DougReid's exhaust mods

[Kiwiscoot]

Hi Doug, could you "show & tell" us what you did?? Even this weekend on my 800km trip I got the feeling that the Citycom has some more urge in it, but suffers a bit of "asthma" - a need to breath better. I've done the upstream side - foam filter with excellent results, but that 8kgs of muffler just asks for some surgery. Less weight and more flow.

[DougReid]

Hi Kiwiscoot,

The CAT comes directly from the main inflow and widens to about 50mm and then narrows again. I had cut the exhaust close to the edge of the mounting bracket and ended up having the CAT sticking out about 100mm. I then cut off the CAT's top revealing a metal honeycomb mesh which I drilled out with a big bore drill.
I also took out the muffler box and fibreglass wool inside the box as well as another pipe that's in there.
To put it all back together I used a strip of galvanised iron sheet which I pop rivited into place.
Quieter than I thought it would be but breathing much better, maybe should open up the exit pipe a bit too.

With hindsite I should probably just bought an aftermarket exhaust with a few baffles for back pressure.

My scoot is very quick, I also have an iridium sparkplug which helps. My fuel consumption also improved to 3.35l/100 compared to 3.5 prevously.

Good luck,

Doug

[stoepsl]

  Very interesting.

Have you pics at this instruction? 

[Kiwiscoot]

Doug, your muffler looks pretty much the same as the Citycoms. The Citycom muffler has a weld just in front of the mounting, where the front cone is welded to the can. It also has a weld just next to the shock absorber. Did you cut both these welds?
 The Citycom Service manual has a drawing of the inside of the muffler under the Emission system chapter, but I don't know if the muffler realy looks like that on the inside.

[DougReid]

Sorry for late reply, Citycom is different from my 300i GTS EVO 13" wheeled scoot.

I think the trick is to cut the exhaust where you have enought space to get it back together but still have enough access to cut out or drill out the CAT - also I think just opening up the exit will help because it seems my scoot is much happier being able to get rid of more emmissions quicker.

Maybe an idea would be to drill some 1/2" holes on the back after having taken the chrome bit off, you could always thread them and put bolts in to be emmission compliant again. I think the CAT is only part of the problem and the lack of a free flow is the other part.

Once you have cut the exhaust like mine then it is buggered and because the material is so thin you wouldnt be able to weld it back together again.

Good Luck,

Doug

[DougReid]

[DougReid]

Hi Guys,

Finally got a pic up.

This is a very rough job but achieved the objective.

Fuel consumption now 3.19 litres per 100 kilometres

And quick!

Bottom line - it's worth investing in a decent exhaust.

I have an exhaust company who has quoted me a price to make a nice shiny proper one and I think it will be a good investment.

Regards

Doug

[stoepsl]

Hard-Core Design! 

Nice, verry nice.....

[Kiwiscoot]

Hi Guys,

Finally got a pic up.

This is a very rough job but achieved the objective.

Fuel consumption now 3.19 litres per 100 kilometres

And quick!

Bottom line - it's worth investing in a decent exhaust.

I have an exhaust company who has quoted me a price to make a nice shiny proper one and I think it will be a good investment.

Regards

Doug

I've communicated with a local custom motorcycle exhaust manufacturer here, Zorst, http://www.motorcycleexhausts.co.nz/ but they want NZD650. Nice in Stainless and tunable with removable baffles, but pricey. Could look cool tho if it was raked up like a Yamaha T-Max.

Looking at your photo is seems your scoot's exhaust and the Citycom's is identical except for a longer extension piece (5cm) behind the back weld of the Citycom's. A few questions:
1.) when you cut yours, did you just cut around the muffler thru the outside sheet metal?
2.) did the two halves then come apart?
3.) do you think if one were to cut around the sheet metal just behind the front weld and just in front of the back weld, would the thing come apart. One could get someone then to just gas weld along those seams again and it all should look like factory standard??

I still think that Gianelli will fit your scoot, it will just stick out further at the back. Heard some good reports on them from Vespa riders, but with the Euro-ZAR exchange rate it would be pricey.

[DougReid]

With hindsite I should have just got a new straight thru exhaust and narrowed down the exit a bit. My tacked on plate with pop rivits keeps coming loose as the rivits destruct with the heat and vibration.

Right now all the rivits are nearly out and I need to get it back together, but its almost free flow and goes beautifully.

I know guys spend a fortune on yoshimora exhausts on superbikes and I think the investment is probably worth it.

My advice: take off stock to put back when you need to sell the scoot and get a decent aftermarket one

Regards,

Doug

[steve_rolfeca]

Drilling out the guts of the Cat without suitable protective gear sounds like a bad idea, too. Don't they contain fairly noxious stuff?

[scooterscott]

Drilling out the guts of the Cat without suitable protective gear sounds like a bad idea, too. Don't they contain fairly noxious stuff?

I don't think there is anything that noxious in a cat, BUT I think it is mostly a waste of time if you don't also increase airflow and re jet the carb. Without making those other changes, the performance is actually hindered not helped....it just sounds cool I guess. The problem without more air flowing (changing the air filter/box to something more free flowing) is that the bike already comes running pretty lean to pass emissions. Opening up the exhaust without other mods is going to add to that already lean condition and is not such a good idea IMHO.

[steve_rolfeca]

 Just assumed that these guys were going up a size or two on the pilot and main jets, and shunning the needle.

Opening up the exhaust without rejetting, is a good way to burn a valve, or even fry a piston...

[Kiwiscoot]

Guys it's an EFI scoot

[scooterscott]

Guys it's an EFI scoot

Oh, that complicates things even further. You need to remap or fool the computer then. EFI does allow for slight adjustments that would be necc for changes in elevation etc, but usually the range is not sufficient to adjust for an exhaust mod. On other motorcycles that I have owned in the past you needed something like a power commander or Race tuner to overide the factory mapping, while something like a race fueler simply tricks it but is effective as well.