82 Seca - As Found Jetting Questions

[kirkn]

Hi, all,

My son bought an '82 Seca 400 6 months ago and now he's upgraded and sold the Seca to me. When he first got it, we completely disassembled the carbs, cleaned 'em (Simple Green, aerosol carb spray, compressed air) and put 'em back together. The bike has always run great for him. I haven't really ridden it much until now.

Now that I ride it regularly, I think I'm going to go back into the carbs again. Runs great under acceleration and at speeds over 40 ~ 45 mph. Less than that or at "steady state", it stumbles and hesitates. It sat for about a month from when he stopped riding it to when I started. Been through one tank of gas since then. We installed a new pleated-paper stock-type air filter back when he got the bike. Maybe 8k miles ago.

My question has to do with the jetting as we found it.

The manual calls for:
35 pilot jet (starter jet)
127.5 left-hand main jet (132.5 for Germany)
117.5 right-hand main jet (130.5 RH main for Germany).

What we found (and went back together with) is 42.5 pilot jets and 127.5 main jets on both carbs. The LH main jet was brass, but the right hand main jet was a kind of hard plastic. I'd never seen a jet made of that material. Also, the RH main jet (the plastic one) was taller than the LH brass jet. Taller by maybe 5mm. Also, there were washers under the needles.

What's the story behind the offset main jet sizes? I've never seen anything like that from an OEM before. Thoughts on returning it to stock?

Thoughts on returning pilots back to stock? Removing the needle shims?

Overall, it looks like someone was going for richer settings at the bottom and midrange, although they stuck (mostly) to stock main jets for the top.

Hmmm.....

Thoughts?

Thanks,

Kirk

 

[drewpy]

does it have pods or after market exhausts on it.
the nylon mains are a fairly new design so its fairly recent this has been done!

 

[kirkn]

Hi drewpy,

No it doesn't have pods. Has the stock airbox with a new stock-type replacement pleated-paper air filter.

It DOES have aftermarket universal looking clamp-on mufflers clamped on right at what used to be the stock weld from headpipe to muffler. However, I recently bought a parts bike that had nice stock exhaust system on it, so I'll be going back to stock fairly soon.

Interesting about the nylon jet. Never saw one like it before.

What's the deal on the offset main jets though?

Thanks for the reply,

Kirk

 

[lhaolpa]

I have an'82 rj seca,and it has a 127 main jet on the left and a 117 on the right,both brass.I've never seen plastic jets,but see no reason why they wouldn't work.The washers are to shim the midrange to enrich it,and it sounds as though it doesn't need it. If you don't have a manual,you can download one for a DOHC motor on the tech pages for specs on the carb,as different years have different specs.Good luck. lha