Front muffler/ collector box

[GB.]

The front muffler as BMW call it on my PD is looking a bit scruffy. Personally I don’t like the look of the big box under the swingarm so was looking to replace it with a Keihan Y piece. Apart from the looks is there any benefits for fitting the Y piece?


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[Bubb]

It’s lighter…..
Don’t know if that’s a Benefit…..

It was designed with the collector box, so there must be a reason bmw didn’t just do a Y piece…..
Think it’ll flow the exhaust gasses better, but make it louder…

 

[DrFarkoff]

The front muffler as BMW call it on my PD is looking a bit scruffy. Personally I don’t like the look of the big box under the swingarm so was looking to replace it with a Keihan Y piece. Apart from the looks is there any benefits for fitting the Y piece?


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They are a bastard to set up a decent Idle !

The usual Y piece for an Airhead is more like a Tee where the two cylinders connect and it doesn't really "flow"

 

[Garry H]

They sound nicer with the Y piece but run a fair bit better with the original box

 

[GB.]

Thanks for the comments guys, that’s interesting. It raises the question then that do all these custom bobbers and scrambler airheads with weird exhausts and open air filters run worse than stock bikes?
But if you spent time on the jetting etc I can’t see why you couldn’t get them to run right. But mine runs so well, idles perfectly and pulls so strong I wouldn’t want to lose that.


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[Paradiso]

I tried a Keihan Y piece on a paralever 100 gs. Much louder; irritating loud. Also runs much better with the collector box. I was glad to get it off.

 

[DrFarkoff]

Thanks for the comments guys, that’s interesting. It raises the question then that do all these custom bobbers and scrambler airheads with weird exhausts and open air filters run worse than stock bikes?
But if you spent time on the jetting etc I can’t see why you couldn’t get them to run right. But mine runs so well, idles perfectly and pulls so strong I wouldn’t want to lose that.

Its a case with form over function for those twats!

The money that they throw at carbs etc etc etc to Get "the Look"

there was a guy here made a fortune selling complete SNOTTERS of custom bikes A couple of people asked me to work on them and I refused I said If I go near that thing! You will think I did something to it! Welds looked like maggots on something dead! Wouldn;t trust them with tosser weights

Anyway BM spent a LOT of Money to develop their fuelling and Bings did a LOT of options I have even heard of people taking Dellortos of 90S (And draining and storing them!) because they were too sharp

 

[GB.]

Well that’s settled that then, the rusty box is staying on.


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[Tbolt]

I ran my R80G/S with original collector box.

My recently purchased paralever R80GS has a Y-piece fitted to original front pipes with balance pipe.

However, it doesn’t look to be made by Keihan as it doesn’t join in a T like joint but a proper Y where the pipe bends up.

I have had the bikes top end and carbs refreshed by Charlie Pedals and I am extremely pleased with the way the bike is running and I don’t have any issues with loudness.

Gerry

 

[JohnnyBoxer]

Thanks for the comments guys, that’s interesting. It raises the question then that do all these custom bobbers and scrambler airheads with weird exhausts and open air filters run worse than stock bikes?
But if you spent time on the jetting etc I can’t see why you couldn’t get them to run right. But mine runs so well, idles perfectly and pulls so strong I wouldn’t want to lose that.


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Yes , ask Steptoe
Airheads run best with the collector box as it creates back pressure I do believe

 

[GB.]

I ran my R80G/S with original collector box.

My recently purchased paralever R80GS has a Y-piece fitted to original front pipes with balance pipe.

However, it doesn’t look to be made by Keihan as it doesn’t join in a T like joint but a proper Y where the pipe bends up.

I have had the bikes top end and carbs refreshed by Charlie Pedals and I am extremely pleased with the way the bike is running and I don’t have any issues with loudness.

Gerry


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You could be onto to something with the more equal length Y piece compared to the Keihan exhaust, maybe I should be looking for one like that.


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[BillN]

Doesn't the Y piece affect the performance ..........reduce the torque ...... years since I fitted one but I seem to remember that it was not advisable to replace the OEM collector box

 

[Ken g/s Brooks]

Its a case with form over function for those twats!

The money that they throw at carbs etc etc etc to Get "the Look"

there was a guy here made a fortune selling complete SNOTTERS of custom bikes A couple of people asked me to work on them and I refused I said If I go near that thing! You will think I did something to it! Welds looked like maggots on something dead! Wouldn;t trust them with tosser weights

Anyway BM spent a LOT of Money to develop their fuelling and Bings did a LOT of options I have even heard of people taking Dellortos of 90S (And draining and storing them!) because they were too sharp

Exactly This!!

 

[ChasF]

The collector box on my 100GS clearly had something rattling around inside so I chopped the top off to find one of the baffles inside had completely broken off. I brazed the top back on and it’s been like that for 10 years or more. Can’t say I’ve noticed any difference in performance or idle.

 

[GB.]

Well I took the plunge and got the Keihan Y piece. I know it’s going against the grain of more knowledgeable folks on the forum but I did it anyway. Fitting was straightforward enough. I took it for a ride yesterday and I can’t notice any drop in performance whether it be mid-range torque or how it revs, probably picks up a bit quicker to be honest.
Personally I think it looks loads better, before.

And after.

It is definitely louder but it’s not offensive in any way shape or form. The original box is currently being cleaned of rust and corrosion.
The only difference I’ve found is it needs a touch more throttle to start it but that’s negligible. The idle is at the same revs with no noticeable shaking. It is quite a bit lighter but I didn’t weigh it so not sure how much.
Getting back to how the boxer engine runs, I’ve found on my previous oil heads and wet heads, losing the front balance pipe does really effect running of these bikes, robbing them of midrange and changing the overall feel of the engine.
So I’ll definitely be keeping the original headers with the balance pipe.


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[Kenny]

The early 'Y' pieces did affect the mid-range etc as one of the pipes was virtually 90 degrees entering the other one ! Yours looks like it is a proper 'Y' piece connection..hence why you will hardly notice much difference. Looks good

 

[GB.]

The early 'Y' pieces did affect the mid-range etc as one of the pipes was virtually 90 degrees entering the other one ! Yours looks like it is a proper 'Y' piece connection..hence why you will hardly notice much difference. Looks good

Thank you, I’m happy with it, the bike looks cleaner now.


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[Jem Wilton]

I've had the y piece for a long time - it's been fine for my adventures!

 

[Mistacat]

Years ago I welded lambda sensor bosses into the header pipes on an airhead and using wide band lambda sensors and a dual band Innovate LM2 was unable to get the mixtures on both cylinders to get close.
In the end it turned out to be the Keihen Y or should be called T piece.
Cut the T piece out and fabricated a proper Y piece problem solved.

 

[DrFarkoff]

Years ago I welded lambda sensor bosses into the header pipes on an airhead and using wide band lambda sensors and a dual band Innovate LM2 was unable to get the mixtures on both cylinders to get close.
In the end it turned out to be the Keihen Y or should be called T piece.
Cut the T piece out and fabricated a proper Y piece problem solved.

Thats my intention too!

Take my "T piece" Cut it and slot it and fit it to bike and tack it up so that it sits the way that it should ! and take it back off double check ease of assembly

Tack it to a plate and cut the T junction out and fabricate a flowing bend at that point tack it all up and remove the tacks or brackets securing it to the plate!

They are a horrible Exhaust Piece!!