Seca Turbo System on an Xj750 Bobber

Hello Everyone,
I guess Im the newest guy on these forums and not much of an internet guy, however I have something I wanna do and perhaps you guys can help a fella out with a deathwish...
I always wanted to turbo charge my 82 Xj750 Project or any bobber for that matter, just to get a checkle outta messing with the crotch rocket folks....* I have one too, but I just like messing with them.
Anyways, I stumbled on the fact that the Turbo Seca was essentially the motor with minor tweaks and all the other relevant info. Blah blah blah I get it.
Not to get all bent outta shape, but yes I wanna turbocharge my Bobber with seca parts.
Not that Care too much for the aesthetics of my bike, I just want this pig to be boosted....
If you were to take on this endeavor, what pasrts of my 750 motor can be retained and what would be needed from the SECA?
any help is greatly appreciated.
PS my backgrounds is a retired Marine/Helo eng Mech/ drifter with 19 years experience living in Japan etc etc...
thanks and the names Booney

 

You might be able to do it. You'll need the exhaust headers to run to a collector box, then on to the turbo. On the 650turbo, the headers themselves are dual wall(stainless on the inner) and of smaller ID then the standard 650 to increase the flow to spin the turbo....if you can overcome the issues getting the exh mounted, the intake should be fairly straighforward but the 650 turbo carbs are specialized carbs(ability to pressurize) and again, smaller then the standard 650 carbs to increase flow. Prob the best option for the intake sure is the seca's turbo and airbox with plumbing and a micro-squirt FI system with throttle body's in place of carbs.

good luck with your project,

 

Thanks for the info. Believe it or not but I've located 5 in the local scrap yard. That is I've located 5 Seca turbos in various states. I think the hardest parts to find is the TCI.
I have a fairly good understanding of the electrical workings of the wiring harness of the XJ750 as I've rewired mine 8 times in attempts and finally on the 9th try realized i simply had the pulser coil wires mixed up coming outt eh TCI. so to say im completely comfortable wiring a bike up is the understatement of a lifetime.
Im also fortunate to have my own 82 Turbo Seca in complete and whole condition for reference.

**No Im not going to kill that bike to make a turbo bobber!**

Ive also built several turbo cars and etc. I guess my primary concern is this.

-Will the XJ650L Block bolt into my XJ750 frame?
I've seen the XJ650L block used for rebuilds and in XJ750 Seca frames, but That makes me question the peculiarities of the frames.
Any guidance is appreciated.

-Turbo manifold- My intents are to mount the turbo closer to the left side of the valve covers with some creative plumbing. I understand the necessary exhaust pulses required to push the turbo efficiently and that's the toughest part regarding the build. Due to the firing order of the cylinders it'll cause plateaus in the turbos spool and so forth through operation.

-Turbo - Yes, I plan to boost the motherloving hades outta this poor motor. i have three turbos left over from my car days.
* I have one T25 from my old stock Nissan Silvia from Japan (Sr20DET 2.0L) Its rather large I know, I guess i just wont be cranking on the boost controller.
* I have two turbos that used to feed a 20B triple rotor Mazda Cosmo. Its another 2 liter engine, but due to its capability to rev higher, i grabbed them. I dont know CFM fo rthem but again if i stayed of the boost controller id fair long enough to make it to the store for smokes and back...

-driveline - how much diffrent is the drive spline from the the Seca Turbo to the rear wheel and is anyone here experienced enough to say that its either a direct fit or not. i know for a fact ive bolted XV920 rims onto my Xj750 bike and been fine so im hoping to strapp this motor and maybe at the most swap in a swingarm and boost myself to either boosted bliss or an early death...

Again, thanks for the advice, Im just more concerned with structural diffrences and or driveline complications....
Theres pics of my black bike,"Leroy" in my profile pics and im also on Instagram ;Hingabooney
Feel free to follow or add me and provide guidance..

thanks in advance,
Booney

 

Welcome to the site !!
The 650 engine will fit into the 750 frame, and that will be the easy way to get all the beefed-up and hardened components, the correct TURBO cams, reduced compression in the pistons, the correct oil pump and plumbing to scavenge the turbo, and ignition with a knock sensor.

The turbo is almost identical to the one used in the Mitsubishi Colt 1.5L
If you go too large, you'll only get "on boost" past 7,500 RPM (example) and the bike will only be good for drag racing, and no fun on the street.

Why would you need the TURBO's swingarm and final drive??

If "Leroy" is running good, leave him alone, get another frame and build your monster "fresh" as this could take a while to sort out. (just my opinion).

 

TBH I have a second XJ750 sitting in my storage that Im building...His names Nasty Jack...Hes gonna be my daily while i refresh Leroys old Motor. In the mean time, I have my 82 turbo Seca Complete and will get that up for Riding around as well....I currently am farting around on my 81 Suzuki GS450L bar Hopper, I call Lilly.

Im asking about the swing arm because I need to know will the motors driveline bolt up with Maxims rear end ....Gotta make sure, before I go down that road...as far as turbos...that's good info about the colt turbo.....As far as big turbos,...I'm gonna put this thing on the highway so it'll be fine with boost and lots of it....

Thanks again for the info and Im gonna jump on this!

 

SEMPER FI MARINE!!!!

I've chewed sand and ate bugs with a lot of fine Marines over my 22 yrs of service.

I'm a retired Navy Chief, 14 yrs fixed wing aviation (worked on, flown in,, jumped out of, and instructed)/ 8 yrs recruiting.

I too have built turbo cars and have owned and modified four turbo bikes (3 Seca Turbos and 1 GPZ750). I'm a Ford guy myself. Mustang SVOs, TurboCoupes, Merkur XR4Ti and some Ford/Mazda builds. Probe GTs and 626s. So I am with you as far as building and tuning

Okay here is my hat in the ring.

Here is some inputs I made on another post and will add more with this one.

http://xjbikes.com/Forums/viewtopic/t=2 ... illis.html

The turbo 650 motor is a direct swap and built with some pretty stout stuff, but so is the old XJ750. Really depends on the boost you run. I've ran 18-20psi on my 650 Turbo. I like the higher compression in the 750 compared to the turbo motor, but the 650 was built for boost. (Tougher rods, clutch, 2nd gear in tranny, some other small stuff)

Here is a list of what you will need to remove from the 650 turbo bikes you found and some possible performance mods

Get the wiring harness and all the stuff connected to it. TCI, knock sensor boost sensor, so on. fuel pump and FPR, If you could get a whole bike and take it home that would be better.

Oil pump and lines. the oil pump on the turbo has a scavenge to draw the oil out of the turbo due to it being lower than the oil pan.

The downpipes leading to the collector are super restrictive. This bike was built in the early '80s and was essentially thrown together by Yamaha to get a Turbo bike to market. They did a nice job, but left a lot of room for improvement. They used old school ideas of tiny carbs and intake ports, tiny valves, exhaust ports and header collector for the VELOCITY was the norm for a turbo build BACK THEN.

You know as well as I do that this line of thinking is more hindrance than help on any motor. The motor just isn't efficient this way, especially a turbo motor.

Get a header (I used an XJ 550 header that I heated up and fit to the XJ650 head and a flange for the T25) or build one that has larger ID tubes and a nice round collector. (The stock collector is flat, restrictive and has a tiny 1" hole going to the tiny inefficient turbo.)

If you are staying with the 750cc bottom end, then the T25 should be about right. The T25 or maybe a bit smaller is a perfect swap for that size of motor. The GPZ 750 turbo guys use the T25 all the time with great success or get the HCT-10 from a GPZ turbo bike. I haven't tried it but I hear the GPZturbo header will fit with minimal mods.

You will also need the 650 head and steel head gasket. It is machined for the knock sensor and has the proper cams for the turbo. I am bouncing around sending a set of turbo cams to Delta Cams for a 10% over grind. Should really wake the motor up with an intake cleanup and hogging out the exhaust ports.
Also, the valves are small (33i/30e) which decreases efficiency. If you could find a set of XJ900 valves (36i/33e) it would give the motor better efficiency.

The pressurized carbs are not as important as I once thought. I hear there are other carbs we can use. BIGGER and part friendly carbs, unlike the POS turbo carbs. If you could find a set of CV carbs from an older CB750 as the spacing is about right and pressurize them like the guy did on the Turbo R1 build. www.turbo-bike.net/

The surge box is a must, but could use some work such as removing the entire internal reed valve and BOV set up and using a flapper or recirculating valve at the opening. You have to have this box, I have tried running with the air opening for the reed valves blocked off and the low end boost is TERRIBLE with it blocked off.

If you are running the higher compression, I would go with an intercooler or alky injection to keep things nice and cool.

Also check out this sight: TMIOA http://www.turbomotorcycles.org/

A ton of info about turbo bikes, all of them!

 

daymn, thats some crazy turbo info, good shit!

 

Thanks Brother!! You've just made one happy sicko with a death wish very happy...I have to hide this page from my Preggo Girlfriend, she doesn't need to know that i am in the know and that I'm making headway on a bobber that'll surpass a sonic boom butt-test!!
I've scoured the interwebs and the Google Oracle hasn't produced near enough guidance as you have...To hear the T25 is a suitable turbo made me wanna run around and chase my tail!!
As time permits I'm gonna do some cheesy paint drawings of my idea and get them together and put them up for thought. if i knew how to HTML code a pic Id do that but its a compy skill I've long forgotten since my," I'm freshly divorced and tryin to hump everything on Myspace"..Days..
Ill look through all the reference info and follo-up after a weekend of yanking Leroys motor outta his carcass...

many thanks and please don't stop giving me pointers...i check this thing everytime im off the bike and since the main man leroy is down, ill check back more often!!

Thanks again,
Booney

 

Thanks for nod brother! I try to help when I can. What so bad is I know just enough to be dangerous and it has been a lot of trial and error. I hope what info I have given you saves you some time and money

If you are really want some dedicated factory turbo bike info for tuning and performance, go to : www.750turbo.com

If you are megasquirt tuning savvy you could get a microsquirt set up and go with GSXR 600 throttle bodies.There are several members on here that have done or doing the FI mod.

I also know that Perfect Power makes a nice setup as well. I have used a Perfect Power SMT6 on my Capri XR2 running 550cc RC injectors, GT28 turbo and the 80mm universal throttlebody you can get on ebay. It is about the easiest piggyback I have ever used and get this, if you use the auxillary injector maps it is a standalone. They have several models of their units and offer maps for various vehicles.

I haven't seen it done yet, but I am sure a set of GSXR TBs with a GPZ750 turbo wiring harness and computer would work on our bikes as well. Oh yeah checkout the automotive coil pack mod that a couple of members have done on the boards. It frees up a ton of area, well not a ton but you know what I mean and gives you a much hotter spark.

I hope this gives you more ammo to fire down range at a hotrod turbo bobber Yamaha. Oh yeah stay out of trouble with the GF! LMAO!

 

As 82seca says, if you can, do something, ANYTHING with the stock turbo coils. They have to be the weakest coils I've ever seen....on any machine! There's a catch though, they need a certian impedence(sp?) or they can supposedly damage the TCI unit from what I've read but I don't know for fact. There's a link that will tell you everything that you wanted to know about the TCI's;

http://www.jetav8r.com/Vision/TCIRebuil ... build.html

I feel lucky when I have a weak yellow spark, that's how bad they are!

jeff

 

thanks again all,...Im selling my old drift car to a buddy so thatll mean there will be some turbo happiness headed my way in the very near future. i thik ill stick witht he stock guts etc until I get the major bugs worked out, until then Im gonna keep plugging away at this idea...
thanks
Booney

 

Booney, instead of wiring in the knock sensor and timing retard from the turbo bike you could use a MSD DIS2 I think? You could use two MSD BTMs.

 

care to expound on that more....all of your advice has been terribly insightly thus far..

Thanks in advance

 

Here some new picts of my 100
00 buy 1982 seca turbo was all apart put it back together only thing missing was headlight bezel so I made one for it if you nottice its alot deeper than factory was fun to make as well.

 

Don't forget fleabay for parts...TCI's run 50 bucks or less so keep an eye out. Body parts are cheap too because there's no real market for them...guys are giving them away.

Always nice to hang with other High Boosters...I've been running 18PSI since I first finished my bike years ago with zero issues....Accel coils cure the poor iggy!

jeff