Quieter Exhaust

Needing nearly full choke to run doesn't sound like an exhaust issue to me.

 

Blocked pilot jets.

 

You will definitely have to re-jet them, I've an EFI and every time I had to change pipes. BC PREDS to 2 into 1 to TORS I have to re-map them,
Unless the fact it's not running right is that it wasn't re-jetted for the pipes you have now.

 

Yes i agree with the fact the bike may not have been jetted to suit. And the possibility that the carbs are gummed up will not help. You need to check all the rubbers for cracks and leaks as well and baffles if you know someone who is handy with a welder and metal pipe they could knock something up quite quickly.

 

Hello there! Regarding exhaust DB killer inserts.

Before buying new exhausts try the DB killer inserts. These come in various sizes.

I'm in the UK but I've googled US companies and found a couple :-

https://www.yoshimura-rd.com/collec...RFlXbsPOU_Ks_1RkJ4OXUy1gXNGIXIyMPyTBmRdADtuk4

https://www.competitionwerkes.com/products/wx125

Various options here :-
https://www.ebay.com/sch/i.html?_nk...killer+&_sacat=0&_from=R40&_trksid=m570.l1313

I'm sure you'll be able to find a suitable item. I don't know how affective they are but if you also wrap them with acoustic exhaust packing, it will quieten the noise further. (This is from a UK site but you'll be able to find similar in the US, I'm sure)

https://www.demon-tweeks.com/uk/aco...M0BJul6xlDWITj730TWj5Om5Z3LoRFjqLAwM4GLy-s7qa

Hope this helps....

 

If the issue WAS caused by a freer flowing exhaust - what symptom Would you expect? A too-lean mid-range bog?

 

Yes, freer flowing could give a lean condition in the mid-range which would probably show as a flat spot. A reversionary pressure wave is created by the baffle and this can assist cylinder filling hence why some restriction can be a benefit.
The result is more power and not just sound reduction.
An over restrictive system, or baffle, could also show up at a certain rpm so without a feel for things, or a gas analyser on a dyno, often it can only be experience or a best guess situation.
As time goes on, and emissions (gases and noise) get tighter, the net result is a poor performance sector in the rpm range to conform.

My latest purchase a Kove 450 has now had x3 different ecu's (map change) and a fair bit of tinkering with the exhaust to get to where I'm satisfied with it now.

 

Gas flow through the cylinder head and the exhaust is a science in itself but broadly speaking, little or no restriction will help max power at high rpm and some back pressure in the low to midrange will help increase torque.
Yamaha's EXUP system, introduced in the late 80's, was designed to offer the benefits of increased gas flow at high rpm for max power and back pressure lower down for max useable torque. It also helped in the drive by noise tests.
The first GSXR1000 also adopted the system and is used quite widely now. It effectively provides a variably tuned exhaust with slightly more complexity and cost.