missing carburator inside part: important?

Hello everyone. I'm cleaning my carburator on my 1982 seca 750 and I'm missing the air jets cover
in all 4 carbs. I can see the hole next to the jets where the cover screw would fit. I figure if Yamaha installed that part it must have a purpose.
Thanks

 

The cover plate was used on earlier model Hitachi carbs, but not the later models. No one is sure why, although like you said, it must have served some purpose or they would not have wasted $$ on it and the really funky especi-al screw that held it in place........

 

All right then, thanks.

 

Look closely to see if its threaded or not.....

 

I think they are all threaded, whether they used the cover plate (and thus its screw) or not.........?

 

The carbs I pulled off of my 83 750 had the holes. However they were not threaded. The original 81 650's were threaded(with the plates). And the third set, wich I was told were 83 xj 650, we're not threaded.

My assumption is as follows....

The Yamaha engineers placed this item above the air jets to prevent dirt/contaminants from clogging the air jets by placing a barier directly above them. However, later found that they did nothing to prevent said condition. Then discontinued installing them to save on build materials, on later years.

 

I agree with that assumption, but it was the Hitachi engineers that did it

 

Not the case.... Those that got the plate and the bolt were threaded-- the others were not.... I just went out and checked some.

Dave F