A forum for owners of Yamaha TTR250 trail and enduro bikes!

yamalama · Veteran Member

Fork Oil Level Questions

noeyedear · Senior Member

I think there is a sticky on the subject, if not about fork oil it's definitely about fork seals,

Yuraku · Veteran Member

Yamalama,

If you look at the top most picture on page 6-43 (shown below) you will see where the oil level (the grey shading) is supposed to be.

It is shown as filling the main fork leg almost to the top of the outer slider, which is measured as 130mm below the stanchion top.

Click HERE and it takes you to the article in the FAQ section and you can read how to do it.

Yuraku

yamalama · Veteran Member

Hi,

Thanks for the replies.

I have looked at the fork seal sticky, and seen the diagram in the repair manual, but they don't answer my questions.

I want to know how to distribute the new fork oil in the forks to remove any air pockets that would upset the oil level reading.

Anyone able to answer my specific questions?

Thanks

Lama

TTRfan · Super Guru

Hi Lama

It says in the manual to pump the damper rod up and down at least 10 times after filling with oil to get rid of air etc.

I will try and remember to update the sticky.

Cheers

Brian

-- Edited by TTRfan on Tuesday 25th of June 2013 02:12:49 PM

yamalama · Veteran Member

Hello again,

I'm finally getting round to answering my own questions, in case the info is helpful to anyone else.

See inserted comments below

yamalama wrote:
Hi all,
I've got a few questions about distributing oil in the forks to get the correct oil level reading.
The service manual that I downloaded from this forum gives details of how to distribute the fork oil when refilling the forks, but I am still not totally clear on the process.
In the Front Fork, Assembly section (p6-40 to 6-44) it states the following:
Step 7: Fill * Front Fork Oil To the top of the inner tube with the recommended fork oil.
Does this mean the inner fork tube, number 11 on the exploded parts diagram? Surely that would require far more oil than the 555cc specified. Or is it badly worded and really means let inner fork tube and the piston rod slide all the way down, so allowing the oil to get inside the damper rod assembly?
Still not sure what this means but I just let the inner fork tube (aka stanchion) and piston rod slide all the way down and poured the 555cc of oil in.

Step 9: After filling the front fork leg, pump the damper rod slowly up and down more than 10 times to distribute the fork oil.
At this point, should the fork inner tube be all the way down inside fork outer leg, or fully extended?
I left the fork inner tube all the way down, but suspect that it doesnt really matter so long as it isn't raised more than 150mm

Step 10: After filling, pump the inner tube slowly up and down (about 150mm) to distribute the fork oil once more.
Is the 150mm measured from the fully extended or the fully compressed position?
I spoke to two motorcycle mechanics and both told me that this is measured from the fully down position. It the inner tube is raised too high the holes in the bottom of it introduce air into the oil
After doing all the above my oil level was only a few mm too high (Excess removed using Brian's syringe method)

And finally, will temporarily refitting the fork spring and cap apply enough force to prevent the damper rod from turning when I tighten the base valve into the damper rod?
It didn't for me! I made a damper rod holding tool by having a M18 nut welded onto each end of a 300mm length of tubing (a long reach spark plug spanner that I no longer needed) It needs to be hollow tubing (more tham 10mm wide on inside) to allow the part of the damper rod that screws in to the fork cap to fit in side. Similarly, I needed the second nut at the top because the tommy bar hole was blocked by the damper rod. The M18 nut is 27mm across flats, which fits perfectly in the recess in the lower part of the damper rod assembly
Sorry for four questions in one mail!
Your thoughts much appreciated
Lama