Leaking Crank Seals

[jandyb]

Hi

The other topic touched the question, but i thought I would make a new one..

The crank seals on my 04 Pro 300 is probably leaking on both sides. First symptom was tha the piston was knocking heavily. My local dealer said the reason was that the engine runs lean. Since the carb is clean and jetted as it shoud, the reeds are OK he ment that it was taking in air through the crank seal. I momentarily solved that when I fitted a bigger jet and raised the needle maximum.

Now it has begun to smoke some more, and the smoke smells nothing like strawberries (uses IPONE "strawberry oil". Smells like strawberries - goes like s*h*i*t )and the gear oil slowly dissapears.

The question is wether this is dangerous for the engine? Should I fix it now in the middle of the season, or can I wait till the season end in oktober?

Thanks

-Jan

Edited July 7, 2008 by JanDyb

[mikee]

Yep take your engine out and get them done...

I did my main bearing and crank seals a month ago. Not a big job. Parts where not too bad and came next day from gas gas UK.

Took about half a day and a few cups of tea.

[jse]

Hi

The other topic touched the question, but i thought I would make a new one..

The crank seals on my 04 Pro 300 is probably leaking on both sides. First symptom was tha the piston was knocking heavily. My local dealer said the reason was that the engine runs lean. Since the carb is clean and jetted as it shoud, the reeds are OK he ment that it was taking in air through the crank seal. I momentarily solved that when I fitted a bigger jet and raised the needle maximum.

Now it has begun to smoke some more, and the smoke smells nothing like strawberries (uses IPONE "strawberry oil". Smells like strawberries - goes like s*h*i*t )and the gear oil slowly dissapears.

The question is wether this is dangerous for the engine? Should I fix it now in the middle of the season, or can I wait till the season end in oktober?

Thanks

-Jan

Jan,

I think that maybe the dealer was incorrect in the diagnosis. The Pro will not likely run "lean" if the crank seals are leaking as the inside seals are not exposed to "outside" air, but to transmission fluid on both sides. The knocking is probably a buildup of carbon in the combustion chamber caused by incomplete burning of the tranny fluid, thus raising the secondary compression ratio beyond the octane rating of the fuel and causing the "plinking", as the English say.

I'd fix it as soon as possible as it will only get progressively worse and a reduction of lubricating fluid in any transmission is dangerous, especially in the Pro as the crank bearings are also lubricated by the same fluid.

Jon

[jandyb]

Jan,

I think that maybe the dealer was incorrect in the diagnosis. The Pro will not likely run "lean" if the crank seals are leaking as the inside seals are not exposed to "outside" air, but to transmission fluid on both sides. The knocking is probably a buildup of carbon in the combustion chamber caused by incomplete burning of the tranny fluid, thus raising the secondary compression ratio beyond the octane rating of the fuel and causing the "plinking", as the English say.

I'd fix it as soon as possible as it will only get progressively worse and a reduction of lubricating fluid in any transmission is dangerous, especially in the Pro as the crank bearings are also lubricated by the same fluid.

Jon

Thanks

(By the way: I used the word "momentarly". I did mean "temporary" of course.. )

I also thought that was strange but took his word. The knocking (or plinking) also stopped after fitting bigger jet and raising the needle. Would this help if it is like you say?

Anyway I guess I should fix it soon. Problem now is that the dealer (theres only one in Norway) doesn`t have the parts yet..

-Jan

[jse]

Thanks

(By the way: I used the word "momentarly". I did mean "temporary" of course.. )

I also thought that was strange but took his word. The knocking (or plinking) also stopped after fitting bigger jet and raising the needle. Would this help if it is like you say?

Anyway I guess I should fix it soon. Problem now is that the dealer (theres only one in Norway) doesn`t have the parts yet..

-Jan

Jan,

Clint Eastwood, in one of his "Dirty Harry" films had a famous phrase that seems to apply here, "Well, how lucky do you feel?"

Keeping the fluids up could buy you a little time and quite possibly no engine damage, but, in reality, Trials engines are built for competition and in competition we often push them more than we mean to, so given the choice, I'd opt to fix the problem as soon as you can just to be safe.

The bigger jet and needle adjustment (by lowering combustion chamber temp and modifying flame front behavior) would address the symptom, but not the disease, if it is, in fact, carbon build-up and it would still be there.

Let us know what you find. We're all just making educated/experienced guesses based on words on a computer screen, so any feedback will help us in the future. If it's your first time inside a Pro engine, you'll find it very interesting....

Cheers and good luck!

Jon

[jandyb]

Jan,

Clint Eastwood, in one of his "Dirty Harry" films had a famous phrase that seems to apply here, "Well, how lucky do you feel?"

Keeping the fluids up could buy you a little time and quite possibly no engine damage, but, in reality, Trials engines are built for competition and in competition we often push them more than we mean to, so given the choice, I'd opt to fix the problem as soon as you can just to be safe.

The bigger jet and needle adjustment (by lowering combustion chamber temp and modifying flame front behavior) would address the symptom, but not the disease, if it is, in fact, carbon build-up and it would still be there.

Let us know what you find. We're all just making educated/experienced guesses based on words on a computer screen, so any feedback will help us in the future. If it's your first time inside a Pro engine, you'll find it very interesting....

Cheers and good luck!

Jon

Thanks again! I think I need it...

Must say that the gear oil is disapearing very slowly (yet) and I am keeping an eye on it...

In the mean while should/can the combustion chamber be cleaned in any way to get rid of the carbone? (again of course it does not fix the disease)

And an other thing: The engine is always running very hot. Only after a short time from cold start - between 30 sec and a min I think - the fan comes on and mostly stays on the whole ride. Is this normal for a 300? I think the thermostat is functioning as the fan don`t start until the engine is hot.

If this isn`t normal can this also be a symptom of the same disease? Or anything else? (The radiator is containing coolant, and the water pump is functioning.)

-Jan

[peterb]

Hi Jan,

It is normal for the PRO fan to switch on soon after start up, and then on/off very frequently.

I use 100% anti-freeze as the coolant which has a higher boiling point than 50/50 anti freeze/water mix.

If the LHS (mag side) crank shaft inner oil seal has worn then it will definately draw in gearbox oil to the combustion chamber and there is a chance that slugs of air could also be drawn in via the gearbox - just guessing there as the oil usually finds its way to the LHS crank bearing by capillary action, now being exposed to a partial vacuum may draw in air.

You really need new head O ring seals when you strip the motor, and a crankcase and clutch gasket.

You can use either the older style main bearings (6205 C3 or C4 extra clearence) with separate seals, or the later combination bearings with integral seals. On the mag side, there are two oil seals, an internal one and a teflon outer seal.

The motor's do not usually run very hot, if your fan is on all the time (more or less) then is the fan blowing strongly, a bit like a hair drier blast? If not then the fan may be faulty.

The English word for pre-detonation is "pinking" - and I don't know why!

Bye, PeterB.

[jse]

Hi Jan,

It is normal for the PRO fan to switch on soon after start up, and then on/off very frequently.

I use 100% anti-freeze as the coolant which has a higher boiling point than 50/50 anti freeze/water mix.

If the LHS (mag side) crank shaft inner oil seal has worn then it will definately draw in gearbox oil to the combustion chamber and there is a chance that slugs of air could also be drawn in via the gearbox - just guessing there as the oil usually finds its way to the LHS crank bearing by capillary action, now being exposed to a partial vacuum may draw in air.

You really need new head O ring seals when you strip the motor, and a crankcase and clutch gasket.

You can use either the older style main bearings (6205 C3 or C4 extra clearence) with separate seals, or the later combination bearings with integral seals. On the mag side, there are two oil seals, an internal one and a teflon outer seal.

The motor's do not usually run very hot, if your fan is on all the time (more or less) then is the fan blowing strongly, a bit like a hair drier blast? If not then the fan may be faulty.

The English word for pre-detonation is "pinking" - and I don't know why!

Bye, PeterB.

Peter has a valid point and I could see where the aerated trans fluid might skew the air/fuel ratio. My Pro fan cycles on fairly constantly on warm/hot days and there have never been signs of engine overheating, so I'm assuming your condition is normal. As Peter says, the fan should blow fairly strongly and you'll hear it with a helmet on.

"pinking", ah, yes, my internal spellcheck was on the fritz. Here in the States we call it "pinging", supposedly an "onomatopoeia", words that sound like what they are describing, but "ping" is not what it really sounds like to me. I guess it's a cultural/language thing. A friend in Japan assures me that cats absolutely do not "meow" in Japan, they do, however, "murr".......

Jon

[jandyb]

Peter has a valid point and I could see where the aerated trans fluid might skew the air/fuel ratio. My Pro fan cycles on fairly constantly on warm/hot days and there have never been signs of engine overheating, so I'm assuming your condition is normal. As Peter says, the fan should blow fairly strongly and you'll hear it with a helmet on.

"pinking", ah, yes, my internal spellcheck was on the fritz. Here in the States we call it "pinging", supposedly an "onomatopoeia", words that sound like what they are describing, but "ping" is not what it really sounds like to me. I guess it's a cultural/language thing. A friend in Japan assures me that cats absolutely do not "meow" in Japan, they do, however, "murr".......

Jon

Me and my lad has had 4 Pro`s over the last year and the fan on my 300 seems similar to the others - exept the fact that when it first comes on it runs all the time. I wonder if the 300 are running a bit hoter than the rest of the models. When I had my cylinder off I noticed that the cylinder walls seem thinner due to the larger bore and then smaller space for coolant? There must also be a reason that all 300`s I have seen has mounted a heat sheald on the exhaust manifoil...

Some language issue: In norway we call it "Skj

[jandyb]

Could anyone help me with a complete part list for the parts I need before I "take a dive" into the unknown (=pro engine)?

Other things I should examine or change while it is open?

Thanks

-Jan

[jse]

Could anyone help me with a complete part list for the parts I need before I "take a dive" into the unknown (=pro engine)?

Other things I should examine or change while it is open?

Thanks

-Jan

Since ordering individual assembly parts may be difficult for you under your current dealer circumstances, it may be easier to get a complete gasket kit (part # MT280244100, I think) and that would give you all the gaskets, washers and o-rings you would need.

PeterB listed the bearings/seals possibilities and http://d-mis-web.ana.bris.ac.uk/personal/H...f/media/gasgas/ is access to the on-line video service manuals that were made here in the U.S., which you will want to review several times so that things will look familiar when you open up the engine. There are several little tricks you will need to know upon assembly, like rotating the kickstart shaft a little for the gear to clear the nylon stop so the upper shell will drop on etc. but these should be covered in the video.

The rest will be "standard" inspection and measurement, like ring end gap to assess ring wear or inspecting the gear tooth faces and exposed bearings to look for any galling or pitting, but if you find any problems and have a digital camera, you can post photos for opinions.

Jon

[jandyb]

Hello again..

Finally I have managed to get some parts for this job. I have got one small seal, two larger ones and the center gasket. I addition there should be (two?) O-rings that he still hasn`t got from GasGas. Could this be the ones with part number MT280212025?

In the part list the measurement of these O-rings say 25x1,5mm. If I manage to find O-rings with these measures in other places can I use them?

Last the videos are very spesific on how to disassemble and assemble the engine, but they don`t say anything about the crank. Am I missing a part of the videos, or is it because the crank bit is so straight forward that it is not neceserry to show?

I`d also like to put in a language question in this posting too: I have noticed that some of You use "motor" and others use "engine". How come?

Thanks

-Jan

[jandyb]

Hello again..

Finally I have managed to get some parts for this job. I have got one small seal, two larger ones and the center gasket. I addition there should be (two?) O-rings that he still hasn`t got from GasGas. Could this be the ones with part number MT280212025?

In the part list the measurement of these O-rings say 25x1,5mm. If I manage to find O-rings with these measures in other places can I use them?

New question:

The two O-rings mentioned before is in the part list for 2004. In the part list for 2008 there is another two O-rings with measurment 49x1,5 mm. Can, should or should I not use those in my 2004 model?

-Jan