Underseat exhaust

madivi · Post by **madivi** » Sat Jun 23, 2007 1:44 am

Hi all

Has anybody ever given a thought to fitting an underseat exhaust? Is it feasable at all? Height looks quite limited...
How to route the downpipes to the mufflers?

Thanks for your experiences or just any thoughts

Marco

Quan-Time · Post by **Quan-Time** » Sat Jun 23, 2007 2:07 am

anything is possible. The biggest problem is where are you going to route the pipe when its around the foot peg / swingarm pivot area ? theres hardly any room for you to get it up.. Might have to run it from under the bike where the 2 pipes are closest, merge into one pipe, do some fancy bending and try to get it up somehow without being too close to your foot / swingarm travel and tuck it back under..

anything is possible tho.. im sure with enough crafting its do-able..

Glen1TRX · Post by **Glen1TRX** » Sat Jun 23, 2007 3:03 am

Marco, try this on.

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madivi · Post by **madivi** » Sat Jun 23, 2007 12:36 pm

That quick answers! Thanks.

@Quan-Time
You name the problems - but as far as I've seen your posts, you just don't fear any technical challenge. One alternative to your description could be a longer swingarm - but then you shortened yours (R1 I believe), why really?
Or then a one sided swingarm (financially this is out of question).

@Glen1
If it wasn't for the fairing which I dislike and if I had some really heat resistant boots, I'd go for this mod (ok, money plays a role too).
It looks to me that the swing arm is impeded in its operation. What do you think? Would the rear frame need a lift?

Alternatively I'd like a muffler like the Buells have it. Though short downpipes and the low hanging sump seem to avoid this too.
Solutions?

Marco

Trixz · Post by **Trixz** » Sat Jun 23, 2007 2:24 pm

Hmmmzz this is once done by a French and a Dutch TRX rider...

Goodluck

hmmzz the pictures don't appear....

earywig · Post by **earywig** » Sat Jun 23, 2007 11:23 pm

If you want it to look like a Ducati ............................ buy a Ducati

Quan-Time · Post by **Quan-Time** » Sun Jun 24, 2007 2:39 am

trixz was trying to link this

As you can see, you REALLY need to route the exhaust out a fair bit.. its right near your heal....

But as stated, yes, anything is possible.. personally i prefer the twin exhaust, but even then, its too "ducati" for me.. but when has that really stopped me ? damn, my bike is more R1 than trx now

@Madivi

OK.. ill try to explain as best i can (its morning here, im a little tired). I do currently have a 2000 R1 swingarm inplace of the stock unit. By some photos you will realise this new swingarm is 72mm longer. This alters the handling of the bike.
Its very stable at higher speeds because of this. At the cost of the turning circle being bigger and the way the bike "drops" into corners.
I re-shortened the swingarm to make it handle identicle to a stock swingarm. So all i have really done is made it look different without actually changing the handling.. Its the same as putting a YZF750 swinger in there.

Ill also give you a few tips on this area. The 2000 R1 swinger has the suspension coil in the middle of the bike, the same position as the trx. Which made it very nice. The 2004 (which i could have used, as i know where a spare one is !) is offset.. Meaning the coil is actually to the gear side of the bike not the brake side (hope you understand).
By doing this the hole where the coil sits in is off set to one side, and there is more space now on the gear side. The exhaust actually comes up right next to the coil in the middle of the swing arm.

Not the best picture, but you get the basic idea of how i mean. (i hope)

One thing to observe here is that a longer swingarm will always provide more stability. The smart boffins at honda realised that the "optimum" pivot point for a swingarm is actually the front wheel axle.. Obviously this is retarded so they try to make their swingarm as long as possibe, but the wheel base is still short as possible while maintaining practicality.

What this means is if you were to mount your engine say 30mm FORWARD and bring your mounting brackets forward by 72mm (check TRX of the month, the big alu silver part where the swingarm bolts to,, move it towards the front 72mm) and then put in a R1 swingarm. The effective wheelbase is STILL the same as the factory trx swingarm.. but you get the added bonus of having better geometry for it.

If you did indeed do this you would have PLENTY of room to put a nice underseat exhaust thru the swingarm (you would have to side-mount your suspension pieces.. But if your going to the extent modding everything else, why stop there

I hope i made some sense.. now.. coffee then shed time..

madivi · Post by **madivi** » Sun Jun 24, 2007 11:49 pm

Hi all

This early morning I took my Trixie for a strol in the surroundings of lake lucern (Switzerland).
Marvellous, the landscape and the motorbike. No traffic.
So now I find time to answer.

@earywig
I guess you would take a Ducati too, wouldn't you?
Honestly, the past years' design didn't suit me really.
And I consider twins (not v-twins) the ideal configuration.

@Trixz
The french mod is really pleasant. Thanks for pointing me to it.
That could be a solution to go for.

@Quan-Time
Thanks for your exaustive answer I appreciated much.
Despite your sunday morning and me myself, you made
it all clear to me.
Two good ideas: Setting of the damper and moving the engine forward.
Whereas the latter looks quite feasable to me, relocating the damper
probably needs welding. My welding holds fast but isn't really something
to look at.

To spin ideas a bit further (not necessarily keeping feet on ground) the best aesthetic
solution I know of is seen on an Aprilia RXV 4.5 (450 ccm).

I realize that a TRX has about twice that displacement. On the other hand it never revs
that high. Such all exhausts should be!
Hope you had good fiddling today.

Marco

bobtrx · Post by **bobtrx** » Mon Jun 25, 2007 8:57 am

madivi I have a mate who has done the pipe under the seat if I can I will get pics of it and your right earywig they should have brought a duck
but I also wanted a trumpy shouldn't take the piss

madivi · Post by **madivi** » Mon Jun 25, 2007 6:45 pm

Hi BobTrx

Yes, do so. I'd appreciate for sure.

Marco

CULater · Post by **CULater** » Tue Jun 26, 2007 11:05 pm

Here's a pic with the bodywork on the bike.

The owner recently sold his TRX (he now has a Priller RSV)

But good news is he sold it to another clubmember (one of the guys who crashed his TRX during one of our ride outs, as you can read in an other topic)

The reason why he made the pipework on the outside of the swingarm is, that, if you want to make it inside the swinger the pipe dia becomes to small to be efficient.

Peter850 · Post by **Peter850** » Wed Jun 27, 2007 9:43 am

That is a very clean execution of a long thought idea. Well done old chap.

madivi · Post by **madivi** » Wed Jun 27, 2007 12:11 pm

Yep, looks definitely professional!
Can I get one too?

TRXHooL · Post by **TRXHooL** » Mon Jul 23, 2007 5:39 pm

I have it done!!!

madivi · Post by **madivi** » Mon Jul 23, 2007 9:11 pm

Hi

Yes that's it.
As I read in the other thread the swing arm belonged to a Honda VFR?
Could you tell me which modifications it needed to fit?
Have you left the bike's geometry the same?

Why I ask?
I've seen one in 'evilbay'.
http://cgi.ebay.de/ws/eBayISAPI.dll?Vie ... :middle:de

Besides, where do you get the tubing (which one) to weld the pipes?
Have you built the 'manifold' (2 in 1) yourself?

Looking at the picture the rear wheel's movement seems restricted by the silencer.
Would a hard bump make it touch the silencer?

Well, must have been pretty difficult to do it all but now I'm really eager to do it myself.