Front fork mods.(long)

COMMANDO FRONT FORKS LEFT STOCK HAVE LOTS OF ROOM FOR IMPROVMENT. THE FRONT END HAS ONLY 4 ½ INCHES TRAVEL IN STOCK COMMANDO FORM. IF YOU CHECK EACH END OF THE TRAVEL YOU WILL FIND A MECHANICAL CLANG AT EACH END. MY BIKES TOPED OUT REAL BAD, AND MY FRIENDS BOTTOMED REAL BAD. TO MAKE MATTERS WORST YOU USE UP AN INCH OR ONE AND ONE HALF OF THE 4 1/2 WHEN YOU SIT ON THE BIKE.
WE STARTED TO FIX THIS BY BUYING AND INSTALLING THE ALUMINUM FORK DAMPNER TUBES FROM BRITISH SPARES IN NZ AND INSTALLING “THE COVENTREY KIT”. THEY COME WITH THE OIL FLOW HOLES IN A NEW HIGHER POSITION SO AS TO ADDRESS THE TOP OUT PROBLEM WITH A FLUID STOP. BUT “THE KIT” ALSO ADDED LOOSE FITTING BUSHINGS 1 ½ LONG BETWEEN THE STEEL BUSH AND THE TOP HIGH HAT BUSH.
WHAT IS MORE IMPORTANT IS THE OVER ALL TRAVEL. THE THREADED ROD THAT SUPPORTS THE VALVE IN THE DAMPNER TUBE DOWN IN THE OIL IS THE MECHCANICAL LIMIT OF THE DOWNWARD MOVMENT OF THE SLIDERS. THE CLANG YOU HEAR ON TOP OUTS IS THE DAMPNER VALVE HITTING THE ALUM. CAP ON THE DAMPNER TUBE AND IT IS HELD BY A TWO MM DOWEL. THIS ROD SCREWS INTO THE FORK CAP AND IS HELD IN PLACE WITH A LOCK NUT.
IT'S NOT A BAD IDEA TO INCREASE THE LENGHTH OF THIS ROD BY TWO INCHES SO YOU GET 6 INCHES OF TRAVEL. WE HAVE DONE THIS WITH THE USE A KIT WITH NEW ALUM. RODS THAT ARE TWO INCHES LONGER THAN STOCK AND ADDING FORD VALVE SPRINGS 2 ½ LONG ONE SPRING ON EACH SET UP. WE REPLACE THE OLD STOCK THICK WASHER WITH FOUR GRADE EIGHT THIN WASHERS, TWO FOR IN-BETWEEN THE NEW PROGRESSIVE SPRINGS AND TWO UNDER THE REUSED JAM NUTS IN-BETWEEN THE EXTRA SPRINGS AND JAM NUTS. IF YOU HAVE ALREADY INSTALLED THE COVENTRY KIT, YOU WILL NEED TO REMOVE THE EXTRA ALUMINUM BUSHINGS THAT YOU INSTALLED WITH THE KIT. THEY LIMIT TRAVEL AND ARE NO LONGER NEEDED FOR TOP OUT DAMPNING BECAUSE YOU HAVE PUT THE VALVE THAT GOES UP AND DOWN IN THE TUBE ON THE END OF THE ROD DEEPER INTO THE OIL. NOW YOUR GETTING 1 ½ MORE TRAVEL AND THE ROD IS TWO INCHES LONGER TO KEEP THE VALVE AWAY FROM THE CAP ON TOP OUTS. IT MAY BE FOUND THAT IF YOU HAVE THE MORE MODERN DAMPNER TUBES WITH THE HOLES IN THE TAPERS THEY MAY WORK AS IS. YOUR STEEL DAMPNER TUBES CAN BE CHANGED BUY BLOCKING THE HOLES AT THE TAPER ON THE BOTTOM OF THE TUBE AND REDRILLING THEM SO THAT THE NEW HOLE IS JUST ON TOP OF THE TAPER. SO NOW THE BOTTOM OF THE NEW HOLE IS EVEN WITH THE TOP OF THE TAPER.
THE NEW ALUMINUM DAMPNER TUBES ALREADY COME THIS WAY. I MOVED THEM WHEN USING THE OLD STEEL TUBES ON ANOTHER BIKE BECAUSE THE NEW TUBES HAVE THE HOLES MOVED UP OFF THE TAPER. YOU CAN ADD HOLES SMALLER AND HIGHER YET TO TUNE THE FLUID STOP BUT THIS MUST BE DONE FOR THE RIDERS WIEGHT. THE ALUMINUM DAMPNER TUBES HAVE TO USE 8MM FINE TREAD BOLTS TO HOLD THEM IN THE BOTTOM OF THE SLIDDERS AND ARE NOT PROVIDED WITH THE NEW TUBES. SO YOU NEED TO BUY THEM. WE USE A LONGER BOLT THAT STOCK BECAUSE THE THEAD IS IN ALUMINUM.
THE THING WE ARE AFTER HERE IS A MORE COMPLIANT WORKING FRONT ENDS WITH FLUID STOPS AT EACH END. DEPENDING ON RIDER WIEGHT I LIKE TO SEE AT LEAST 1 ½ INCHES OF SETTELING WHEN THE BIKE IS SAT ON BY THE RIDER. WE HAVE BEEN USING ATF FOR FLUID AND THE RIDE IS VERY GOOD. I HAVE TWO COMMANDO’S ONE WITH STOCK SPRINGS AND ONE WITH PROGRESSIVE’S I LIKE THEM BOTH BUT THEY ARE QUITE DIFFERENT. THE STOCK SPRINGS PRELOAD THE SET UP MUCH HIGHER THIS MAKES USING THE CENTER STAND A LITTLE FITTILY AS IT’S NOT QUTE TALL ENOUGH FOR FLAT GROUND NOW. BUT HAVING TWO INCHES FOR POTHOLES AND FOUR INCHES FOR BUMPS IS REAL GOOD. WE NOW MAKE KITS FOR THIS MOD AND THEY ARE 55.00 US DOLLARS PLUS SHIPPING. YOU GET TWO NEW ALUM DAMPNER RODS. TWO NEW FORD VALVE SPRINGS, TWO NEW 2MM DOWELS AND FOUR NEW GRADE EIGHT WASHERS IN THE KIT. FINE TUNNING THE KIT TO YOUR NEEDS IS YOUR PROJECT. PRE- LOADS, SPRINGS, FLIUD TYPES CAN ALL BE PLAYED WITH FOR BEST RESULTS. NORBSA

Wow

I'm impressed, how did you know one of my next questions was going to be about the commando front end ? Specifically the progressive fork springs n aluminium fork dampner tubes from British Spares in NZ.

I read the earlier article about "What weight oil people prefer" but this one goes a bit further. Very informative, thank you.

As I am in the process of building a "920-950" commando, some of you will understand why I am asking other questions in future. There is a bloke not far from here called "Jim Murphett". He claims to have successfully raced some large capacity Commandos in the USA.

Have any of you ever heard of him at all ? He seems to know what he is doing but, I would like to know if he has really done OK in the USA as he claims he has....?

The brembo disc brake setup from CNW would be a perfect stopper for a "Nortanic", with the progressive fork springs..etc...etc & it does look pretty slick.

Ideally, can I put a 19 tooth g/box sprocket on the bik so it has more "lift", especially when my wife & I are both on the bike but change top gear ratio, so the bike can still be a relaxed interstate cruiser ?

If you have the time to read this and reply, I thank you already.

The Commando front wheel for disk brake models is a well known piece of bad design the off set and spoke pattern are no good for racing appications. So it makes no sence to put a 1000.00$ into a reved up brake on a wheel that can't take high loads. Nothing wrong with doing the master cylinder down sized bore, the stainless fluid line, drilling and grinding the stock roader than puting on some EBC pads. But mods beyond this are a false economical move. If you need brakes that good change the wheel as well, hell change the whole front end. norbsa

Maybe you just don't make enough money norbsa 8) I buy what I like/want and I certainly like the look of that brembo on the front of a commando. The brembo is a beautiful set up, you keep your old rusty cast iron disc if that is your desire.

roadholder forks

Norbsa,

Commando forks are the last incarnation of the original Norton designed Roadholder forks from the original model 7 500 twin in 1948. It would be correct to say they are a lengthed version of the Atlas/Dominator forks, but what's up with saying they are a Matchless design?

roadholder forks

Norbsa,

Commando forks are the last incarnation of the original Norton designed Roadholder forks from the original model 7 500 twin in 1948. It would be correct to say they are a lengthed version of the Atlas/Dominator forks, but what's up with saying they are a Matchless design?

In an article by Peter Crespin called Norton Roadholders-The whole Story. He goes thru the start of the design 1946 the double-taper damper rod called the Long Roadholder to 1953 when the Short Roadholder took over and was used till the mid seventies. So yes you are right it's a Norton design. But the short version never worked right because they lacked hydraulic bump stops at each end of the travel. Matchless used the design but chaged it to get the fluid stops back in the design that Noton Never fixed. So the last version of Shortroadholders that worked like forks are Because Macthless fixed them. And my 72 and my 74 Commandos both have forks that don't work. So it's my back handed way of saying that the last people to get this thing to work should get the creidt for it. Sorry to confuse but I am glad you caught it. norbsa

Roadholder article

Norbsa,

I need to do some more reading. Where is this Peter Crespin article? I know the Commando forks aren't the best, but I haven't had any problems with topping or bottoming out. My complaint is the stiction.

Here's a link to the article http://www.nocnsw.org.au/forks.html it' 12 pages and will geive you feel of what went down. Page two last paragraph shows the link to the Matchless fix. If your in the 175 lb range never have a passenger and have never used the front brake hard while turning you may think that the front end is just great. The article is a good read. norbsa

The problem stiction you need to fix would probobly be fixed buy thining the rod were it's pinned to the valve. This would allow faster fluid flow quickening the over all action. There's a man on another site who uses 170cc 0f trans fluid to get simular results. Another race bike uses 170cc fork oil, external springs and alum. dampner tubes with modified hole pos. norbsa

Well were up to two front ends out of a dozen or more to fix and it looks like 5 1/2 inches is all you can get. The top high hat bushing and the steel lower bushing come together at full extention. That's ok just have to get the fluid stops working at each end of the travel. Looks like the next thing is to get some 3/4 hex steel and drill an tap the center for 3/8 fine thread right thru.Each piece will be squared up at 1 5/8 long. Using a short stud one inch this will be locked down to the forkcap and the extra thread used to remount the dampner rod with the stock jam nut. So far two alum washers same as stock size 1/8 thick and the 150cc of 20wt forkoil is working. norbsa

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Learning more today about Commando forks. May have found the reason we only got 5 1/2 inches travel while other bikes have a full six inches. Seems that the front ends that were being worked with have after market replacment fork legs the inside hole at the bottom of the leg is hitting the taper on the dampner tube stopping the travel buy 1/2 inch. The full travel measurment is important to know for all the other parts to be made correctly. We have a bike on the road did some testing today and it is good. This is the state as it stands now. The dampner rods have been modifiyed so that they are 1 5/8 longer. This allows the extra travel. We have added a spring from a ford tractor valve 2 1/2 long and removed the stock spacer washer. Put in 160 ML of 5 wt fork oil not 150 of 20wt.Stock jam nut and a thin hardened washer to hold it all in place. The bike just floats over bumps that you use to avoid like the plage. The progressive springs can be felt nice and easy for first bit of travel going to good and firm under braking. Pre load seems just right two iches of dampened downward travel for pot holes and lots of cushtion for the bumps. Still more to learn but wow this is what they should have been from the start.norbsa

I went to the British Spares website but didn't find the aluminum damper tubes? Have they stopped selling them? I've got a '75 MK III, will it benefit from these tubes and the lengthening of the damper rods? Thanks for the help.

Scooter
Too much old junk to list but a pint of Guinness to anyone else with a Rumi Formchino :shock:

The site and company are in NZ not Canada the site is http://www.britishspares.com/ the part # is 06-1888A they are about 38.00 each now. 60.00NZ norbsa

Thanks NORBSA
At $38 each plus shipping the set looks like it will run about $100. Do these tubes offer any advantage other than the relocated oil holes? Also if I extend the damper rods per your post could I use a 2 1/2" section of one of my old fork springs instead of a valve spring like you used?

A sweet working front fork is critical to riding enjoyment (don't want the dentures flying out over every bump do we)

Thanks, Scooter

There just a bit lighter is all and they don't rust. If your tubes are not rusty they can be fixed to run real well. To do this find a 1/16 pipe tap and four 1/16 pipe plugs. You than tap the old oil holes to a depth that gets the plugs flush and stop the tap is tapered. Take your time get the first one right then mark the tap. We used red locktite on the threads.Now you just redrill the holes for the oil just like they were only higher in the tubes. At the bottom of the dampner tube there's a taper you need your new holes just above this taper. (Some Commando's all ready have this fixed so check it be fore you start.) The springs are not worth cutting cause the ford springs cost three bucks a piece. The other reason is that on each end of the spring the coils don't provide a colapsed lenghth long enough to do the job. You need the intake valve spring for a Ford 9-N or 8-N tractor. A grade 8 3/8 washer to go inbetween the springs is a good idea too. norbsa

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Found more info today. Well the alum. dampner tube goes right thru the fork leg when it's not bolted into the bottom of the slider. And yes there is some scraping going on down at the bottom of the taper. And so it looks like since all the parts are brand new I will have to indicate each one in to find the part thats at falt. But at least I found the six inches of travel the front end was to have had.norbsa

Found the fault in the fork system that was limiting travel. Seems that the fork legs although new were not finished well. The hollow tube at the bottom on the inside was not the right size and there were some large burrs on the holes for the oil flow. Had to go over inside and out to get the fits right. Useing sand paper on the lathe. The chrome on these went right down to the end of the tubes. I have other sets were the chrome stops or is ground off were the lower steel bushing is fitted. Took apart another front end today and found that the small pin that retains the valve cup were bent bad. This was on a bike that had the coventery kit installed. I have pulled apart two others that have this kit with out this damage to the pins. I know that the bike with the bent pins was driven hard cause it's mine. So reassembled it with two inch longer alum. dampner rods and the Ford valve springs with ATF for fluid. Rained real hard so no test drive today. But it feels good in the action. The bike sits a bit taller and now may require some 3x3x1/2 shimms for the center stand on soft ground. norbsa

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Got a kit in my alum. bike road test today man I got a new bike. I had to back off the back shock adjusters to make them more compliant and all of the buck board is gone. The thing handles great. I just can't belive I have been riding with this thing so stiff for all that time. I did some pot hole hunting and haven't found one big enough to unsettle this bike now. We got the alum rod stock for 12 sets whole sale at 35.00 got the ford valve springs whole sale at 3.00 a piece.four hardened washers at .08 each.So for under 10.00 in material we can fix the front end real well and you use ATF for oil. norbsa

Good work, my compliments