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[Woody]

I have a 1974 750GT and I've owned it for about 10 years. Recently I started having some problems with it. At first it was only running on 2 cylinders but after warming up some it started running on all 3 cylinders. It was running very well but then started to just stay running on the 2 cylinders the 3rd never kicked in. I parked it trying to find someone who knew how to work on a 2 stroke. One day I notice oil on the floor underneath it. As time went on it got to be quite a bit of oil on the floor and I couldn't see where it was coming from. It also developed a water leak. I have a friend that's more of a Harley mechanic helping me with it but I'd really like some input from folks who truly know about two stroke engines. We think we've solved the leaking water issue, it was coming out of the water pump cover but we still aren't sure where the oil is coming from. We drained the transmission oil and it appeared to be full. But I checked the injection oil reservoir and it seemed to be lower than when I parked it. Any and all comments will be helpful and Appreciated!!! Thanks!

[Coyote]

By comparison, 2 strokes are bone simple There are no valves, no camshaft and no internal chains. I haven't had a Buffalo in a while, but there is a weep at the edge of the water punp that burps a little coolant once in a while. What kind of oil is on the floor? If it's 2 stroke oil, check for a cracked hose between the tank and the pump. When you drained the transmission was the oil milky looking? if so It's a blown o-ring seal that keeps the 2 systems separate. Sorry to say the motor requires complete tear down and the cases split to fix. You might get lucky by adding some extra stop leak to the coolant.
What cylinder is not firing? If it's the center, welcome to the club. I just finished my third triple and I have yet to build one that fires on the center. Red hot spark, ample fuel and they just don't run for me. All 3 will pick up the center when you get the revs up, but forget at idle.
You should drain the coolant and look for oil contamination. There is a large hex head plug at the right front of the crankcase. That is your drain.. You should also pull the SRIS valves out to drain out any oil that has accumulated in the crank chambers.

[GT750Battleship]

Hi & welcome,the water leak out of the pump housing is usually an indication that the water pump is about to fail ! you can sometimes get oil as well mixed with coolant,as Coyote pointed out what colour is the oil ? It maybe coming from the gearbox drain plug or the one that is at an angle which is the gearbox detent bolt,oil getting past a washer ? Two Stroke oil is usually coloured,can be red,blue,green etc,gear oil normally yellowish.Good luck tracking it down
Cheers,
Roger

[Woody]

When the transmission oil was drained it looked normal and not milky. I haven't put the new oil back in the transmission yet, but today I see more oil on the garage floor so it must be coming from the two stroke oil injection tank. I will try to see where the leak is today. This is a really low mileage bike with under 6000 miles and has always been garaged and well cared for. I am the third owner and the bike came from California. I have not ridden the bike very much but have not let it sit for more than a month or two even in the winter. It really started running bad and was low on power the last time I rode it and was lucky to make it home. It has been sitting at least a year since then. When the center exhaust pipes were removed to replace the leaking water pump cover they had a lot of unburned gas in them. The middle cylinder was the one not firing, nothing but cold air coming out of the center exhaust pipes. It is getting spark to that plug. Maybe the carbs need to be cleaned? Any advice is very much appreciated.

[Coyote]

Today's fuels do nasty things if allowed to sit. I would say that your pilot jets are clogged and the mains have gunk in them too. I assume you have CV carbs. The nice thin about those is both jets are in the float bowls and easier to deal with. Remove the bowls, then remove the jets. Ethanol coagulates in these jets. Chances are you won't even see light through the pilots and their tiny cross holes. Stiff wire is a no no., but you (I) use a soft copper wire like a single strand from an electrical cord.. What I do is use about a 6" length. Stick the straight part through. Then kink up the remaining wire and drag ii through. Use some magnification so you can really see what you are doing. Soak them in some thinner. After you put the jets back in, fill each orifice with WD-40 and make sure it drains through easily.
I realize this does nothing for your leak.Surely you can tell what kind of oil is on the floor. If it's black and burnt smelling, it's coming from your exhaust. You mentioned a lot of unburned fuel an oil in the center pipe. Some pipes (but not all) have a small weep hole at the lowest point in the system. Could be that. 2-stroke oil can only leak in a few places. Cracked tank (not likely), cracked hose between tank and pump, banjo fitting where the oil line enters the pump. Rarely they can leak under the pump, but that would be obvious.
Take heed on the first paragraph. Ethanol does clog systems up. I think once you clean out those jets she'll run like she used to. Lucky for me there are several stations around town that sell non ethanol fuel. If you have access to it, use it!
p.s. Glad to hear your tranny oils looks normal. That's one headache you don't need

[Woody]

Good news on the oil on the floor of the garage. The bike is on a motorcycle lift that my Harley mechanic friend supplied, and it appears the oil is leaking on the floor from the lift cylinder. I don't see any leaks from the oil injection tank or lines. If my friend is feeling up to it (he has some health problems) we are going to work on the bike today and put in new transmission oil and fill up the cooling system with distilled water and antifreeze. I noticed in the manual it says to put in some Bars leak if you completely drain the coolant. Is this a good idea and should I put this in? I looked for Bars Leak but have not been able to find it. If I need some "stop leak" what product would be best.

[Coyote]

Any liquid 'stop leak' that's for use or safe for use on aluminum. Don't use the pellet type. They never seem to dissolve. The amount to use should be on the bottle. And yes, you should use it.
New oils and liquids won't have any effect in the way it runs. I think you need to clean those jets to get any joy.

[Woody]

We worked on the bike today, put Amsoil 20w-40w in the transmission filled the cooling system with distilled water and antifreeze. I will add stop leak to the coolant tomorrow. My friend tried a amsoil product carb cleaner/fogger spray in the carbs but it did not help still running on 1 or two cylinders. He pulled the carbs off the engine and opened up the float bowls which looked dirty and we need to get gaskets and diaphrams, basically need carb rebuilding kits. I don't see any numbers on the carbs and the manual doesn't really specify what they are. I was wondering if you know where to get kits or the parts needed to rebuild them. He is going to completely clean them in carb cleaner and make sure the jets are clean and open. Thanks for any help or suggestions. The help I have gotten is much appreciated.

[Coyote]

we need to get gaskets and diaphrams,

Diaphragms? You need diaphragms?? Note that the diaphragms and the carburetor slides are one piece. It's not a device you can fool around with. Under normal circumstances they do not need to be replaced, Especially since they are right at $200 EACH!!!. Yes EACH!! The only time you need to replace is when one has a tear. Small tears or cracks can be repaired with silicone sealer BUT if you get even the slightest bit of too much then that diaphragm will be stiffer than the other two. Meaning it will not rise and fall at the same rate as the others and the bike will never run right.
So look them over really well. If there are no cracks or splits and they are reasonably flexible, re-use them. Also be sure to put them back in the same carb they came out of and the tab on the diaphragm fits in the recess at the top of the casting. If they seem to be a tad too small from shrinkage, invert them and put the top of the diaphragm in a shallow tray of gasoline for about 10 minutes. They will expand and you need to cinch them down before they shrink back.

[GT750Battleship]

Hi,yes not cheap from NRP Carbs UK £34 pounds each to fit new diaphrams,Very rare to have a problem with them...only replaced one in 34 years of owning GT750's
Cheers,
Roger

[Woody]

We worked on the bike today and had the carbs apart. The jets were clogged and the slides were sticking on the two outside carbs. We cleaned everything up being careful not to get carb cleaner on the diaphragms. Good news is the diaphragms are in good shape and I am very glad about this. I had no idea how expensive diaphragms are and did not realize the slides are part of them. I was able to get some of the parts from Bike Bandit. The carbs are back together and next time we will be putting the carbs back on the bike and firing it up. I hope it runs good and am ready to go out for a ride! I will let you all know how it goes.

[tz375]

Carbs are Mikuni BS40 and there's some info over on http://pinkpossum.com/GT750/carb/BS40carbs.htm" onclick="window.open(this.href);return false; that you might find useful. Pilot jets are not the usual Minuni type. They look very similar but are different. I hope you got the right ones.

Many bikes used a 34 or 38mm version of those carbs and some parts are interchangeable.

[rngdng]

I'm a little concerned about the concept of AMSOIL in the transmission. I think your clutch will slip.



Lane

[Woody]

I tried to get new jets but could not get them at least not from "Bike Bandit". The jets were mostly blocked but we soaked them in carb cleaner and ran a wire strand through them and tried to be gentle about it. Hopefully they will be alright? Now I am worried about the Amsoil in the transmission. Has anyone used this in a 750GT transmission and did work well? Thanks for the help it is very much appreciated. I'm a 71 yr old guy trying to muddle through this, and the Forum is a great resource for me.

[ConnerVT]

I tried to get new jets but could not get them at least not from "Bike Bandit".

Available from Jets R Us -- https://jetsrus.com/a_jets_by_carbureto ... series.htm