1978 gs750 turbo questions

[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

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,

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

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.