So, I need a new chain ...

[RookieRider]

Ya know, for an '82 XS400J ... they aren't presenting any gear ratio for 6th gear.

That's because the XS400J (Maxim) only has 5 gears.
The XS400RJ (Seca) has 6

A per the manual

Transmission:
Primary Reduction System -- Gear
Primary Reduction Ratio -- 89/29 (3.068)
Secondary reduction System -- Chain
Secondary reduction ratio -- 38/16 (2.376)

Operation
Gear Ratio

1st --41/15 (2.733)
2nd --37/19 (1.947)
3rd --34/22 (1.545)
4th --31/25 (1.240)
5th --29/28 (1.036)
6th --27/29 (0.931)

Hope this helps.

So the answer to your question..
You have 16 teeth on the front sprocket.

 

[tritowns]

Why would you need to change the speedo? changing gear ratios doesn't effect it as it's driven off the front wheel

 

[robindean]

I have my chain/sprockets on hand (ordered off of ebay). I was little bummed to read "made in china" on the chain's box but whatever.

Do I need any special tools for this job?

 

[FUBAR]

for the chain just a pliers

 

[lhaolpa]

If the chain is too long,you'll need a chain breaker to shorten it. If it fits,then the pliers are correct. lha

 

[drewpy]

If the chain is too long,you'll need a chain breaker to shorten it. If it fits,then the pliers are correct. lha

or and angle grinder

 

[robindean]

All is well. The new chain be on! I learned a ton.

It already has a master link. The guy who helped insisted on both the tool AND grinding. All worked out

 

[WulfgartheBlack]

Well, I'm thinking I'll just stay stock after all.

However, I'm not sure how many teeth are up front / in back for my specific model. I'll go count witmefingas.

Yamaha site has drawings and matching part number for every machine they ever sold in the U.S.
http://www.yamaha-motor.com/sport/m...L2hvbWUuYXNweA==/Parts Catalog/starthere.aspx

The front sprocket on your RJ shows to be a 16 tooth [find it in the transmission section] and 38 on the rear [rear wheel section]. That looks like about normal for all their 400's.

If I pushed the right buttons on the calculator one tooth more or less on the front is about 6% difference in the RPM's at a given speed. Remember these bike were built when 55MPH was the legal max- they aren't engineered to run at 70 all day long.

Every sprocket I ever handled had a number stamped into the steel - saves counting. If the maker didn't care enough to mark it I'd wonder about the quality.

Aluminum sprockets? Maybe on flat out racers where every ounce counts and the factory foots the bill. But for those of us with thiry-year-old bikes and shallow pockets who go more than a few hundred miles metween complete tear-downs - steel is the only way to go. Titanium? Sure, if I worked in the aircraft plant and the boss wasn't looking but on this planet?.

 

[WulfgartheBlack]

oops .