Posted by David K on December 14, 2002 at 03:28:22:
In Reply to: David K LS engine posted by George M on December 13, 2002 at 20:42:10:
KTM DUKE 620 Single Cylinder Thumper
(Can the Duke be modified to perform with 600cc multi cyl sportbikes?)
With a few reasonable modifications the Duke can hold its own with F3's, ZX's and FZR's. The engine is very understressed in stock form, with the following mods the engine will produce over 70 HP at the rear wheel. Drop one tooth on the countershaft sprocket, install a MegaCycle TT grind cam, either install a 11:1 piston (Cosworth) or have the head milled for a 11:1 CR, Port and polish the head, .5mm larger valves, Malcom Smith competition stainless steel exhaust with 6 supertrap discs and a White Bros billet 'snuff or not' end cap, throw away the Quick Silver II carb and replace with a 40mm Dell'Orto carb from a KTM 620 EXC(Email me for details on carb set up).. These mods will cost around $1,000 and will produce over 70HP. Now for the suspension; install a Race Tech gold valve in the forks, use 1mm less oil, have the shock revalved for softer initial compression, set the sag at 3.75 inches (200 lb rider), install good DOT race rubber, such as Dunlop SportmaxII , Pirelli Dragons, Metzler MEZ 1. In the stock sizes, air pressure 36 front, 40 rear. The brakes are fantastic in stock form. I have cut the pad width by half on the rear brake because it tends to lock up very easy.
(What problems are occurring with the Duke)
Hard starting cold is the single most reported problem (7 cases), The 40mm Dell'Orto carb swap will cure this problem (Email me for carb set up info)
Three cases of hot hard starting (all carb problems are due to the QuickSilver II carb)
Electrical problems, indicator lamp failure, coil failure these problems have been caused by sloppy assembly of the wiring harness at the factory. Warranty will cover these as they all appeared within the first month of ownership.
(What level of performance can I expect with all the modifications?)
The Duke against a 93 Ducati 900 Superlight. From a dead stop to 100 MPH the Duke won by several bike lengths, after 100 MPH the Duck would pull on by. Stopping from 80 MPH; the Duke stopped 20 feet sooner than the Duck.