not to beat this chaincase thing to death but...

[welterracer]

Ive got 2200 miles on my sled.. Ran sled WFO for miles on end racing my buddys and i have no problems..

HERE IS MY THERIORY... it could be that condensation has frozen inside the chain case of some of the sleds blocking the vent and causing the seal to blow out..

 

[YammiMoose]

Ive got 2200 miles on my sled.. Ran sled WFO for miles on end racing my buddys and i have no problems..

HERE IS MY THERIORY... it could be that condensation has frozen inside the chain case of some of the sleds blocking the vent and causing the seal to blow out..

Good idea,
But I in my case I would disagree because I also blew mine in Northern Maine coming out of Van Buren. Our sleds are always kept in a heated garage. Every morning we come out to sleds that are warm and dry. I had just checked my oil level the day before and that’s when we headed towards Portage Lake down trail 90 and had plenty of WOT while trying to loose my buddies Mach.

 

[markusvt]

Think about this, what if the excessive heat in the chaincase, (after it had no oil), caused the rubber on the dipstick to deform? Could be the dipstick was AOK until it got super hot. Have you found deformed dipsticks on sleds that were full of oil?

I myself don't like the Yamaha oil. Some kind of nasty stinky stuff, especially when hot. I changed it to a synthetic Spectro Oil I like a lot.

Markus.

87gtNOS,

Your points are well taken.

I have heard about the seal not being properly installed, and so has Yamaha.

My dealer wanted to see what happened to my brothers sled. They had seen two different scenario's.

The big question for my dealer was; Is there any oil in the chain case, or was the chain-case totally dry?

We all stood around while his mechanic pulled the chain-case.

There was residual oil in the bottom of the chain-case, therfore the conclusion was a venting problem. The dipstick deformity was also a pretty decisive clue.

Since the repair and dipstick mod, the sled has been run "rail bed" hard on numerous extended runs for another 1,554 miles without any further incident.

All said and done, where is Yamaha's quality assurance?

Never-the-less, my brother really likes his new Attak much better than his 05 MachZ.

Jerseyjoe,

It's a tough issue. This venting problem is something very different and probably very rarely seen. Just a guess.

 

[gkw]

Another good theory, but mine had leaked enough oil to have none showing on the dipstick, but there was still lots of oil (1/2 full??) in the chaincase when we took the cover off.

So it probably wasn't heat.

It also didn't seem to leaking once I had stopped for a while.

And the gasket appeared to be properly seated when we removed the cover, so there doesn't seem to be a manufacturing defect.

I am still thinking pressure. Replacing with Spectro today for one last ride next week.

GW

 

[hondo]

markusvt,

Real good point! A plausable senario.

In our case maybe the heat did deform the dipstick rubber.

Do the chain-cases come from the factory with Yamalube chain-oil, or synthetic? I don't know.

If they do come from the factory with Yamalube, Yamaha may be aware of a problem because the repaired chain-case was re-filled with full synthetic chain oil.

We even bought a bottle of synthetic to have on hand should the case need some oil.

Bottom line with the synthetic we have not had a problem. The dipstick may have needed to be re-vented due to the heat deforming it.

Thanks for taking the system analysis one step further!

 

[ROCKERDAN]

anyone think about venting the case more?..is there a way to open something up somewhere to AID in venting for high speeds/long hauls?

dan

 

[GYT-R]

I have been reading the posts about this chaincase issue and here's my .02 cents. When the chaincases have blown and been taken apart the gasket ends up leaking because the gasket is found partially routed/sucked inside the case (correct?). My question is if the dipstick is vented - isn't it vented the way it is to let pressure out of the case without letting oil get pushed out. If the grooves in the dipstick were an issue wouldn't this cause pressure to build up inside the case and either lead to the dipstick getting pushed out or the gasket getting pushed out - not sucked in like the ones in question.

 

[87gtNOS]

I have been reading the posts about this chaincase issue and here's my .02 cents. When the chaincases have blown and been taken apart the gasket ends up leaking because the gasket is found partially routed/sucked inside the case (correct?). My question is if the dipstick is vented - isn't it vented the way it is to let pressure out of the case without letting oil get pushed out. If the grooves in the dipstick were an issue wouldn't this cause pressure to build up inside the case and either lead to the dipstick getting pushed out or the gasket getting pushed out - not sucked in like the ones in question.

I'll give you 2 more cents....this is just an internet problem, not a real issue. I am sure before the internet, 1990 650 INDY's (for example) blew chaincases too.....but when they blew, there was no internet to tell the world!!!! So Paul in Wisconson blew one, George in Thunder Bay blew one, Rick in OldForge blew one...but that was it........

 

[ReX]

I'm convinced the problem is with the new magnesium chaincase and the lack of thermal conductivity of the magnesium. In all previous years, including 2005, Yamaha cast the chaincase out of Aluminum. In 2005 they moved to a magnesium chaincase cover and in 2006 they went to a fully magnesium chaincase.

The thermal conductivity of typical cast aluminum alloys is around 170 W/m.K (as high as 250 W/m.K for some). Typical magnesium alloys have a thermal conductivity in the 55-90 W/m.K.

On top of that the thermal interface between the chaincase and the tunnel will be greatly compromized because Al/Al conducts very well, yet Mg/Al conducts relatively poorly.

With 2-3 times less heat transfer (possibly worse), the chaincase oil will be running approximately 2-3 times hotter. This will thin and break down the oil, soften the seals on the shafts, and require much more airflow in/out of the chaincase (due to thermal expansion of the air inside).

The increased ventilation requirements in combination with the softened seals and thinned oil will allow the oil to be pumped through the seals and lead to a lack of oil and the following catastrophic failures that have been occuring.

Using a higher temperature rated oil (higher viscosity at high temperatures like a fully synthetic 75w140) combined with a higher temperature rated seal and increased ventilation will probably fix most of the problems, but I would prefer to install an aluminum chaincase. The difference in weight is not all that significant and well worth it for the durability of the sled IMO.

 

[ViperTurboPete]

A friend of mine with a GT obliterated his chaincase and he is always wide open at every opportunity and for long runs. Another couple of friends have GT's with no problems and are much less haywire than the other guy.

ReX, your post makes 100% sense. Great post.

 

[SledFreak]

I'm convinced the problem is with the new magnesium chaincase and the lack of thermal conductivity of the magnesium. In all previous years, including 2005, Yamaha cast the chaincase out of Aluminum. In 2005 they moved to a magnesium chaincase cover and in 2006 they went to a fully magnesium chaincase.

The thermal conductivity of typical cast aluminum alloys is around 170 W/m.K (as high as 250 W/m.K for some). Typical magnesium alloys have a thermal conductivity in the 55-90 W/m.K.

On top of that the thermal interface between the chaincase and the tunnel will be greatly compromized because Al/Al conducts very well, yet Mg/Al conducts relatively poorly.

With 2-3 times less heat transfer (possibly worse), the chaincase oil will be running approximately 2-3 times hotter. This will thin and break down the oil, soften the seals on the shafts, and require much more airflow in/out of the chaincase (due to thermal expansion of the air inside).

The increased ventilation requirements in combination with the softened seals and thinned oil will allow the oil to be pumped through the seals and lead to a lack of oil and the following catastrophic failures that have been occuring.

Using a higher temperature rated oil (higher viscosity at high temperatures like a fully synthetic 75w140) combined with a higher temperature rated seal and increased ventilation will probably fix most of the problems, but I would prefer to install an aluminum chaincase. The difference in weight is not all that significant and well worth it for the durability of the sled IMO.

I agree REX, I also believe that most of these chain cases that have blown have the wrong oil in them. (some have said that motor oil was used, go figure) Having the right amount of oil and a fully synthetic 75w140 will defintely cure alot of these issues. I have 1400miles of hard fast groomed trail riding/lake racing and I have no problem. I noticed last when I made a gear change last week, that my oil had way to much gear oil in it and it did not smell like gear oil. I know have the recommended amount of Fully synthetic 75W90 and no problems so far.

 

[King44]

It kinda sounds to me like vescosity breakdown in the oil.The smell might just simply "burnt" oil- and the cure, like some of you said,could be to use the senthetic chaincase oil.I have this smell problem too with my 04 Warrior and I'm going to try the senthetic.(I guess these Yammys are just too darn powerful!!)

 

[King44]

Did I spell "vescosity" right?

 

[FormulaPro]

Nope... viscosity.

 

[waldo1]

I have a gt and run it on long top speed runs all the time - at 1500 miles, i changed to 75 90 mobil 1 - at 1800 - blown seal and stuff - i check it all the time (because of this site - thank god) and luckly smelled that nasty smell last week in canada - filled it up on the trail with 2 stroke oil - at the first stop bought some 90 weight gear lube - had to fill er up every 60 miles - tightened the chain adjuster alot (5 turns or so) - stoped at the yame dealer in hearst - no chain, just seals and canada does not warrent us usa dudes - you have to pay (alot) and hope to get rembursed - limped it another 350 miles to finish our trip. There is a definate issue with these cases and yamaha never heard of the issue. I cant figure it out - the tred about case material difference is the only thing that makes any sence so far. Ive tried everything else (i think)