Front fork mod

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Mar 21, 2006
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Further to a recent posting concerning front forks, I have recently modified my 850 Commando forks by fitting progressive springs and the Covenant damper conversion, both obtained from RGM in England.

I can confirm that this modification is an improvement over the stock forks. The ride is more compliant over choppy surfaces yet does not bottom out during big impacts on the road. The forks do not now knock at full extension when the bike goes light over humps etc. thanks to the proper hydraulic lock-up provided by the Covenant mod. I use SAE 20 fork oil with about 15 ml of Molyslip, totalling 150 ml in each leg. The Moly reduces friction and slip/stick/slip tendencies, making the forks very progressive silky and fast-acting. Well worth the effort. Regards to all.
 
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Thanks scim77
I have the parts on order and I would have picked them up this week but I went to the Motorcycle show in Toronto and bought me a Belstaff Trailmaster jacket and a pair of Boots instead. Next week...I'll get them sorted. I have heard good things about these small mods to make the suspension system work as it should.
CNN
 
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Hi CNN. This is a staightforward job to do. It is easier if you support the bike on a hydraulic lift of some kind so that you can 1) ease the tension from the springs whilst removing the large top leg nuts and 2) help to push the springs back up out of the legs when reassembling. If you think about it carefully you can reassemble the forks into the bike without any effort used in trying to compress springs and wrestle nuts on. Let the bike weight push the springs and damper rods out of the top of the tubes. Use the jack to raise the bike and drop the spring units back inside the legs when locating the top nuts.

Use the bottom triple clamp to grip the stanchion tubes when initially refitting. Nip the bottom clamp bolts when the legs are located in the top triple clamp tapers. Then fit and tighten the top nuts to draw the tapered leg into the top triple clamp taper. You can then remove the top nuts again and add 150cc oil. Also release and retighten the lower clamps to make sure they are gripping in equilibrium with the newly locked top clamp tapers.

It is probably easier to add the oil to each leg whilst they are detached from the bike, then you dont have to faff about, like I did, by undoing the top nuts twice!

A lot of waffle for what is really a fairly logical procedure. Also check the alloy sleeves provided in the Covenant kit. They should be dimensionally ok but mine had significant burrs on the inner bores, easily removed with a scaper or suitable knife blade. This is important since the alloy sleeves are supposed to be free floating. Cheers.
 
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Ever read this?
THERE WERE THREE GUYS WORKING ON THIS KIT. WE TALKED AND LOOKED,
AND LOOKED SOME MORE.
FIRST STAGE, STRIP DOWN FORKS TO ONE
FORK STANCHION, ONE SLIDER, ONE STEEL BUSHING WITH CLIP TO RETAIN,
ONE HIGH HAT BUSH, ONE SEAL AND ONE SEAL RETAINER ASSEMBLE DRY
AT THIS POINT. CHECK TRAVEL, GOT SIX INCHES PLUS WITH NO DAMPENER TUBE,
VALVE, ROD OR SPRINGS.
OK SECOND STAGE, ADD STOCK DAMPENER TUBE
WITH VALVE SUPPORTING ROD, TUBE CAP, SPRING, STOCK SPACER, JAM NUT.
NO FORK CAP NUTS OR FLUID SO WHEN YOU SLIDE THIS BACK AND
FORTH THE SPRING ASSEMBLIES ARE COMING IN AND OUT OF THE TOP OF
THE FORK STANCHIONS TOPS. THE TRAVEL WAS FOUR AND ONE HALF INCHES.

NOTE THAT IN THIS STATE THE SPRINGS ARE LOADED AGAINST THE TOP OF
THE DAMPENER TUBE CAP AND ARE TRAPPED BY THE JAM NUTS AND THE
SPACER ON THE OTHER END SO THE DAMPENER VALVE IS TIGHT UP TO THE CAP.
UNTIL THE BIKE IS FULL ASSEMBLED WITH THE DAMPENER ROD JAM NUT
TIGHT TO THE FORK CAPS AND THE WEIGHT OF THE RIDER IS FELT THE
VALVE IS ALWAYS GOING TO STAY THERE UP AGAINST THE CAP.

THE STOCK LENGTH OF THE ROD IS LIMITING THE DISTANCE THE
SLIDERS CAN MOVE. DO THE SAME TEST WITH TWO INCH LONGER RODS AND
AN EXTRA SET OF SPRINGS FOR PRELOAD AND YOU GET BACK THE
SIX INCHES OF MOVEMENT. THE TRUE LIMIT, THE MAX TO BE HAD,
IS WHEN THE TOP OF THE STEEL BUSHING HITS THE BOTTOM OF THE
HIGH HAT.
NOW YOU DON'T WANT TO RIDE THE BIKE IN THIS STATE WITH
THE TWO BUSHES TIGHT TO ONE ANOTHER THERE'S JUST NOT ENOUGH
SUPPORT AND THE FRONT TIRE WILL BOUNCE BACK AND FORTH AT
STOP LIGHTS. SO WE CAME UP WITH THE TWO INCH LONGER MODIFICATION
FOR THE ONE AND ONE HALF INCHES OF TRAVEL GAIN SO THAT UNDER
NO CIRCUMSTANCES COULD THE DAMPENER VALVE BE USED
TO LIMIT THE TRAVEL FOR THIS WE WANTED A FLUID STOP AND NOT A ONE AND
ONE HALF LONG LOOSE FITTING BUSHING BETWEEN THE TWO
BUSHINGS ALREADY IN THE FRONT END LIKE THE COVENANT KIT HAS.

THE SPRINGS THAT COME WITH THE KIT ARE FROM FORD TRACTORS AND ARE
THE SAME O.D. AND I.D. AS NORTON AND PROGRESSIVE SPRINGS.
THEY START WITH A TWO AND NINE SIXTEENTHS FREE LENGTH AND HAVE
HAVE A BOUND LENGTH OF ONE AND NINE SIXTEENTHS FOR ONE INCH OF TRAVEL
. FROM WHAT WE KNOW THE STOCKS SPRINGS HAVE ONE HALF OF AN INCH TO GO WITH
THE SLIDER BOTTOMED OUT, THAT IS THE BOTTOM OF THE STANCHION HITS
THE BOTTOM OF THE SLIDER. WE ADD ONE AND ONE HALF OF TRAVEL
WITH LONGER RODS AND THE EXTRA SPRING ADDS ONE INCH AND
THE OLD SPRINGS HAD ONE HALF INCH TO GO SO THE SPRINGS SHOULD
BOTTOM OUT JUST AS THE FORK STANCHIONS DO.
NOW FOR THE FLUID CONTROL
IF THINGS WERE IDEAL ONE WOULD HAVE FULL MOVEMENT WITH HYDRAULIC
STOPS AT EACH END THAT IS NICE AND SLOW ACTING RIGHT AT THE
ENDS OF TRAVEL. THE BEST WE HAVE COME UP WITH SO FAR
IS USING ATF FOR FLUID AND LEAK PROOF BRAND SEALS IT WORKS
ON FIFTY BIKES SO FAR WITH NO ADJUSTMENTS NEEDED NOT
THAT THERE ARE NO ADJUSTMENTS. I HAVE ONE BIKE WITH STOCK SPRINGS
AND ONE WITH PROGRESSIVE SPRINGS AND I HAVE TO SAY
THAT I FIND THE PROGRESSIVE BETTER BUT THE STOCK SPRINGS WORK
WELL TOO.
ON THE CENTER STANDS THESE MODIFIED BIKES DON'T
LIFT THE WHEELS OF THE GROUND ANY MORE BUT STILL WORK FOR ME.
THE IDEA IS TO GET THE BIKE TO GO DOWN FROM YOUR WEIGHT
AT LEAST ONE AND ONE HALF INCHES. THAN RIDE AROUND WITH FOUR
AND ONE HALF POTENTIAL INCHES FOR BUMPS AND THE
ONE AND ONE HALF FOR POT HOLES. NORBSA
_________________
 
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