Hoosier "Cobra" project begins; yes...another T500!!

I was able to tear down the engine yesterday... The heads came off no problem and the pistons/cylinders looked to be in good shape!

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It took a while to get the rest of it apart. The biggest struggle was the engine case, but a few taps with a rubber mallet helped. Here are a few pics of the process...

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Here you can see the crack in the top half of the engine case (which is upside down on this pic)...

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I don't have pics, but was able to seperate the case halves, remove all the tranny gears (which looked to be in good shape), and remove the crankshaft assembly. Everything was bagged in an orderly fashion.

I stripped two screws that held a small bracket. I tried to drill them out and remove them with a extraction device, but that broke too! So I had to bring the bottom half of the case to a mechanic friend who is going to extract those screws for me. Hope to have it back tomorrow or Friday. I also brought the top half of the case to a guy who can fix the crack for me. Sorry, no more pics right now.

As soon as I have the parts back, and progress continues, I will update... cheers!
 
I'm guessing that crack was caused by the chain somehow. Doesn't look to be a big issue.
 
Yea, I think the chain must have broken loose and done some damage. You'll also notice some bent screws in that pic, that used to hold a neutral switch cover. It was in pieces when I removed the sprocket cover. The crack involves the top flange that only serves as a location that the sprocket cover bolts to. But, since I had it all apart, I figured I would have it fixed.
 
That's pretty typical broken chain damage......chain snaps, and bunches up round the sprocket, bursting out and taking the neutral lamp switch with it........I had a chain let go on a Gixer 11 one time, I was doing about 100mph at the time, when there was a big slap on my back, followed by a lack of drive. Coasted to a halt to find the chain dangling over the nearside rear indicator, and a big oily line down my back where the chain had hit me. On inspection, it had bunched like your one, and fractured the case very slightly before breaking free and hitting me!

The piston top looks spotless? Or did you clean it?
 
Titan performance said:
I had a chain let go on a Gixer 11 one time, I was doing about 100mph at the time, when there was a big slap on my back, followed by a lack of drive. Coasted to a halt to find the chain dangling over the nearside rear indicator, and a big oily line down my back where the chain had hit me. On inspection, it had bunched like your one, and fractured the case very slightly before breaking free and hitting me!
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OUCH! :eek:

Titan performance said:
The piston top looks spotless? Or did you clean it?
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What you see is how I found it. I think someone had the engine apart to do the oil modification, cleaned everything, put it back together and let it sit. I was surprised at how nice it was inside. Some fine metal shavings were laying in the bottom, but altogether not too bad. I'm having the crack welded at the moment, so not much to report...
 
CobraRad said:
Thanks all... :)

Someone has been in there before, the gearbox oil modification has already been done!
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What is the gearbox oil mod? I am just stripping my engine so if there is a suggested modification I'd like to do that while it's apart.
 
The gearbox oil mod increases oil capacity to prevent gear damage due to oil starvation. Later model T500's had this done from the factory, earlier Titans should have the mod done. My '75 already has the increased capacity so I haven't looked at the particulars of doing it but I believe it involves adding a small oil dam inside the crankcase.
 
Here is a pic if the oil dam mod with a Suzuki part installed. No longer available I think, but you could make one.

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Ok thanks. My engine is a 75 GT500 so I assume it will have the mod. I will check it when I get it apart.
 
Still waiting for the crack repair to be finished... In the meantime, I was able to clean up the bottom half of the case. In these pics you can see the oil mod. It was done with a piece of aluminum from some food packaging (you can see part of a nutritional label on it).

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I then repainted the engine parts, following the advise of wingspan and others on the forum (Thanks guys!!).

I first started with Rustoleum high-heat "aluminum" but it turned out very grey.

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So I went with the duplicolor "cast coat aluminum" and they turned out much better!

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The cylinders had previously been painted black, so I cleaned em, scuffed em, taped em, and resprayed.

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Today I spend inspecting the engine/transmission parts. I'm happy to report that everything is in really good shape. I cleaned things up a bit, and am now just waiting for the top half of the case to be repaired. Then the engine goes back together.

In the meantime, I took some more measurements to find a seat that will work with my original tank.
 
Wasn't going to... Here's a newbie question...how do I tell if the crank seals need to be replaced, or if the crankshaft needs to be rebuilt? I have been pleasantly surprised at how this thing looks on the inside. Everything looks like new. The pistons have virtually no wear or carbon build up. There is no rust or wear on the cylinders, the rings look new. All the transmission parts are clean and in great shape. Also, before the teardown, both cylinders had good compression.

Wingspan said:
Are you replacing the crank seals?
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Typically the crank seals are tested by vacuum or pressure testing them with the engine assembled.

o
 
When I raced 2strokes we changed crank seals after every other meet. If they have been in there a while they really should be changed. I imagine the seals are relatively cheap so why not do it since you have the engine apart?
That silver paint looks really good btw, I am going to buy some today for my engine.
 
Wow, that bike is awesome! I know what I am getting for my next project, haha. Great work, keep it up.


JR
 
johnu said:
When I raced 2strokes we changed crank seals after every other meet. If they have been in there a while they really should be changed. I imagine the seals are relatively cheap so why not do it since you have the engine apart?
That silver paint looks really good btw, I am going to buy some today for my engine.
Click to expand...

FWIW, I have roughly $40 in seals and $125 labor in my rebuilt crank, plus another $40 or so in shipping costs.
 
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