2007 CRF250r Knocking every other stroke. stopped running

Bike all of a sudden started knocking and slowly died. Then would not run.  

As you slowly turn the motor over with the kick starter, you can hear a knock every other stroke.

So I shimmed the valves.

Valves where out of tolerance a little but not real bad.

After shimming still has the knock every other stroke.\

 

So I removed the head thinking a valve was bent and hitting the piston.

.Valve look good no indication of valves hitting piston. 

I didn't think to do a compression check until after I had the head off

 

Any clues of what the problem might be??

 

Thanks

Edited by ronqqq

Crank's big-end rod bearing is toast???

Wow,,  That is not what I want to hear!!  thanks,

 

Do you know of a way I can test this to make sure before I tear it down?

 

The bike really don't have that many hours on it,  never had a wrench on it, 

Thanks Ron

Fail fail fail

The "knock" is the automatic decompressor, totally normal, it is the spring loaded thingy in the cam, it clicks off every other rotation.

Most likely your only problem was the valves.

The shims will fix it for a little while, but you need to replace your valves, most likely just the intake valves. Which ones did you shim? What were the measurements?

That said, you already have the head off, so you might as well check out the crank, make sure it doesn't have any up and down play, and that the thrust washers are in good shape, also the condition of the cylinder and piston.

You can also remove oil filter and check for shavings that would help verify a worn out crank

Fail? So you think the motor was running, it started knocking and then died as a result and now will not start, and you think that knocking is the normal decompressor actuation noise? I think your diagnosis is the fail... something is not right inside the motor and he needs to diagnose and fix it. Could be decompression system busted and it's making noise (?), could be auto-tensioner failed and valves are tapping piston, could be lower rod bearing. Knocks while running are typically not good and usually are not decompressor system related.

Fail fail failThe "knock" is the automatic decompressor, totally normal, it is the spring loaded thingy in the cam, it clicks off every other rotation.Most likely your only problem was the valves. The shims will fix it for a little while, but you need to replace your valves, most likely just the intake valves. Which ones did you shim? What were the measurements?That said, you already have the head off, so you might as well check out the crank, make sure it doesn't have any up and down play, and that the thrust washers are in good shape, also the condition of the cylinder and piston.
Edited by Eddie8v

Fail? So you think the motor was running, it started knocking and then died as a result and now will not start, and you think that knocking is the normal decompressor actuation noise? I think your diagnosis is the fail... something is not right inside the motor and he needs to diagnose and fix it. Could be decompression system busted and it's making noise (?), could be auto-tensioner failed and valves are tapping piston, could be lower rod bearing. Knocks while running are typically not good and usually are not decompressor system related.

 

 

It sounds to me like the bike died and wouldn't run, made a "knock" as the engine was coming to a stop (like it always does), and then wouldn't start.

 

Now the OP is sitting there with his ear to the engine, wondering what that "click" is every other stroke of the engine, thinking his engine is broken

 

 

So i'm saying valves....since he already said they were out of spec. Maybe he needs a new plug, and that's why the bike died, or maybe the fuel was off and the bike died, who knows.

 

But yeah, he should look in the oil filter and pull the cylinder off since he's gone this far already.

They were out of tolerance, but not bad he said, so they may have been a little tight or a little loose, but it's not the valves.

Edited by Eddie8v

yes,  The bike died slowly lost power (is in one min slow)   Now  I here a knocking noise every other stroke,  I don't really think it is a clicking noise.    the noise is rather like a light hammer pinging on metal sound,,,,,     Yes the valves was a little out of tolerance, I re shimmed back into specs.  Knocking noise still there.   Pulled the head,  I was thinking a bent valve and is hitting the piston.  The valves all look seated and no sign of any contact with the piston  ,,

 

 

Like I said the bike has very few hours and was not ridden hard.

 

Maybe the noise is normal???  But it did stop running is what drew me to the noise.....

 

History of bike,,,   beginner rider had ir since new,   rode it very little and was not hard riding when it was ridden. 

I bought it for my son,  he put days at our track and bam!!     So it has very few hours.

Edited by ronqqq

it does sound like the noise is from the top

Ok, pull of the valve cover again. cycle the kickstarter slowly, and you will hear a click each time the cam goes around. The click comes from the decompressor, which is the thing in the middle of the camshaft, looks like a little bump. 

 

Watch the decompressor while you cycle it slowly and see if the click is coming from it.

I still have the head off.   I guess if the crank is ok and the valves are seated good,  I might as well put the head back on?

 

I saw the decompressor on the cam, I bet that is what the noise is..    

 

do they go bad? what should I look for to make sure it is operating proper.

Thanks

When your remove the head, you usually unseat the base gasket, which means you should replace the base gasket, otherwise it might leak.

 

So, next step remove cylinder.

 

Drain coolant using bolt on side of water pump. It will shoot out in a stream so have a big drain pan ready.

 

Remove coolant line from side of cylinder by unscrewing the single bolt that goes into the head.

 

Remove brackets which hold cylinder to frame.

 

Slide cylinder up. It might stick a little at first, tap it lightly with a rubber mallet. Be very careful to not damage the piston & rings.

 

 

Now, you should be able to see the crankshaft. Check for up, down, forward and back play. On each side of the connecting rod where it attaches to the crankshaft, you will see thrust washers. Make sure they are in good condition. Get a helper to hold the timing chain and piston up, and slowly rotate the engine, check for any binding, play, or noises from the crankshaft.

 

Check the wrist pin where it connects to the piston. It should slide left to right, but should not have any other play.

 

Once you do that, check back in here with the results, takes some pictures if you can.

What's going on with your bike man? Did you get lazy? Get off the couch and pull that cylinder off!

OK   Here is the deal,

I bought the bike for my son,  They guy I bought it from said he just changed the oil.  So I didnt check the oil before riding

 had to replace the crank shaft.    

The knocking noise is normal compression release.    new to 4 strokes so that was a weird on for me.

 

 

 Got the crank in, running great, except when it is wrecked or laid over,  oil saturates the piston.

 

Not sure where it is coming from

 

 

Any ideas??

 

 

thanks for the help everyone!!

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