DB4 Mods - TwoWheelForum: Motorcycle and Sportbike forums
 
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post #1 of 11 (permalink) Old 09-11-2006, 09:03 AM Thread Starter
 
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DB4 Mods

Before buying this little beast I had done enough research to know that most Bimotas needed some initial "tuning"; they often came with "issues". The Db4's in particular had some low-speed, small throttle opening roughness and the stock Mikunis were noted for not keeping synch. In addition, the stock "shotgun" exhaust was a major cork in knocking a large chunk of top end off the all-but-stock 904 Ducati mill. I had ordered some flatslide Keihins, as well as a Moto Corse full titainum system which not only increases drivabilty, but has the added benefit of knocking off almost 30 lbs of weight (over 20 lbs saved on the exhaust, plus the airbox, evap canister, and a couple other bits go bye-bye. I also chucked the heavy cast folding footpegs and saved a few more ounces with some billet items.) The old rubber hydraulic lines went in the can, replaced by stainless braided.

The new flatslides have no choke or enrichner circuit, so starting is accomplished by turning on the fuel petcock (yep), waiting a few seconds, and then cranking a few turns on the throttle to actuate the accelerator pumps. Turn the key and the motor fires right off, hot or cold.

The Corse system is mellow on the bottom and midrange, and, as the motor is still in break-in, I don't know how the top end will sound, but if a couple of half-throttle short bursts are any indication, it should howl. It's raspy, but the tone doesn't have the hard edge that my old ST2 with the Duc carbon cans had...that thing could be downright embarrassing in town. This has more of a mellow Harley chuff on light throttle.

The clutch feel is "relatively" light (for a Duc motor, Bimota changed the piston ratio on their master cylinder)) but has the characteristic "jangle" when disengaged. Shifting is very smooth, and requires barely a touch, a welcome change from the stiff shifter on the Ducati.

First gear is VERY tall, requiring a bit of throttle to get things moving, but once the tach is over three grand things get busy IN A HURRY; although, with 9 or 10 year old tires, the amount of playing around I was willing to do was minimal, putting this thing on its side with less than 50 miles on the clock was to be avoided. Stock, the 904 mill makes horsepower in the mid 80's...the carb and exhaust changes are worth about 8-10 hp...not much by todays hyperbike standards, but then, not many hyperbikes weigh-in in dirtbike range, either. The end result is a reasonable amount of horsepower in a very light package. The big bonus is the torque...gobs and gobs of it from right off the bottom.

Suspension is on the very firm side; the owners manual doesn't even address the 5 way adjustable forks or the 4 way shocks...Paoli supplies a separate manual for the forks and addresses service and rebuilding, but doesn't even mention the adjustments, so I'm going to have to do some research once I'm through break-in and put some decent tires on it.

Brakes are Brembos...and they stop right NOW. Its the same system used on my old 150lb heavier ST2, so there is more than enough power to stand it on its nose with two fingers....and on the other end is this teeeny 'lil 8 inch disk and two-pot setup, with just enough oomph to settle the suspension going into a turn, but very little slowing capability at all.

So, what we have is a small, light 900cc bike, with a wheelbase 1.5 in shorter than an R-6, double the torque, and weighing in twenty lbs less than an RD350 Yamaha....even with the hard tires, exiting ANY turn with more than 1/4 throttle nets you a little headshake as the front tire first patters over the road and then loses contact entirely as the front heads skyward. Interesting. Looks like a steering damper is in order......ohh and look, under the left fairing shroud is a bracket already in place for an Ohlins unit.

The bike flicks into a turn with no effort; steering is neutral and solid, not nervous feeling like you'd expect such a teeny bike to feel. Even on some of the choppy pavement up in wester Md, hitting bumps mid-turn never unsettled the bike. Very confidence inspiring even with the dicey tires.

A little more work with some good tires, maybe some titainiam or carbon bits, and maybe send the seat out to Sargent this winter for some real padding and I'll be there.
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post #2 of 11 (permalink) Old 09-11-2006, 09:11 AM
 
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Sweet bike and good write up.



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post #3 of 11 (permalink) Old 09-11-2006, 12:45 PM
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Quote:
Originally Posted by marko138 View Post
Sweet bike and good write up.
I would love to sport that.

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Currently ride 1987 GSXR 50, 1996 Ducati M900, 2005 GSXR 1000
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post #4 of 11 (permalink) Old 09-11-2006, 11:20 PM
 
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Beautiful, and that swingarm, wow. I always wanted the Bimota with the Yamaha FZR1000 engine.
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post #5 of 11 (permalink) Old 09-26-2006, 09:51 AM
 
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You might want to contact Greg Rammel in Michigan. He was a Bimota dealer for years, owns a DB2 himself and really knows about all the possible mods. Call him on 248-347-9638.
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post #6 of 11 (permalink) Old 09-26-2006, 11:45 AM
 
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sweet ride...
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post #7 of 11 (permalink) Old 02-16-2007, 03:47 PM
 
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Damn. Good write up. So what is the weight?
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post #8 of 11 (permalink) Old 02-16-2007, 03:53 PM
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Originally Posted by DLIT View Post
Damn. Good write up. So what is the weight?
but its not "in dirt bike range" My bike was 230 race ready. That thing is at least 300lbs.
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post #9 of 11 (permalink) Old 02-16-2007, 03:57 PM
 
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What size rear tire is that?
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post #10 of 11 (permalink) Old 02-17-2007, 04:02 PM Thread Starter
 
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Quote:
Originally Posted by Rider View Post
but its not "in dirt bike range" My bike was 230 race ready. That thing is at least 300lbs.
These are yr 2000 models (as is my Db4):
These bikes average about 43-49hp.

KTM640.....348 lbs dry

MZ 660 Baghira.... 348 Dry

Suz DR600.... 352 Wet

Yam TT600.... 337 Dry


Bimota Db4 current wt 331. Current hp in the 85-90 range.
Guys are racing these with 105-110 hp; with all the street stuff removed they scale in at 250 lbs . (Track plastics, racing wheels and brakes, lotsa Ti and CF, lightened flywheel, alt, crank, carillos, lw pistons ect.)

Rear tire is a 180/55 17. Have new Michelins waiting for warm day.
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post #11 of 11 (permalink) Old 02-18-2007, 10:30 AM
 
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Too bad most sportbike guys only go for the big HP numbers. The DB4 is an example of a bike Ducati should build - a new, lightweight SS model. The combination of light weight and broad torque band creates a real fun machine, and if Ducati built it (instead of Bimota), it might even be affordable.
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