Limited Production Factory Turbocharged Motorcycle. 1982 &1983



Air Filter

Paint Restoration

Running Lights

Battery Warning Bypass

Front-end Mods

Speedometer Swap







seca image       seca image

seca image   seca image



I was fortunate to be active duty Air Force, stationed at Yakota Air Base, Japan (50 mile outside Tokyo) in from 1980 to 1982.  For those of us into motorcycles at the time, we experienced a motorcycle world gone nuts!    It was the beginning of change. For the first time, performance bikes were being introduced to the general public, place predominantly in showroom floors, and overshadowing the common street machines of the time.  (Being stationed there was interesting as we often saw models a year before introduction to the US, not to mention models that never made it there!)

My memory is drawn back to the awesome Suzuki Katana, Hondas VF750F Interceptor, or the lightening quick Yamaha RD/RZ 350, 400 and 500 famed by the legendary rider Kenny Roberts.  Each manufacturer began releasing race ready bikes which caused the best of us to leave pools of drewl on the showroom floors, and a yearning to go dash through the twisties.


Japan was also quick to apply new technology to the market, and in the late 70’s the turbocharger had come of age.    Promising liter-bike performance in a small package, Japans big 4 each released turbo bikes. Honda had the CX 500Tc, which later grew to a CX 650Td , Yamaha jumped into the ring with the stylish XJ650LJ/K Seca Turbo, and Suzuki showed up with the awesomely agile XN85D , and finally Kawasaki unveiled the pure brute and unparalleled king for turbo muscle, the ZX 750E1/2 .

Unfortunately, the turbo bike was not well received by the riding public, as it was high priced, complex by current standards, and never really lived up to the power to weight ratio originally promised.  Normally aspirated bikes operated very near the turbo's capability, but at a lower initial cost, and without the dreaded problem of turbo-lag.  After only a few years, these turbo bikes vanished from the dealership floors, to become a representative of a very unique time in motorcycle history.



        Leap to Aug. 2001, my memory of the Seca nearly forgotten, I happen to stumble across this piece of my past and wound up buying an '83 XJ650LK! Although well maintained, the prior owner(s) chose a rattle-can option to change colors. I opted to return the bike to the factory image from my past.

        I quickly discovered that the turbo today is indeed an orphaned machine. Parts are scarce, decals and trim nonexistent, and willing help from local dealers frustrating (I can't tell you how many times the parts man has laughed and said "buy a new bike").

        My quest to return to showroom status was thwarted by lack of badges, decals, or information (including simple paint codes)! Fortunately, with the aid of fellow owners, I have recreated all of the decals, and come close to a color match.

Check back to see my progress.




   Please remember, I am not a motorcycle specialist, and these views are of a personal nature only.  Use them only to aid you in researching a bigger picture.  There are many sources on the net with knowledge and skills far beyond those I posses.

   Links to other sites and products is not meant to be an endorsement of any kind.  As always, shop with a "buyer beware" attitude to protect yourself


I will not be held responsible for damage or losses caused by following any of my mods or tips!




Air Filter

Paint Restoration

Running Lights

Battery Warning Bypass

Front-end Mods

Speedometer Swap



Future Projects:

1.)    Finish side decals   (DONE)                Check out the different paint/stripe variations on the Seca!
2.)    Rebuild front suspension (DONE)
3.)    Upgrade Brake Lines (DONE)
4.)    Installed voltmeter (DONE)
5.)    Install upgraded Speedometer (DONE)  **
6.)    Add a blow off valve (BOV) to the turbo to keep the compressor from stalling. (A BOV from a 1st generation Mitsubishi Eclipse should work...)

 7.)    Aux lighting.


**      Of note to other owners, we now suspect the Seca came with at least five possible speedometers! The 80mph US version, the kph/mph international version, a full 150mph version, a full KPH version, and another full KPH version with speed reminder!  If I can squeeze some room here on my site, I'll try to post all the pics soon.

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Shop Talk:


   Please remember, I am not a motorcycle specialist, and these views are of a personal nature only.  Use them only to aid you in researching a bigger picture.  There are many sources on the net with knowledge and skills far beyond those I posses.

   Links to other sites and products is not meant to be an endorsement of any kind.  As always, shop with a "buyer beware" attitude to protect yourself


I will not be held responsible for damage or losses caused by following any of my mods or tips!



Common Problem areas

Other Shop Tid-Bits



   OFTEN ASKED:  What is the difference between the 1982 and 1983 model turbo?

Really only about three things changed for the 1983 model year.  1st was the front forks were replaced with a thicker (by a whopping 1mm... and I'm being sarcastic here!) design.  2nd was an increase in gas tank capacity. (Up an extra gallon) and last was the addition of the turbo "Power up Kit" which brought an extra 4 lbs of boost to the bike.


   All these upgrades can be retrofitted to the 1982 Seca, And you will find the power up kit has probably already been done, however for the other two, cost .vs benefit will dominate your decisions to do so.    V.

Common problem areas:

Burning Oil

Fuel in crankcase/Big puddle under turbo

Unstable steering

Battery warning

General electrical issues

Power-up kit

Poor braking

Cracked or glazed windscreen



   Several common problems with the Seca's design have plagued owners for years, others are just starting to crop up as the bikes old age sets in.  Here are some of them, and possible fixes:

   Keep in mind that this bike is now VERY OLD.  Most rubber parts are well beyond their life expectancy, and you should consider replacing any that you run across during any type of disassembly.

1.)  BURNING OILBike smokes when started, but quits smoking when warmed up.
   This problem can be two-fold, and the first assumption that most leap to, is bad turbo bearing seals.  On a 20+ year-old bike, this is a definite possibility, however you will want to look at the check-valve in the oil line that feeds the turbo first (Lower front of Crank Case).  This valve has been known to get gummed up and stick.  This allows oil to continue to be gravity fed from the crankcase to the turbo.  The oil then slips by seals and pools in the exhaust side of the turbo.  Light the bike, and you find yourself burning off (and spitting out a drain hole at the front to the exhaust) a lot of oil..... Not a pretty sight, and often frightening to the uninitiated.  The check valve is no longer available from Yamaha, so your only hope is to attempt to clean it as best as possible.  I found this to be my problem, and the burning oil issue vanished. A note of warning here, Use caution removing the check-valve!  The banjo fitting with oil pipe is easily damaged, and expensive if not imposable to replace!
   If  you still feel the turbo seals are bad, then several rebuild shops are available.    (FYI: The Seca uses a Mitsubishi TC03-06A)  See Turbocharger below

2.) FUEL IN CRANKCASE/BIG PUDDLE UNDER TURBO: Running rich, rough idle, poor mileage

   This happens from leaking carbs.  Raw fuel drains into the cylinders, and slowly seeps by the rings, filling the crankcase with extremely diluted oil.  Gas can also run out the exhaust side, down the pipes, and on to the turbo.  WARNING! This is BAD MOJO!  Do NOT try to run the bike with this problem!  Fist off, liquid in the cylinders can cause "Liquid Lock", which has the power to literally punch holes in pistons, or bend piston rods...  Secondly, the oil diluted with 50 percent or more gas, is like no oil at all!  Fire the bike up, and listen to the metal scraping! Sadly, you must drain it all, and refill with clean oil.  Turn your fuel off with the petcock for extra safety. (In fact, make sure the petcock seals are good too!)

   This problem also has several  possible areas of failure.  However first and most likely is bad needle and seats in one or more of the carbs.  These little gems must be made of gold for what Yamaha charges for them (about $38 each in 2002) But they do typically fix the problem.  Other owners have commented that simply cleaning the N/S assembly with WD40, and replacing the aged o-rings associated with them, has fixed the problem for a lot less.  You might give it a shot, before spending the big bucks on new seats. 

   Yamaha also placed a check-valve in-line after the fuel pump to help control excess fuel entering the carbs when shut down.  However they too have rubber o-rings inside, that often harden and fail to function.  The o-rings are also discontinued, but can be found at your local hardware store. (Just make sure they are compatible with gasoline.)

   Another word of warning for you new owners working on this problem.  Many people try to fix the problem in the cheapest possible manor.  Opening the carbs, replacing one or two o-rings, and slapping it back together. Only to find the problem still there.  When you are angrily looking at pulling the carbs for the third or forth time, you may well ask yourself why you didn't just do it all right the very first time!  Consider yourself warned!


* Newly added  Fellow Seca owner TurboJohn points out he found his fuel return line from the regulator pinched, causing a very rich condition as well.



 On 1982 models, the front fork diameter was considered ridiculously small, providing no confidence when running your favorite sweepers.  A fork brace is a must for these models if you can still find one. (At one time, I actually bought two of them from eBay, so you might keep an eye out there.)1983 models got slightly thicker forks, but a brace is still a worthwhile investment if you can find one.
   The final glitch comes from Yamaha using a standard set of bearing in the steering head.  These allowed far too much play as they aged.  An aftermarket set of tapered bearings is a common upgrade to both model years.  (FYI: I got a set from a fellow Seca enthusiast. I know nothing of the manufacturer, however the package states "All Balls Bearings and Seals, P/N 22-1015, Made in CN. )  Power Sports Industries Inc.  (All Balls Racing Products)

   I have Some details and pictures here on the upgrade process.

4) BATTERY WARNING: Often missing component

   As the years have passed, the battery sensor has often vanished from our bikes, leaving us to stare at the battery warning day after day.  I finally got around to bypassing the missing sensor!


   I cannot do nearly the quality write-up as you will find HERE.  You'll find it a worthwhile site to visit.

6.) HIGH RPM STUTTER Aged/deteriorating gasket material, possible failing coils 

   Seems many are now experiencing very rough running at higher RPMs.  A couple possible causes have been found so far.  First is the gas cap.  Seems the cork material is hardening, and not allowing the tank to breath properly. This places a vacuum in the tank and limits fuel to the motor.  You can easily check with a visual inspection, or by listening for suction release when opening the tank.  Also, coils seem to be reaching the end of life for many bikes (20+ years isn't bad folks!).  I don't know if demographics (hot or cold climates) have a contributing factor or not, but we are seeing more and more failures as of late.


7.) POOR BRAKING:    Design flaw

   Although archaic by modern standards, the Seca's front brakes were woefully inadequate even for 1983.  Boosting the bike up to speed was easy, but hauling it back down quickly shows a frightening side to this old bike.  Soft fork springs, a single puck caliper, and aging lines can put riders in a dangerous position daily.  Some of the more common upgrades to overcome these limitations are:


a.)  Upgraded fork springs. (I purchased a set from Progressive Suspensions which were significantly thicker than OEM)

b.)  Upgraded brake lines. Replacing the OEM lines with braided stainless steel will firm up the feel. (Russell Performance and Spiegler offer upgrade kits)

   I have Some details and pictures here of the upgrade process.

c.)   Upgrade brake pads.  Several pad manufactures exist, and formulas change regularly, however something like a set of Carbon Kevlar pads are a leap ahead of OEM in grip power. (with trade offs in noise and brake dust.) EBC is one such company.

d.)   Finally, if your a real hot-rodder, you may even consider upgrading your brake fluid to DOT4  as it has a higher boiling point that the standard DOT3.( Warning: DO NOT USE DOT5 as it is incompatible with our system!)


   As a FYI, a fellow Seca owner has upgraded his front brakes to a pair of Dual Caliper units and rotors from a newer model Yamaha R3. Impressive.



   The trouble here is not easily repairable.  The plastic has been badly damaged by years of exposure to direct sunlight.  You can try Mirror Glaze products to restore some of the appearance, but you will most likely need to purchase a replacement.  If your windscreen is still good, keep it covered as much as possible to protect it.  I have a simple T-Shirt sewn into a windscreen "sock", that is easy to store in the faring pockets, and handy to slip over the screen when parked at home or work.  Aftermarket replacements exist from War Eagle and Gustafsson although I understand you may have to drill your own mounting holes (ask first!) 


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Other Shop Tid-Bits


Tuning Carbs

Carb Parts


Power-up Kit

Tire Choices

Fuel Pump

Fuel Tank Capacity




Tuning the carbs:  
   Requires a special YICS tool, ( see photo of one here ) manufactured for Yamaha.  As of this date(2003), it is still available from:
Kent Moore,  1-800-345-2233   Part Number YM-8025     (Approx $200, and must be ordered through a Yamaha dealer...) I bought mine off eBay for $40.  A fellow Seca owner (PositivePressure) on the TMIOA web site makes a good version of the tool as well.
Or you can build your own crude tool following this diagram :


Carb Parts:

   The Pressurized carbs are certainly considered one of the Secas significant downfalls.  While other manufacturer chose fuel injection, Yamaha cut corners to limit production costs, and contracted Mikuni to build a proprietary set of sealed carburetors.  As the years go by, and seals age, these unit require more and more maintenance to remain operational.  However, now that Yamaha has stopped production of most replacement parts for our bike, the carbs are now becoming our Archilies heal as they were offered ONLY on the 2 years of Turbo production.

   I Contacted Sudco about alternate sources for Mikuni Carb parts, as Yamaha discontinues them.  No easy route here, as Yamaha owns all the rights to the turbos sealed design and custom parts.  However I was told several of the more common parts may cross from other model carbs, and an offer to come look was made.... I do not live in CA so I cannot.  If you would like to research this further, feel free to contact me .



   As stated earlier, the Seca uses a Mitsubishi TC03-06A turbocharger.  This unit is capable of developing up to 14psi (unregulated), but was limited to 7psi on the 1982 models, and then increased via a "power-up kit" (see below) to 12psi for 1983.  the 06A seems to be exclusive to the Seca, however the TC03-9A was common on Mitsubishi Colt and Mirage, both with 1.8L engines.  According to Turbo Power of California, the 9A differed from our 6A by using staggered veins on the compressor for improved volume at high RPMs, but it was a trade off for slightly slower boost rise down low.  I was told the clipped veins also let the compressor come out of a stall quicker.

   I found a great technical write up on turbocharger on TurboMustangs.com that is worth reviewing for those interested.


Power-up Kit  

   Yamaha increased the boost on the 1983 model Seca with the simple addition of a add-on kit.  An increase of 4 PSI brought the Seca a significant kick in the pants power wise.  The power-up kit was offered free to owners of the earlier 1982 models to match to output for the 1983 bikes.  A quick review of the instructions will tell you if the kit is installed on your bike.    Here is the kit installation instructions  (180k pdf)



   In searching to replace old tires, I asked about as to what oversized rubber would fit the Seca.  The chart below seems to be the consensus (If you have discovered otherwise, please let me know.)  * Got an email from fellow owner Paul, and he tells me he put a Shinko 230 Tour Masters  front and rear without fitment issues!






110/90-19 *



130/80-18, 130/90-18 *

   The 19 inch front tire seems to limit us the most, as you can find nothing in the performance class of that size.  However several sport-touring treads exist (Often only one per manufacturer!).  Dunlop    Metzeler    Bridgestone    Pirelli    Continental

   Also recently brought to my attention is that the 1982/83 Yamaha Vision uses the same style rim as our Seca, but has an 18" unit up front.  I have not seen a Turbo owner make this mod, but at least the possibility exists!


Fuel Pump:  

   I understand that Carter makes a suitable replacement pump for our bike. Part Number P74017  (About $90 in 1999).  I have not verified this, so if you know differently, please feel free contact me.  (FYI: The Carter specs. are 20-30gph at 10-14psi) Someone else posted that they use a VW fuel pump, so obviously other options exist for those willing to do the research.


Fuel Tank Capacity:

   The Seca was first released with a 4.2gal(US) tank in 1982.  At some point in production, the capacity was increased to 5gal, making this a much sought after upgrade for the owners of earlier tanks.  I have yet to conclude exactly when the production line shifted to the larger tank, but my bike, built 10/82 still had the 4 gallon version.  I assume the change date occurred sometime after that.  The Seca has been around long enough to see the hands of second, third, and even fourth owners, so many lucky owners have told me their bikes built earlier than mine already had the 5 gallon version, which until proven otherwise, I must assume was upgraded somewhere in the bikes life.  The distinguishing feature for determining tank size visually, is by looking at the tank where the fuel fill overflow tube runs down from the top of the tank.  If the drain tube resides in a deep formed channel in the tank, then this is the larger tank.  If it simply runs down a flat toped tank, this is the smaller capacity one.



   If you are using anything other than the recommended grade, I hope you have taken the time to research your choice.  Far to often I get into conversations with fellow turbo (car) owners asking about everything from Synthetics to additives.  To cover this area would take far more time than I currently have.  However I live by a few rules that I will pass on.  If you disagree, and have taken the time to research your opinion, fine...  Just don't email me touting that things work better by adding crap to your oil (This just tells us you listen to professional salesmen, not professional mechanics).


1.) Standard oils work great!  Just be sure to change them regularly.**

2.) Do not switch to a synthetic oil on a high mileage engine, unless you enjoy leaks!

3.) If you have a fresh engine, Synthetic oils are the way to go on a turbo!

4.) Avoid anything with PTFE added to it!


** Because the oil lubricating the turbo is also the same oil constantly bathing our rapidly wearing clutch disks, I recommend a you avoid relying on extended life oils, and stick to frequent changes.


Finding Parts:

   Lets face it, this bike is old, and parts fit into one of two categories.  Nonexistent, or expensive!   When stuck needing new parts, those particular only to the Turbo model bike are the most difficult to find.  Fortunately much of the Seca Turbo was created from an existing platform (the standard Seca650), that ran in production for many more years, and in much higher numbers.  So common parts to that bike do often work for us.  Learning to use the Yamaha parts breakdown link I provide below, will often help you find identical parts, from a different year (and even different displacement) bike!


   As for used parts, eBay is the best source, but check out TMIOA's parts for sale section of the forum, for some of the better pieces first!



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Odds and Ends:


Yamaha XJ750D
Interesting note: Seems the Yamaha XJ750D (a non-turbo) sold in Japan ('82-'85?) utilized the Seca frame and fairing! (It was also fuel injected, unlike the Turbo!)  Peter M of New Zealand writes, and tells me about some of the more interesting features, like a factory stereo system where our fairing pockets reside!  Also the stems for the mirrors are indeed longer by a couple centimeters than the turbo model.




Paul Schleck writes me, and asks if I recall the Yamaha advertisements of the time.  He stated that Honda ran a popular "Follow the leader." campaign.  
Yamaha's ad countered with "
Follow no one."   If you have any memorabilia from this bold Yamaha ad, please let me know!

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Sites of interest:

Yamaha online parts breakdown!  FREE!

Here is a Yamaha site with Illustrated parts Breakdown for nearly every bike they produced!  A great resource for the do-it-yourselfer!  (and to think people are selling copies of this on eBay for $30! Yeash!)


Turbo Motorcycle International Owners Association
If you are interested in learning more about these and other factory turbo bikes, be sure to visit TMIOA!

Vintage Japanese Motorcycle Club
Yup the Seca is old enough!


Vintage Japanese Motorcycle World

Another site dedicated to older Japanese bikes!

XJ Owners Page  

Has a great section on electrical problems!


Unofficial Suzuki XN85

Another great site dedicated to one of the Turbo's of the past!


Has a comprehensive list of technical articles worth checking out.


Pashnit.com "Its all about Passion"

A great site documenting all the best motorcycle roads to be found in California.

Motorcycle Safety Foundation









--------------- Vender Sites --------------


Cycle Gear

A small west coast employee owned chain.

For those that appreciate knowledgeable staff supporting quality products, this is your store!


Majestic Turbo 

Texas company that does turbocharger rebuilds.



Also has an online parts fiche, and order system (look for "parts fish") .


Turbo Power 

Another rebuilder in Sacramento California

BDesigns Reproduction Decals.

Fellow owner Brian Dallner, started creating decals for the Seca, and decided to go all the way!  A must for anyone restoring to a pristine condition!  

(Honda stuff too.)


Cycle Parts  

Sells discount Yamaha parts. ($100 minimum order.) (I have used them in the past.)

Gustafsson Windscreens



Look about, I saw Tapered bearings there, as well as a few other items for our bike 

(Note, I have NOT used this vender, so let me know it they are good or bad!)

War Eagle Windscreens


Power Sports Industries Inc.

(All Balls Racing Products)  Tapered bearings


Aftermarket YICS Tool

Offered by a fellow Seca owner! 




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Jump Points

Intro    Modifications    Shop Talk    Tid Bits    Links

Recreating the Decals    Picture Gallery    Front-end Mods    Battery warning Mod



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Keep it shiny side up



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Last updated April 15, 2008