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Now that I've been riding it for a while... I've noticed that my seca 400 will have a very minor hiccup occasionally above 6000 rpm. Nothing like before when I had my jets reversed. I think my abnormally high resistance measurements for my spark plug caps is the culprit... I need to replace the caps ...

I was beginning to think nobody cared.
Thanks ZaGhost!!!

Went for a test ride after swapping the jets.
My bike is running perfect!!! Good as new!!! Not bad for an 82.
Pulls hard all the way through the rpms.

I hope my experience helps someone.

Good Luck!

I just pulled the carbs and sure enough.... the right jet was larger than the left jet.
However, they should be in reverse.

Here is a photo of the jets...

http://home.comcast.net/~panofish/carbjets.jpg

I think I've got it figured out....
When I took off the carbs for cleaning (after 3 years sitting idle)...
I took out all the jets and bits to clean carefully.
The dual carbs appear to be exactly the same as each other, so I assumed that all internal parts were interchangeable.
Checking my service ...

I found a suggestion to pull the choke a little while running the bike... the hesitation problem above 5000 rpm appeared to go away and there was noticeably more power.

This make me think I'm still missing something that is gummed up inside the carbs. (The bike has been sitting still for the last ...

After further research on the web... I came across this post...

The bad things are as follows: Petcock failure from an inverted diaphragm, which could be caused by running the motor with the petcock in the off position. Petcock failure due to a vacuum leak. And of course fuel flow, at high rpm ...

My 82 yamaha xs400rj starts and idles perfectly. It runs and pulls up to 5000 rpm perfectly.

http://home.comcast.net/~panofish/WEBLOG/2007-08-25_1982_Yamaha_Seca/index.html

If I push it beyond 6000 rpm ... the engine hesitates randomly (as if it is misfiring or fuel trouble).

What I have done so ...