Frame rails offset

[Capt_Zoom]

Does anybody know why Yamaha made the seat rails offset about an inch to the right of the bike? I have a 1980 s model and if you look at the upright where the lower frame curves up to meet the seat rail its bends in slightly and then up again? Was this done to keep the bike balanced? Anybody have any answers?

 

[650Skull]

Sure it hasn't been hit some photos would help

 

[Capt_Zoom]

Definitely hasn't been hit. Its also on my '77 and looks like an intentional bend. Its on the vertical tubing just below and in front of the left rear shock mount..

 

[WacoBrian]

yeah buddie has the offset on the chain side. why? the chain man the chain

 

[Capt_Zoom]

If it was due to the chail would the offset be on the opposite side to create more room? Or are you saying its offset to offset the weight of the chain?

 

[jay760]

I looked at mine the other day the left side comes up then offsets in at the top, can only assume it's slighly wider at the bottom on this side to miss the chain.

 

[WyoRay]

I came here with the same question... I'll keep looking.

 

[WyoRay]

1980 Special
Left side frame, looking rearward --

v right side frame --

 

[gggGary]

I came here with the same question... I'll keep looking.

And I have the "answer"? Gotta remember this bike was designed pre CAD days. ;^)
The early bikes were narrower and didn't have the "offset". There simply wasn't enough room for a decent shock to clear the chain, when they made the big frame changes for the 74 model year they widened the frame and swing arm for more room back there.