Changing fork oil on a Z750

[mbroyda]

hey guys

I recently bought an 05 Z750, and the forks feel very soft on it, so as a start I would like to change the oil to a heavier oil 15, or 20.
this is something I have never done before so here are a few questions to start:

- on a scale of 1 - 10 how difficult is this?
- are there special tools required for this job?
- do the forks need to be removed in order to do this?

Cheers
Max

 

[Flywheel]

It's not that difficult, just time consuming, but you can do it two ways:

1) Suction the old oil out (leaving potential gunk inside). Check your service manual, but it's likely the handlebar clamp will need to be undone and bars moved to access the fork caps.

2) Remove the forks one at a time and drain them. This is more involved and thorough. If the fairing blocks access to the triple tree's pinch bolts, you'll need to take the fairing off, which can be a PAIN.

Most of the tools are pretty common. The NA Z750 has conventional forks, which probably makes things simpler. Lots of little details to observe (nothing tricky), so do some research first.

 

[frekeyguy]

For me....1

For you..maybe a 10.

Depends on your skill set.

Just so you know, heavier oil = slows everything down, not the best solution to your issue. You prob need more preload...heavier springs

 

[mbroyda]

For me....1

For you..maybe a 10.

Depends on your skill set.

Just so you know, heavier oil = slows everything down, not the best solution to your issue. You prob need more preload...heavier springs

Its possible that it needs both, the bike has 30k on it, and im not sure if either the springs or oil were ever changed.
Most people that I spoke with recommended changing the oil before I change the springs.

 

[beverage]

Just so you know, heavier oil = slows everything down, not the best solution to your issue. You prob need more preload...heavier springs

+1. I tried 20W oil in my SV forks since I found them soft, but the ride became very harsh over sharp bumps. Cheap damping rod forks like the SV and Z750 basically have holes drilled through the rod to allow oil to pass through, thus controlling the damping. A heavier, thicker oil will be more slow to pass through the opening. Going to 20W you'll get less fork dive under braking, and the bike may feel more solid and planted in the turns, but, at least with the SV, the oil was too heavy to quickly pass through the damping rod holes. The result was that the oil couldn't pass through quickly enough to deal with sharp bumps, creating a hydrolock situation, making the front end feel as though it essentially had no front suspension at all. The solid and planted feel in the turns quickly goes MIA if the turn is bumpy. I've since installed Ricor Intiminators and 7.5W oil. Much, much better. Springs are next.

If you're intent on doing just the oil, I'd suggest going no more than 5W above the OEM specification to start.

 

[tpit]

+1. I tried 20W oil in my SV forks since I found them soft, but the ride became very harsh over sharp bumps. Cheap damping rod forks like the SV and Z750 basically have holes drilled through the rod to allow oil to pass through, thus controlling the damping. A heavier, thicker oil will be more slow to pass through the opening. Going to 20W you'll get less fork dive under braking, and the bike may feel more solid and planted in the turns, but, at least with the SV, the oil was too heavy to quickly pass through the damping rod holes. The result was that the oil couldn't pass through quickly enough to deal with sharp bumps, creating a hydrolock situation, making the front end feel as though it essentially had no front suspension at all. The solid and planted feel in the turns quickly goes MIA if the turn is bumpy. I've since installed Ricor Intiminators and 7.5W oil. Much, much better. Springs are next.

If you're intent on doing just the oil, I'd suggest going no more than 5W above the OEM specification to start.

Do you have stck weight and amount for the 05z750?

 

[meester_jamie]

forks I have worked on have a lower drain... so I put the bike on a jack,, opened the drain,, and let most out. then I put a vac pump on to get out some more.. then I vac pumped again till I thought there was enough vac to pull the new measured amount of oil in.

this involves making a way to connect a hose to the drain hole,, I used a tapered nipple,, and 2 ft of clear hose....comes with the vac pump.. I had the measured amount of oil in a $1 picnic ketchup bottle with the pointed tip,,,

i pumped the vac.. pinched the hose.. pulled the vacuum pump off the hose,, stuck the ketchup bottle upside down into the hose.. un pinched the hose and watched the fluid draw right in.... and the cheap ketchup bottle collapsed from the vacuum...

 

[frekeyguy]

forks I have worked on have a lower drain... so I put the bike on a jack,, opened the drain,, and let most out. then I put a vac pump on to get out some more.. then I vac pumped again till I thought there was enough vac to pull the new measured amount of oil in.

this involves making a way to connect a hose to the drain hole,, I used a tapered nipple,, and 2 ft of clear hose....comes with the vac pump.. I had the measured amount of oil in a $1 picnic ketchup bottle with the pointed tip,,,

i pumped the vac.. pinched the hose.. pulled the vacuum pump off the hose,, stuck the ketchup bottle upside down into the hose.. un pinched the hose and watched the fluid draw right in.... and the cheap ketchup bottle collapsed from the vacuum...

For the SV- you will need to remove the front wheel / axle to get to those drain bolts.

The better way is to remove the forks from the trees and drain the fork oil and bushing material out from the top cap and set the oil height correctly.