Simple fork question

Hey Guys,

I don't know anything about how the oil in the front forks works, so I'm just curious if adding more oil will make the forks more firm? Seems like the front end dives pretty easy just by putting weight on it. I have 5 oz (I think thats right, whatever the book said is what I put in) of power steering fluid in each fork. Stock 850 forks. I know there are upgrade kits and such, I was just looking for any improvement for the time being.

Thanks again,

Ben

Power steering fluid is too light.

Use the specified oil and you'll get the appropriate fork response.

Power steering fluid is too light.

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20 grade is the book recommendation and ATF over here is 20 grade, works fine for me. I found that if the forks needed 30 grade the rod bushes were wearing.

Cash

Adding more oil ? the fork action, will tend to "stiffen" on compression , because the air space is compressed more,
BUT they will rebound by the same degree, 5 weight oil will render them allmost inoperative, try 150cc of 20 grade...or if hot climate...30 grade.
OR...better still
www.lansdowne-engineering.com

DO NOT FILL OVER !75-180 ml >>> or the fork pumping out air action will suck the fork down completely hydraulic locked >>> but only after about 1/4 mile >>> depending on roughness of the road >>> to suddenly cause reversed control action to every little bump and pilot correction. BEWARE!
Even on Ms Peel the wonder handler 15 mph almost ruined my panties and bike finish.

The grade of oil will depend most on the fluid gap between the damper cap and damper rod. Worn or new 'big' factory gap will require thicker grade to dampen to matter. Grade controls the speed of fork compression, springs control the amount of compression and hydraulic stop should controls the bottoming w/o a clank. Kenny Cummings has extensive fork oil grade chart that shows there is little relation between listed and actually tested grade, so can not go by anything but your own trial and error.

I've mixed and matched various expensive specialty 5-20 grade oils to left over engine 20-50 grade to settle on power steering fluid, but Peel has proper built > as was originally designed-intended <, instead of what was sold as Cdo Roadholders - so may not apply to anyone w/o Greg Fauth's 'cheap' kit.

Single most effective mod for fork dive w/o doing anything else is cut a few inched off factory spring and stick in a stronger spring spacer. This is Not the way Greg's kit works but will improve the dive resistance yet not affect just riding around action or resting sag height, while still retaining all the other NOT-designed in faults of forks sold us. Cutting a spring also stiffens it.
Above gives dual rate action but can easy add 3rd, 4th and 5th rates like I enjoy no end.

cash said:

Power steering fluid is too light.

Click to expand...

20 grade is the book recommendation and ATF over here is 20 grade, works fine for me. I found that if the forks needed 30 grade the rod bushes were wearing.

Cash

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Oil weights are not consistent across fluids. So a hydraulic fluid is not the same as motor oil or fork oil. Plenty written on this.

I don't know about anybody else, but it is near impossible to find single grade oil where I live. So I am running hydraulic oil. ISO 46 (also called AW46) is 20 weight. NAPA sells it in 5 gallon pales for 45 bucks, a lifetime supply. So instead I went to the local Bobcat dealer and they sold me a pint for a minimal charge.

So far it seems to do a good job.

Are the predictions of catastrophy correct on overfilling? I don't quite follow the mechanical issue with it other than reducing the airspace.

Russ

A smarter and more capable Nortonneer than me, maybe LAB or Landowne, has put air gauge on forks to find they pump air space down, not up, so finally solved reasons I also crashed going 20 mph and barely made it back upright to shed with both feet out dragging ground barely going above old man waking speed. A freaking bucking bronco I tell ya. NEVER AGAIN PLEASE. BEWARE!

It was very similar to pulling to a stop on a blown out front tire.
I've had that terror occur on Peel Combat/hobot forks and SV650 with Race Tech fork internals to compare for those not yet experiencing this Terror.

The single best advice I can offer for safest racing skills beyond traction and frame tolerance for emergency built in reflexes - is a few 100 yd practice with low air in either or both tires. It can save your life and bike, DO IT and KNOW forever more.

Low air/flats will just feel like bit of wind gusts, until ya lean or slow very much and everything happens in sudden reversals. YIKES!!!

Typo I ^Almost^ crashed after turning around careful half way down drive way at first hints something really bad was about to happen and by gosh it almost did. 15 mph was sheer terror, with a bit of ok interval to temp ya to go faster than slow waking speed. Only other times I roll with feet down is crossing deep mud which is also Always an Immediate Emergency Crisis State to me.

If one was to over fill forks in civilized pavement conditions - pump down delay may hit solid while going highway speed before front tire blow out behavior onsets instantly after an interval of fine handling. BEWARE!!

Burp air out a tire till you get the sense of this and never ever forget it.
Burp air out fork and I grantee you'll never forget it like me either.

rvich said:

I don't know about anybody else, but it is near impossible to find single grade oil where I live. So I am running hydraulic oil. ISO 46 (also called AW46) is 20 weight. NAPA sells it in 5 gallon pales for 45 bucks, a lifetime supply. So instead I went to the local Bobcat dealer and they sold me a pint for a minimal charge.

So far it seems to do a good job.

Are the predictions of catastrophy correct on overfilling? I don't quite follow the mechanical issue with it other than reducing the airspace.

Russ

Click to expand...

They make fork oil, you know. :mrgreen: Perhaps shopping at your finer motorcycle emporium, if not local than for sure online...

swooshdave said:

rvich said:

I don't know about anybody else, but it is near impossible to find single grade oil where I live. So I am running hydraulic oil. ISO 46 (also called AW46) is 20 weight. NAPA sells it in 5 gallon pales for 45 bucks, a lifetime supply. So instead I went to the local Bobcat dealer and they sold me a pint for a minimal charge.

So far it seems to do a good job.

Are the predictions of catastrophy correct on overfilling? I don't quite follow the mechanical issue with it other than reducing the airspace.

Russ

Click to expand...

They make fork oil, you know. :mrgreen: Perhaps shopping at your finer motorcycle emporium, if not local than for sure online...

Click to expand...

Fork oil is a great idea if you can find it in 20 weight. The local shops all carry 10 weight. If I am going to run that I might as well use ATF! Youze guys that live in more civilized places might find it at the motorcylce shop, but around here you go see the Bobcat dealer.

hobot said:

Typo I ^Almost^ crashed after turning around careful half way down drive way at first hints something really bad was about to happen and by gosh it almost did. 15 mph was sheer terror, with a bit of ok interval to temp ya to go faster than slow waking speed. Only other times I roll with feet down is crossing deep mud which is also Always an Immediate Emergency Crisis State to me.

If one was to over fill forks in civilized pavement conditions - pump down delay may hit solid while going highway speed before front tire blow out behavior onsets instantly after an interval of fine handling. BEWARE!!

Burp air out a tire till you get the sense of this and never ever forget it.
Burp air out fork and I grantee you'll never forget it like me either.

Click to expand...

Hobit, never just a plain answer from you! must admit i need to read your post's a couple of times to "break the hobit code" :lol:

I will admit to sleeping through my "Hobotese" classes in school too.
I generally break his sentences down into bite-size chunks and translate the chunks into English and then reassemble them in my head. There is normally some good info buried in his odd-prose!

Vince

Ugh, Just don't fill a fork leg over 175 ml for surprise delayed bad ju ju and you'll be fine.

Who ever designed Roadholders got it righter than any thing I've tried or could imagine, but Cdo bean counters cut one foot off at the ankle by the too short spring and the other foot off at the knee by damper rod shorted to be able to sell that dangerous piece of crap, no one- me included is secure on. With help I figured out where it went wrong and the simple way to restore Roadholders to their full function glory and adjustable features I've yet to hear anyone but me mention. May be better, hope there is but me and Peel just couldn't handle it.

Brly - In my opinion, every Commando's forks should be modified, if for no other reason than to get rid of that awful clanking.

Jean de Rosiers posted an excellent writeup here -

norton-roadholder-modifications-t3645.html


That thread is about the dampers, not about the springs. You mentioned dive; how much "sag" do you have? Generally, when you sit on the bike, neither the front or rear suspension should settle more than aboout 1/3 of total travel. If your sag is 1/2 or more, then you need springs of a greater rate, depending on your weight.

My view has changed from modified to simply corrected back as intended.

xbacksideslider - From what you've said, the sag isn't bad at all. My weight is 190 lb. I just filled the forks up for the first time since I've had everything apart and when I straddle the bike and bounce the front end, it feels weak. Just seems like I shouldn't be able to push it so far. Maybe I'm wrong.

Anyway, thanks for all the help. I will definitely be upgrading the suspension a little further down the road. I'd love to do it all now, but this project is getting to be a financial burden. I need to start making a list of future improvements like, new electronic ignition, primary belt drive, wheels and spokes, negative ground swap, etc, etc.

Might be able to start it up this weekend!



Ben

Hello Ben,
Bike is looking good, and yes spend your money getting it on the road, These projects are money pits. Fork upgrades? well see how she handles first, quite a few Commandos are still running the originals, and excepting a few clonks once in a while...some call it normal.
Best of Luck
www.lansdowne-engineering.com

Thanks John,

I think I've done a good job of making the bike safe to ride. All the wheel bearings have been replaced, new tubes and tires, steering stem bearings, rebuilt gearbox with new bearings all around, new swingarm bushings, new chain, rebuilt caliper and new master cyclinder, all that stuff. Now I'm getting really anxious to start it up. I didn't rebuild the engine because the PO told me it had been done recently. I know, I know, I cringed a little just typing it out. I did have the bike running briefly before I tore it down, but you never know I guess. So I took a risk by not rebuilding the engine, hopefully it will work out. If not, I rebuild the engine and get on with it.

Thanks,
Ben

I had the engine apart on mine, everything looked good on the bottom end, put it all back together. Then at 100 miles into finally having it on the road, both main bearings spun and one piston skiry dissapeared. I'm fairly certain I had an oil issue, but i'm back to where I started. This time i'm crossing all the t's and dotting the i's.