Front fork issue

Austech

Joined
May 14, 2008
Messages
51
Location
cochrane alberta
Bike
05 St 1300 Hond
I changed the fork oil by taking the cap off, pumping the forks and dampner, and letting them drain upside down overnite. I added 22.5 ounces of oil into each fork, and pumped the forks and dampner up and down a bunch of times. The height of oil in the left fork was 55 mm and the right was 35 mm.
Question is why is oil so high in one fork. I?m afraid to suck it out. Spec?s say the height should be 62 mm in both. Have I done some thing wrong here, and should I stick with the 62 mm, which I?m assuming is measured with the dampner rod pushed down all the way.

John
 
Assuming everything is stock you should stick with the 62 mm recommendation. It is weird as you describe it with the levels so different. I add fluid to the level I want and measure that that way. Are you sure the cartridge (damper) is all the way down in both tubes and the stanchions are all the way down in the fork legs? No springs inserted?
 
Austech said:
I changed the fork oil by taking the cap off, pumping the forks and dampner, and letting them drain upside down overnite. I added 22.5 ounces of oil into each fork, and pumped the forks and dampner up and down a bunch of times. The height of oil in the left fork was 55 mm and the right was 35 mm.
Question is why is oil so high in one fork. I’m afraid to suck it out. Spec’s say the height should be 62 mm in both. Have I done some thing wrong here, and should I stick with the 62 mm, which I’m assuming is measured with the dampner rod pushed down all the way.

John
Click to expand...

I'm going to assume you're working from the Honda Service Manual, in which case the instructions are clear on page 15-30. "Be sure the oil level is the same in both forks". Measure the oil level from the top of the fork tube with the fork fully compressed and the spring removed.

There is a school of thought that thinks the weaker initial spring rate of the OEM progressive wound springs is compensated for by a smaller air volume in the fork. Sonic Springs (I'm running them now) engineers recommend a 125mm oil level, about twice the Honda spec. when using their straight rate springs spec'd for your weight and riding style. This gives you twice the volume of air in the upper tube. Many of us are using an oil level less than the Honda spec. with aftermarket springs, but you should probably stick with the Honda spec. using the OEM units.
 
Don't know what caused the difference in oil level unless you didn't get it all out of one of the forks or it wasn't pumped to fill completely.

As previously mentioned oil level will vary based on setup. My Hyperpro setup has 7.5 wt oil set at 160 mm.

If you think it has been pumped/filled properly then suck out and set at factory setting.
 
I thought about this again and the first time I drained my forks I did not let them drain overnight and when I refilled them using precise measured amounts of oil there was a significant difference in level. I drained them again this time overnight and the refill went better the next day. The levels were closer.
 
I did re-drain the right fork, thinking that I had made a mistake, but about 22 ounces came out again +-, and I did drain them overnite. The only thing I can think of is that somethong got trapped somwhere. I'm not familiar with the guts of the fork. I have had them standing for a day with the new oil in them. I'll pump them again, see where I end up and stick to the 62mm as suggested. Thanks for all your help. Love the feedback boys!

John
 
One thing I've found is that the damper cartridges won't completely drain just hanging upside down, even overnight. I pumped and pumped them until the damper rod became super easy to stroke through its entire travel, no resistance at all. Only then do you know for sure that you've thoroughly emptied the cartridges. Upon adding fresh oil, again stroke the damper rods until there is pretty firm resistance throughout their stroke, only then do you know the cartridges are completely refilled. Don't try to take a level reading until you have finished all of the above, then adjust to spec.
 
I agree with what Jeff is thinking . The cartridge can trap a lot of oil inside them and just turning them up side down wont always do it .You have keep pumping and changing position till completely free and empty and like wise when refill,pump damper cartridge to make sure all air is out to accurately measure oil height ! some times this takes quite a few strokes ! Ah ,don,t you just love it when you work on oily ,messy parts.?

:slv13: MIKE


!
 
I watched that 40 minute video from 10-11-09, and you guys are absoutely right! pumping the forks up and down a few times is the answer, as well as doing the same when they are refilled with the new oil. I agree oil gets trapped in there somewhere, so I might have a bit of old oil in there, but that's ok until next time. Another good lesson learned. I have now changed every fluid in the bike, and checked the valve clearances, new tires, and new brakes. Anybody think of anything else that should be done??

John
 
I'd suggest a complete systems check... Go find a nice winding road and ride it for a few hours. Repeat as necessary until you're satisfied. :D
 
Glad to see you have success on the fork issue . I got my baptism by tearing apart and rebuilding many a dirt bike forks ,even did a few shocks also , yeah those are fun too !



:slv13: MIKE
 
Well after all the work of changing my fork oil, we went on a 4500 km ride thru Utah, N. Mexico, Arizona, and Texas. My right fork was weeping on day three. When I got home, I pulled them apart again, cleaned everything with brake clean and got all the oil out of the dampers which I removed this time. Even at that, when I turned the dampers upside down the next day, some oil (not much) still ran out. I put in new seals, and when I added the oil this time, it balanced out in both forks really close. Now to hit the road again and test it all out. I'm thinking that in the original oil change, I must have ended up with different levels in the shocks. Old seal seemed to be ok, but the eneven levels might have forced oil past the seal.
 
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