|Dieci Care and Feeding
This is a list of things that I’ve done and learned about my ‘91 Dieci.
1. I can get about 140 miles out of a tank of gas. At that point, I only have an itty bit of gas left in the tank. My “magic red button” fuel reserve solenoid has been disconnected, too. I understand that running bikes with fuel pumps out of gas is typically not a good idea, as the fuel lubricates and cools the pump impeller area. Therefore, I usually chicken out and get gas at the 120mile mark. Gas mileage seems constant at around 30mpg.
2. I replaced the 7mm head brake caliper bolts with standard M10’s (8mm allen head). 7mm allen heads are a very strange choice for caliper fasteners- many wrench sets go from 6 to 8mm allen wrenches with no 7mm. The 8mm is much more commonly found. I discovered this all when I tried to get a brake caliper off on the side of the road one hot summer day. Speaking of calipers, I can just sneak the left caliper off the fork if I take out the pads first. Not so for the right caliper. Otherwise, you have to take the front wheel off to remove the brake calipers.
3. The back tail section bolts are huge 12mm allen head fasteners. You’ll be hard pressed to find an allen wrench that will fit this. I welded a 13 mm nut to the end of a 12mm hex head fastener. I stick the 12mm side in the tail section bolt and use a 13mm wrench to turn it now. Works great. Be careful with these bolts, too, as my right side bolt hole is stripped, and the bolt is missing. What are the chances of finding a replacement? Slim to none, I’m assuming, though I have my eyes peeled for a suitable good-looking fix…. UPDATE: MOTO POINT USA had replacement bolts for $15 each. Kool.
4. You can jack the front end up by using M10 bolts and hollow cylindrical spacers with the threaded holes on either side of the engine. Stick jack stands under the bolts and you can get the front end of the bike off the ground for tire changes, etc. You still have to drop the lowers to access these holes, but I’ve gotten that down to a 10-minute job now.
5. Compared to other USD forks, the Marzocchis are relatively easy to work on. You don’t need any special tools to get the damper rods out, unlike Showa USD forks (as found on GSXR’s). With only a single damping adjuster, they don’t have quite the adjustment that the Showas (with separate compression, rebound, and preload adjustments on each fork leg) do, though. As San Diego Dieci rider Steve pointed out, the Dieci's Marzocchi USD forks have rebound adjustment on one fork leg and compresssion adjustment on the other, which was near state of the art in '91. :-)
6. Diecis do not like the combination of hot weather, high altitude, and low speeds. Mine overheated and wouldn’t start when I drove it a mile down a gravel road in 5200’ altitude, 85 degree weather, 5mph forward speed conditions. Go figure. Guess I won’t be running the Dakar rally on it this year.
7. My bike came with no steering damper, so I added one, as the steering felt a bit unstable at speed. I had a damper unit from a late model GSXR, so I used that for the time being (until a suitable Italian unit can be found…). I machined a bracket that bolts onto the right fork leg. The body of the damper is mounted to the front fairing frame- there is a convenient M6 hole right in front of the steering head (where the stock damper went, I’m sure). Ahhhhh…much more stable stering now. UPDATE: I fitted an adjustable Bitubo damper (swiped from a Guzzi) on the Dieci, and it works very well.
8. If you haven’t already, check your cush drive bolts! These are the 5 bolts that transfer power from the cush drive to the rear wheel. 3 of 5 of mine were loose, and 1 was broken! Torque and Loctite those suckers!
9. My gas tank was already modified so that the auxiliary fuel solenoid was disconnected. I took the entire fitting out for the solenoid and replaced it with an M10 bolt in the tank and covered the whole mess with JB Weld. This prevented the solenoid from leaking as it was previously.