Power loss

[BA80]

Anyone had problems with Mac turnout mufflers being restrictive?

I slipped the turnouts off the headers and this thing turned into a ROCKET. 0 to 90 in like 5 seconds. The clutch can't even hold the engine back, slipped the whole way and I have Barnett heavy duty springs in there.

[IanDMacDonald]

Can never count-out the exhaust . . .

I removed my Mac turnouts to OEM, and will never look back!

[BA80]

Yeah, try and find a decent stock exhaust for a Special.

[MPittma100]

Obvious

I have a stupid question. How is it possible that any XS11 would run "rich" with stock (and especially smaller than stock) jets and correct float and needle jet settings? Maybe it is me, but it just doesn't add up in my calculator.

[dbeardslee]

Anyone had problems with Mac turnout mufflers being restrictive?

I slipped the turnouts off the headers and this thing turned into a ROCKET. 0 to 90 in like 5 seconds. The clutch can't even hold the engine back, slipped the whole way and I have Barnett heavy duty springs in there.

Hmmm. Sounds like maybe you found the problem. Did it get rid of the stuttering?

I wonder if the mac taper mufflers work any better than the turnouts. Or maybe a harley muffler?

[BA80]

I have a stupid question. How is it possible that any XS11 would run "rich" with stock (and especially smaller than stock) jets and correct float and needle jet settings? Maybe it is me, but it just doesn't add up in my calculator.

I still have to get some other mufflers on there to test the theory, or if that's even the issue.

If that's what it is it makes perfect sense. If the exhaust is restricted instead of getting rid of all the burnt and unburnt fuel mixture it either stays in the cylinder or is blown BACK into the cylinder by the back pressure in the exhaust. The exhaust isn't plugged, it's just restricted and causing too much backpressure. That's my theory anyway.

[BA80]

Hmmm. Sounds like maybe you found the problem. Did it get rid of the stuttering?

I wonder if the mac taper mufflers work any better than the turnouts. Or maybe a harley muffler?

I didn't feel the stutter at all when I test rode it without the mufflers on there. Just bad ass power until I shifted 1-2-3........90 MPH QUICK. And that was with the little 127.5 jets.

The only other Mac mufflers I have, I think, are another set of turnouts. I'll have to go root the shed.

Harley mufflers are 1 3/4" inlet I think, These Mac's are 2 1/4"

[XJOK2PLAY]

Greg,
I still have a set of good XJ1100 Maxim mufflers.
Tod never came by to get them.
Would they help ya?

[dbeardslee]

I don't think I'd leave those skinny jets in there too long with the exhaust open. Next thing you'll be fixing is a burned piston.

So how are the plugs reading now after the rocket ride?

[MPittma100]

You may be on to something

I still have to get some other mufflers on there to test the theory, or if that's even the issue.

If that's what it is it makes perfect sense. If the exhaust is restricted instead of getting rid of all the burnt and unburnt fuel mixture it either stays in the cylinder or is blown BACK into the cylinder by the back pressure in the exhaust. The exhaust isn't plugged, it's just restricted and causing too much backpressure. That's my theory anyway.

I have experience with restricted/stopped up exhaust. It will make you pull your hair out diagnosing it. When you do find it, it is only because you have done everything else in the world to attempt to fix it. Hopefully, new/different mufflers will end this thread. Then you can post a picture of your bald head. LOL

[BA80]

I don't think I'd leave those skinny jets in there too long with the exhaust open. Next thing you'll be fixing is a burned piston.

So how are the plugs reading now after the rocket ride?

They were almost white. Still sooted up from before but cleaning up.

I put the mufflers back on to ride home and I was getting a little pre ignition rattle. Too lean for the highway now.

I have experience with restricted/stopped up exhaust. It will make you pull your hair out diagnosing it. When you do find it, it is only because you have done everything else in the world to attempt to fix it. Hopefully, new/different mufflers will end this thread. Then you can post a picture of your bald head. LOL

I've got a set of faux mufflers I made out of some SS exhaust tips a few years back. I'll slip those on there (loud ) and put the 140 jets back in there and see how it does.

Here's those homemade mufflers. I knew I had a pic of them somewhere.

They are straight through with just a perforated baffle and a VERY thin wrap of SS wool.

[BA80]

BTW........anybody know if a stock XJ exhaust system will fit a special? I know a Special system will fit on an XJ because Tod has one on his.

[motoman]

I thought that was the 80's Tod. Seem to recall my midnight special having that jetting.

Agree.......and they were the 'bastardized' carbies.

[BA80]

BTW........anybody know if a stock XJ exhaust system will fit a special? I know a Special system will fit on an XJ because Tod has one on his.

Nevermind, found my answer in the interchange guide.

[motoman]

BTW........anybody know if a stock XJ exhaust system will fit a special? I know a Special system will fit on an XJ because Tod has one on his.

Shoukd since they are slip-ons.