XS "XJ Twin" 400 owners (DW, Uzi?) I need your help

Any XS400 YICS owners out there who have a service manual help me out if you would. What are the published compression specs for the "XJ twin" (YICS XS400) motor? Need to do a compression test on one and don't know what I'm looking for.

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

Half an XJ? That comes across as a bit of a slam.

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

I worked on an 80 XS400 some time ago but cant remember what PSI it had when checked.

YICS, Must be a Seca eh ?

I have a PDF Service manuals for an XS400 Maxim and a Seca if you need it.

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

Found it, for an 82 XS400 Seca:

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

Not at all. The "true" XS was the old SOHC rocker-valve motor; the much more advanced "late" DOHC shim-over-bucket YICS XS motor was more like half an XJ than an XS.

Never quite sure why Yamaha stuck the "XS" on those instead of "XJ" especially in light of the fact that in 1982 there were THREE "XS's" the monoshock Seca and Max with the new motors (XS400J and RJ) and the twin-shock "Special" with the old motor (SJ.)

What REALLY sucks is that the monoshock/YICS XJ-XS's seem to have been completely missed by the aftermarket, most everything offered for the "XS400" is for the old style twin shock SOHC bikes.

Thanks, Rich. And no, it's a Maxim, they had the YICS motor too. (With some giant-a** Mikunis look like they came off a 900...)

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

The rest of the world got real, complete, "whole" XJ400 models, complete with 4 real cylinders..................

 

Re: XS "half an XJ" 400 owners (DW, Uzi?) I need your help

Yeah I know, dammit. BOY would I love to get my hands on an "original" 400 Seca, the 4-cylinder variety. Although the "half an XJ" motor, doubled, would be a 798cc...

Was the YICS "XJ twin" motor used elsewhere in the world in a different displacement? Or was the 400 the only incarnation of that motor?

*edit* I went back and changed the name of the thread didn't mean to ruffle any feathers, I LIKE the "XJ twins."

 

big,

Thanks for clarifying that for me. Sometimes I get a little overprotective of my 400. LOL. I've ridden a lot of other bikes over the years, but the only one I ever kept, is my Maxim 400 that I bought new off the showroom floor. Something about it being my first and all.

You are right on about it being ignored by the aftermarket, which is too bad because it really can fill a niche. It is the perfect commuter for what I need right now. Someday, when the kids are older and the economy is better, I might add a VStar 950 to my garage, or an FJR, but for right now, I get to roll my classic every day!

One of the really funny things about it is the number of people that see my 400, and then start telling me stories of their 550s, 650s, 750s, and 1100s. Talk about a marketing tool! I think that's the beauty of what the Maxims and Secas are. They truly are timeless. Maybe not in the way your Norton is, but still timeless nonetheless.

 

I have heard of Yoshimura Cams and other hops ups too but I don't think that they ever made it stateside.