Y Pieces

Mine ran so much better for having the needle dropped a notch. Better again though with a standard collector. The Y piece bark is nice though.

I sent Keihan an Email a couple of weeks ago asking if they could make a copy of the original collector in Stainless steel. I had this reply back.

"In the last few months we have re-designed our y pieces due to customer comments like yourself, this has made them free'r flowing so improving the performance.

We have no plans at present to reproduce the collector box.

Regards
Mark Regan"



I've got five airheads, apart from Sito silencers on my 90/6 all of the systems are Keihan. It's only the Y piece for the Para I have a problem with, hopefully the new design will improve them. Good company and good products :thumb2
 
Some people have no problems with the Y piece , so I think there is a bit more to it than that.

The standard muffler is quite restrictive , and it can get blocked ,if, or when, the aluminium gaskets between the various section of the exhaust disintegrate and vanish down the pipe and into the muffler.

Air leaks dont help too. I have found it essential to have all the joints real airtight, if it pops and bangs it wont run right either.

The entry hole into the muffler is easy to open up a bit, and the plate at the back can be bent over at the edge easily too. I did this and ended up with a pile of melted bits of aluminium out og the muffler , a pleasing burble to the exhaust and a better and cleaner running engine.

Removing the snorkels from the air box, rerouting the engine breather and fitting a foam filter helped too.

San Jose got a decent increase in both power and a reduction in consumption simply by fitting a less restrictive Supertrapp, removing the snorkels and some unspecified carb changes .

I feel that BMW simply got it wrong with the GS - the reduction in compression from 9.5 to 8.5 shouldnt have cost 10 hp, there has to be more to it, and it is most likely to be bits unique to the GS.
 
Beemerboff said:
Some people have no problems with the Y piece , so I think there is a bit more to it than that.
Click to expand...

There is a new (?) Y pipe available in Germany. See here.

Bit of a stinger, price wise, but looks like a much better thought out unit. I believe it is also one of the very few that has an ABE doc for use in Germany. That means it adheres to the legal regs for the GS exhaust... Thats part of the reason it costs so much.

John
 
Beemerboff said:
I feel that BMW simply got it wrong with the GS - the reduction in compression from 9.5 to 8.5 shouldnt have cost 10 hp, there has to be more to it, and it is most likely to be bits unique to the GS.
Click to expand...

I along with several of the UKGSers owned that red R100GS that appears in the top right corner it was an American bike imported by Givitsum. The bike is fitted with 32mm carbs, standard exhaust and collector box and is probably the fastest R100 I've ridden. It makes me wonder if it isn't the 40mm carbs messing things up with the low compression engines the other low comp motors from the same era all have 32mm's
 
I have a pair of Wossner (Sebenrock) 9.5 to 1 pistons to go in over what passes for winter here (think Scottish Summer) so I will test that theory.

Problem with my experimenting is that I like to do a few things once I have the bike appart, so it isnt always easy to pinpoint exactly what has made the difference.

The idea is to have the heads machined to give squish bands too, so if I do get a result it I wont be certain which has made the biggest difference.
 
I know its been done to death but there may just be a bit more mileage in it:rolleyes:

I have the Keihan Y pipe and a genuine BMW Stainless silencer. I have decided that its piggin' LOUD and is becoming annoying on a run.
What to do? Don't want to refit the collector box.

Anyone tried a DB-killer? A guy was selling a 41mm unit in ebay last week and although it looked a bit cheap and not made of stainless, how hard can it be to knock one up.


41mm OD for the bit that slips into the tailpipe and 100mm long 25 -28 mm inner pipe welded centrally in it to give room to fit a stainless "rivnut" between the tubes for anchoring it.
I was talking to the guy that makes the Wings silencers for KTM's and the said the diameter if the inner makes more difference than the length - heard that somewhere before:rob.... and there is no need for the holes in the on pictured.

Maybe this would be the answer to the flat spot some experience.

Can anyone make such a thing?

John
 

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John Armstrong said:
Use plenty of dyno time if you go away from standard and are after more power / torque.
Click to expand...

Ah. No just after using the Y pipe as the collector is u/s.
At the moment it "feels" fine. No holes in the power delivery.
It just sounds like the can is completely devoid of baffling so I want to take that edge off it.

Sounds a bit like an old Norton with a straight tube in place of the silencer:D

John
 
The baffling had been completely blown out of my original silencer I had to fit a Keihan replacement (£350 ish :( )

I reckon you could save an awfull lot of dyno time by fitting a Lamba sensor (with the two heaters) and one of those gauges that shows whether the mixture is weak or rich. Big bucks and a bit of hassle but then Dyno time is as well as finding the time to get along there.
 
I have a book on tuning SUs, and it suggests a rather,err, heroic method of tuning them.

The suggestion is that you fit a couple of colortunes, get the back wheel up off the ground on the center stand and run the engine against the back brake, while observing mixture on the colortunes. If I put a spring balance in place of the lower link on the paralever I could probably work out the horsepower too.

Havent tried either but even if it cooks the brake shoes it is probably a lot cheaper than dyno time.
 
You could always hang off the bike with your eye to the colour tune while doing a flat out run :D

I had one of these in mind so you could simply see what the air ratio was at any given RPM

Ebay Link

Colour tunes and high speed runs sounds far more entertaining though.
 
With a GS on the stand the drive shaft angle is a bit steeper so probably another reason why it is not a real good idea.

I hope no one took it seriously!

However if you could borrow a set of car starter rollers and had a reliable way of supporting the bike ----------------.

That tester looks a good bit if gear, but I think that there are simpler bits of kit which would do the job on an Airhead for a lot less.
 
My local dealers got the innovator kit in stock.. I can feel a spend coming on :eek: It reads fault codes for OBDII cars and can bus systems as well so I can use it on our BMW 3 series car instead of paying the dealership a small fortune when the "Check engine light" comes on.
 
The LM2 is worth it's weight in gold. Very pleased with it.

Beemerboff,

Your idea about the standard air box funnels not working correctly is right. I''ll do a little more modifying but I'm currently running two large inlet tubes (instead of one large and one small) and have the needle down one notch. The jetting is spot on through the rev range. The standard airbox doesn't flow enough air.

I'm going to fit one of the old style RS filters and airbox to see how that compares.
 
I'm going to stuff one of these up its jacksy and see what difference it makes.
Its a cheap looking thing but of the correct dimensions and if it works I will make a stainless one,

John
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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