GT500 oil leak.

GT500Andy · Post by **GT500Andy** » Fri Nov 06, 2009 10:31 am

Hi I've now made the photos public. Sorry for that I’m new at this

rngdng · Post by **rngdng** » Fri Nov 06, 2009 12:34 pm

Well, I must admit that seeing those pictures almost gave me an organism! What a beautiful bottom end! Too bad it leaks a little.

Lane

Post by **Suzsmokeyallan** » Fri Nov 06, 2009 4:20 pm

The early T500 engines used brass inserts for the bearing holders instead of the steel ones. It would stand to reason the softer brass will be more forgiving than the later steel versions.
Thanks for the tip about the edge around the oil feed holes Stu, its obviously an issue on some engine cases.

bikegeezer · Post by **bikegeezer** » Fri Nov 06, 2009 8:10 pm

Suzsmokeyallan wrote:The early T500 engines used brass inserts for the bearing holders instead of the steel ones. It would stand to reason the softer brass will be more forgiving than the later steel versions.
Thanks for the tip about the edge around the oil feed holes Stu, its obviously an issue on some engine cases.

Understand, I'm not claiming that Andy has the same problem I had. But those pictures of his leak look exactly like mine did. I was in the process of assembling the engine for the third time when my finger caught some roughness on that bearing. A happy accident.

Stu

GT500Andy · Post by **GT500Andy** » Sat Nov 07, 2009 10:05 am

Hi just finished the pressure and vacuum test. Result: leaking between ignition side bearing and the lower casing at 12 o’clock just like you said Stu. You could hear it hissing must be in the area of the dowel pin? Going to strip down the engine and do a good investigation
Many thanks for your input
Andy

Post by **Suzsmokeyallan** » Sat Nov 07, 2009 12:41 pm

Andy before you touch the section where the leak is can you post some close up pics so we can see how the area looks..

GT500Andy · Post by **GT500Andy** » Sat Nov 07, 2009 1:00 pm

I've made a film of the leak its blowing bubbles. how can I upload it?

tz375 · Post by **tz375** » Sat Nov 07, 2009 3:04 pm

As I suggested earlier, there's a possibility that the bearing is sitting high on the locating pin. It's worth trying a feeler gauge between the bearing outer sleeve and the crankcase to measure the gap there.

bikegeezer · Post by **bikegeezer** » Sat Nov 07, 2009 4:04 pm

tz375 wrote:As I suggested earlier, there's a possibility that the bearing is sitting high on the locating pin. It's worth trying a feeler gauge between the bearing outer sleeve and the crankcase to measure the gap there.

The leak is at the top. The locating pin is on the bottom. I realize the picture makes it appear it's leaking at the bottom, but it's just running around the OD of the bearing and puddling at the bottom.

Stu

Post by **Suzsmokeyallan** » Sat Nov 07, 2009 5:04 pm

Heres a photo of what the top case half on the left side looks like.

tz375 · Post by **tz375** » Sat Nov 07, 2009 6:18 pm

If the leak is from the top then that issue is not because of the pin. A longer than stock pin or a pin that isn't fully seated will lift the whole bearing (and sleeve) and push it hard against the bearing saddle in the upper case half.

There are a few conditions that would result in a leak at teh top.

Bearing OD smaller than the saddle diameter

Bearing OD larger than the saddle so that it cannot seat correctly

Raised metal holding the bearing off the surface

Gouges in the saddle allowing oil to pass out.

There's probably more that don't come to mind, like the crankcase expanding away from the steel bearing when teh motor gets hot.

The motor needs to be stripped and inspected. I like Stu's idea of using fingers to feel for rough spots. Fingers can detect surface imperfections of less than 1 thousandth of an inch.

I'd start by cleaning the case halves and inspecting the joining surfaces. I'd countersink all the stud/bolt holes and use a clean new fine file to cross file the mating surfaces gently to identify and remove any high spots.

You can use bearing blue to see how well the case halves mate.

Then I'd smear some bearing blue on the main bearings and lightly assemble the cases with the crank in place. Strip it again and look at the blue to see where the bearings are contacting the saddles.

When you are happy with all the above, use new O rings around the bearing outer sleeves and reassemble with a smear of Hylomar on the case halves.

When you slip the new O rings onto those bearing outers, check that they are proud of the surface. It is quite possible that they were re-machined to take a thicker O ring and stock rings may be too thin to seal.

bikegeezer · Post by **bikegeezer** » Sat Nov 07, 2009 8:17 pm

TZ,
You may have been right on in your previous post. I watched Andy's video. Turns out the leak is at 6 0'clock, not 12, and it's quite a bad leak. We can take guesses all night long, but a strip and careful inspection is the only way to reveal the cause. I like your idea of deburring all holes, and I'd even pull the knock pins to do those holes as well.

Stu

tz375 · Post by **tz375** » Sat Nov 07, 2009 9:50 pm

Stu,

I agree 100% about the need to strip clan and inspect. Before it comes apart, it might be an idea to slip a feeler gauge in to the gap between the bearing and teh case to get an idea of the thickness of the gap.

It sounds like it is only a few thou, and it would be hard to measure the height of the pin versus the depth of the hole in the bearing, but that looks like it could be an issue.

bikegeezer · Post by **bikegeezer** » Sun Nov 08, 2009 7:55 am

tz375 wrote:Stu,

I agree 100% about the need to strip clan and inspect. Before it comes apart, it might be an idea to slip a feeler gauge in to the gap between the bearing and teh case to get an idea of the thickness of the gap.

It sounds like it is only a few thou, and it would be hard to measure the height of the pin versus the depth of the hole in the bearing, but that looks like it could be an issue.

Andy,
If you can slip a feeler of any thickness between the bearing and case, then I'd say you have a major issue. I have a couple of spare cases here with pins that I could measure the pin and hole if you need dimensions.

Stu

GT500Andy · Post by **GT500Andy** » Sun Nov 08, 2009 10:48 am

I've tried to get a feeler gauge in there but it doesn’t fit .0015 thou. The smallest that I have got.
Andy