clean the valve more often if you have frequent roll overs.

Just sayin.

 

[dutchie]

Guys, If i where you i would check the operation of your roll over valves.
Mine is stuck for the second time this season. The first time i had to replace it, this time I managed to get it loose by using warm soapy water and some wd40. I also had to tap on the solenoid to make the piston come loose.

I talked to Bill, and he recommended to clean the valve more often if you have frequent roll overs.

Just sayin.

thats interesting , when it stuck , was it in the open side

 

[Mtnviper]

dutchie,

The shut-off valves are a normally open valve, which means that the default position is open or venting. By using a normally open valve there is an added built in safety feature, so that if the valve fails or does not operate due oil/sludge build up it will still be in the open position and allow the oil tank to vent normally.

What I recommend is testing and cleaning (if neccessary) the ROV valve during your normal pre-season sled maintenance. Then test the ROV operation a couple of times during the season. A good time to check the operation is while you have the hood off and are doing other mid-season maintenance such as checking the oil level, cleaning the clutches, or performing a general sled check-over before heading out on a trip, etc.
To test the ROV operation I just leave the valve installed in the hose and while touching the valve with my fingers, turn the key on and pull the cord. Normally you'll be able to feel the valve "click" when it closes. For most sledders once a year is often enough for cleaning, while others may need to clean the valve a couple times a season.
How often the valve needs to be cleaned depends on several factors, including miles rode per season, type of riding, boosted or n/a and if the sled has a ROVCM.

There is a cleaning procedure listed on my web site at http://fourstrokesolutionsllc.webs.com/ ... enance.htm and the valve cleaning procedure can apply to all brands of ROV systems.
As Dime stated above warm soapy water works well. The main thing to remember is to NOT use any brake cleaner/carb cleaners as they can damage the seal inside the valve.

Bill

 

[Dimebag]

Well guys, me and kimoaj tore the engine apart today.
Looks like its time for a new crank. Head, cylinders and pistons all look good.

The question is, what else has to be changed? Oil pump?
Or should I just get a new crank, rods and bearings and off we go?

I wanna fix it as cheap as possible, so we'll stay with oem internals.

Heres a picture of the beauty.

 

[couch]

Might be cheaper just to source another short block......

 

[Off Trail Mike]

Dimebag:

Wow!... Yami's version of grenading looks alot better than some of the 2 strokes' I've seen!

Judging by the number of crank bearing particles I see in the pic, I would definitely have a close look at the oil pump. I don't remember if there is a strainer on the inlet to the pump, but if there isn't, it might be a good idea to change the pump out. If the particles were small than no big deal, but if big pieces got through, I would be changing it.

Also you might check the oil cooler for plugging.

At least it's only the crank!

OTM

 

[Dimebag]

Lets say i change the oil pump, what about the oil cooler? Is it enough to change the filter inside it?

Would anyone care to elaborate on the crank bearings.. How do i know which ones we need? What to measure to know for sure?

 

[Mtnviper]

Lets say i change the oil pump, what about the oil cooler? Is it enough to change the filter inside it?

Would anyone care to elaborate on the crank bearings.. How do i know which ones we need? What to measure to know for sure?

Dime,

There are letters/numbers stamped in the block and crank that correspond with a paint mark color on the new bearings. The paint marks are for different sized bearings to custom fit the crankshaft.
It's a good system, but one drawback is you must first order your crankshaft and rods, to see what the numbers are. Then order the bearings based off of the new crank and rods.
I have the info in the service manual, but seem to be having some throuble attaching the file to this post.

Yes, I would put a new oil pump in it and either replace or flush out the cooler, hoses and oil tank. Also I would pull the cams and flush out the oil passages in the head and block as well.
If it looks like some "chunks" went through the pump, then it might be cheap insurance to replace the drive chain for the oil pump. Although not common they can break if they have been stressed enough.

 

[HYFLYR]

Couldnt have said it better myself^^^^^

 

[Dimebag]

Thanks a lot for your quick replies.

I will send an order for the parts tonight. I will get both a new oil pump, and cooler.

The bearing system sounds pretty genius.

What about the cam chain tensioner, should i replace it, or is it safe to continue using the old one? Do they ever "wear" out?

 

[HYFLYR]

I would assume its ok, I personally wouldn't replace the tensioner but that's up to you.

 

[canoehead]

X2 on MtnvIpers comment!