Author Topic: Everyone had a tank slapping good time - forks? (Read 4070 times)

ev0lve · « **on:** May 25, 2009, 01:49:45 PM »

So not really a tank slapper but coming through a turn at a pretty good clip I hit some uneven/wavy pavement and the front end got a little squirrelly. Not piss your pants bad but definitely something I'd like to address before I find some place that is.

I just put new progressive springs in (sans spacers as they measured to the top of the forks) and filled it up with ATF to spec (which I'll have to go look up) sub 6oz IIRC correctly.

So what am I looking at here? Without the spacers the fork springs are bouncy? Not enough ATF? How to diagnose?

Thanks

ev0lve · « **Reply #1 on:** May 25, 2009, 01:54:45 PM »

Search you huskies! Search!

This sounds like my problem. MCRider says:

On the bouncy question: most of our old forks, the spring provides virtually all the control on compression. The oil provides rebound damping. So if the fork is bouncy there is likely not enough oil or too light weight to suit. If you increase the preload with spacers, I think they will just get bouncier.

http://forums.sohc4.net/index.php?topic=49168.msg519741#msg519741

Bodi · « **Reply #2 on:** May 25, 2009, 01:58:24 PM »

What does squirrely mean?
Anyway, I find ATF too thin for my old forks. Maybe they're worn a bit? Somewhere between SAE 5 and 10 I think I settled on, using some brand of fork oil mixing the two viscosities.
The fork action doesn't do much regarding the classic tank slapper, this is usually an issue with tire wear and pressure, excess rear fork play, and the fork brace/fender bracket being tight.

GammaFlat · « **Reply #3 on:** May 25, 2009, 02:03:08 PM »

You could do the "air thing" - schrader valves at the top of the shock - everybody's doin' it

http://forums.sohc4.net/index.php?topic=48076.msg506521#msg506521

ev0lve · « **Reply #4 on:** May 25, 2009, 02:08:43 PM »

Quote from: Bodi on May 25, 2009, 01:58:24 PM

What does squirrely mean?
Anyway, I find ATF too thin for my old forks. Maybe they're worn a bit? Somewhere between SAE 5 and 10 I think I settled on, using some brand of fork oil mixing the two viscosities.
The fork action doesn't do much regarding the classic tank slapper, this is usually an issue with tire wear and pressure, excess rear fork play, and the fork brace/fender bracket being tight.

Squirrelly I think is defined as a rapid back and forth motion of the handlebars, not enough to hit the stops, in a short duration persisting after the event or road hazard causing loss of rider confidence in the bikes ability to not cause him bodily harm with little or no notice. Or at least that's what I call squirrelly

Tires are brand new and pressure is good (or it was a week ago) - fender bracket seems good. Given my history with this bike of having to get it wrong before getting it right I'm thinking I goofed the fork oil level.

Haynes says 10w/30 150-155cc dry (5.24 ounces) and that seems to ring the bell as to what I put in there.

Clymer says something different but I don't have it in front of me. Probably where I got the ATF from.

ev0lve · « **Reply #5 on:** May 25, 2009, 02:13:01 PM »

Quote from: GammaFlat on May 25, 2009, 02:03:08 PM

You could do the "air thing" - schrader valves at the top of the shock - everybody's doin' it

http://forums.sohc4.net/index.php?topic=48076.msg506521#msg506521

Hmmmmmm

jaknight · « **Reply #6 on:** May 25, 2009, 02:31:45 PM »

Hi Iggy,

I would try this. Check your rear shocks. Also, and I think this is far more important, get the bike on the center stand and remove your rear wheel. Grab ahold of your rear frame members (at the very end where the axle goes through) and with each side individually, see if you can get a back and forth movement,..... left to right, right to left,...... any motion.

You are checking for play in your swingarm fittings this way. This can tell you if your bike is subject to "The Death Wobble." I know, sounds horrible, but this does come up and affect handling something fierce.

Just a thought to help eliminate things....

~ ~ ~ jaknight ~ ~ ~

turboguzzi · « **Reply #7 on:** May 25, 2009, 03:01:48 PM »

back to the original subject of the post,

dont know about 750's but at least the 500's where known tank slappers, even with everything in good condition.

My street 500 had a steering damper and the one time I did remove it, got a tank slapper all right.

it was bad enough to push the caliper piston back in, leaving me brake-less approaching the stoplights, time for the second heart attack!

TG

eurban · « **Reply #8 on:** May 25, 2009, 03:30:24 PM »

Get some cartridge fork emulators from Racetech or some knock offs from MikesXS. They will transform the performance of your forks well beyond anything you will achieve with progressive springs and fluid tweaking alone. Tank slappers are one of the things that they are particularly good at eliminating.

jaknight · « **Reply #9 on:** May 25, 2009, 03:31:40 PM »

The Original Subject,

Quote from: turboguzzi on May 25, 2009, 03:01:48 PM

back to the original subject of the post, TG

The original subject was to give some help about a handling problem......., because there is a handling problem does not necessarily mean it is in the front end of the bike.

I gave Iggy an opportunity to eliminate one critical possibility.

Bad swingarm fittings will affect handling far more than what type of oil you use in your front forks or even if you have enough oil up front at all.

A man here in Phoenix drag races his 750 without any oil in the front forks at all. He has won many races...... admittedly, that is in a straight line race. But, somewhere along the line, he does make turns.

As for the part about the rear shock......... try making a left turn with a bad left rear shock absorber......... All things to look at and eliminate if you can't find something wrong with the front shock setup....... oil or otherwise.

~ ~ ~ jaknight ~ ~ ~

ev0lve · « **Reply #10 on:** May 25, 2009, 04:54:32 PM »

Quote from: jaknight on May 25, 2009, 03:31:40 PM

The Original Subject,

Quote from: turboguzzi on May 25, 2009, 03:01:48 PM
back to the original subject of the post, TG

The original subject was to give some help about a handling problem......., because there is a handling problem does not necessarily mean it is in the front end of the bike.

I gave Iggy an opportunity to eliminate one critical possibility.

Bad swingarm fittings will affect handling far more than what type of oil you use in your front forks or even if you have enough oil up front at all.

A man here in Phoenix drag races his 750 without any oil in the front forks at all. He has won many races...... admittedly, that is in a straight line race. But, somewhere along the line, he does make turns.

As for the part about the rear shock......... try making a left turn with a bad left rear shock absorber......... All things to look at and eliminate if you can't find something wrong with the front shock setup....... oil or otherwise.

~ ~ ~ jaknight ~ ~ ~

I gave the swingarm a wiggle test back when I was trying to true my rims (fail) and thought it was pretty tight. The rear shocks are what came with the bike until I get some money together to replace them but they too "seem" OK.

The front end dives a bit now that I have the MC working acceptably.

I have noticed the same thing with the front hitting a chuckhole at 20 - 30 MPH in a straight line though.

If it is the rear end should I feel some galloping (wandering) in a long sweeper? I would think I would if the rear end was tweaking but I don't.

Suspension tweaking other than throwing new shocks and topping off fork oil is all brand new to me but I've got a feeling it's likely I don't have enough or the right weight fluid in the forks. Only way to know is pop the caps off and add some I suppose. At least that will eliminate that as a cause.

ev0lve · « **Reply #11 on:** May 25, 2009, 04:56:21 PM »

Quote from: eurban on May 25, 2009, 03:30:24 PM

Get some cartridge fork emulators from Racetech or some knock offs from MikesXS. They will transform the performance of your forks well beyond anything you will achieve with progressive springs and fluid tweaking alone. Tank slappers are one of the things that they are particularly good at eliminating.

I'm leaning towards that as the ultimate solution reading up on it a bit.

andy750 · « **Reply #12 on:** May 25, 2009, 05:02:05 PM »

You dont need to spend a lot of money to get good handling so before you rush off and buy the emulators (will still take time to tweak these in any case) consider the easy solutions

1. Change fork oil to 10w or even 15w and make sure you used the correct amount
2. Check condition of steering head bearings
3. As Jaknight stated your rear end will easily affect your front end - rear shocks set too high? If so will cause bouncing in corners or braking hard in a straight line. Swingarm bushings gone?
4. Front and rear tire pressure? Are they both correct? Over inflated tired will give crap handling in corners - are tired new? old?

Good luck
Andy

Retro Rocket · « **Reply #13 on:** May 25, 2009, 05:02:06 PM »

Every 750 honda i have owned has been ridden hard and most of them had braced frames and good suspension and yes they would all tank slap when ridden hard. Fit a steering damper, this one thing eliminated any hint of a tank slapper and installed plenty of confidence .

JS550 · « **Reply #14 on:** May 25, 2009, 05:04:07 PM »

The progressives that I got for my 750k said to install the spacers. Dont know if that would be the problem?

andy750 · « **Reply #15 on:** May 25, 2009, 05:08:36 PM »

Quote from: retro rocket on May 25, 2009, 05:02:06 PM

Every 750 honda i have owned has been ridden hard and most of them had braced frames and good suspension and yes they would all tank slap when ridden hard.

Not my experience...Ive only had a couple of 750s in the last 20 years...and all have been ridden hard on some of the best roads in the world (Pacific coast highway, USA, the Alps, flat out on the Autobahn etc etc)....no tank slappers (so far

). I am not saying you havent had them on your bikes, but its not been my experience...and I dont ride them softly

cheers
Andy

ev0lve · « **Reply #16 on:** May 25, 2009, 05:14:45 PM »

I think I should just ditch the Clymer and Haynes and stay with the shop manual.

Haynes says the K5 has a dry capacity of 155cc but specs the K0 - K2 at 230cc

The Honda shop manual makes no distinction between models- 220 to 230cc. Period.

I bet my fork oil is low and I should go burn both these manuals at my earliest opportunity.

Retro Rocket · « **Reply #17 on:** May 25, 2009, 05:32:15 PM »

Hi Andy, i think the difference is that you rode them on, "the best roads in the world" our roads at the time were all goat tracks, very common in Australia in the late 70's and 80's, actually we still have plenty of goat tracks now..

. The tank slappers usually occurred hitting sharp bumps in corners at speed and i have had some serious tank slappers as well as slow wallowing ones in high speed sweepers. The standard Honda forks are too weak and poor bracing in the swingarm area are limitations to the Honda's handling. Apart from making sure that your suspension is up to scratch, a steering damper is a priceless addition to these bikes.

Mick

andy750 · « **Reply #18 on:** May 25, 2009, 05:46:28 PM »

Hi Mick,

Ah yes good point about the road quality and those little bumps in the road. I also rode some really crappy roads in Mexico (maybe it was a dried up river bed instead - try riding for 10 hrs on that kind of road and only getting 150 miles....that was tough and very low speed). Anyway your dead right about the weak forks and I forgot to mention I had improved my forks before setting out on those roads mentioned.....progressive springs with spacers and correct fork fluid/amount. Everything else was also good.

Someday I want to ride in Australia!

cheers
Andy

turboguzzi · « **Reply #19 on:** May 26, 2009, 02:40:33 PM »

Quote from: retro rocket on May 25, 2009, 05:02:06 PM

Every 750 honda i have owned has been ridden hard and most of them had braced frames and good suspension and yes they would all tank slap when ridden hard. Fit a steering damper, this one thing eliminated any hint of a tank slapper and installed plenty of confidence .

thanks rocket, that is exactly what I was trying to say at the end of the day... :-)

so yes, fit a damper, the ones from mikeXS are cheap and cheerful,

Cheers

TG

MCRider · « **Reply #20 on:** May 26, 2009, 02:53:56 PM »

There's no question a steering damper would be a good addition. After all, so many racing sanctions require them, regardless of whatever fork and/or modifications one might have. Better to make the broad safety decision and put one on everything.

Having said that, I wouldn't stop there. If one has the post K2 fork, it would be best if one didn't have to decide one or the other, emulator or damper, and do both.

Stopping the excess force coming into the chassis at its source seems to me the more elegant route. The damper comes into play after all else fails, and the chassis is stressing from loads.

For some, not all, dampers can be misused as a bandaid for other problems which should be addressed, as well.

Nothing I'm saying here takes away from the effectiveness of a damper, I've had one on my CB750 since the late 70s..

andy750 · « **Reply #21 on:** May 26, 2009, 04:45:41 PM »

One question I have about the dampers - you need to lose the fork gaiters is that correct? For early forks (like 72) what do you use for fork seal covers?

If someone could post a couple of photos of how the damper is mounted that would be really helpful!

Thanks
Andy

fuzzybutt · « **Reply #22 on:** May 26, 2009, 05:04:10 PM »

i'm being lazy and i dont want to read all the way through. do youhave your front fender or a brace?

Retro Rocket · « **Reply #23 on:** May 26, 2009, 05:04:54 PM »

Hi Andy, i have no pics but i always had mine mounted under the bottom triple clamp across to a small mount welded on the frame, no need to touch the gators. I have different forks on the K2 i am building now and i am mounting the damper in the same place.

Mick

Retro Rocket · « **Reply #24 on:** May 26, 2009, 05:06:22 PM »

And as Fuzzy is hinting at, a fork brace is also great for holding the front end all nice and straight.

Mick

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Author Topic: Everyone had a tank slapping good time - forks? (Read 4070 times)

fuzzybutt