Front wheel hop

[OldNick]

This is not some nbew "Trike Ballet" trick!

98 Valk 1500 triked. I recently had my front forks re-sealed as they were leaking. WHen I rode them afterward, I noticed that they were a heap firmer to the point of discomfort. I asked on the VRCC forums and it was suggested I remove some of the oil to provide a sort of air spring effect. Others suggested I change to a lighter oil, such as ATF. I tried removing oil and got as far as the right leg only (23cc) as I found I have to remove the left leg to get any oil out. If experimenting, that could get to be a PITA. It did soften the ride and _seemed_ not to affect handling.

If it comes to it, I will replace the oil with ATF etc.

I am not sure if it's because I am riding harder(I probably have 2500Km up now and I am just getting used to the new feelings and forces of a trike on tougher turns), or because of the change in fork oil and quantity since my forks were resealed, but I am finding that in a tight corner, if I push things and accelerate, if there are any small bumps, the front wheel tends to hop out a little. Several small bumps can cause over steer, "ploughing". This is not unmanageable, but is a bit disconcerting. It's fun, but it is the first time I have found a limit that the trike has, where I have not backed off before we reached it.

I do not have enough experience of trhe Valk's handling, let alone with the different forces of a trike, to know if this is just what happens to a front wheel hard pressed, with the trike's lack of lean and greater weight making it worse. I can see that on a bike, accelerating would help to keep the front wheel on track as you lean (you only have to watch MotoGP and see guys wheelstanding in a corner!), whereas a trike does not do that and in fact accelerating would lighten the front wheel and make it worse.


I am just wondering if the more viscous oil would cause any of this, by damping the rebound of the fork too much. In other words, will lighter (ATF) oil help with rebound speed and road holding......or, I have to admit, because I am riding with one fork leg (the right one) depleted and the other not....OR, do I need to learn to ride differently, and not accelerate as hard? As I say I am happy to change the oil and experiment, but it seems less wasteful of time and oil to ask first!

Thanks for any help

Nick

[tfdeputydawg]

Sometimes referred to as "pogo sticking".
This is an indication of to much fork oil! Are you sure you or whomever did the seals, measured the correct amount when refilling???
+What kind of front tire and what pressure?

[OldNick]

HI and thanks. AH! Now I have a name for it . And a very descriptive name as well.

It feels right that too much oil would slow the forks...that's what it's there for....

I can't be sure at all that they used the correct amount. I just assumed. If I am seeing the symptoms of too much oil I will get the forks off and reduce it.

I guess if I have the forks off and upside down to empty, I will try the ATF as well. It's a darn sight cheaper than the "true" fork oil! A few guys have said go for ATF.

EDIT: Sorry, yeah, front tyre is Avon Cobra at ~40 psi. I do know I noticed this problem after the fork build.

Nick

[tfdeputydawg]

HI and thanks. AH! Now I have a name for it . And a very descriptive name as well.

It feels right that too much oil would slow the forks...that's what it's there for....

I can't be sure at all that they used the correct amount. I just assumed. If I am seeing the symptoms of too much oil I will get the forks off and reduce it.

I guess if I have the forks off and upside down to empty, I will try the ATF as well. It's a darn sight cheaper than the "true" fork oil! A few guys have said go for ATF.

EDIT: Sorry, yeah, front tyre is Avon Cobra at ~40 psi. I do know I noticed this problem after the fork build.

Nick

Thanks.
Let us know what you find to resolve your problem.
The only comment on ATF for me is, I use what my service manual calls for!

[FuzzyWuzHe]

Fork oil volumes are very sensitive ... like to a half cc ... I always use a syringe to put oil in. Very accurate. Too much will cause hop, too little will feel spongy. Weird stuff happens if they are not the same for both.

Mechanical 101 on troubleshooting .... when looking for the issue, always go back to the last thing done. I'd guess either the amount off oil is wrong, or the weight of oil is wrong.

[Old Fard]

Last year I rebuilt my GL1800 forks to change dampening and ride height. I do know that fork oil viscosity will definitely change dampening and ride characteristics. Over filling can cause a hydraulic lock that feels similar to "bottoming out". In some cases left and right forks use different viscosities. Incorrect installation of the dampening valves can create issues. With the trike sitting still you should be able to bounce the front end up and down to observe travel, rebound and sag. If the forks feel solid it's a sure bet you have too much fork oil or the wrong viscosity. This assumes that the forks were assembled properly. I recommend referring to the Honda Shop Manual or dealer for viscosity requirements. The fork oils on my trike are pretty thin. IMHO.

I hope that this is any easy fix for you.

[OldNick]

Sorry Old Fard missed this one.

Yeah it defintely felt very hard and was uncomfortable over bumps, apart from the hopping in turns. It would feel like I was going to lose grip on bad bumps!

Since posting here I have had several discussions about this issue and learned/relearned a lot. I have removed 23cc of oil from the right leg and (with more difficulty) 23cc from the left. Each removal softened the bumps. I have yet to try the trike after the left hand leg oil was lowered, because it has been wet and I am not about to worry about how much fork oil on wet roads .

Interesting that you say some forks do use different oil on each side! I wondered about that and posed the question on the VRCC forum. Nobody offered any feedback about the idea IIRC. I have to imagine that Honda would design their valving etc to suit the diffrerent actions of each leg, but experimenting would be interesting.

Some of the trouble is that a trike behaves totally differntly from a bike in corners and over bumps, so gouing "by the book" does not necessarily work

- - - Updated - - -

Fork oil volumes are very sensitive ... like to a half cc ... I always use a syringe to put oil in. Very accurate. Too much will cause hop, too little will feel spongy. Weird stuff happens if they are not the same for both.

Mechanical 101 on troubleshooting .... when looking for the issue, always go back to the last thing done. I'd guess either the amount off oil is wrong, or the weight of oil is wrong.

Without a doubt the change was to do with the rebuild and refill! So far I have removed some oil and today or tomorrow I will try the result. Luckily I have sussed out how to get oil out of the left fork without removing it (yay!) so I can experiment with ease. I would imagine I could even empty the fork, but I would be concerned about leaving some in and of course that throws out the refill amount.

Yeah a syringe is the only way to go and that's how I took oil from the fork. They are very accurately marked and you have complete control over adding or removal

Nick

[OldNick]

Thanks.
Let us know what you find to resolve your problem.
The only comment on ATF for me is, I use what my service manual calls for!

Yeah I have been strongly warned off ATF. Apparently it used to be OK but now has additives that make it bad for a situation that requires a lot of slippage.

Still working on a solution, but even lowering one leg's oil helped with the stiffness and hopping. Handling was greatly affected by having uneven amounts of oil, but I will see now that I have evened that up.

[OldNick]

I had a couple of rides today with both forks depleted in oil by 23cc. A lot better ride over bumps and easier on the wrists. I hit a really washboarded corner today from off a highway onto a side road. There was still some jitter, but much more controllable. WIth an easy way to suck out oil, I am going to try another oz or so and see what happens. Given this is a triked bike, I see the need to trial.

If I have to buckle and change oils, then so be it! But so far so good.

Nick

[OldNick]

Well. If anyone is interested, I ended up taking 120ml (!) out of the right compression fork, and 90 out of the left reound fork. I discovered that if I took an amount from the right tube, the ride would improve, but if I then depleted the left tube by the same amount, the ride would stiffen again and the pogo sticking would get worse. What I have now seems to give not only a more comfortable ride, but also p;revenbts the hopping.

Thanks to all ou guys for the inpout and help.

Nick