FJ600 Project |

FJ600 Project


Here is a picture of a project that has been in the works for years that I am finally rebooting. My goal is to be roadworthy by June 1, 2018. Here's what has been done so far:

- Motor : 1984 FJ600 bored out to 652cc with Megacycle cams
- Front End : GSXR - not sure what size or year - important part to me was upside down forks and 6 piston calipers
- Rear End: Single Sided swingarm and wheel from a VFR750
- Tailpiece: Ducati 916, including underseat exhausts
- Turbo: 1982 Seca Turbo (you can kinda see it in the photo just in front of the engine)
- Carburetors: (Not shown) Mikuni RS34 smoothbore
- Other: Nitrous. I was using this on the FJ before I decided that I needed a turbo. Nitrous is AWESOME!

The rest is currently under construction...I will add pictures as I go.

For now, the immediate steps of the project are:
1) Airbox. Carbs will be mounted inside the airbox as the float bowls need to be pressurized in order for the turbo to work. Currently about 25% built. I'll add pictures of the progress soon.
2) Rubber mount the turbo. The shop that originally mounted it in California mounted it directly to the frame. Not wise with a rubber mounted engine...
3) Finish the exhaust. Need to plumb from the turbo to the mufflers.
3) Intake piping. Add an air filter near the neck of the frame. Not sure how yet...that's part of the fun!
4) everything else..make a tank...electrics...etc.
5) Ride it.




gringo diablo
Site Supporter
Nitrous and a turbo... Cool.... Gonna dyno it to see what it makes? Before it detonates??

Matt Rain

Well-known member
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Oh my! My dead-stock FJ600 feels inadequate.

What pistons did you use?

That front end looks HUGE on the narrow & wiry FJ frame. Damn.

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It will be dynoed, but I have to get it built and running first. I'm not too worried about detonation as the turbo I am using is a factory Yamaha turbo, which is very mild with only 6~7 psi of boost. I will also start with some very conservative (small) jets in the nitrous system. No need to go big right away. The ignition system I plan to use is mostly from the Seca Turbo and includes a knock sensor which automatically adjusts the ignition when detonation is detected. Fortunately, the FJ motor was derived from the Seca motor and the electrical parts should work.

The frame is spindly, no doubt about it and it will need to be addressed. Especially around the steering head. It will be boxed in and used as an air filter housing. Not 100% worked out yet, but I have some ideas. I won't be using a stock FJ tank, so I have some leeway here. The frame will probably be addressed as soon as the air box and exhaust are mostly sorted.

The piston kit is a Wiseco kit. 652cc with 10.25:1 compression (without the turbo).

I'm hoping to get it on the lift tomorrow and post some more pictures...

until then, stay safe.


Well-known member
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It's a really cool project. Have you found anyone that will insure it? If you were building on a seca turbo frame insurance would probably be much easier.


I'm using the front half (including the VIN) of an FJ600 frame. I've owned the bike since 1988 and it has been insured for about a dozen years before I pulled it off the road. I'm hoping that my age (47) along with the bikes age (33) and my driving record will make insurance fairly easy.



Here is a picture of my FJ before I started the latest rounds of modifications. I had already put it through a significant transformation as it looked nothing like a stock FJ600.

Some of the changes at this point were:

1) gas tank from an 1982 CBX550 (only because it fit fairly easy on the FJ frame)
2) tail piece from a 1985 VF1000R - reupholstered green seat
3) swingarm from a 1986 FZ600
4) rear wheel/rear brakes from a 1985 GSXR750
5) front discs - 310mm - from a 1982 Vision 550
6) front calipers from a 1987 FZR750R
7) Headlight from a 650 Honda Hawk
8) Mikuni RS34 carbs
9) you can see the nitrous injectors between the carbs and the cylinder head

King - Right Side before any mods 2.jpg

Stay safe,


A few pictures today, just to give a better idea of where this project currently sits.

Here are a couple pictures from the front axle of the exhaust system including the turbo. You can see the exhaust exiting out the left side of the bike in the second picture. I need to build a pipe from there to the mufflers



Well-known member
I'm using the front half (including the VIN) of an FJ600 frame. I've owned the bike since 1988 and it has been insured for about a dozen years before I pulled it off the road. I'm hoping that my age (47) along with the bikes age (33) and my driving record will make insurance fairly easy.

They will or at least most of them do, ask if any modifications have been done.......once you tell them what you have done, they might not insure the bike and or the rates are going to be, well who knows, what they will be......

it's like the guys who do a 7/11 engine swap, and forget to tell the insurance company what they did, and if a problem arises, then the claim they make is not processed as there was no disclosure of the engine swap...

but I like your build....


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Uh oh...seems my photo quota has been reached...anything I can do about that???

More tomorrow...hopefully.

Use imgur or other similar free image serving site. GTAM sucks for hosting pics (probably to keep the serving costs down).

Wow, that was a lot of finicky work to make that turbo piping. Is the Y pipe is going over the top of the engine compressed intake air? Will you be able to do a valve check/spark plug change without pulling things apart?


Ok, I figured out how to use Imgur...I think. Here should be some links to some photos

Before I add any commentary, can someone please let me know if these are working! Thanks!

FZ750 Rider - I hope to ride it in 2018.
Gatekeeper - I have owned this thing for 30 years and will deL with the insurance people when it is built. It won't be a daily driver and will probably get less than 5000km per year.
Greygoast - you are correct. Those 2 pipes going over the cylinder head carry the compressed intake. I don't like the look of going around the cylinders and going under the engine (like the Seca Turbo) was messier and, in my mind, would have more turbo lag. The additional maintenance during valve adjustments (and oil changes) is something I'm going to have to live with....

stay safe,
Last edited:


My apologies for the length of time between updates. I spent the majority of August in England watching the British Superbike and MotoGP races. Very cool. It was a bonus that Ducati won that round :)

Here is what I've been working on since then. Please let me know if this is too many pictures or details and I will adjust accordingly.

Picture 1: The exhaust as it comes out of the turbo. RuT1t6o (Please let these links work...)

Picture 2: Measuring the angle of the pipe to go under the engine. The meter says 240. TBHOnWd

Picture 3: This is the picture of the U-Bend that I need to cut and make 240 degrees. Subtracting 240 from 360 leaves the 120 desired. rMWmvJ3

Picture 4: The hardest part with cutting pipes is cutting straight towards the centre of the curve. I created a wood template to go into the curve and mark where I needed to cut. ar4kKIt

Picture 5: Here are the cuts made. Lj932qd

Picture 6: Here are the results with the wood and tape removed before welding. At34xgi

Fast forward a little bit...

Picture 7: Here is the pipe that connects to the short pipe coming out of the turbo (left side of this picture) and runs under the engine and comes up by the right footpeg. cR1BIX3

Picture 8: Here is the pipe as it fits on the bike using a zip tie. 0DQlUYM

Picture 9: My goal was to keep the bike as close to the bike as possible, which meant a few extra curves. No additional cost, it just took more time. Here is the next curve added. nqWJ4sp

Picture 10: additional pipe added and test fit. MDBzaPx

Picture 11: This is where it gets ugly...please excuse the glob welds. I'm new to welding and this was the first ever stainless steel that I welded. It's ugly, but can be ground and polished at a later date. Here is the pipe on my bench after additional sections were added including the rubber mount that I stole from my race bike.. nLSBKqH

Picture 12: Test fit above pipe. You can just make out part of the rubber mount behind the footpeg bracket JPRBcV3

Fast forward...much of the details the same as earlier...

Picture 13: created tubes to connect the first pipe to the mufflers. Green tape helps hold things together, but sags after awhile. NTjjMTR

Picture 14: All welded up, tape removed. 61b7an6

The only things left to do on the exhaust is grind the welds down and polish it. Next on the list is the Airbox!

Talk soon,
Chris (man I hope these links work....)

Mango Rider

Well-known member
They indeed work! And that's a snazzy ass job, nice!

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