How far down the rabbit hole will I go... `78 GS750

[bottobot]

Here`s the backstory on this bike. I gave it to a freind as a wedding present almost a couple years ago. I bought it for a $1000 bucks. It ran ****ty then and runs ****ty now. Well he bought himself a new Triumph Bonneville and gave the bike to his semi-estranged father. Now they got something in common and were able to bridge a few years of never talking with motorcycle riding. Nice warm fuzzy story. In the meantime I had left the country for a year and had returned with no real bike to ride. Friends Dad had gotten himself a new bike, and now have no need for beater. Its been sitting and no one else in the family wants it so they give it back to me

Now its in my workshop getting a workover.


Now I am not really sure what I am going to do to this poor beast as I have a number of other projects in the queue, but this bike has really grown on me. So first thing I do is hit the net and find you all here at GS Resources. What a great bunch of helpful people you are. The welcome kit and a few others say ``Dip your carbs and do a rebuild!``

Tutorials are read and I commence. A completed carb rebuild which can be found here.

Now I am going to attack my gasket set and replace my head gasket.

I am pretty good about posting photos and such so stay posted as I go to work on this puppy.

If any of you are in the Vancouver, BC area and would like to drop by my shop and say hello please do! Just send me a message with your number and I`ll give you directions.

[7981GS]

There are almost as many GSR members on Vancouver as there are in the East-central US.
A few may be dropping by.

Eric

[tkent02]

Watch out, they're all Canadians.

[john82q]

some will want to talk hockey too, eh?

[bottobot]

Well I got deep into the cylinders today. Found a few things to indicate where the oil was getting in. There is a rubber square-ring that seals the cam chain area from the head and it was definitely pooched. So that would explain some of it. There were also tears in some of the o-rings that go around the bottom of the cylinders themselves that were torn, though they might have torn during cylinder removal. It was pretty clear that wear the top half of the cylinder meets the base there was oil weeping all the way around pretty much. I am pretty confident it was a gasket issue and not worn rings that were causing the fouling. I'm out of my budget for this bike for parts and such so even if worn rings are the issue, I'll just have to put up with it till I can order some in a few weeks. Give it another couple weeks to get em and then we are looking at a month before I could do em anyway. Might as well see if it goes in the meantime and get my other projects happening.

If I do need new piston rings then I'll go whole hog and repaint the whole engine, get the valves re-seated, do the shims, then bore out and size-up the pistons.

For now here are some progress pics. I like to put things in ziploc bags and label em. If I am disciplined it makes for a much easier putting back together process.


I give everything a nice place to rest while I bang on other things.


I love looking at a bike with its guts hanging out. I wonder if its worthwhile to try cleaning the pistons? They have some buildup from the oil burning.


Tommorrow I'll start putting these fresh gaskets on

[gearhead13]

Did you get valve guide seals too? I would run a light hone through the cylinders before reassembly if it was me. You might have a tough time finding o/s rings and pistons for some older bikes.

[bottobot]

Did you get valve guide seals too? I would run a light hone through the cylinders before reassembly if it was me. You might have a tough time finding o/s rings and pistons for some older bikes.

Yeah I got the seals. I don't have a honer so I won't be putting a hone on even though I would like to.

[cowboyup3371]

Watching Steve tonight clean the pistons on his 650, doing it isn't that hard. Take some carb cleaner and a wire brush and go at it. Should clean up fairly quickly (his did and look about the same as those) and you can then inspect them for any damage.

[Nessism]

The pistons in the photo look good. Very little or no dark coloring on the piston skirt which means the rings were sealing nicely.

Better say six Hail Mary's when you assemble the engine. Aftermarket gaskets are a real gamble and we don't want you getting an oil leak.

[bottobot]

The pistons in the photo look good. Very little or no dark coloring on the piston skirt which means the rings were sealing nicely.

Better say six Hail Mary's when you assemble the engine. Aftermarket gaskets are a real gamble and we don't want you getting an oil leak.

Well today I start putting things back together so I am definitely be saying my prayers. I'll be saying a few more things if these gaskets don't hold up...

[bottobot]

Got the gasket off the top of the valve section. Some has stuck on and I am loathe to take it off with any kind of tool lest I nick the surface. Think I could use some 400 grit?




Now the bottom side looks really scored, maybe a gasket was stuck on at some point and one of the PO's really went to town with a flat head or a chisel or something. I'm thinking of sanding it to make sure that the surface is good. It may be one of the reasons why it was weeping oil from this area. The paint is also in really bad shape. Pretty clear they didn't paint it properly. I'd also like to get at the valves so I can put new seals in but I don't have the right tool so thats gonna get skipped.

[Mekanix]

Watch out, they're all Canadians.

Daam straight eH!



I wouldn't recommend sanding the gasket. A plastic scraper works. Some here Carefully use razor blades

Gasket remover works as well. Its just like paint stripper.

You could have the head planed. I'm estimating it would be $30-50.

[bottobot]

I am having some trouble putting the base cylinder on. I can't squeeze the rings together enough by hand to slide the cylinders down. I may have to go to crappy tire and see what they got that I can use. I need to find an oil filter anyways. Any suggestions would be real welcome.

[7981GS]

Use a popcycle stick or a piece of plastic.

Eric

[TeamDar]

You may want to check the diameter of those pistons and maybe the lift on the cams. Those look like Yoshimura pistons. Do they say POP Y on the side next to the wrist pin bore. The pistons look to have more dome than stock. If you have a stock head gasket it may not fit the bore. The cams look like they have some serious lift also. You just may have yourself a hotrod.