I while back before the Hacking incident. I had a post re Modifying one of my stock Mufflers

I cut out some of the internals. But got a little carried away and cut out the spark arrestor

I have now fitted a off the shelf arrestor and buttoned it up

sand blasted ready for a coat of paint tomorrow

When fitting a Muffler. IE FMF, DG Ear bleeder, Pro Tune etc

Should there be a Jetting Change

Yes, more that likely one to two jet sizes, depending on how much the muffler has been modified.

Rand

Thanks Rand

I assume the jets should go UP

I and running 142 main jet which is Stock
When I got the oddy it had a 140 main

I have the duel air box running a Uni filter
With the 142 main it has always been a little fat up the top end
If i run the 145 it is very doughy wont rev

in the carby box 140, 142, 145 main jets

would you suggest i should get 138 or 148

A

Were you running the 142 main with the intake modifications BEFORE you made the exhaust change?

If it's been running a little fat with the 142 with the intake modifications then the opening of the exhaust should make it run a tad leaner.

You will need to go up on the main. I would try the 145 again and she how she run with that.

Remember, the easier she breathes, the more fuel she will need.

At what altitude are you running?

Rand

I haven't fitted the muffler yet

will do in a couple of weeks

0 to 1000 meters

Were you running the intake modifications before you decided to modify the muffler?

Rand

Yes
I did the air box Duel intake 5 years ago. and there was a big improvement with a Uni filter and
upgraded bits since then

I did the muffler mod after reading that it had been done before. May of been on this site or another

I had a spare and thought I would give it a go.

I liked the trying to keep the stock look of the muffler

The first 2 days I left the stock silencer on then changed out to the Modified silencer

Just a small sound difference a little more pop but a good noticeable power increase right across the rev
range. ran on and off for the day checked plug on a number of occasion. All good but I did try a larger Main jet
and ran like a hairy goat so back to the 142 main. It runs great and it pulls right through to Full throttle, it has
never been flash on the top end, but now its great.

But my bogging down problem raised its little head again
Runs great all day the hit a hill and it runs but wont rev found a fouled plug
this has been happening for the last couple of years

so its a full carby service. I think the float may need adjustment as on a couple occasion I had fuel drip from
the over flow while running.

always something to do

Ah the joys of owning an antique ATV!

Rand