Is this a common sound characteristic of a 750 ?

[pearljam724]

I know this is going to sound stupid. During, light engine braking ( under 40 miles an hour ). My motor makes a sound as best described as a " gluck, gluck, gluck " sound up around the head. It doesn't do it during hard, soft acceleration or higher engine braking. I know my 550 doesn't make that sound. I'm not talking about the " nin,nin,nin,nin " sound all two stroke make when decelerating. Is the gluck, gluck, gluck sound a normal sound characteristic of the 750 ? The bike runs great, no problems what so ever. I also have a crank seal leak. The second question I have, after removing the motor. Can I simply remove the very bottom half of the crank case to replace it ? Or do I have no other choice but to disassemble the motor, from the top of the head down ?

[oldjapanesebikes]

The only time I've heard a 'gluck, gluck' sound is when the outboard engine fell off the transom ! Luckily we did have a safety chain attached and so were able to retrieve it back into the boat

Regards your other question - its a full tear down. You can't remove just the bottom of the crankcase, or more accurately, if you do, you'll never be able to get it all back together as there is no way to refit the transmission properly. Plus you can't get the crankshaft out without first removing the pistons.

[pearljam724]

The only time I've heard a 'gluck, gluck' sound is when the outboard engine fell off the transom ! Luckily we did have a safety chain attached and so were able to retrieve it back into the boat

Regards your other question - its a full tear down. You can't remove just the bottom of the crankcase, or more accurately, if you do, you'll never be able to get it all back together as there is no way to refit the transmission properly. Plus you can't get the crankshaft out without first removing the pistons.

I'm not talking about removing the crankshaft itself or the transmission. I'm talking about removing the lower half of the crankshaft encasement. There are two halves. The upper portion and the lower portion. The gasket goes in between the both. If that still can't be done. I gothcha. Picture example.

[pearljam724]

One more pic.

[ConnerVT]

Ian is right. It doesn't work the way you want it to.

I'm not a GT expert, but have torn my T500 down into little pieces, and put it all back together. More the same than different.

First, there is no gasket that goes between the upper and lower engine cases. A gasket sealer compound (preferably Threebond 1184 or equiv.) is used between the case halves.

These engines are really built from the bottom case up. In the bottom case, the crankshaft, transmission, kick start, oil pump drive, etc., are installed. Then the top halve of the case is positioned into place, then the bolts torqued to pull the 2 case halves together.

You can't invert the engine, and remove the bottom case. You'll never get the internals back into place properly.

Assembled lower case.jpg

[Coyote]

Conner is right. The lower case is not simply a cover. By the way Conner, that's looking really clean! Nice job!

[oldjapanesebikes]

... I also have a crank seal leak. ...

The leak you refer to - is that what you are pointing at in the photo ? It looks more like an exhaust gasket leak (quite common), or I suppose it could be a leak in the SRIS hose. It would be unusual for the a leak from between the crankcase halves to start on a 38+ year old engine that hasn't been apart.

[Barry S.]

Yeah, that looks like goo from around the exhaust pipe. It has a crush washer in there that's supposed to smash when the two bolts in the flange are tightened up. If your flange is up against the cylinder and doesn't have a gap between the flange and cylinder it can leak. Take the 2 bolts out of the flange and screw the flange down so there is a gap between it and the cylinder and put the bolts back in, don't strip the aluminum threads or you will have to put in a heli-coil.

[ConnerVT]

By the way Conner, that's looking really clean! Nice job!

Thanks, but that one isn't mine. It's a borrowed photo from elsewhere on the forum.

Mine only has two connecting rods.

T500 bottom casy Assy.jpg

[cl4yd0h]

I know exactly what noise you are talking about, and mine makes it.

[tz375]

It sounds like surging that big two strokes have when they decelerate lightly. The fix is the air jet mode that richens up the slow speed circuit on decceleration

[pearljam724]

The leak very well could be exhaust gaskets. Both my 550 and 750 had leaked in the same exact place. However, with the 550 ( actually the bike I showed pictures of ) I dabbed a small amount of Ultra Grey Gasket Sealant where I suspected the leak to be coming from and it hasn't leaked since. The 750 however is leaking a lot in the same exact location. With that bike I was unaware that there is suppose to be a gab between the collar and the cylinder head. I tighted that collar above the leak, against the cylinder. So, if a gap is needed. That very well may be the cause of the leak. But, it leaks no where near the collar. And it leaked before I tightened it. If ridden hard enough the front side of the timing cover is covered in oil. Like it's coming from the same place as the 550. In between the crankcase halves. There is no mistake about the gluck, gluck, gluck sound. I'll have to record it on my GoPro so you all have a better understanding what noise I am referring to. Thank you, guys.

[pearljam724]

I know exactly what noise you are talking about, and mine makes it.

I'm thinking it's characteristic of these models. Maybe some guys have never noticed it ? Or I am not describing the sound well ? Or maybe I'm wrong that it is not characteristic and I am beginning to have a problem. I just would like to clear that up with guys that have been around these bikes for a long time. Which I have not.

[pearljam724]

It sounds like surging that big two strokes have when they decelerate lightly. The fix is the air jet mode that richens up the slow speed circuit on deceleration

Which I've read about. So, after air jet is changed. The sound I am describing disappears ? My bike doesn't surge that much. Seldom, but it does. Where as the " gluck " sound is always consistent at lower speeds and engine braking.

[Suzukidave]

What could be happening is the exhaust collar is not correctly set , the collars turn on the exhaust pipe so they can be adjusted so there is a gap between the collar and the cylinder http://www.oldjapanesebikes.com/mraxl_G ... /sr73.html" onclick="window.open(this.href);return false; this is so the gasket between the pipe and the cylinder is slightly crushed sealing it up .