front fork problem

[outasight20]

i think understand what you are saying, but i also know if i put the correct oil in (as i did 1st time round) i still have the problem, so it cant be simply the oil grade thats causing me to have little or no damping

but surely heavier oil will move through the holes in the damper at a slower rate that lighter oil?

i'm confused

You are right, heavier fork oil moves through the holes in the damper at a slower rate. This means that when you hit a bump with heavier oil, the oil doesn't have time to travel through the damper rod and you feel the full brunt of the bump through the handlebars. With a lighter oil, the fork can move more freely, meaning a smoother ride over bumps at the expense of increased fork dive under heavy braking. Imagine if you had no oil in your forks. You would hit a bump and not feel the initial jolt at all, however then the fork would start bouncing up and down.

I had 10W oil in my shocks for a whlie and recently went back to 5W. I like it a lot better.

 

[FinalImpact]

i think understand what you are saying, but i also know if i put the correct oil in (as i did 1st time round) i still have the problem, so it cant be simply the oil grade thats causing me to have little or no damping

but surely heavier oil will move through the holes in the damper at a slower rate that lighter oil?

i'm confused

I think that split ring you refer to is letting to much oil past. I tried to find actual pictures of our fork but no luck. So after a 1000 miles of pogo stick action on the fresh 5wt oil you dumped it and went w/15 and there was no change? I wonder if there is something that is supposed to tension that split ring outward (an expander spring) and it broken, stuck or collapsed!? Thus making a massive oil leak so no oil is metered to control motion.

 

[darius]

i think understand what you are saying, but i also know if i put the correct oil in (as i did 1st time round) i still have the problem, so it cant be simply the oil grade thats causing me to have little or no damping

but surely heavier oil will move through the holes in the damper at a slower rate that lighter oil?

i'm confused

You are correct, but if the oil is flowing slowly in its passage through those damping holes, the fork's action is also slow.

If the fork cannot move fast enough to react to bumps, they will jolt the bike, upset the steering and feel harsh.

The fork oil also lubricates the internals. The FZ6 fork is designed for use with Yamalube 01.

People try heavier oils to add damping but you don't want to go too heavy because that side effect of slowing down the action of the fork. Yamalube 01 is night and day from 15W.

You will never get really good compression damping out of this fork, but you should be able to make it work as good as new again and that's not bad at all. It rolled out of the factory nice enough with the 01 in it.

Even with an expensive cartridge fork, you cannot set the compression damping to max and expect a plush ride. You'd have the same problem. The action will be too slow. Nothing comes free.

What oil did you put in the first time around?

 

[FinalImpact]

You are correct, but if the oil is flowing slowly in its passage through those damping holes, the fork's action is also slow.

If the fork cannot move fast enough to react to bumps, they will jolt the bike, upset the steering and feel harsh.

The fork oil also lubricates the internals. The FZ6 fork is designed for use with Yamalube 01.

People try heavier oils to add damping but you don't want to go too heavy because that side effect of slowing down the action of the fork. Yamalube 01 is night and day from 15W.

You will never get really good compression damping out of this fork, but you should be able to make it work as good as new again and that's not bad at all. It rolled out of the factory nice enough with the 01 in it.

Even with an expensive cartridge fork, you cannot set the compression damping to max and expect a plush ride. You'd have the same problem. The action will be too slow. Nothing comes free.

What oil did you put in the first time around?

With 15 wt the forks should have responded by jarring and jolting. At a minimum slowing the the fork action down. That is NOT what he reported.

So it appears something else is at fault and that restoring the oil to the OEM wt is NOT going to cure it and will not make it like new again.

What i failed to add in my statement above, is that piston ring (split ring) is simply worn out or so scored that it fails to stop oil flow past it. You need to measure the bore and the piston ring. I see no specification for them tho and measuring the bore would take tool few will have. An automotive machine would have bore gauge capable of reaching into the fork tube. If the difference between the ID of the tube and OD of the piston ring is substantial, you may need some new parts!

 

[JTL]

I've had good luck with 10W fork oil in mine + I filled it just a bit over the specified amount. The fork feels less bouncy and firmer now -> success.

 

[darius]

With 15 wt the forks should have responded by jarring and jolting. At a minimum slowing the the fork action down. That is NOT what he reported.

So it appears something else is at fault and that restoring the oil to the OEM wt is NOT going to cure it and will not make it like new again.

15W doesn't make the bike unrideable but we know the forks will not work correctly so long as 15W is in there.

Will going OEM fix the issue? I don't know. His original posts w/ symptoms could be clearer.

It sounds like the forks could be upsetting the whole bike which an excessively heavy weight oil can cause.

OP:
How is fork dive under braking? Is it excessive?
Rider sag measurement?

 

[FinalImpact]

hi all

whats the chances of the damper rods simply wearing out? my bike has done 28000 miles

symptoms are pogo-like forks! bounce all over the place like theres no damping.

I've changed the oil, even put heavier weight in (currently 15w) the springs are the correct length, there is no play in the bushings and everything is assembled properly with no obvious signs of internal damage

cheers guys, i'm a bit stuck!

Hi

I've triple checked the level already and it seems right

Travel isn't limited at all, you don't have to brake very hard for the forks to fully compress. I can get 3/4 travel just by bouncing the front end

You're right, they are steel. But they have a plastic collar on them, wondered if that may be a weak point? And letting oil past instead of going through the damping mechanism??

OK

When you did yours, did you notice if the collar was a loose fit on the damper, as mine is. Also it's split, but it looks like it was made that way

I did the same but it made no appreciable difference

Thanks a lot

Review of thread says, the piston ring is worn out and needs replaced! It should be a snug fit with no gaps in the bore.

 

[darius]

Review of thread says, the piston ring is worn out and needs replaced! It should be a snug fit with no gaps in the bore.

Thanks. Makes sense. A rider sag measurement would still be helpful to rule out springs that may have had a hard life and worn out or simply being too light for the rider. (There could be more than one problem.)

 

[Motogiro]

What is your front tire pressure?

 

[darius]

What is your front tire pressure?

And what weight air do you have in it? :thumbup:

 

[Motogiro]

And what weight air do you have in it? :thumbup:

LMAO! :rof::rof:

 

[FinalImpact]

And what weight air do you have in it? :thumbup:

There is a YouTube somewhere of theses teens filling there friends bmx tires with water. Needless to say it didn't handle well. They were all :rof::rof:

 

[Nevstah]

thanks for all the replies guys

fwiw i managed to buy some 'heavy' air at the local flea market, so all sorted there! tried heavy water in the tyres but it leaked out when i got a puncture!!:BLAA:

anyways, on a serious note, thanks for all the replies!!!! it sounds like its quite possible that the piston ring is goosed, possibly with all the pot holes we have and possibly the previous owner never changing the oil didnt help.

a pair of new rods sounds like the way to go! as you dont seem to be able to get new rings

thanks guys

 

[dpaul007]

Depending on the price of new hardware (i have no idea how much they cost) it might be worth it to just do a fork upgrade.

 

[Nevstah]

i seem to remember they were 40-50gbp each so not too bad!!