Got a problem...I've got an 85 Yamaha Tri-Z 250 that has milky looking oil in it. The top end is fresh (head gasket SHOULD be ok), and I just recently put a new clutch in it. What are the different areas I should be looking at. I didn't see any oil in the radiator when I took the cap off, so I am assuming the head gasket is ok. So does this tell me I need to look at the impeller and that seal??? What else should I look at. The oil is a light gray, whitish color. Caught this problem early, so I hope no other damage has been done. Please help.

Same thing happened on 2 of my bikes. Waterpump seal was shot. Might wanna check that. Kept riding on one of the bikes and it overheated and shot the top end. If you caught it early, shouldn't be any damage. My RM250 just needed the seal replaced since I caught it early. First trip after a new top end too.

you would be wrong to assume no oil in Rad fluid equals anything. When your bike warms up, the water/rad fluid expands, creating pressure in the system. A leaking headgasket could cause this to only happen when the bike is warm, however, the exhaust would be spitting out white smoke when water entered the combustion chamber, and you would notice a significant decrease in power.
Usually, leaking head gaskets do not affect the oil, as the oil is usually sealed to the transmission part of the motor. I would look at the waterpump as well.

Big Had are you sure? I'm dealing with the same thing now. Every seal and gasket was new two trips ago(1 last season and 1 for Halloween this year) and I notice that the head gasket was leaking(someone forgot to retorque it??). Also noticed the oil was all milky.........so can I assume that even though the head gasket went bad, that isn't why I have milky oil? The oil issue is the seal behind the water pump? I hate to say it but it does sound logical........the cooling system is completely isolated from the bottom end except for the water pump.......doh!!!!!!

the top end is for the piston, combustion chamber, and the bottom end, all which do not use your transmission oil-hence why you have to add oil to the gas to lube these things....2 strokes use oil inside the case, which is the transmission for all intents and purposes. I would be confident that the gear driving your waterpump is also bathed in this oil, via a seal from the shaft. That is where I would look......I could be wrong, but deductively speaking, where else is the water jacketed and running along the bottom end where the gear oil is????

Hey I am with everyone that it is the impeller seal. Tecateman, if you are riding the tecate I would guarantee that is your problem I have had the same thin in my tecate and it took me like 3 tries to get it fixed it is a bugger but that is your problem I am sure everyone is on the right trail here.

I figured it was the water pump seal as well, but wanted others advice to be sure. Parts are on order, and thanks again for the help.

Check the water pump seal.

Did you order a new impeller too?

Didn't order a new impeller...may be a good idea though. Damn parts take so long for this bike though

Its about a 100 bucks, but Order all the parts. Impeller, shaft, seals, nuts and bolts. When I had the same problem, my shaft was broken.
Look real close at the water pump cover. If you see ANY scratchs on it or nicks you need to make sure they wont hit the impeller.

If you replace all the parts, your sure repair the problem and save the good parts as spares.

Wow, another Tri-Z owner???

Impeller seal, brotha... bank on it!

It doesn't sound like it has been sitting long. If it has been, it's possible that it's had enough condensation built up in the oil to cause it to turn white like that.

The Pastor

Another issue I'm having with this bike is the powerband. I bought the wheeler from my uncle whose had it since stock, and it is cherry for an almost 20 year old bike. First thing I did was change the top end (bore job, the whole works) and put a new DG pipe and silencer on it. The thing sounds mean now! The problem is that it seems like there is no power down low and tons on top...kinda like a banshee. Seems you have to be on it to have anything at all, and feels like I have to push the bike too hard. Haven't really played with jetting too much because it starts right up and idles nice (pilot circuit) and plug is a nice color. Do you think I can bring the power down in the band a little with a clip adjustment??? Thanks fellas.

you put a new pipe on it? Is it a top end pipe? Resitricting the fuel flow and air flow will affect top end more then low end....I think the issue is the pipe, put the old one on and try it out ....also, you bored it, not went to a "Bigger" head size, example 250 with a 300 kit, right?

The cylinder had your basic bore/hone job, that's it. The pipe wasn't specifically advertised as a "top-end" pipe, but who knows. It is a full DG system and sounds very pipey. The piston set is Wiseco. Jetting is at stock settings from what I can imagine. Never have done anything to the carb. The old pipe/silencer system was quite restrictive and sounded real wipmy compared to the new one. I was thinking the additional air flow may have had something to do with the way the bike runs, but that is just what pipes do..provide backpressure and "tune" your bike for a specific powerband. I will try a swap and see what happens. Can't imagine what it's gonna look like. The new one has a bright nickel finish and looks (@)(@)'s!!!

My Tri-Z is just like this. Mine is far from stock since I bought it used. The air box is gone and it's got some no-name after-market pipe.

The air cleaner has a lot to do with things, and I doubt that stock jetting is right.
My problem was that the K&N that I was using was much too small.

My bike is very fast... but very difficult to ride since the power band is like a Banshee's.


The Pastor