GStwin.com GS500 Message Forum

Main Area => General GS500 Discussion => Topic started by: slipperymongoose on July 12, 2011, 03:14:45 AM

Title: Fork oil level question.
Post by: slipperymongoose on July 12, 2011, 03:14:45 AM
Hi was wondering about what measure/comparison I use for my k3. My Haynes tells each fork has a capacity of 389cc and a level of 91 mm. Haynes tells me to pour then measure, but in the few threads ive gone through mention nothing about the amount you pour in. What do you guys usually do? Cheers.
Title: Re: Fork oil level question.
Post by: noiseguy on July 12, 2011, 07:58:54 AM
Amounts seem about right. They only tell me how much to buy at the store, though.

I always measure the air gap to top... it's much more consistant then volume measurements. The air gap is what you're trying to control, ultimately... why not just measure it directly?
Title: Re: Fork oil level question.
Post by: slipperymongoose on July 12, 2011, 01:45:23 PM
Cheers yeah I'll go that way and measure it.
Title: Re: Fork oil level question.
Post by: burning1 on July 12, 2011, 04:11:06 PM
Never rely on a volume measurement; always measure the air gap; only exception is when adding a small measured amount of fork oil in each leg to tune the performance of the forks (E.g. adding 10cc of oil to both sides.)

Air gap is an extremely critical measurement for fork performance; the air in the fork acts as a secondary spring, and relatively small differences in volume can have a huge impact on how the forks perform at bottom of travel. Two worst case scenarios is to over-fill the forks (causing them to become solid before they hit the bottom of travel, and likely blowing out the fork seals) and filling the legs to different levels (causing the wheel to pitch at bottom of travel.)
Title: Re: Fork oil level question.
Post by: burning1 on July 12, 2011, 04:18:14 PM
BTW... 91mm is fine with stock springs, but if you are going aftermarket, I'd suggest you lower the oil level to 120mm to start with, and go no higher than 100mm.
Title: Re: Fork oil level question.
Post by: slipperymongoose on July 12, 2011, 04:52:25 PM
Yeah going .80 sonics.
Title: Re: Fork oil level question.
Post by: burning1 on July 12, 2011, 05:46:21 PM
Compare them to the stock spring. If they are anything like the racetech springs I ran, they are much longer than stock, and use much thicker coils. Because of that, they displace more oil. Since oil level is measured with the springs removed, it means that the oil level with the springs installed would be much higher than stock, and you should use the 120mm figure to start with.
Title: Re: Fork oil level question.
Post by: RichDesmond on July 13, 2011, 06:41:57 PM
Quote from: aussiegs on July 12, 2011, 04:52:25 PM
Yeah going .80 sonics.

115mm with the Sonic Springs. :)