R1150RT noise at cruise

[T800]

Hey guys. New here. I just picked up a 2004 RT-P and not a lot of info over at advrider for RTs. Been riding an airhead GS for many years, but this is my first oilhead.

 

I didn't get a lot of info on history, but the bike had 11,800 original  miles when I got it last week. It runs and appears to be in fair shape mechanically. I rode it home, about 200 miles. He said it was a parade bike for a PD in Alabama.

 

During the test ride I wasn't able to get to a high speed road in a reasonable distance so this went unnoticed until I hit the interstate on the way home. At RPMs above 4k and holding steady speed, there is what sounds like a loud rattle coming from the engine with some light vibration. If I twist the throttle it goes away until I level off. If I get off the throttle it goes away. Otherwise it's running quite smooth after a valve adjust and TB sync.

 

It had a pretty good rattle at idle  too. I did the left cam chain tensioner upgrade and that sounds much better. No help on the top end though. The fairings are off at the moment, in case you were wondering.

 

I know noises are very hard to diagnose over the internet, but was hoping maybe someone had experienced it or similar before. I'm probably not explaining it real well either so hit me with questions.

 

Thanks in advance.

 

Edit: Was just reminded that the prev owner said he had changed the alternator belt. Haven't pulled the cover yet, but is there something up there that could be a cause? Thx

[dirtrider]

11 hours ago, T800 said:

Hey guys. New here. I just picked up a 2004 RT-P and not a lot of info over at advrider for RTs. Been riding an airhead GS for many years, but this is my first oilhead.

 

I didn't get a lot of info on history, but the bike had 11,800 original  miles when I got it last week. It runs and appears to be in fair shape mechanically. I rode it home, about 200 miles. He said it was a parade bike for a PD in Alabama.

 

During the test ride I wasn't able to get to a high speed road in a reasonable distance so this went unnoticed until I hit the interstate on the way home. At RPMs above 4k and holding steady speed, there is what sounds like a loud rattle coming from the engine with some light vibration. If I twist the throttle it goes away until I level off. If I get off the throttle it goes away. Otherwise it's running quite smooth after a valve adjust and TB sync.

 

It had a pretty good rattle at idle  too. I did the left cam chain tensioner upgrade and that sounds much better. No help on the top end though. The fairings are off at the moment, in case you were wondering.

 

I know noises are very hard to diagnose over the internet, but was hoping maybe someone had experienced it or similar before. I'm probably not explaining it real well either so hit me with questions.

 

Thanks in advance.

 

Edit: Was just reminded that the prev owner said he had changed the alternator belt. Haven't pulled the cover yet, but is there something up there that could be a cause? Thx

Morning T800

 

The 4K engine buzz is normal for the BMW boxer, the rattle isn't normal.  

 

You are correct, diagnosing an engine rattle over the internet is almost impossible without WAY more info.

 

If it is throttle position sensitive it could even be spark knock or even worse pre-ignition. 

 

Can you describe the rattle (compare rattle to something that is a known, like woodpecker, or hammer on a nail, or shaking rocks in a can, etc. You are our ears on this so the better you explain it the closer we can get. 

 

If it sounds like something (like a shield or panel rattling then go over the engine, panels, exhaust, etc with your hand (or a rubber mallet) rapping on things to try to find what might be loose & rattling from engine buzz.  Make sure the exhaust system isn't contacting the side stand or center stand.

 

On the belt, that can make a noise if too loose but usually not a rattle. The 2004 1150RT belt is difficult to adjust as it is adjusted by distance between the lower pulley & alternator pulley using a special tool. It uses an elastomer belt (stretchy belt) 

[Lowndes]

Hey, T800!!   Welcome to the forum!!

 

Dirtrider will get it sorted.  He is acknowledged by all as THE GURU here.

[T800]

Dirtrider,

 

Sorry I'm so late getting back to this.

 

What I initially thought was engine noise is actually, I believe, intake noise.

 

What I've found thus far is there is blowback on the right cylinder. The throttle body and intake runner were wet on the right cylinder, but the left is dry. Was hoping it was a bad fuel injector, but it wasn't.

 

Compression left is 150 psi, right is 160 psi, which are both low I believe. Don't have a leakdown tester at the moment. Apparently I loaned it out.

 

So I'm thinking the exhaust valves are burnt. Thoughts?

 

Thanks for the help.

[dirtrider]

8 hours ago, T800 said:

Dirtrider,

 

Sorry I'm so late getting back to this.

 

What I initially thought was engine noise is actually, I believe, intake noise.

 

What I've found thus far is there is blowback on the right cylinder. The throttle body and intake runner were wet on the right cylinder, but the left is dry. Was hoping it was a bad fuel injector, but it wasn't.

 

Compression left is 150 psi, right is 160 psi, which are both low I believe. Don't have a leakdown tester at the moment. Apparently I loaned it out.

 

So I'm thinking the exhaust valves are burnt. Thoughts?

 

Thanks for the help.

Morning   T800

 

Probably not a burnt exhaust valve if it is blowing back through the intake. Possible a leaking intake valve but your side to side compression is fairly even. 

 

Did yo do the cranking compression test with the #5 fuse removed (that stops the fuel injection) & with the throttle held wide open? 

 

Engine cranking speed can effect compression readings, did it sound like it was cranking at normal speed? 

 

You probably do need to run a leak-down test, if OK there then make sure the R/H lower spark plug is not oil fouled & that both spark plugs on the R/H side are sparking. 

 

See if your engine will run on JUST the lower spark plugs, then see if it will run on JUST the upper spark plugs. 

[T800]

Yeah, bad intake valve is what I meant. Distracted typing ...

 

I didn't remove the fuse, throttle open, cranking normal speed, engine slightly warm.

 

I had already been thru the ignition system. Had a bad stick coil on the left. Replaced that and all plugs are firing. Lower plugs looked ok - not oil fouled.

 

I'll try to run down my leakdown tester. I'm pretty sure I know what I'll find though ...

 

Thanks

[dirtrider]

1 hour ago, T800 said:

Yeah, bad intake valve is what I meant. Distracted typing ...

 

I didn't remove the fuse, throttle open, cranking normal speed, engine slightly warm.

 

I had already been thru the ignition system. Had a bad stick coil on the left. Replaced that and all plugs are firing. Lower plugs looked ok - not oil fouled.

 

I'll try to run down my leakdown tester. I'm pretty sure I know what I'll find though ...

 

Thanks

Afternoon T800

 

If you can't find anything obvious then maybe drop the exhaust from the cylinder heads, then use a light & look in through the exhaust ports. Look closely at the underside of the exhaust valve heads. If that motorcycle was an oil burner then the  back of the exhaust valves could be heavily coked up restricting the exhaust flow. If all the exhaust can't get out after firing  then it can retain positive pressure in the combustion chamber then pop back through the intake valves when they open.