dgoodsy's '72 gt750 revival/log thread

[dgoodsy]

Hello everyone,
i'm creating this thread to document the work I do to the bike, ask questions and opinions and discuss things etc.

I recently purchased a ’72 gt750. It’s not great looking at the moment, with dust, scratches, dents, corrosion, oily mess, etc. It was parked in a garage for the last 10 or 15 years, owned by a neighbor of a family friend. My friend had never seen the previous owner ride the bike and didn’t even know he owned a bike at all. The previous owner recently passed unexpectedly and his family was moving all of his stuff from his property and while cleaning out the garage, moved the bike to the yard. My friend inquired about the bike and sent me pictures wondering if I was interested. I am admittedly not familiar with this era of motorbikes, and didn’t even know a 2 stroke watercooled triple existed . I did a bit of reading about these bikes and after a bit of a runaround I paid some money and hauled it back to where I live. It seems that the bike was brought from British Columbia to Saskatchewan when the previous owner moved here, and has likely never been licensed here in SK.

I also have a smaller bike that I enjoy riding in the city but am not terribly comfortable taking it on any decent length of trip on the highways. My plan was to find a better bike for highway cruising when the gt750 fell into my lap. For the most part my highway riding would be mostly weekends, which leaves me time during the week to work on the gt750 without worrying too much about rushing to finish to ride the next day. So my plan for this bike is to get it running reliably first and then fix aesthetics and make it look pretty as I have time and ambition for. Maybe in the winter I can do an in depth tear down and refresh of the engine, if I don’t have to do it before then.
So I have a few questions right off the hop here.

1. Are there any pro tips for attempting to start these bikes for the first time in a decade or more possibly? As I mentioned my friend never saw his neighbor pull this bike out of the garage since he moved there 10 or 15 years ago, so I think it’s best to assume he never even kicked the thing over in that time. The engine has been kicked over a few times since my friend inquired about the bike, to ensure the engine was not seized.

I plan to drain the fuel and put new fuel in, fresh spark plugs, clean the carbs, flush coolant (probably just leave water in it for now, until I know the bike runs), drain and replace gearbox oil, and drain and replace motor oil and clean out the oil pipes as well as I can. I am concerned with the crankcase and seals that have likely been dry for a decade, is there an oil to spray in there to help lube things and keep seals from tearing until the engine is lubricating as designed? Or do I not have to be concerned about that? What else should I be concerned about?

2. This one is silly, how do I get the seat off? I see a tab on the bottom left side of the seat that I assume is the seat release but I can’t seem to move it. Looking underneath it looks to me like the tab needs to be pushed straight down, I pushed till my finger hurt and it wouldn't budge. Then tapped it with a socket (what I had handy) and it didn't budge. I tried to slide it forward and back but still no luck. I had to run so I left it without figuring it out.

I will no doubt have more questions as I begin to dig into the bike but that’s a good start.

[dgoodsy]

I got the seat figured out, I was trying push the tab that is part of the hinge on the left side when I needed to push a lever under the right side of the seat. Oops.

Got the bike sprayed off this evening but couldn't find my degreaser so it's still oily. Hoping tomorrow to flush the cooling system.

[dgoodsy]

http://www.ebay.ie/itm/Suzuki-GT750-oil ... xy63FSnMu9" onclick="window.open(this.href);return false;

Has anyone come across and used these? (and I wonder what it would take to get them to sell in logical quantities - 6) Are there any other alternatives for these banjo fitting/check valves? I have read it mentioned that there may be some similar Polaris parts that we could use, but never read specifically what machine they would be found on.

While trying to verify the oil injection system was working yesterday I used compressed air (low pressure) help clear some of the pipes/check valves. I was unaware that is not recommended until now and now fear I may have done damage to the check valves in the banjo fittings on the engine side of the oil lines. I will have to check and see if the check valves still function.

If I do the hanging leak test and no oil drips out of the banjo fittings is that conclusive that they are undamaged and functioning correctly? Any ideas how to test that positive crankcase pressure won't push the oil back up the pipes, or is the hanging drip test sufficient?

[GTandcbr]

I am a 550 man but i will try to help. If the bike has been laid up for that long it is likely the seals as you say could be shot. A method that you could try is to lift the head and barrels off and fill the crankcase with diesel. Then turn the engine by hand every day for about a week. Then remove the sris valves from the front of the engine and let all the deisel out. When you try to start it it will smoke a lot but should eventually clear. This method has been used by some members of this forum with success.
Blowing out the oil lines with compressed air is definately a big no no. The checkvalve which attaches the pipe to the engine has a very delicate spring and a ball bearing which closes off the oil when the engine is switched off. Hanging the pipes up full of oil is the way to check if the pipes leak. There is only a small amount of crankcase pressure going the other way.
Here are some links to help you
http://www.pinkpossum.com/GT750/Oilpump.htm" onclick="window.open(this.href);return false;
http://oldjapanesebikes.com/blog/2012/0 ... ion-lines/" onclick="window.open(this.href);return false;

[dgoodsy]

thanks for the help. when I blew out the lines I blew them out from the oil pump side, not from the banjo fitting side, would that make any difference?

Can anyone tell me what is inside the engine where the oil line banjo fittings attach? I assume there are sprayers of some sort. Would it hurt them to blow them out with carb cleaner or something similar, just to make sure they aren't gunked up and clogged? or would that cause damage spraying a solvent into the crank case?

[dgoodsy]

Well after doing the hanging drip test with these it does look like I'm in the market for a new oil pipe assembly or maybe just the check valve banjo fittings. They all leaked, some just barely, but others leaked quite heavily. No correlation between the amount of air I gave the specific oil pipes and the amount of leakage though. So I am soaking them in kerosene just in case it is issues of just being gummed up. I don't have my hopes up about it though, we will see tomorrow or Thursday.

[GTandcbr]

Unfortunately any direction compressed air is not good. The hole into the crankcase is just that and is unlikely to clog up and as you rightly say i would not be putting any solvent in there. There are a number of oip lines on ebay some your side of the pond. Good luck

[dgoodsy]

So I got some time on my time off to look at the bike. I took the carbs off and started to clean them. I was pleasantly surprised that they weren't awful, and the jets I did remove were really easy.

I wanted to remove the needle jets but it wasn't obvious to me how they come out. I noticed a pin in the side of that body where the needle jet slides it, surely that doesn't have to be drilled out? I have read that is how some of the needle jets come out. Can anyone help me or and tell me how the needle jets come out?

[rngdng]

Remove the main jet, and push the needle jet straight up. I use something that won't damage it, like a chop-stick.



Lane

[dgoodsy]

Aah, thanks. Hopefully I can get to that soon and finish cleaning the carbs. Like I said, the jets that I knew how to remove, they did come out fairly easy. There was a tiny little bit of rancid gasoline in the float bowls, and a bit of varnish and sludge, but it looks like corrosion hasn't gotten to too much inside yet. (of course I can't see inside many passages, who knows what things are like in there. It looks to me like nobody had done any hack mechanic-ing on the carbs, which was a relief after seeing masking tape used to insulate and secure rear signal light wiring on the bike.

[Jimroid]

On occasion the needle jets can be pretty stubborn. A hardwood dowel and some light tapping may be necessary. Or the plastic handle end of a screw driver.Tap,tap. And yes they go out from the bottom up.

[dgoodsy]

Just to confirm what pushing/tapping the needle jets "up" means, it is tapping the jet from the bowl side into the throat of the carb and out the slide area, correct?

[GTandcbr]

The answer is yes have a look here for help https://youtu.be/AOJlHIUUBk0" onclick="window.open(this.href);return false;

[dgoodsy]

thanks guys.

GTandcbr, thanks for the video link. I searched youtube for "mikuni vm" and watched a few of them but didn't see anything that showed me what I wanted. I didn't feel like watching every mikuni video on there, that one is great though!

[dgoodsy]

I have been wanting to put diesel in the crankcases of this bike to sit for a few days and hopefully help the seals soften up a bit before I get trying to turn the motor over too much. I got a chance to do that tonight, I looked in the carb mounts to see which pistons were not covering the intake ports and I could see the bottoms of the left and center pistons. Using a funnel with a hose on it I poured about 500ml of diesel in the left intake port. I thought it would stay in the crankcase but I saw a puddle form on the ground as it was all leaking out. I got an oil catch pan and caught most of it, but it's hard to tell exactly how much drained out and if any diesel is left inside. My first thought was that a crankcase drain bolt was loose I tried looking underneath to see exactly where it was conning from and it looks like it is coming from the rear of the engine case rather that a drain bolt at the front. I tried to get a picture of the bolt where I think it's is coming from but I couldn't really get a look at it.

gt750 crank case leak by Damen Goodsman, on Flickr

Towards the center of that picture is a bolt with a cleaner head compared to the muck that is on everything else. The picture is looking up facing the rear of the motorcycle, looking between the left cylinder pipe and the center cylinder left pipe. I tried tightening that bolt but it wasn't loose. What is that bolt for and does it make sense that the diesel is leaking from there? Anywhere else diesel might be leaking from and maybe just running to that bolt head before dripping?