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Old 12-31-1969, 8:00 PM

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post #1 of 9 Old 03-26-2012, 1:45 AM Thread Starter
 
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Showa front fork problem

Brought the grand old lady to the Shanghai F-1 track yesterday, and she enjoyed it all over ... one problem though, with the front fork (all standard, 2002 SP-2).

It seems the forks bottoms out some 4 cm (1.5 inch) above the end of the travel.
I already noticed this during some test rides, but even on the track at hard braking it does not change.
I initially thought the oil level was too high and thick, and changed it out for new one.
Problem persists however.

Oil 10W, 498cc each leg
Pre-load: 10 turns clockwise
Rebound: 1 1/2 turn from full closed
Compression: 16 clicks from full closed
I am around 100kg full dressed
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post #2 of 9 Old 03-26-2012, 5:33 AM
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Re: Showa front fork problem

Quote:
Originally Posted by ericjansen View Post
Brought the grand old lady to the Shanghai F-1 track yesterday, and she enjoyed it all over ... one problem though, with the front fork (all standard, 2002 SP-2).

It seems the forks bottoms out some 4 cm (1.5 inch) above the end of the travel.
I already noticed this during some test rides, but even on the track at hard braking it does not change.
I initially thought the oil level was too high and thick, and changed it out for new one.
Problem persists however.

Oil 10W, 498cc each leg
Pre-load: 10 turns clockwise
Rebound: 1 1/2 turn from full closed
Compression: 16 clicks from full closed
I am around 100kg full dressed

If you undo the fork cap and compress the fork it compresses 40mm further than it does while riding?
You set the oil level to 135mm as specified?

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #3 of 9 Old 03-26-2012, 5:44 AM Thread Starter
 
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Re: Showa front fork problem

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Originally Posted by bladeracer View Post
If you undo the fork cap and compress the fork it compresses 40mm further than it does while riding?
You set the oil level to 135mm as specified?
1. Yes, with fork caps off, its got full travel.

2. I did not disassemble the forks, but I left the forks 2 days upside down with regular pumping. I am pretty sure the legs were empty of old oil.
I filled up with 498cc each leg, but did not measure the level (as this is measured with springs out, right)?
I am pretty sure the volume I inserted is close to the 498cc required.

I hear what you say though, The problem looks like air-gap related.
The strange thing is that exactly the same happened with old and new oil.
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post #4 of 9 Old 03-26-2012, 5:51 AM
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Re: Showa front fork problem

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Originally Posted by ericjansen View Post
1. Yes, with fork caps off, its got full travel.

2. I did not disassemble the forks, but I left the forks 2 days upside down with regular pumping. I am pretty sure the legs were empty of old oil.
I filled up with 498cc each leg, but did not measure the level (as this is measured with springs out, right)?
I am pretty sure the volume I inserted is close to the 498cc required.

I hear what you say though, The problem looks like air-gap related.
The strange thing is that exactly the same happened with old and new oil.
So you only have 80mm of travel of the full 120mm?
Maybe whoever changed the fork oil last time did it the same way instead of setting the air gap? The oil volume is irrelevant - the air gap is what matters.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #5 of 9 Old 03-26-2012, 11:11 AM Thread Starter
 
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Re: Showa front fork problem

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Originally Posted by bladeracer View Post
Maybe whoever changed the fork oil last time did it the same way instead of setting the air gap? The oil volume is irrelevant - the air gap is what matters.
You are absolutely right. I just opened up the forks and they definitely had too much oil in it. Set them at the correct level, added a titsy pitsy to be sure they will not bottom out, and just installed everything back.
Will not be able to ride before the weekend, but even from pushing by hand it feels different, so I guess it is solved.

Thanks for the advise!
Good to know there were no other hidden defaults in the fork.
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post #6 of 9 Old 03-31-2012, 5:04 PM
 
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Re: Showa front fork problem

Dont forget the SP2 has a long topout spring, so theres about 20+mm of lost travel.
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post #7 of 9 Old 03-31-2012, 7:11 PM Thread Starter
 
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Re: Showa front fork problem

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Originally Posted by mondo View Post
Dont forget the SP2 has a long topout spring, so theres about 20+mm of lost travel.
Yeah, learned that.
I thought to take a shortcut by not removing the springs, just add the oil by volume. As always, shortcuts don't work.
The fork is working fine now, using it's full travel minus the last 5 mm at softest setting.
Thanks for all advise!
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post #8 of 9 Old 04-01-2012, 2:43 AM
 
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Re: Showa front fork problem

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Originally Posted by ericjansen View Post
Yeah, learned that.
I thought to take a shortcut by not removing the springs, just add the oil by volume. As always, shortcuts don't work.
The fork is working fine now, using it's full travel minus the last 5 mm at softest setting.
Thanks for all advise!
I dont mean the compression spring, the topout spring is inside the valve tube, if you pull on the forks you will see how much travel they take off.
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post #9 of 9 Old 04-01-2012, 5:24 AM Thread Starter
 
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Re: Showa front fork problem

Quote:
Originally Posted by mondo View Post
I dont mean the compression spring, the topout spring is inside the valve tube, if you pull on the forks you will see how much travel they take off.
Yes, i know, but that can only be solved with a re-built, which I do not want to do right now.
What I missed was the lower 4cm of travel.
Altogether, the topout problem, plus bottom problem left not much suspension left. But as said, all fixed.
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