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Discussion Starter · #1 ·
Hey guys I have a 99 TRX 426 with 11:1 wiseco 87mm piston, stage 2 hot cam, Curtis Sparks full exhaust, Jetted Carb and K&N cone filter running without airbox lid or snorkel. I am pouring oil out into my breather box. The engine ran fine before I had to replace the right case side due to a crack (unrelated to case pressure). Once I changed the right side case half, I started blowing oil out of the breather. I have replaced some parts such as new rings, piston, had the cylinder honed etc... I have done a ton of research on this and it is a very uncommon problem and have added answers to the common questions on the other threads I have read to assist in narrowing down the problem.


The cylinder was freshly honed with the piston well within the service limits.

The ring gap is within operation range, All of the rings are installed with the gaps staggered as per the manual and with the correct side up.

The Oil cooler and lines are free flowing and not clogged.

The wire mesh oil pickup screen is clean and free of debris.

I did check the tolerance in the oil pump with a feeler gauge.

Everything is torqued to spec during the rebuild.

I did not overfill the oil tank. Used less than 2 quarts after rebuild. (2.3 recommended)


It really seems like the oil is not making it back to the right side of the case fast enough once it is pumped into the left. The only thing I have not done is split the case back open and that is simply because I would not know what to look for if I did. I am mechanically inclined but unfortunately I do not know how the oil would flow from the left side to the right side so have no clue where to check for any restriction. If anyone could help me and possibly explain in a little bit of detail what I should be looking for I would really appreciate it. Also do I really need a case splitter tool or is it possible to split the case without it. Thanks a million in advance for any help you all may be able to offer.
 

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I presume you have a TRX400EX with a 426 kit in it?

When you refer to replacing the RH case do you mean the RH engine cover or the RH case half?

What caused the crack?

Did you buy new or used parts?

Did you get new gaskets or use a sealant?

If you used a sealant, what did you use?
 

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Discussion Starter · #3 ·
I presume you have a TRX400EX with a 426 kit in it?

When you refer to replacing the RH case do you mean the RH engine cover or the RH case half?

What caused the crack?

Did you buy new or used parts?

Did you get new gaskets or use a sealant?

If you used a sealant, what did you use?

Correct on the model specifics,

The crack occurred before I bought the quad. I replaced the RH case half because I didn't trust the weld to hold up and I really wanted to check the rest of the motor to ensure nothing else was broken that couldn't be seen.

I bought a good used Case off of ebay and just used the RH side.

I used a new gasket kit (moose) for the bottom end. For the top end, I used a Tusk big bore gasket set.

I used a very thin line of high temp RTV (permatex red) to hold the outer cover gasket in place during rebuild.
 

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The oil almost has to be getting in the air filter through the crankcase vent hose located on top of the engine cases kinda below and behind the carb. For oil to come out there it's almost certain the crakcase has to be "wet sumped" or the internal baffle is damaged or you got the wrong case half. The cases were changed in 05, but I do not know what the change was.

For the engine to be wet sumped there has to be a problem with the oil pump or the oil passages. Check the filter in the oil tank, check the oil tank venting, leave the oil fill plug out of the oil tank, start the engine and observe to see if the oil is returning to the tank.

The oil pump is two-sided. The low volume side pumps the oil in and the hi volume side pumps the oil out of the engine. If there is a problem getting the oil back to the tank, the engine will wet sump. Also, there is a check valve that prevents oil from bleeding from the oil tank into the engine when the engine is not running. Run the engine for about 3 minutes before checking the oil level. If the check valve is not working, you might be over-filling it with oil without knowing it.
 

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Discussion Starter · #6 · (Edited)
I appreciate your reply. When I bought the case half it was described as 1999 and up. I trusted the seller to be honest and I assume he was. I have no idea if I have the wet or dry sump. How would I know? After I finished putting the engine back together I added oil to the tank and it did not drain into the case until I let it run. The oil started shooting into the air box after about 5 mins of idling. It occurs to me that I don't know nearly as much as I thought I did initially. I understand the premise of wet and dry sump but have know idea if mine was changed or not. I will check the tank with the dipstick out this weekend. If the oil is returning to the tank what would that indicate?
 

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Discussion Starter · #8 ·
Got it

The case gasket was obstructing the oil making back to the oil pump fast enough. The right case half was the right year and everything is fine now. Of course Murphy's law got me. Now the tranny is locked up. I am not sure what I did wrong when I put it all back together but I screwed something up. The it runs fine in neutral but when I put it in gear and let the clutch out the motor dies. any ideas. I am going to do some research on here and see what I can find.

Thanks a million to "Here 2 help" you were awesome to talk to and your knowledge helped me out a lot.
 
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