1978 gs750 turbo questions

[Kaptain Ketchup]

If repairs are needed you'll probably double your invested cash pretty quick. Seals and bearings are still available for the 300 series rajays but the E and F parts are normally picked up for a high price even on ebay. The B parts are seen more often but not many racers use them. I would get a decent boost gauge first, then back out that bolt of the bottom of the wastegate until it comes out, turn it back in until it just seats on the spacer under the spring (if you've had it apart you know what I mean). Then use the locking nut on the bolt to hold it in place there. I would pull the exhaust pipe off and check the condition of the turbine side. Check for wet oil and turn the shaft to see how easy it spins. Check to see that the turbo is getting oil (pull the feed line and turn the bike over and check the return line). If you feel confident its spinning freely (mine requires a tiny bit of force to spin it) then fire the bike up, with the exhaust off, and see if the exhaust spins it. Mine does not spin at idle but a blip of the throttle will have it turning. The HSR carb is a good sign. It's the most streetable of the applicable carbs for turbo bikes these days. I would be interested to see what jets (pilot, needle, and main) are in that carb.

Good luck with that bike. Send some pics and I'll get you info/pics on the FJ.

[rspector]

well... infortunatly I pulled the turbo apart today, it was leaking oil and the bearings are shot, it wore grooves in the housing on both sides and the fins are bent,so I think that answers my questions but on a lighter note I got a friend to split the cost of the repairs, its a b series i believe the number was 25 my camera ran out of juice so the pics will have to wait until tomorrow. The carb says zenith on the top of it and thats it. Any suggestions on where to send it iout to get rebuilt? also at what point do you need to just throw it away and start with a fresh product?
Thanks alot guys
Rob

[lecroy]

Do I hear an echo....

LMFAO!! I hate to say it but your little ride may have just added a couple hundred to the bill!!! Put a new turbo on the old girl and the crank blows out next. Fix the crank and the tranny goes. Its best to see and understand a little about what you have before mucking with stuff. You must have one nice friend to pay for what may have been something you did! The bill could now very well be more than you paid for the whole bike!

Now that you have it apart, look at the two bearings on my site. Is yours a single or dual fed bearing? If it is a dual and the housing is shot, your done. Terry could maybe repair it but there are no replacements. If it's a single your in luck. These are a dime a dozen and can be seen on eBay. If both the turbine and compressor touched you may as well toss it. About the only thing you may save is the clamp that holds it together.

I bought an old single feed on eBay a couple of years ago and ended up putting about $450 into it with parts and the original price when it was all said and done.

Give Terry a call, tell him what all you have done and see what he would charge for a whole new turbo. If you do manage to get one off him, don't just bolt it on and go for another spin. You need to start checking things first.

You can always give me the bike if you get tired of it.

Good luck.

[lecroy]

This one is calling your name!!!

http://cgi.ebay.com/ebaymotors/USED-RAJAY-TURBO-RAYJAY_W0QQcmdZViewItemQQcategoryZ6755QQihZ007QQitemZ170036562764QQrdZ1QQsspagenameZWDVW

[rspector]

I don't consider myself "mucking with stuff" I've had plenty of bikes this being the 3rd gs, I purchased the bike, I changed the oil and took it for a 5 minute ride after inspecting the brakes and tires. It never created boost since the first time I started it.

[Kaptain Ketchup]

Hmm... so the turbo is shot.. I would give up the turbo mod on that bike then. Like lecroy said: The bills on that motor will add up very fast. Zenith carb eh.. I didn't know they had an acc. pump too. It sounded like a HSR to me when we talked. It's fubar'd pretty good if the fins are bent.

If it was me personally... You are at the point where "you need to just throw it away and start with a fresh proJECT" I would part out the exhaust tubing, tailpipe, manifold, wastegate, etc. and go over the motor to see what else was done to it (dropped compression pistons, any trans work, turbo cams, funky ignition, ...) I think you could get your money out of it by parting the whole bike out. It would pay for some nice mods for the Bandit.

You can watch ebay for a new turbo, but the term "new" on ebay is often stretched beyond useable condition and you will most likely need to rebuild a ebay turbo as well. Dragbike.com may have some but I have not seen many B25s flost across their pages.

Like lecroy said, Good luck.

[lecroy]

I don't consider myself "mucking with stuff" I've had plenty of bikes this being the 3rd gs, I purchased the bike, I changed the oil and took it for a 5 minute ride after inspecting the brakes and tires. It never created boost since the first time I started it.

To me, mucking is what happens when you hit the starter switch before pulling the motor down or at least doing some simple checks. A turbo that has any sort of minor problem can go up in smoke in a few seconds, let alone minutes. Just how deep you pockets are.


Kaps right, pull it down and see what you got. Even if you convert the bike back to normal, you may be in for a surprize. Turbo pistons are normally 7.8 - 8.5 :1. If the bike was setup for a turbo, then just replacing the setup with carbs may make for a poor running engine. Again, compression test first. Easy way to tell if it is stock.

[rspector]

what i meant by start with a fresh product, was shold I buy a whole diff turbo or can they pretty much rebuild everything? I really want to get a functional turbo on this bike, if the crank blows then I will address that issue when I come to it. I have plenty of other bikes to ride, I just think that the turbo idea is very interesting and i'd like to see it. So any suggestions on who to call for the rebuild in northern new england ?

[Kaptain Ketchup]

Heres where I got mine done in Ontario.

http://www.cherryturbos.com/

No idea on any in your area. Any turbo dedicated shop will be able to help you. Most will comment on how old that turbo is, or about how they don't see any like it these days. If you really want a turbo bike then you can trade your bandit for mine (not sure if I'm really serious about that..).

As far as rebuilding goes. Sounds like you need more than seals/bearing kit. You're going to need the turbine wheel/shaft combo, turbine housing, compressor wheel, compressor housing, possible backing plate along with the bearing and seals. Thats big bucks right there just to get off the ground going on the description given/broken parts found thus far.

Got any pics of this machine yet?

[rspector]

i will have some tonight, I got a few qoutes in the 350 range for a standard rebuild, I dunno if mine is gonna be that easy or not, and I wouldn't trade my bandit for the world gsxr intake cam, jet kit pipe busa suspension, its right wher eI like it

[Frankenzuki]

turbo

Rspector,

I'd be interested in buying the turbo stuff if you are going to not use it. I have some GS1000 stuff that would bolt into your 750 frame. I'm in southern CT, I have family north of you in NH. I also have cash if you 'd just like to sell.

You can e-mail me at Frankenzuki@sbcglobal.net if you're interested.

[rspector]

i brought the turbo to a rebuilder today, he said it seamed ok and that the turbo wasn't the problem, I did a compression check and all cylinders are at 120psi, I'm wondering if this could be a fuel delivery problem keeping the manifold pressure too low to turn the turbo?. It has a zenith carb on it, didn't know if they made rebuild kits for them? was also thinking it could possibly be the fuel pump, and didn't if any one had a suggestion on to where I could by something that pushs the same pressure and volume

[Frankenzuki]

Turbo,

I use a Holley electric pump and regulator. You should be able to check the pressure on your pump with a standard fuel pressure gauge to see if it is the problem.

In a previous post you mentioned that the turbo was leaking oil, bearing shot and fins bent...Then the rebuilder said it was OK?? If the turbo is still off why don't you take it apart and see if the impeller has hit the sides of the housing? you should have very little end play ( in/out) as well as minimal side play( nothing should touch anywhere between impeller and either housing).

Also back to the oil thing, is there oil on the intake side of the turbo or intake manifold?

[rspector]

I guess I was wrong about the fins,there was not oil in the intake but there was some on the spring loaded disk bhind the impeller. Asuming that the pump is shot, what did you tune the regulator too? How much psi

[Frankenzuki]

fuel pressure

I don't have any experience with the Zenith carb but 3-4psi works well with my 42mm Mikuni. Even a couple of PSI should be enough to get it to run, I'd be careful about boosting it up without fuel pressure as they can get real lean , real fast.