Diff temperature

[Epping]

After searching for related posts, I could find no mention of the very high diff temperature I have. After only 10km, the diff is hot but after an extended ride, forget about holding a hand against it. You could fry an egg. I recall seeing posts with photos of leaking diff seals after extended off road rides. Related posts do mention concern about water entry after deep water crossings. I expect a rapid internal pressure drop from this extremely hi temperature would suck in water if the seals were not perfect. As a comparison, on the same ride last week end, a GS1200 diff was only half the temperature. Any thoughts?

 

[Checkswrecks]

We've had the same discussion a couple of times on the FJR forum. Recounting them, the long story short is to make sure your rear brake is not dragging, make sure the differential is full of lube, and ride on.


With respect to the brake, there is a "proper torque" but the point is to make sure not to tighten the bolts at each end of the drag link so tight that they prevent the link from being able to pivot at each end.


Nobody's been known to have a problem with a Yamaha or Star cruiser bike rear that has had oil and we forget that the quantity of their bikes collectively is a lot more than what BMW has delivered over the last 20 years.

 

[Tremor38]

After searching for related posts, I could find no mention of the very high diff temperature I have. After only 10km, the diff is hot but after an extended ride, forget about holding a hand against it. You could fry an egg. I recall seeing posts with photos of leaking diff seals after extended off road rides. Related posts do mention concern about water entry after deep water crossings. I expect a rapid internal pressure drop from this extremely hi temperature would suck in water if the seals were not perfect. As a comparison, on the same ride last week end, a GS1200 diff was only half the temperature. Any thoughts?

I generally don't regard hot differentials as a problem. That said, I don't remember mine ever getting that hot, though I don't obsess with checking it. I'll have to pay more attention to it when riding season opens again. Might even bring the handy dandy IR thermometer to post some data for more objective comparision.

 

[EricV]

Its not a problem. But I understand your concern. As the others have said, we have a very high quality assembly there with the diff and it has a strong history of zero issues.

However, if it still bothers you, do what a lot of riders before you have done and simply change out the fluid for some Valvoline SYNpower full synthetic 75W-90 gear oil. This oil meets and exceeds the Yamaha specs for the diff fluid and is less expensive than the Yamaha High Speed diff fluid, plus it runs noticeably cooler.

I ran this for the 162k miles I had my FJR and have it in the S10 now for the last 10k or so. The fluid change interval on the S10 is 16k miles, (US spec), but I typically change it every engine oil change for the first 4-5 intervals and have found it to start coming out clean after a few changes. Easy and cheap to do. Most auto parts stores will carry the Valvoline. IIRC, I got the last bottle at NAPA or Autozone.

Hope that helps!

 

[Maybert]

Its not a problem. But I understand your concern. As the others have said, we have a very high quality assembly there with the diff and it has a strong history of zero issues.

However, if it still bothers you, do what a lot of riders before you have done and simply change out the fluid for some Valvoline SYNpower full synthetic 75W-90 gear oil. This oil meets and exceeds the Yamaha specs for the diff fluid and is less expensive than the Yamaha High Speed diff fluid, plus it runs noticeably cooler.

I ran this for the 162k miles I had my FJR and have it in the S10 now for the last 10k or so. The fluid change interval on the S10 is 16k miles, (US spec), but I typically change it every engine oil change for the first 4-5 intervals and have found it to start coming out clean after a few changes. Easy and cheap to do. Most auto parts stores will carry the Valvoline. IIRC, I got the last bottle at NAPA or Autozone.

Hope that helps!

+1

The tuner that dyno'd my bike had recently done a 2009 Concours and noticed the "fry an egg" temp on the final drive. I cannot recall the exact temps he quoted (I was there for MY dyno) but he said the IR thermometer measured about half that temp after changing the final drive oil with Motul synthetic.

I for one have no worries about the final drive... any company that build one for the Vmax has my vote of confidence

 

[Epping]

change out the fluid for some Valvoline SYNpower full synthetic 75W-90 gear oil. This oil meets and exceeds the Yamaha specs for the diff fluid and is less expensive than the Yamaha High Speed diff fluid, plus it runs noticeably cooler. Hope that helps!

Thanks Maybert & EricV. I will do as suggested. It does not really worry me. I was just surprised at the high temperature & reckon cooler is better. Guess that's why some cars run diff coolers.