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MAC exhaust with stock jetting

  • Thread starter Thread starter Audioslave784
  • Start date Start date
A

Audioslave784

Guest
As my 850GL "rescue" is looking better and better, I think it might be time to replace the patched up, rusty stock pipes for aesthetic reasons. The bike has been running quite well with the stock airbox and stock jets (with shimmed needles), and I would like to keep it that way if possible.

While I like the look of the V&H, I have read that for the MAC 4-into-1, "most of the time, jetting is not needed". I have no need for more top-end power, and would probably go with the MAC exhaust to save time and money if it truely mimics the stock exhaust, but I have only found this claim from sellers, and haven't been able to find a definitive statement one way or another from somebody who has actually made this switch.

So my question is this: Does anyone here have personal experience going from a completely stock set-up to the MAC system with a stock airbox? If so, what sort of carb tuning (if any) was needed?

Thanks!
 
I did not do the change myself, but #2 son's 850 had a pipe of unknown origin on it when we got the bike.
(Click on the picture link in my sig to see the pipe.) Actually, the pipe is still on it.
I rebuilt the carbs and checked the jetting. Previous owner had changed the stock 115 mains to 120, needles were not shimmed.
I re-assembled with the same parts, I think the idle mixture adjustment screws are out about 2.5 turns.
The bike runs really well, plug chops look good.

If this is a MAC pipe, chalk it up to one guy's experience. If it's not a MAC, well, just take it any way you want.
Suffice it to say that not all headers require massive jetting changes, but I doubt you could leave it stock.

.
 
As Steve alludes, as long as the stock airbox is left in place the jetting will be reasonably close. I'd try the 120 mains and see how some plug chops look.
 
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