[Willis]

I just finished changing the second gear in my 99 yamaha r6 and everything went great. I got it all back together and back in the bike and it ran and drove great. A few days later I'm riding down the freeway, 70MPH nothing crazy and all of the sudden the bike won't accelerate and keeps slowing down, so I pull in the clutch and she dies and won't start again. The temp guage was reading normal and the oil pressure light didn't come on. The bike has no compression now. I initially thought that I somehow overheated the head by not having enough coolant, but the radiator is full, and I think that I would have had a problem with this earlier.

Here's what I think it is: I think that I blew the timing chain somehow. There is no water in the oil nor any oil in the water so I'm pretty sure I didn't burn a head gasket. When I was tearing down the engine for the second gear I did take the bolt that holds the crank gear off, but when I re-installed it I used blue loctite and torqued it to the specs in the book.

Here's my question: Is the Yamaha R6 engine an interference engine?

The bottom end of the engine spins freely when the starter is engaged and I don't here any carnage, so I hope that the pistons and valves survived and I just have to change the chain/tensioner/gears.

Any input on this is greatly appreciated.

 

[Willis]

Here's me bumping my own thread. Apparently nobody wrenches on their own bike.

 

[ShanMan14]

Plenty do... I'll bump it up too. :dthumb:

 

[bumblebee]

Plenty do... I'll bump it up too. :dthumb:

same for me...so I'll make it three!!! :wink:

 

[Earlzach]

I just finished changing the second gear in my 99 yamaha r6 and everything went great. I got it all back together and back in the bike and it ran and drove great. A few days later I'm riding down the freeway, 70MPH nothing crazy and all of the sudden the bike won't accelerate and keeps slowing down, so I pull in the clutch and she dies and won't start again. The temp guage was reading normal and the oil pressure light didn't come on. The bike has no compression now. I initially thought that I somehow overheated the head by not having enough coolant, but the radiator is full, and I think that I would have had a problem with this earlier.

Here's what I think it is: I think that I blew the timing chain somehow. There is no water in the oil nor any oil in the water so I'm pretty sure I didn't burn a head gasket. When I was tearing down the engine for the second gear I did take the bolt that holds the crank gear off, but when I re-installed it I used blue loctite and torqued it to the specs in the book.

Here's my question: Is the Yamaha R6 engine an interference engine?

The bottom end of the engine spins freely when the starter is engaged and I don't here any carnage, so I hope that the pistons and valves survived and I just have to change the chain/tensioner/gears.

Any input on this is greatly appreciated.

I wouldnt want to think every exhaust valve is stuck open . It just would seem odd if they all did. You say No compression. Is that over all four cylinders or just one?
The entire lack of compression in four cylinders is wierd. You would have to have all four pistons with holes in the tops of them or all exhaust valves stuck open. I would say timming is way off, may have jumped time on you. :scratch:

 

[carlmorrell]

Well I can offer some GUESSES. Since I am not familiar with you engine.

If I had to change gears in any motor I have worked on, I would have to first put heads, and cylinders to split the case. Is that true on your motor?

To pull the heads, you have to pull the cams? The last couple of motors I worked on, to pull the cams, I had to remove the cam drive gears. Is it possible that gear came off? If the cam caps came loose? Did you pull the valve cover to inspect?

Good luck. :sorry:

 

[SpeedWerks.com]

Here's my question: Is the Yamaha R6 engine an interference engine?

Yes it is. Almost every japanese bike is.

If you can turn the motor over right now and you're not hearing valves being hammered into your pistons, I would doubt the timing chain has broken. Or ... you got VERY VERY lucky when it did and nothing is hitting.

- Roach

 

[SpeedWerks.com]

Well I can offer some GUESSES. Since I am not familiar with you engine.

If I had to change gears in any motor I have worked on, I would have to first put heads, and cylinders to split the case. Is that true on your motor?

Nope. The R6 motor is stacked where you can access the tranny. Pretty cool design.

- Roach

 

[Willis]

The motor does not have to be completely split to access the tranny. You have to remove the lower crankcase from the upper crankcase, but you leave the top end alone.

I may have compression in one cylinder. The motor spins pretty freely but I hear a puff from one cylinder once in a while.

The reason I think that I lost the chain-- if the valves are not moving at all, there will be some valves open and those cylinders will have no compression. one or two of the cylinders may be on power or compression stroke, meaning that all of the valves are closed. Air is neither coming in nor going out because the valves are closed. This wouldn't have compression in the cylinder because there is no way for air to get in or out. The cylinder(s) most likely has bled out any pressure and is at atmospheric pressure.

I think that the puff that I here is from a cylinder with the valves open.

 

[Earlzach]

The motor does not have to be completely split to access the tranny. You have to remove the lower crankcase from the upper crankcase, but you leave the top end alone.

I may have compression in one cylinder. The motor spins pretty freely but I hear a puff from one cylinder once in a while.

The reason I think that I lost the chain-- if the valves are not moving at all, there will be some valves open and those cylinders will have no compression. one or two of the cylinders may be on power or compression stroke, meaning that all of the valves are closed. Air is neither coming in nor going out because the valves are closed. This wouldn't have compression in the cylinder because there is no way for air to get in or out. The cylinder(s) most likely has bled out any pressure and is at atmospheric pressure.

I think that the puff that I here is from a cylinder with the valves open.

for the most part you make sence, however it has to draft in air on the down stroke or like a plugged sirenge it would snap the piston right back up with vacume. So to have all valves closed you would still show some compression or have resistance on the down stroke if they were seated that good. I still dont rule out a chain or cam are the problem. Did you notice if your water was pressurised when you pulled the cap. not necessarally over heated but cylinder head blow by will force combustion to pressurise the water system. It will also result in low compression.

 

[larryg]

Well, if you lost the cam chain you bent valves. An easy way to check is to pop off the carbs and look down the intake runners. Assuming you don't see any immediate carnage, turn the motor over and watch to see if the valves are opening and closing. If they are moving, you didn't loose the cam chain...this would be a good time to get farther into it and confirm your cam timing is correct.

Larry

 

[Willis]

Well, if you lost the cam chain you bent valves. An easy way to check is to pop off the carbs and look down the intake runners. Assuming you don't see any immediate carnage, turn the motor over and watch to see if the valves are opening and closing. If they are moving, you didn't loose the cam chain...this would be a good time to get farther into it and confirm your cam timing is correct.

Larry

Well I did similar to this, I pulled the exhaust manifold off and cranked the engine over. All eight exhaust valves are actuating. So, I didn't lose a chain. I did notice that when I pulled the tank there was gas in it, but none dripped out of the hose when I disconnected it. I now think that I may have a plugged fuel filter that caused it to run lean and possibly burned valve(s). I'll dig more into it tonight to see. One problem I have is that I don't have a fitting for a compression tester that will fit that small motorcycle spark plug hole. Any ideas?

 

[Mojo]

Well I did similar to this, I pulled the exhaust manifold off and cranked the engine over. All eight exhaust valves are actuating. So, I didn't lose a chain. I did notice that when I pulled the tank there was gas in it, but none dripped out of the hose when I disconnected it. I now think that I may have a plugged fuel filter that caused it to run lean and possibly burned valve(s). I'll dig more into it tonight to see. One problem I have is that I don't have a fitting for a compression tester that will fit that small motorcycle spark plug hole. Any ideas?

MAC makes one that will work.

 

[Willis]

I was hoping to rent one somewhere. I don't really need one all that often. Would autozone's tool rental have anything like that?

 

[Earlzach]

I have the one with the rubber nipple it fits any hole. Toobad your half way across the states from me though. I would let you use it for sure. How did you come to the NO compression theory? Maybe it did just run out of gas. or top getting gas from a clogged filter or shut off petcock.
With electric start and no gauge how are you certain of no compression.

 

[Willis]

I have the one with the rubber nipple it fits any hole. Toobad your half way across the states from me though. I would let you use it for sure. How did you come to the NO compression theory? Maybe it did just run out of gas. or top getting gas from a clogged filter or shut off petcock.
With electric start and no gauge how are you certain of no compression.

When I hit the start button the engine spins freely. A lot faster than before it quit and I only hear the starter bog down on one cylinder. It used to spin slower because all the cylinders were compressing on the compression stroke.

I think that it ran with little fuel, and lean mixtures burn much hotter than rich ones so I think I burned something. Tonight I should know a little better. If I cant find a compression tester then I'm just gonna pop the cylinder head off and inspect the upper end.

 

[Earlzach]

This may sound stupid but are the spark plugs out?

 

[Willis]

This may sound stupid but are the spark plugs out?

They are now, but they weren't when I was trying to start it.

 

[Earlzach]

They are now, but they weren't when I was trying to start it.

Well there is your high speed cranking. Nothing in the hole to create compresion.

 

[Willis]

Well there is your high speed cranking. Nothing in the hole to create compresion.

No, they were not Out when I was cranking, they are Out now.