Chris M.
New member
- Location
- southern downs, Qld
G'day all. I'm doing the teflon bush conversion on a set of 38mm Marzocchi forks that Vince has mentioned. To do this has been a fair bit or of rooting around and I'm not sure I'd bother doing it again and I'm still not finished so I can't report on whether it's been worth it. Anyway, I started with a set of 38mm Marzo's sliders I bought off Ducati Paddy which were slightly bent for some reason so they're perfect for this modification, a set of VT/VFR Honda Showa fork cartridges and a set of 38mm Yamaha XJ Seca forks which are 595mm long. The idea has been to use the Marzzo sliders, the Yamaha bushed stanchions and the Honda cartridges.
The first job was to get the sliders machined/honed and this took me months to find someone capable of doing it. No one in Australia seems to have the capability (as far as I can work out) to machine the legs so honing seems to be the only available option. I used a mob in Sydney (Diamond Hard Chrome) who apparently did some for Laverda Oz but I've never heard if they were successful or not. I chose the Yamaha legs because they already have a bush seat on the bottom of the stanchion and I could also get the I.D. for the slider. Breganzane is right and the clearance needed is 39mm. This cost me $400 after they quoted $300 but then tried to charge me $500 after snapping the lip off one of the sliders. They had it fixed but then wanted to charge me for it as well so we negotiated a price. I then had a local bloke machine the top bush seat in the Marzzo sliders for a carton of XXXX Gold so the leg now sides beautifully up and down. Yamaha teflon bushes aren't cheap and cost me $80 for the set. That's been the easy bit.
I chased up Ron Young, the Ducati engineer near Maitland and he says he's done quite a few variations from just modifying some Showa cartridges to adding bushes. He reckons the simplest way to add bushes is to use Ceriani stanchions because they have enough meat to machine in the lower seat. I can't comment on this method because he didn't say whether he'd honed out the sliders or not or kept the bush inside the 38mm clearance. Road and Race sell Ceriani legs for a couple of hundred bucks so I'm tempted to change tack here. The reason being is that there is a lot of rooting around making various spacers to shoe horn in the Honda cartridges into a Yamaha stanchion. The main problem is fitting the cartridge through the bottom of the tube and mating it with the standard 12mm cap head screw (Showa use 8mm) used to join the damper rod and the slider. I've designed a top hat type plug to fit a longer 8mm cap head (which I might change still) but I reckon it'd be easier using Ceriani legs because the cartridge can fit right through and would be easier to make a joining top hat spacer similar to what was there from standard.
The other side to this adaptation is fitting the top caps and shortening the adjuster rods. Ron Y. hides his inside the forks to keep the period look but I decided to have them exposed so I can muck around with it. I've kept the Honda caps and had them re-threaded to fit the Yamaha threads. Marzocchi ones are too small and can't be used. The beauty of the Honda cartridges is that there are a number of simple modifications anyone can make to improve them. Or you can swap out the cartridges, which are removable and have then tricked up by a suspension shop. There's numerous options available to play with the shim stacks.
This project has taken me years to get this far and I still haven't had the time to finish it though I hope to later in the year. Cost wise I've spent about $1500, re-hard chroming the Yamaha legs, honing the sliders, buying the various fork bits and pieces, some Race Tech springs and supplying beer for a few blokes with lathes. That's a set of forks for $1500 and with a pair triple clamps makes them reasonably priced considering the technical level of improvement. Maybe it's good value, time will tell? My guess is that it will transform the front end because it will have reduced stiction so I can then try to improve the damping control. If you own a 38mm forked bike then you either put up with what it came with, use emulators which are fine on a race track and (I reckon) average on the road or use something bigger, more modern or try this.
If you want photos just ask and I'll get some posted.
Cheers
The first job was to get the sliders machined/honed and this took me months to find someone capable of doing it. No one in Australia seems to have the capability (as far as I can work out) to machine the legs so honing seems to be the only available option. I used a mob in Sydney (Diamond Hard Chrome) who apparently did some for Laverda Oz but I've never heard if they were successful or not. I chose the Yamaha legs because they already have a bush seat on the bottom of the stanchion and I could also get the I.D. for the slider. Breganzane is right and the clearance needed is 39mm. This cost me $400 after they quoted $300 but then tried to charge me $500 after snapping the lip off one of the sliders. They had it fixed but then wanted to charge me for it as well so we negotiated a price. I then had a local bloke machine the top bush seat in the Marzzo sliders for a carton of XXXX Gold so the leg now sides beautifully up and down. Yamaha teflon bushes aren't cheap and cost me $80 for the set. That's been the easy bit.
I chased up Ron Young, the Ducati engineer near Maitland and he says he's done quite a few variations from just modifying some Showa cartridges to adding bushes. He reckons the simplest way to add bushes is to use Ceriani stanchions because they have enough meat to machine in the lower seat. I can't comment on this method because he didn't say whether he'd honed out the sliders or not or kept the bush inside the 38mm clearance. Road and Race sell Ceriani legs for a couple of hundred bucks so I'm tempted to change tack here. The reason being is that there is a lot of rooting around making various spacers to shoe horn in the Honda cartridges into a Yamaha stanchion. The main problem is fitting the cartridge through the bottom of the tube and mating it with the standard 12mm cap head screw (Showa use 8mm) used to join the damper rod and the slider. I've designed a top hat type plug to fit a longer 8mm cap head (which I might change still) but I reckon it'd be easier using Ceriani legs because the cartridge can fit right through and would be easier to make a joining top hat spacer similar to what was there from standard.
The other side to this adaptation is fitting the top caps and shortening the adjuster rods. Ron Y. hides his inside the forks to keep the period look but I decided to have them exposed so I can muck around with it. I've kept the Honda caps and had them re-threaded to fit the Yamaha threads. Marzocchi ones are too small and can't be used. The beauty of the Honda cartridges is that there are a number of simple modifications anyone can make to improve them. Or you can swap out the cartridges, which are removable and have then tricked up by a suspension shop. There's numerous options available to play with the shim stacks.
This project has taken me years to get this far and I still haven't had the time to finish it though I hope to later in the year. Cost wise I've spent about $1500, re-hard chroming the Yamaha legs, honing the sliders, buying the various fork bits and pieces, some Race Tech springs and supplying beer for a few blokes with lathes. That's a set of forks for $1500 and with a pair triple clamps makes them reasonably priced considering the technical level of improvement. Maybe it's good value, time will tell? My guess is that it will transform the front end because it will have reduced stiction so I can then try to improve the damping control. If you own a 38mm forked bike then you either put up with what it came with, use emulators which are fine on a race track and (I reckon) average on the road or use something bigger, more modern or try this.
If you want photos just ask and I'll get some posted.
Cheers
