?? much metal ok in gear oil?

chainsaw · Post by **chainsaw** » Tue Aug 18, 2009 6:36 pm

So, when you change gear oil, there has always been some presence of a few flakes of metal in the oil. Dont know if all GTs have a magnet on the oil drain plug but mine does. It had a bit of metal on it as well as the bottom of my drain pan after I cleaned it up.

How much is too much?

Coyote · Post by **Coyote** » Tue Aug 18, 2009 6:55 pm

I think any at all is too much ---- BUT--- if your clutch is working okay and she shifts just fine, I wouldn.t worry about it. Seems they all produce some. Only if the tranny is extremely noisey would I give it a second thought.

chainsaw · Post by **chainsaw** » Tue Aug 18, 2009 7:06 pm

well therin lies my problem. It is hard to shif from 3rd to 4th. It has gotten a little better over the 177 miles I have put on it but still is not like the other gears.

what could it be? how to fix? how much harm riding as is for a while?

rbond · Post by **rbond** » Tue Aug 18, 2009 7:25 pm

A little is expected from new for two or three oil changes. But from what you describe, PULL that engine and take it apart. Don't want to sound alarmist, but it sounds like some major parts are self destructing in there and needs attention right now before it gets worse and more expensive. Even if it turns out minor (?), better to really KNOW what the problem is and that it is fixed.

Coyote · Post by **Coyote** » Tue Aug 18, 2009 7:47 pm

Sounds like that might be a bent, distorted or badly worn shifting fork. Japanese trannys are sort of a masterpiece in engineering. When working correctly, the clutch is really not necessary after second gear on acceleration by just playing the throttle. I almost never use it past third.
A few sparkles in the oil is normal. Heavy deposits are not. Sorry but this means splitting the cases to address the problem.

chainsaw · Post by **chainsaw** » Tue Aug 18, 2009 9:07 pm

I guess it will have to wait as I am/was trying to sell it. Not to mention, I suck at engine rebuilds. If I go as far as pulling it all apart, I might as well plan on new pistons shouldnt I?

There is a guy close to me that has 5 or 6 GTs. He may be my best bet to try and do this on the cheap. I may approach him and see if he will "ASSIST" me (more like me assist him) and help me through this. I couldnt really sell the bike knowing it has a bad tranny.

NOT a good thing to hear while out of a job

tz375 · Post by **tz375** » Tue Aug 18, 2009 10:54 pm

Chainsaw,

If possible, post a few pics of the flakes, preferably with the drain bolt in the picture so we can gauge how much is there.

One could argue that anything above zero flakes is too much, but many trans shed some metallic sparkles. The question is how much is yours shedding and if you change the trans oil, is it just as bad after another say 50 - 100 miles?

What has been done to the bike during your ownership? It's possible that the flakes are old and have been dislodged by you changing the oil ( I'm always an optimist.

I'd drain the oil and try to flush it through with flushing oil - a mix of kerosene and highly detergent oil - light load only though. Drain that, repeat and see if comes clean. Then clean good oil for a 50-100 mile run and drain again. If the flakes are back there is 100% probability there is a trans problem.

By the time a trans makes a lot of noise it is often far too late. Fortunately there's lots of old GT750's around, so there's lots of tans available.

chainsaw · Post by **chainsaw** » Wed Aug 19, 2009 6:40 am

too late for pics. the tranny makes no noises. it is fairly quiet when just cruising. The difficulty of my shifting problem is not always constant. Sometimes a bit easier to go from 3rd to 4th and sometimes its a booger to get it in there. Eric said he put in 80wt oil when he did the change before I picked it up from him. I put in 20/50 but have not had a chance to ride it yet to see if that makes any difference.

I may do as you suggest and go another 150 miles then redrain to see what the metal conteny may be.

so how long does it take to pull motor, split and put back in bike usually?

Post by **oldjapanesebikes** » Wed Aug 19, 2009 8:43 am

chainsaw wrote: so how long does it take to pull motor, split and put back in bike usually?

That's a bit like asking 'how long is a piece of string ?'

It all depends on what you find, and whether you have absolutely everything you need to put it back together on hand. With no problems, a weekend should cover it.

chainsaw wrote:Eric said he put in 80wt oil when he did the change before I picked it up from him. I put in 20/50

A the risk of starting an oil discussion

, I think SAE 80 grade oil would have been gear oil, which is about the same viscosity as SAE 20 or 30 weight engine oil, so 20w50 would be about the same once its warm.

tz375 · Post by **tz375** » Wed Aug 19, 2009 1:45 pm

Err. Not exactly. But a 20W50 motor oil may help to clean out the garbage. It really is not ideal for a transmission, but for a short distance without excessive load should be fine (given the suspicion that there may be a problem)

Lots of people use Auto oil and have no problems, I just don't happen to be one of them.

chainsaw · Post by **chainsaw** » Wed Aug 19, 2009 3:34 pm

tz375 wrote:Err. Not exactly. But a 20W50 motor oil may help to clean out the garbage. It really is not ideal for a transmission, but for a short distance without excessive load should be fine (given the suspicion that there may be a problem)

Lots of people use Auto oil and have no problems, I just don't happen to be one of them.

isnt that what is reccomended in the manual? I thought thats what I read!

Post by **oldjapanesebikes** » Wed Aug 19, 2009 4:22 pm

tz375 wrote:Err. Not exactly. But a 20W50 motor oil may help to clean out the garbage. It really is not ideal for a transmission, but for a short distance without excessive load should be fine (given the suspicion that there may be a problem)

Err - actually pretty close. SAE uses different grading systems for motor and gear oil as the formulations are quite different

The original manual actually calls for 20W40, but later was changed to 20W50 motor oil - see page 12 here. Of course, there are other things you can use depending on the service you put the engine in - racing would differ from pleasure riding. As its a topic that always seems to generate lots of comment

there is a special thread on the board for 'oil'

Chainsaw - I've always used 20W50 motor oil, and its been fine.

tz375 · Post by **tz375** » Wed Aug 19, 2009 5:37 pm

Ian, good point, but Viscosity is but one of several factors to be considered in choosing an oil.

The first is suitability for purpose. a general purpose automotive oil may be OK most of the time for many people and generally it's not a bad oil.

Back in the day, that's basically all that was available other than straight 50wt which was too thick. But since the seventies oils have come a long way.

Most motorcycle two stroke specific oils have an additive package designed to work in a transmission and do not have Molybdenum Disulphide which can make some clutches slip.

Most automotive oils have a lot of detergents which we don't need in a trans and they have those pesky long chain polymers to make everything slippy - including clutch plates.

Sometimes people get away with general purpose oils and sometimes they don't. The more "gentle" the rider the more likely they can use any oil they want from Crisco on up.

As has been said many times, almost any oil today is better than most oil back in the day. And that's true in some aspects, but the best oil to use in a 2 stroke transmission is the one I use....

I personally would recommend a 2 stroke specific oil and the one I use for street bikes is Honda's oil for their CR motocrossers. Good oil at a cheap enough price point.

For racing I use Motul or Silkolene. They cost more but they can carry higher shear loads and have lower wear under extreme conditions than cheap oils.

But that is just my opinion. Yours may vary.

chainsaw · Post by **chainsaw** » Wed Aug 19, 2009 6:47 pm

UPDATE:

ok, so I contacted my local gt guy and he has made me an offer I almost cannot refuse. He has a spare motor with a known top end problem/ like getting the jugs off. He is going to front me the motor, which he said I can pay him at a later date after I get a job, so I can then swap out my top end and put it on his known good lower end. No case splitting, no big unknow expense which I could not do anyhow.

his motor is off a 74 model. mine is a 76. any issues there?

Now I have to be honest here, I have never done a top end on a multicylinder bike. I did a topend once, many years ago on my dt 250 enduro bike and thats it. So, needless to say, I have zero confidence I can do this correctly or efficiently. nor do I have all the correct tools to do this with.

So, anyone close to ga that might be able to help a fellow 2 stroker out of a huge jamb? All I could do right now is make a promise to make it up to you in the future and maybe buy a few beverages for you! any suggestions or ideas? I may just be screwed for now and have to wait for better times.

Post by **oldjapanesebikes** » Wed Aug 19, 2009 9:01 pm

tz375 wrote: But that is just my opinion. Yours may vary.

Yep !