Yamaha TRX850 Enthusiasts Forum

Damping force adjusting screw on the right side has been leaking
Oil for months , have been cleaning it and sealing with gasket compound
. The other day the left side fork D F A S o ring gave way and sprayed
Oil on the inside of the screen . I have tried standard o rings with no luck .
Just got back from a 80 k ride on some crap roads after fitting
japanese size o rings number " P8 , 7.8 mm x 1.9 mm ", there is a difference
between Japanese and other metric sizes . No oil leaks and forks finally working
as a pair . Now i'm a happy chappy .
P8 , 7.8 x 1.9 . Hope this helps

Dino wrote:Damping force adjusting screw on the right side has been leaking
Oil for months , have been cleaning it and sealing with gasket compound
. The other day the left side fork D F A S o ring gave way and sprayed
Oil on the inside of the screen . I have tried standard o rings with no luck .
Just got back from a 80 k ride on some crap roads after fitting
japanese size o rings number " P8 , 7.8 mm x 1.9 mm ", there is a difference
between Japanese and other metric sizes . No oil leaks and forks finally working
as a pair . Now i'm a happy chappy .
P8 , 7.8 x 1.9 . Hope this helps

Oooookay chaps, remember that Japan had their own standards (JIS, Japanese industrial standard) up until 1968 then adopted then international ISO for metric for SOME parts. These can be seen on the bolts of most Japanese bikes they will have either an "8" or "9" on the head or for the nuts a pimple. This indicates that the bolt etc meets the ISO Metric (which is a direct copy of the German DIN Metric).

If you have ever worked on 1960's Japanese bikes you may remember that the Philips head screws always were a bitch to get out as the screw driver never quit fitted. The reason…JIS screws that required a JIS screwdriver.

That's a real handy piece of info Dino, Excellent, well done mate. I will have to jot that part size down in the manual for reference.

Rod.s wrote:
Oooookay chaps, remember that Japan had their own standards (JIS, Japanese industrial standard) up until 1968 then adopted then international ISO for metric for SOME parts. These can be seen on the bolts of most Japanese bikes they will have either an "8" or "9" on the head or for the nuts a pimple. This indicates that the bolt etc meets the ISO Metric (which is a direct copy of the German DIN Metric).

If you have ever worked on 1960's Japanese bikes you may remember that the Philips head screws always were a bitch to get out as the screw driver never quit fitted. The reason…JIS screws that required a JIS screwdriver.

A lot of the vintage Japanese amps we work on have the JIS screws in them, I still haven't managed to actually find a JIS screwdriver!

Pretty sure some of the TRX screws are JIS also...

Edit: Oh yeah, my forks are leaking too, are they a Yamaha part or generic?

I have bought some JIS drivers in HK.
Good quality Japanese manufacture, not cheap Chinese clones.
Let me know what you want, I can get some next time I'm back there if you don't mind the wait.

Part is not listed by Yamaha and hasn't been listed for years.
So take note of this reference and just jot it down on the workshop manual on the exploded view of the forks..

Yamaha produced some quality amps back in the 80's .
Beautiful warm sound and plenty of headroom.
You could drive them hard all day and know they would be there for you the next day to do it all over again. much like the TRX...

dicky wrote:I have bought some JIS drivers in HK.
Good quality Japanese manufacture, not cheap Chinese clones.
Let me know what you want, I can get some next time I'm back there if you don't mind the wait.

Mate you're on, I'll PM you my wish list….

Rod

cobbadiggabuddyblooo wrote:Part is not listed by Yamaha and hasn't been listed for years.
So take note of this reference and just jot it down on the workshop manual on the exploded view of the forks..

Yamaha produced some quality amps back in the 80's .
Beautiful warm sound and plenty of headroom.
You could drive them hard all day and know they would be there for you the next day to do it all over again. much like the TRX...

Yep, my current amp is a Vintage-ish Yamaha CR-620, I've played with amps more 10x the price that weren't as good! Not that it's amazing, just the other terrible for the money! Value for money drops off really quickly with audio gear. That said, I'm playing with some digital amps at the moment which are also great for very little money.

dicky wrote:I have bought some JIS drivers in HK.
Good quality Japanese manufacture, not cheap Chinese clones.
Let me know what you want, I can get some next time I'm back there if you don't mind the wait.

Oh yes please!

The standard (if there is such a thing) JIS driver will do me, but if they come in a set, I'll be keen for that too! Not having the right tool isn't a big deal in the grand scheme of things, but it does annoy me

Phillips screws are meant to ramp out under torque which is why the screwdriver comes out. JIS (like posidrive) do not have a tapered but parallel slots If you cannot get JIS screwdrivers use a posidrive instead these have straight blades and not tapered like phillips.

JIS screws are usually denoted by a . on the head.