Swapping stock exhausts - 1981 for 1978 jetting difference?

[mtnbikecrazy55]

Hey all!

My 81 special (sohc) came with a 2-1 when i purchased it.

Wanting to to return the bike to mainly stock, and I have another 81 parts bike with an original exhaust that i had originally intended to swap with, but it ended up being in worse shape than i had previously thought.

So with the aid of this fine forum I got connected with a guy willing to trade my 2-1 for the stock headers and mufflers from his 1978 sohc.

But comparing the two stock exhausts from the 78 and 81, they differ by the 81 having a crossmember "H-Pipe" and the 78 has just two individual headers and mufflers with no "H" crossmember.

So, what i am wondering is about the jetting -

for one, what jets are supposed to be in there as stock, as i am unsure if they were re-jetted for the 2-1. Considering it ran pretty dang good i would think it may have been.

secondly, if i return to stock jetting, would that be appropriate for the stock 78 exhaust?

i included that they are both SOHC models as that being the only difference in their interchangeability was all that i could find through my searchings on this forum.

Thanks so much!

Chris

 

[xschris]

Stock 81 had 135 mains and 42.5 pilots. The 78 should be 137.5 mains and 42.5 pilots.

 

[mtnbikecrazy55]

so then i should jet for the 78 specs?

 

[xschris]

If you are running a stock air box with a stock (with no holes) 78 exhaust then yes.

 

[mtnbikecrazy55]

Yep, stock 81 airbox, un-modded, with a stock 78 exhaust.

Thanks so much for the help!!