Bucket Suspension

[Pumba]

Ok, I have got my bucket, and in the true spirit of buckets it is a bit of everything. Yamaha RX125 engine and a Kawasaki Frame of some description (Frame No. G4-068055 if this means anything to anyone). Looking at the suspension I wouldent have a clue if this is native to the frame. I decided to have a look at the front forks cause they bottomed out without two much effort at all, and considering I havent had this bike on the track yet this was saying somthing (Thanks for the advice Frosty). I have pulled them apart (always was good at destruction) and need some advice on how to go foward from here.

Being a complete novice at this, now that they are apart im not sure what my next step should be. The oil I took out was thick and black (and smelt like shit) and there apears to be a far bit of gunk (the correct technical term I hope) still in the in the suspension tubes. What would be the best way of cleaning this out?

Now when it comes time to put these back togeather does anyone have a recomendation on what weight oil I should be using? I have made a note of how much oil was in each of the forks (125ml) so I figure this would be a good place to start, but what would be the results of increasing, decreasing this level? Are there any other components of the suspension (springs etc) I should be looking at?

Any advice on any of these issue would be apreciated.:rockon:

[Sully60]

http://www.kiwibiker.co.nz/forums/showpost.php?p=1253710&postcount=1705

I had a similar question so gave this advice, it's a bit generic as most smaller buckets like GP100s RG,RZ50s etc have the same basic type of fork.
Quote:
Being a complete novice at this, now that they are apart im not sure what my next step should be. The oil I took out was thick and black (and smelt like shit) and there apears to be a far bit of gunk (the correct technical term I hope) still in the in the suspension tubes. What would be the best way of cleaning this out?

Disassemble the forks completely, the trickiest bit is usually getting the damper rod bolt out of the bottom, you really need a rattle gun to make sure this comes out, sometimes if you're lucky you can get it out using just an allan key. Use clean kerosine or parts washer, whatever just be fastidious about making sure all the gunk and the metal bits and pieces are completely gone.

As you'll see in the thread above I reckon fiddling with the oil height and weight are your best bet to start out. $20 for a bottle of fork oil is a cheap way to get underway.
You can use thicker spacers and washers under the fork cap to adjust the spring preload, although it may be tempting to try and load the springs up to get the thing stiff enough you have to be a little careful about the springs coils binding at max compression, just go up in small increments (5mm or less at a time)
Save the spring thing untill you get your head around what actually works and doesn't work because when you have the springs right you shouldn't need to change again (unless the bike or you lose or gain a heap of weight. hmm were did all those pies go?)

Give it a go, the cool thing with buckets is you can't really fuck anything up too bad and if you do it doesn't cost much if anything to repair.
Give us a yell if you need anymore help.

[F5 Dave]

If you don't have a rattle gun then some forks have a hex or similar in the top of the damper rod so a long rod with a T handle welded to one end & a bolt welded to the bottom the same size as the rod Hex will do.

Failing that reassemble with the spring in it & hold it in a Vice. Compress the fork, perhaps with a tiedown. This should usually work.

Always remember springs can be dangerous when in compression like above. Use your brain as to what would happen if it was suddenly released. Also don't clamp the vice up hard on the sliders or they could be squashed. Brake mounts etc are ok.

A G4 was a trailbike I believe G4TR was the 100. Do a google.

10 or 15 weight oil will be the go, there are advantages/disadvantages but that is damper rod forks. If you have no idea what they are try oil level 6" from the top compressed with no springs in & work up from there.

Really you need to put them back together with right amount of oil & see what they feel like. Forget preloading them up it won't help, do a search to see why. Stiffer springs may be required, they can be cut down but that isn't really a job for the uninitiated, getting them straight after requires some care.

[FROSTY]

One thing you do need to do is get rid of that abomination of a fork brace .I think its doing more harm than good. The steering head bearuings felt pretty loose too.

[Pumba]

Thanks Guys.

I have managed to dis-assemble the forks by removing the damper bolt (wasent that hard using an allen key with the largest ring spaner that would fit for extra leverage) and know the fork tube and fork slider are seperate (I am using the picture attached to make sure my terminolagy is correct), but I cant see any way of getting to the spring (the top cap of the forks dont look like they are removable).

I dont think this is really to much of an issue as I dont think I should be messing with it at this stage anyway.

So just to clarify what yoiu guys are saying, to refill the forks you would reassemble the forks, compress the spring, and then fill from the top past the fork seal? Or am I missing somthing here?

I agree Forsty that brace on the front is prety dodge, in your opinion is it needed or will it be alright to run without it, either way I have acsess to the facilitys to make or get made somthing else more apropriate.

EDIT: When the Thumbnail is enlarged it makes alot more sence

[F5 Dave]

erm, I'd have to say that the top cap is removable, post a picture, it should just be threaded in there, sometimes they have internal hex or square drive & sometimes they have covers over them. . . . Memory kicks in slowly, there was even one I think you had to push on it to expose a circlip that had to be flicked out before you could get to it. Or was that just a bad dream?

The fork tube is best held in the triple clamp to loosen any cap. The tube & slider can then be separated. On some forks they will just slide out, on others with bushes you need to slide them apart with speed a few times to pull the bush out of it's slot & bringing the fork seal with it.

If you don't need to replace the fork seals then just consider flushing it out with kero & leaving to drain pumping it several times at least overnight.

[Sully60]

Thanks Guys.


So just to clarify what yoiu guys are saying, to refill the forks you would reassemble the forks, compress the spring, and then fill from the top past the fork seal? Or am I missing somthing here?

Before you put the spring back in push the "fork tube" all the way to the bottom of its travel so it is as compressed to the end of its travel. Fill the fork tube with the lovely new clean fork oil until it about 50mm from the top of the tube. Slowly pull the fork up (you'll start to feel the oil bleed through the "damper valve" and "damper rod", go all the way to the top of the travel then slowly compress to the bottom again, do this a few times until you feel the damping works all the way through the stroke of the forkin both directions. You'll notice when you fully compress the fork now that the original 50mm or so gap when you filled the forks intially will now be bigger. This is when you set your level.
I changed the diagram on the right of you picture to what the fork should look like when you do this.

You need to measure from the top of the fork tube with the cap out. You can use a ruler or something similar or you can make a tool like the one below for around $5, this is the way to go as it makes it quick and easy to adjust your levels and make them the same.
Put the springs back in carefully with all the spacers, this is were a vice with soft jaws can be handy or if the bike is nice and stable on a centre stand or something you can use slide them back into the clamps to keep the hole at the top of the forks pointing upwards. (it sucks doing all this work to then knock over a fork and half the oil out of it, doh!) Do everything up properly and go ride!

I gather from what you've said that if your fork doesn't have a hex head on the top then it may have caps retained by internal wire circlips in the fork tube. This system and and hidden internal hex (allan key type) are concealed by some sort of cosmetic cap, someone local should be able to help you there. Just heed F5Daves warning about removing the caps.


i agree Forsty that brace on the front is prety dodge, in your opinion is it needed or will it be alright to run without it, either way I have acsess to the facilitys to make or get made somthing else more apropriate.



The people on the spot always know best!

[Robert Taylor]

Ok, I have got my bucket, and in the true spirit of buckets it is a bit of everything. Yamaha RX125 engine and a Kawasaki Frame of some description (Frame No. G4-068055 if this means anything to anyone). Looking at the suspension I wouldent have a clue if this is native to the frame. I decided to have a look at the front forks cause they bottomed out without two much effort at all, and considering I havent had this bike on the track yet this was saying somthing (Thanks for the advice Frosty). I have pulled them apart (always was good at destruction) and need some advice on how to go foward from here.

Being a complete novice at this, now that they are apart im not sure what my next step should be. The oil I took out was thick and black (and smelt like shit) and there apears to be a far bit of gunk (the correct technical term I hope) still in the in the suspension tubes. What would be the best way of cleaning this out?

Now when it comes time to put these back togeather does anyone have a recomendation on what weight oil I should be using? I have made a note of how much oil was in each of the forks (125ml) so I figure this would be a good place to start, but what would be the results of increasing, decreasing this level? Are there any other components of the suspension (springs etc) I should be looking at?

Any advice on any of these issue would be apreciated.:rockon:

It is either an old 70s G4 trailbike or the G4TR farmbike variant. Either way the springs in those forks are way way too light for your application. As eluded to in another answer shortening them increases the rate, within the limitations of making sure they still have adequate stroke integrity. And believe me it often doesnt take too much decrease in length to increase the rate appreciably.

And Im sorry guys, ever increasing preloading of oversoft springs is just NOT the right way to ''hold'' the bike up.

The damping is of fixed orifice type meaning they are mushy and uncontrolled at upper low fork velocity movements but when you hit something abrupt the flow rate peaks out, manifesting itself as a jackhammer through the bars.

You need a reasonable ''amount'' of oil viscosity to have rebound control on such forks because in part there is so much uncontrolled bleed, plus long term wear issues. But playing with oil viscosity to ''tune'' compression damping feel is frankly a caveman approach. Also, the thicker the oil the more sensitive it is to the temperature of the day. Forks filled with 20 to 30 weight oil are especially lethargic on cold frosty mornings, that can cause a crash if not allowed for.

I am not sure if there may be a sizing small enough, but if I was in your shoes I would be modifying the forks in technically the best way possible by fitting emulators and cutting the springs. That statement may not endear me to those who think everything must be as cheap as possible, but the cheap solutions almost always deliver a similarly cheap result!

[Pumba]

I gather from what you've said that if your fork doesn't have a hex head on the top then it may have caps retained by internal wire circlips in the fork tube. This system and and hidden internal hex (allan key type) are concealed by some sort of cosmetic cap, someone local should be able to help you there.

Figured this one out tonight, top caps push down and then there is a cir-clip that needs to removed to get the cap off. Still havent managed to do it yet but it seems quite straight foward.

[Pumba]

It is either an old 70s G4 trailbike or the G4TR farmbike variant. Either way the springs in those forks are way way too light for your application. As eluded to in another answer shortening them increases the rate, within the limitations of making sure they still have adequate stroke integrity. And believe me it often doesnt take too much decrease in length to increase the rate appreciably.

And Im sorry guys, ever increasing preloading of oversoft springs is just NOT the right way to ''hold'' the bike up.

The damping is of fixed orifice type meaning they are mushy and uncontrolled at upper low fork velocity movements but when you hit something abrupt the flow rate peaks out, manifesting itself as a jackhammer through the bars.

You need a reasonable ''amount'' of oil viscosity to have rebound control on such forks because in part there is so much uncontrolled bleed, plus long term wear issues. But playing with oil viscosity to ''tune'' compression damping feel is frankly a caveman approach. Also, the thicker the oil the more sensitive it is to the temperature of the day. Forks filled with 20 to 30 weight oil are especially lethargic on cold frosty mornings, that can cause a crash if not allowed for.

I am not sure if there may be a sizing small enough, but if I was in your shoes I would be modifying the forks in technically the best way possible by fitting emulators and cutting the springs. That statement may not endear me to those who think everything must be as cheap as possible, but the cheap solutions almost always deliver a similarly cheap result!

Thanks for the input Robert. I understand most of your post and the points you are getting at.

Although at the moment I am not interested in going down the path of emulators, this may be somthing to look at in the near future depending on the enjoyment factor and finances. Call me what you will but that is my current descion.

More out of curriosty than anything else what is the smallesrt size emulators you can get?

[Skunk]

Thanks for the input Robert. I understand most of your post and the points you are getting at.

Although at the moment I am not interested in going down the path of emulators, this may be somthing to look at in the near future depending on the enjoyment factor and finances. Call me what you will but that is my current descion.

More out of curriosty than anything else what is the smallesrt size emulators you can get?
The emulators have helped my bike (still tuning them) with its particular issue. The downside is they cost me three times what the bike did originally - though only a quarter of what the engine rebuild cost.

Does that read right? Point is they work - but at a cost. It's debatable whether it's worth it for a mid/back of the pack rider/bike.

[Pumba]

Does that read right? Point is they work - but at a cost. It's debatable whether it's worth it for a mid/back of the pack rider/bike.

It reads fine. And the reality is at the moment I will imagine I will be further to the back of the pack than to the front

[Robert Taylor]

Thanks for the input Robert. I understand most of your post and the points you are getting at.

Although at the moment I am not interested in going down the path of emulators, this may be somthing to look at in the near future depending on the enjoyment factor and finances. Call me what you will but that is my current descion.

More out of curriosty than anything else what is the smallesrt size emulators you can get?

No worries, my pitch was technical rather than sales focused. Having said that though these will elevate your competitiveness. The smallest emulators have an outer diameter of 23.8mm.

[FROSTY]

Robert--the front end looks to me to be GT185,gp125 if this helps.
The front end felt /looked to me to have a few issues.
1)instant dive to bottom out with barely a hint of downward pressure.
2) A disturbing clunk I diddn't take time to identify but actually felt to me like the steering head was actually moving fore/aft5mm
3)2 pieces of 12mmx3mm metal bolted between the forks as a brace

Puma--Ill defer to RT and others re oil etc -
Fork brace wise Given what I saw--- rip em off and make something thats gonna do the job. A Single piece of aluminum bolted to all 4 fork bolts will be a huge improvement -basicly you need it to drop into place and fall back out if you undo the bolts -Have a look at a FZR400/600 or a TZR250 to see what Im thinkingof