Thanks for the reply DragBikeMike .

I did change my order to the 18" + ends version and if I can leave it open (see-through) then all is well with no restriction at all .   I've made the same design as your using a 12" shorty muffler with a 1.25"-ID. middle pipe and white fiberglass 1" wrap in the large dia. muffler area  .  They are quiet .  The white wrap don't last long enough.    But the Factory Glass pack would solve that !  

Did ya ever figure out where the idea of a little back-pressure is good comes from ?

If I need to make it more quiet then I'll cross that bridge when I get to it , but like the wise + smiley Versey said :

 That's a '400' vs a '650' with the same muf.

maybe you have to increase the muf by a third to get the same results?
so 18" instead of a 12"?  

It will be here in a week .  

MM:

I got to thinking about your mpg issue.

I wonder if you are still using 20W-50 and then adding STP?

That thick mixture could be creating a lot of drag inside your engine.  The ball and roller bearings likely don't care much - but the cam bearings, piston/cylinder and oil pump are likely causing you some losses in HP and MPG.

Enough to make a noticeable difference - I don't know....but I suspect that the reason a lot of modern cars are going to thinner oils is to allow them to increase their MPG numbers.

Why don't you try using the 5W-40 Rotella T-6 next time without adding the STP?

Youzguyz has proven that you don't need any "thickeners" to get high mileage out of a Savage engine.

MM:

I would use whatever Suzuki or Moto Guzzi (or Honda or Chevrolet recommends you to use).  They designed the engine to work with a specific range of viscosity.  If Moto Guzzi recommends 20W-60 - then the inside of their engine has clearances that require that oil viscosity.......if the builder wants 0W-20 you know the clearances are much tighter and designed to work with the thinner oil.  Adding STP changes the viscosity and you no longer have what the manufacturer designed for.

Rotella T has enough ZDDP for the Savage and currently you don't need to add any additional ZDDP.  Youzguyz is still running his original cam and rockers at 212,000 miles, and I don't believe he has ever added supplemental ZDDP.  A few years ago the forum's experimented with adding ZDDP turned out to be a bit of overkill and unnecessary with a proper oil - and the Redline ZDDP was costly and it would get a pink sludge in the bottom of the bottle soon after it was opened.  Once the pink sludge formed in the bottle we had no idea if you could still get any benefits from adding it.  When you use an oil with 1,000 ppm or more of ZDDP you don't need to add any additional ZDDP.  Rotella and Mobil 1 have proven to be good oils in the Savage and they don't need any additives (STP or ZDDP).
https://www.mobil.com/en/lubricants/for-personal-vehicles/auto-care/all-about...

I have attached the chart for the LS650 oil viscosity that Suzuki recommends.  There are a lot of options and although they are all listed - that doesn't mean they will all perform identically.  The 20W-50 is listed - but it will be thicker and require more energy from the engine.


I would stick with the recommended 20W-60 in the Guzzi, and use a 15W-40 or 5W-40 oil in the Savage.  (The 5W number being smaller than the 15W is actually a good thing - as that value shows the oil will allow the engine to start easier when it is 32 degrees......while the viscosity at operating temperature (212 degrees) is the same 40 weight).    







 

Just looking at the information , it would be logical to only use 10w50.  

But

You say 10w30 would be better and easier for the engine to pump around ?

MMRanch wrote on 06/24/21 at 06:32:10:


10W-30 is only recommended up to 86 degrees - you and I often ride when it is up into the 90's.

10W-50 is going to get you back into the oil that is thick......yes you can use it - but it is not necessary to use an oil that stays that thick.

I keep suggesting 5W-40 or 15W-40!

Hay , I tried that new muffler to day.

I was really surprised how quiet it is !  

It is 18" long , made of stainless steel , the hole is 1.25" strait through for zero back pressure.   It has a 2 inch ends on it and a 3.5 inch body .    It also gets too close to the rear foot peg ... so ... I'm getting the 3 inch body model and putting a heat shield on it.

I would have expected a lot more noise , but like Versey said :


refering to the 12' mufflers on the 883 sportster
   
That's a '400' vs a '650' with the same muf.

maybe you have to increase the muffer by a third to get the same results?  

.................

I just ordered the 1.75" version of the same muffler 18 inches long , the hole in the middle can be one inch and still zero back pressure I think.   It should be here in a week , I'll let ya'll know how it works .  

Great YouTube channel.