1977 model leaking exhaust gasses from drain holes ?

[cobbo]

Just bought my first Yamaha 650 XS 1977 all appears to be original 17000 miles American spec , bike runs ok apart from a few flat spots during acceleration , have made no adjustments to the carbs to date.

Have noticed both the exhausts have drain holes , exhaust gasses are passing through these holes. Is this normal ?

Photos attached ..... the idea was to turn the bike into a café racer as a winter project but looks so original may just tidy up , polish the rims and fit stainless steel spokes etc

Thanks

Stew ( Chester England)

 

[Airwolfie]

Hey Cobbo! Welcome!

nice bike you got there, best not cut her up!! You will be hung drawn and quartered if you do!!

the drain holes should not have fumes coming out of them, I would suspect a hole somewhere in the exhaust.

The OG exhausts have double walls, one runs the exhaust gases ,and the other is there to keep the exhaust cooler, it also prevents blueing on the manifold end. Or something like that!

Also , join the UK forum if you want, great bunch of guys there, most of them here too!

http://www.customxs650.com/

 

[cobbo]

Thanks for the quick reply !! planning to remove the exhausts this week so will keep you posted on what I find .... don't fancy the hung drawn and quartered so will probably tidy up and keep as original as possible

Happy days

Stew

 

[Airwolfie]

Hehe good plan bud! My next xs will be that very one! I love that colour layout on the bike!!

 

[racerdave]

The hole is to drain water. A by product of any exhaust is water. Some exhaust gas coming out that hole is normal.

 

[Airwolfie]

Ah ok, learnt something new! Thanks Dave!

 

[retiredgentleman]

I would agree with Airwolfie. The drain holes should not have exhaust gases coming out. Only the inner pipe should have exhaust gases. The annulus space between the inner and outer pipes should only be at atmospheric pressure. The drain hole at the bottom is to allow any condensation to drain out. The hole at the top end is a vent, and allows some air flow through the annulus space.

Gasses from the drain hole would mean the inner pipe has rusted out and now has holes in it.

 

[jayel]

I would agree with Airwolfie. The drain holes should not have exhaust gases coming out. Only the inner pipe should have exhaust gases. The annulus space between the inner and outer pipes should only be at atmospheric pressure. The drain hole at the bottom is to allow any condensation to drain out. The hole at the top end is a vent, and allows some air flow through the annulus space.

Gasses from the drain hole would mean the inner pipe has rusted out and now has holes in it.

or cracked or PO cut off the rear of the header pipes to fit replacement mufflers?

 

[TwoManyXS1Bs]

In the mid-80s, I spent some time at a custom muffler shop, working up a custom exhaust. Everything that left that shop received 'the treatment', carefully drilled 1/8" holes in the muffler bottoms, near the edge flanges. Shop owner talked about condensation drains and said something about standard procedure, shop policy, warranty requirements, state regs, something like that.

That goes thru my mind whenever I see drainholes like that, and wonder if yours received 'the treatment' at some time in its past. Then again, that was in Kansas. Don't know if it was a national policy...

 

[racerdave]

Most cars I ever had on a lift and was either doing exhaust work, or just noticing, had drain holes in the mufflers. From the 70's till I retired Jan 2013. I stated the above because most Jap 70's through 80's bikes I have seen have them also. I agree that If they are double walled at the point in the pic above they shouldn't leak exhaust, but.........................

 

[cobbo]

is it possible to replace the inner tube sections ? could the leaking exhausts be causing the flat spots during acceleration ?

 

[TwoManyXS1Bs]

1. Not really. Would take some serious fabrication skills to rebuild the guts.
2. Possibly, if the innards are badly rotted-out and/or collapsed.

Here's a pic of the bottom of my XS1B muffler. No drain hole(s). Don't recall seeing drain holes on the '70s Hondas back then, either. Then again, don't recall looking for them.

I wonder if this is a 'northern climate' thing?

 

[Airwolfie]

I don't think you can, how will you bend the inner pipe to fit in the already bent outer pipe?

I think you better off getting some replacement pipes or 2nd hand OG pipes

 

[Brian G]

FWIW, my '78 CB550K has the drain holes in the 4-4 Honda pipes. In certain weather conditions, water drips from them right after she starts until she's warmed right up. I think the CBX does as well - I just fitted a replacement Sankei set (OEM suppliers who ran some off on request from owners' clubs recently) but I don't remember for sure and I'm not home to check.

Regards,

 

[Grimly]

Drain holes are commonplace - on some systems / depending on the designer and whether he could be bothered or even knew. They'll make a mild steel system last a bit longer, and I don't think they're as necessary on stainless, unless it's cheap stuff.

 

[fredintoon]

Have noticed both the exhausts have drain holes , exhaust gasses are passing through these holes. Is this normal ?
Stew ( Chester England)

Hi Stew,
pan back a bit, dammit! Where exactly are those holes located?
If they are just under the head to exhaust flange and just before the mufflers they are venting the space between the inner and outer walls of the two layer exhaust pipes.
All that should exit there is a little condensation at start up.
OTOH, if they are in the muffler yes, exhaust gas will exit from them.

 

[XSLeo]

Ok, on the 77 it had the same exhaust as the 76. Both 76-77 looked a lot like the 74-75 exhaust, The difference was the crossover pipe.
The mufflers were a slip on fit to the head pipes. Not welded as the later Special's.
The holes in you head pipe are drain holes. Just as RG described.
If you loosen the header finned clamp at the head and slide it back down the pipe you will see how the header is two pipes, one inside the other.
Just a bit out from the flange the finned clamp pushes on you can see where the outer is welded to the inner. You will also see the holes in the outer pipe.
On the end toward the muffler the inner and outer pipes taper together to seal them together.
As mentioned by RG the exhaust flows only through the inner pipe. With the two pipes sealed together at the muffler end no exhaust can get between the two pipes. If you are getting exhaust between the pipes it could be as Jayel said someone cut off the head pipes ahead of the mufflers and installed new mufflers over just the out side pipe.
Leo