Valve problem

[DOOmsman]

Just thinnen, the push rod dosn't move and when you take the rocker shaft off it does. That is a puzzle, is the cam shaft cracked perhaps? Good luck.

[jak]

Update: I shimmed the worn rocker arm support with an 1/8 inch thick piece of brass and reinstalled it to see how the valves worked. Both valves operated normally.

This morning I took the partial disassembled engine (head was off) to a local machine shop that I use and had the bore diameter checked. There is less than .002 of wear. I also had him look at the valves and valve guides. His recommendation was to lap the valves, replace the rocker arm support and reassemble the engine. He said it didn’t make sense to anything else to the engine with the minimal wear he observed.
Ordered parts this afternoon. They should be here by the end of the week. I’ll report back with the compression reading once I get the parts and the engine reassembled. If it doesn’t make good compression I’ll tear it down and put a new piston and rings in it.

Monster- Agree with the oil system- nothing blocked . There’s a sticker on the frame of this cart stating Assembled in US from Japanese parts. The engine is stamped Made in Japan.

We had four solid days of rain here so I decided to completely disassemble the cart down to the bare frame. The frame is in really great shape considering its age. I sand blasted the areas that had rust and I’m in the process of sanding it in preparation for a good coat of POR-15. Wasn’t planning on doing it at this.

[Monsterezgokid]

Originally Posted by jak

We had four solid days of rain here so I decided to completely disassemble the cart down to the bare frame. The frame is in really great shape considering its age. I sand blasted the areas that had rust and I’m in the process of sanding it in preparation for a good coat of POR-15. Wasn’t planning on doing it at this.

Sounds familar http://www.buggiesgonewild.com/membe...rusher-g9.html

Mine is still in the same spot as it was before..Just been soo busy with other carts. I have been slowly rebuilding the engine the last 3 weeks.. Maby i should update it

That POR-15 is awesome!

[jak]

OK I received the rocker arm support and gaskets I ordered last week. Reassembled the engine and checked compression. It’s a good solid 165 psi. Since I have the cart stripped to the bare frame. I mounted the engine on the cradle and set it on a movers dolly, hooked up the wiring harness, gave it a shot of starting fluid and it fired right up. I then set about connecting the fuel, pulser and oil lines. I found the check valve and lines were bad as was the fuel filter (all rusted and full of crud). The tank also had water in it. Ordered those parts and they arrived today. Connected everything and the engine fires right up and seems to run fine.

The only problem I’m having is there’s no oil feeding the valves. Probably what caused the rocker arm support to fail as Monster pointed out. Both tubes and the metal pipe are open as is the brass fitting going into the block. There’s pressure coming out of the tube when it’s hooked up and the engine running but no oil. I temporally replace the short piece of rubber tube coming from the steel tube to the valve cover with a piece of clear vinyl tubing but don’t see any oil. Should there be a visible amount of oil coming up the tube or is it just an oil vapor? The Yamaha manual I bought doesn’t talk about how the oil delivery system works or how to test it. It only says to check the lines and test the check valve which it gives a procedure for. Any input would be greatly appreciated.

[Monsterezgokid]

Originally Posted by jak

OK I received the rocker arm support and gaskets I ordered last week. Reassembled the engine and checked compression. It’s a good solid 165 psi. Since I have the cart stripped to the bare frame. I mounted the engine on the cradle and set it on a movers dolly, hooked up the wiring harness, gave it a shot of starting fluid and it fired right up. I then set about connecting the fuel, pulser and oil lines. I found the check valve and lines were bad as was the fuel filter (all rusted and full of crud). The tank also had water in it. Ordered those parts and they arrived today. Connected everything and the engine fires right up and seems to run fine.

The only problem I’m having is there’s no oil feeding the valves. Probably what caused the rocker arm support to fail as Monster pointed out. Both tubes and the metal pipe are open as is the brass fitting going into the block. There’s pressure coming out of the tube when it’s hooked up and the engine running but no oil. I temporally replace the short piece of rubber tube coming from the steel tube to the valve cover with a piece of clear vinyl tubing but don’t see any oil. Should there be a visible amount of oil coming up the tube or is it just an oil vapor? The Yamaha manual I bought doesn’t talk about how the oil delivery system works or how to test it. It only says to check the lines and test the check valve which it gives a procedure for. Any input would be greatly appreciated.

I noticed that this system only works at best when you have the head ventalation tube hooked up to the breather box.

In the bottom of the head/block where the valve push rods sit on the cam risers, theres an itsy bitsy little hole to let the oil drain out back into the lower case.. Now the way its supposed to work is.. The engine splashes the oil in the case around the oil feed hole (at the back of the engine)(the one that you put the new hose and is supposed to feed the oil into the head. Theoreticaly theres no suction to suck the oil into the head. So the slight negitive pressure caused by the suction from the intake hose is enough to suck up a bit of oil into the head, through the pipe, even though theres another hole in the bottom of head for the oil to drain out. That little drain hole is too small to equize the vacume between the case and the head, thus it kinda sucks the oil up the tube.

Make some sense?

People who remove the head/breather box vent tube could have oil delivery problems to the head.



Hook up the air box and everything. then rev her around 2500rpm, and you should see a bit of oil drops slowly making its way up.
Before you put the valve cover back on, just splash a bit of oil on everything just to prevent a dry run in the head

[crash12888]

Not sure I'm getting the warm fuzzy on that one.
I would think whatever is going to react to the effect of the vacuum will be from a path of least resistance.
I would think air coming through a small hole would travel more freely than oil through a larger hole. If the hole is too small to let the vacuum that draws the oil up the tube equalize then the oil wouldn't drain back out of it.
Now my thinking is just reflecting back on some old laws of physics and wouldn't be the first time I learn something new at my age. Will need to do some research.

[smallblock450sl]

I may have missed a post, but here's my take. The oil feeder line for the valve train can only work if the "check valve" (on the passangerside of the valve cover) is really working. It is a one way valve witch keeps the oil in the oiler tube in incruments (like a scaleing a ladder) the oil comes up the pipe, the check valve "holds" the oil in the tube till the next "engine pulse" then travels up in steps. I know it is not as good as a "pressurized" system, but it does work. As for that worn rocker arm....In almost 30 years....I've never seen one worn so bad. Thanks for the posts/findings...you will help many with this thread.

[jak]

Monster, crash and small block, my thanks to each of you for your detailed information and analysis.

I fooled with the engine pretty much all day today. I ran it a good six to seven hours. What I observed today was confirmed by each of your posts.

Keep in mind that the engine is out of the cart, mounted to the cradle and sitting on a four wheel movers dolly so I have good access to everything on the engine. Everything that’s suppose to be on the engine was installed and hooked up as it originally came from Yamaha. The fuel tank was sitting next to the cradle strapped to a stool. Again, everything as it would be installed in the cart.

As I previously mentioned, I ran the engine for a half hour to an hour yesterday after installing the new parts I received in the morning. I wanted to make sure I was getting oil to the valves so I replaced the top section of hose coming off the metal oil delivery tube to the valve cover with a piece of clear hose and was expecting to see a good flow of oil thru the tube but I didn’t see any. This morning I ran the engine for about 15 minutes and still no oil. Before I ran the engine yesterday and this morning I removed the valve cover and poured some oil over the rocker arms so they wouldn’t seize and resealed the cover. Since there was still no oil visible in the clear tube, I replaced the metal oil tube and both rubber sections with one piece of clear tubing. As soon as I started the engine I could see a small amount of oil accumulating in the bottom fourth of the tube. Sort of like bubbling but not making its way up the tube. Revving the engine made no difference. After running the engine for a couple of hours increasing and decreasing the RPMs , I noticed that there was a spot a little off idle that the oil would climb about three quarters up the tube. When I increased the RPMs the oil would drop. I continued to run the engine and after another hour or so I noticed I could get the oil to migrate higher in the tube and finally into the valve cover. However, when I significantly increased the RPMs the oil would drop. Were not talking about a lot of oil in the tube here. Sort of like a coating on the walls of the tube. Not the flow I was expecting. The longer I ran the engine the more oil seemed to accumulate on the walls of the tubing to the point that engine RPMs didn’t have a effect on the oil travel. I replaced the clear tube with the metal tube and the small piece of clear tube at the top. Oil was still moving into the valve cover albeit small amounts.

After reading your comments, particularly small blocks comment about the check valve “really working” got me thinking. One of the parts I replaced yesterday was the check valve. The manual said to test the valve buy blowing and sucking into the top end of the valve. The old valve I replaced was completely open. You could see day light thru it. When I tested the new valve before I installed it. It seemed to leak a little on the suction. This was a new Yamaha valve out of the package. I didn’t think anything of it at the time, since it was a new Yamaha part, until I read small blocks post this evening, I went out to the shop, pulled the valve and did the suction test. No leakage. One has to assume that the new valve wasn’t working correctly when it was first installed but gradually started to seal itself allowing oil to move as designed.

One also has to wonder how many of these engines are out there with bad check valves and improperly sealed hoses not allowing oil flow to the valves. I think I’ll keep the small piece of clear tubing installed.

Thanks again for your insight into this problem.

[crash12888]

Glad to got it going and satisfied your concerns.
And like I said before I am still learning, Thanks for taking the time guys..........Monster, Smallblock

[Monsterezgokid]

You know what.. My slight mistake on the check valve issue.. LOL when i wrote this. i was lookin at my engine on the bench, without the valve cover on it, and i totaly forgot about the check valve assembly and the 2nd hole in the valve cover on the side for it..

Brain fart

Glad to hear its workin now.. now get it finsihed up and get out there, and enjoy that cart! lol