Exhaust Header Problem - 1st Gen VR

[twigg]

Posting this simply as a problem solved. Others will have this issue and hopefully they will find this thread in a search, and it might help.

 

1st Gen VRs sometimes suffer from exhaust rattles. The noise is internal and frequently caused by a deteriorating baffle in the collector.

 

Ever since I have had this bike it has suffered from a rattle which isn't evident in a cold engine, but soon makes its presence felt as the bike warms up. At best it is annoying, but now it is fixed.

 

Sometime ago I had the exhaust off to have the collector repaired. It needed new stubs making and welding on and this was done. At the same time I cut open the collector to fix the baffle. To my surprise it was undamaged, so the hole was simply closed up again.

 

More recently I have had an issue with cylinder #2 firing when it wanted to. This too is fixed. New Plugs, Wires and Caps took care of it.

 

I still had the noise and something else unusual. The front downpipe on the right was heating up much faster than the one on the left (#2). That wasn't right. Cylinder #2 was firing correctly so it had to be another issue. Then I realised that those downpipes are "double-walled". What if there was a break internally.

 

Here is what I found:

 

http://i1092.photobucket.com/albums/i418/twigg2324/1986%20Yamaha%20Venture%20Royale/DSCN0277.jpg

 

And another view of same:

 

http://i1092.photobucket.com/albums/i418/twigg2324/1986%20Yamaha%20Venture%20Royale/DSCN0279.jpg

 

Note the break that extends almost the whole way around the internal pipe.

 

Newish downpipe from eBay demonstrated two differences ....

 

Firstly, it had no break, so a good sign

 

Also, the new pipe had a thin but unbroken layer of carbon completely coating the inside. This is normal. As you can see from the pictures the carbon layer is broken, and feathers towards the crack. There was some serious upset in the gas-flow in this pipe, and could be the equivalent of an exhaust hole causing lean condition and an idle that could be reluctant to fall to normal when the motor was very hot.

 

So ... All bolted up, engine running quietly and smoothly, and no rattles.

 

Hope this helps.

[twigg]

A short test-ride later.

 

Who stole my bike and gave me this new one???

 

The difference is remarkable. Gone is the noise and the lumpy low-speed running. No hanging high-idle ... feels like a different bike.

[jasonm.]

In the picture....do I see a "weld" that holds the internal pipe in place ? Is that weld rusted?

[twigg]

In the picture....do I see a "weld" that holds the internal pipe in place ? Is that weld rusted?

 

It's not easy to tell ... I just went and looked.

 

It seems like the flange that bolts to the cylinder head is welded to the pipes, but higher up than the break. That break, btw, goes all the way round, it is broken off.

 

At the collector end the two are held together with a single spot weld.

 

I do know that replacing the pipe has transform the way the bike runs, and hopefully it will have done something for the gas mileage too. We will see when I get the chance to rum 100 miles on it.

 

There is still a very minor "puffing" from somewhere around the collector. I can hear it but it may be normal or just a gasket or joint that is not 100% sealed. Either way it is minor and won't affect the running nearly as much as the damage right by the exhaust valve, if at all.

[jasonm.]

puffing as you call it...is often the rear copper compression gaskets loose. sounds like..."poof pooof poooof" by the rear head area. while running- Remove side covers to confirm. Sometimes tightening the clamps helps enough 5mm allen wrench also lube the threads on that clamp before tightening...wd40 is good enough

[twigg]

puffing as you call it...is often the rear copper compression gaskets loose. sounds like..."poof pooof poooof" by the rear head area. while running- Remove side covers to confirm. Sometimes tightening the clamps helps enough 5mm allen wrench also lube the threads on that clamp before tightening...wd40 is good enough

 

I found it.

 

The copper gasket on the front pipe I replaced is not positioned far enough back to fully cover the expansion slots in the collector stub.

 

I'll loosen it and push it farther back this weekend.