'77 GS750, "Hahn" Stuck engine.

[Guest]

OK I was not going to start a build on this bike until I had got the engine free but now is a good a time as any.
When I was looking to upgrade from my SR250 I started asking around at work if anyone had a GS450 or the likes, one of the blokes mentioned that he had a 750 he was going to restore.
Being that I am still on my "restricted" license (can't ride anything over 650) I was not in the market for a 750, after a bit of thinking I decided I would ask him what he wanted for it.
After a bit of talking he decided he did not have the time or money to do the bike justice so he asked if I wanted it, well yeah of course. A week later I picked her up, all for the cost of a carton of "Hahn Super Dry" hence the name.

The previous owner lives on a farm and this bike was sitting in his shed for two years, but it had been outside for the past 6 months. As with any bike found under a tarp behind a shed I assumed the worst, surprisingly the tyres were still inflated and only a few critters had made it home. Seeing that it is winter here I was expecting a snake to be under the tarp at least but there was only a few large spiders and lizards.

Here is where she sat for six months, picture was taken after the tarp was removed.


After I wheeled her around to the trailer I decided to take a "before" photo. Not to bad considering.


It was then I decided to jump on her and see if she would spin. After putting her in neutral and looking down to see the starter motor was MIA I flicked out the kick and decided to give her a gentle push, which ended up with me standing on one foot in the air. That is when the project got a whole lot bigger.

After I got her home it was off to work so the cylinders were filled with oil to hopefully loosen the engine. after sitting for a day it had not helped so I decided to rip in to the engine as I would have had to anyway to get the cylinders honed and stick new rings on. Here is the progression of the tear down.




Well at least the head is nice and clean. On to the cylinders now to see which and how many are stuck


Cylinder 1 and 2 seem fine, full of oil but fine none the less.


Yep has to be one of these two milky b-tards.

So with a bit of persuasion with a BFH and a block off wood I find it is cylinder 4. I decided that a bit of inox might help to free her up as that was the only thing I could find that would help. So another day later and no go. I have been suggested Kero so that is the plan after I clean up the ungodly about of rust that used to be the exhaust system. If that does not work it will be on to diesel as Retro suggested.

[Sci85]

No offense, but if it were mine in that condition, I would part this one out. Its worth more in pieces then whole and with the money you can find yourself a much better starting platform. Of course its your decision but know that your are going to spend quite a bit of money to get that one reliable and safe.

Good luck whatever you choose!

[Brodie]

I have been considering the same thing. But as it has not cost me much yet I will see how far I can go before I end up needing to spend cash. If repairing it adds up to be to much this might become a parts bike. I do like a challenge though and I am in no rush at all with the build.

[ART]

Everyone should tackle a project like this at some point. It really is a lot of fun. When done.
And tends to build character.

I'll be reading here with joy and applause.

[Brodie]

Not much to update. I still have a stuck engine and I am just letting it soak. It still does not want to budge but I will pull the entire engine apart this weekend when I get a change. Work has been hectic so at least I have had time to leave the thing sit and soak.

When I have had the chance I have been looking into the electrical system. The previous owner said there were some problems. After a quick look nearly every wire is melted. So I plan to build a new harness rather than repair this one.

[sharpy]

Those hubs and rims cleaned up in australia would go for around 200 bucks. Look like H pattern Borani rims, Oil pump gears add a few more bucks. Part it out and upgrading to a better basket case be my choice. Only reason to keep it if u already have exact same make/model

[Brodie]

You are right about the rims Sharpy, Boranni H style. The PO said they were the best thing on the bike and I think he was right. I have another hub the same that is in a smaller wheel that also came with the bike. The PO used it as a sidecar wheel on his Z50J.

As for parting it out I don't think I will with this bike. I have been thinking and my first bike was a basket case '69 Z50AK1 that my father had to pulled out from behind a shed with another 3 bikes. Took him months to find it and a year and a half to get it working. I love that bike and restored it only a year ago.

I think this bike will head in the same direction. Take a while to get it together but once I do it will be mine for the rest of time... or till I carc it. I don't mind spending more on it then I need to as long as I learn along the way. Never dealt with an inline 4 before and I have never dove into a transmission so see what happens.

As for todays update, I was sick of fighting the piston so I have pulled the engine and plan to disassemble it completely and try to push the piston out the other way. If that does not work I think a set of 850 cylinders and pistons might be in order. If I have to order new cylinders I may as well upgrade right?

[Brodie]

Aright so on to the pictures. I will start with the electrical so people can see what has happened to merit a new harness. I don't think this one is salvageable for the amount of effort require to make a new, more efficient version.

Mmm, Rats nest


Wonder if this has something to do with the electrical problems.


Nevermind, here is the problem.


This isn't needed anymore.

[Brodie]

So tonight I was able to get stuck in and pull the engine. Here are the pictures of the progression and where I stopped. I have the lower case unbolted and just want to read up a bit more before I try to pull it off. Just in case there are internal bolts I cannot get to. If I cannot pull the bottom case off then I will have to go to my last resort, which I said I would not do... but it is looking like I might have to. A nice sharp hole saw over the piston crown...

Anyway pictures..

Here is where I started thisarvo.


Getting a bit more pulled off.


And she is out. Man that thing weighs a ton.


Up on the bench for the pull down


This is as far as I got tonight, More tomorrow if I can get time.

[Brodie]

So after about half an hour of trying and failing with my soda blaster I decided to look around for someone else to do it. Found a bloke half an hour away that would do the whole engine for $200. Sounded alright to me so I drove out and had it done while I watched. Should really have taken a few more parts off the cases but some of the stuff I didn't even know was there because of the grime on top.
Here is the end result. Now I just need to give them a nice bath to clean all the soda off so that I can either paint or powder them



Here is the before picture.


And as for the pictures from the last update here we go.

This is what the piston looked like once I had the cylinders unstuck.


And here is the cylinder after a quick clean.


After that I dove into the engine and was faced with my first ever transmission.



Now I just need to save my pennies to get a full gasket kit and stick it back together.

[eil]

Were the cylinders and pistons undamaged then?

I like threads like this. Sometimes it's fun to dig into something and make it run, even if the math says it's cheaper to junk it.

[tkent02]

How did you get the pistons to come out?

[chuck hahn]

BFH was probably involved

[Brodie]

Ended up buying a propane torch and I heated the cylinder until the gasket underneath started to smoke. After that I used some brake fluid whist the cylinder was still hot. I left it overnight and used a plastic tipped hammer directly onto the piston. Worked better than I expected.

The cylinders look like I should be able to get away with just a hone so I will give that a go tomorrow when I can borrow a hone from my grandfather.
As for the piston those rings are stuck on there good. I am not sure I would want to re use it after the amount of times I hit it with a hammer.

[Brodie]

Here are the pictures of the propane torch doing its job