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2V vs 4V - db4 owner help & hint
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fish



Joined: 15 Mar 2010
Posts: 138
Location: australia

PostPosted: Wed Sep 12, 2012 2:06 pm    Post subject: 900ss engines Reply with quote

hi my db2ef has 100 hp at rear wheel with these mods 985 kit,balanced,blueprinted,41 mm kein flat sides,2v cams,some slight port work and roo racing pipes. oh what a toy it is. Laughing
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bimototo



Joined: 03 Jan 2012
Posts: 167
Location: between Imola Mugello and Misano

PostPosted: Wed Sep 12, 2012 6:54 pm    Post subject: Re: 900ss engines Reply with quote

fish wrote:
hi my db2ef has 100 hp at rear wheel with these mods 985 kit,balanced,blueprinted,41 mm kein flat sides,2v cams,some slight port work and roo racing pipes. oh what a toy it is. Laughing


I know that, 100hp is reachable with all those modifications but, with a 4V unit is very less expensive!!!! Very Happy
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bimototo



Joined: 03 Jan 2012
Posts: 167
Location: between Imola Mugello and Misano

PostPosted: Wed Sep 12, 2012 6:56 pm    Post subject: Reply with quote

Desmo_Demon wrote:
I'm not at home, so I am going from meory, but......I believe an ST engine may work, but the 748/916/996 engine will not be a simple drop-in. IIRC, the rear swingarm mounting boss on the DB2 and ST bikes are wider than the SSSA of the SBK. I am not too sure if you could properly use spacers to make up the slack on the SBK engines. Additionally, the heads are taller on the early 748 and 916/996 bikes. The 2002 and the ST4/ST4S enigines have the "Testa Basso" heads. These heads have the cams dropped a little bit lower into the head. This is for clearance of the front wheel on the ST bikes. There really isn't much of a reason that the 2002 748 have these heads, though (and some late 2001 model 748 bikes).

Additionally, if there is a head clearance issue with the 4V head, you'll probably not have any room at all to stuff a radiator in the front of the bike. You may also run into issues with 2-phase vs 3-phase charging systems and ideally would have to get the complete wiring harness and ECU for the engine you are dropping into it.

There are some other issues, but for some reason I can't think of them right now....

A few years ago I started stuffing an ST4 916 engine into a 1988 Paso 750 frame. I had to trim back the engine mounting bosses and cut the frame to clear the horizontal head. I may have tire/head clearance issues and will either retain the Marzocchi forks or get some custom USD SHowa extensions made. For cooling, I was thinking of using an under-the-horizontal-head oil cooler and using some dirtbike radiators in each of the side fairings (where the original oil coolers are located). I have yet to have the frame rewelded, but I have the engine sitting in the frame with a boxed/channeled ST swingarm so it will mate up to the suspension of the Paso.

One of these days I may actually complete the bike. I was thinkingof several ways to do the gas tank to work with the FI engine of the ST4, but believe I will run a fuel cell and cut the bottom out of a rusty Paso tank to only use it as a decorative cover....kinda like a Bimota. Wink


I need at least two hours of absolute quite and silence for understand every single word Very Happy
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Desmo_Demon



Joined: 19 Sep 2011
Posts: 240
Location: Easley, SC, USA

PostPosted: Wed Sep 12, 2012 11:13 pm    Post subject: Reply with quote

bimototo wrote:
I need at least two hours of absolute quite and silence for understand every single word Very Happy

LOL....yeah, that's a little bit of info, and I just remembered another thing........

2000 and earlier engines use a 10mm engine mounting bolt and the 2001 and newer use a 12 mm engine bolt. If you use a newer engine in the DB2 frame, you will need to drill the holes in the frame. Another potential problem you may have is not being able to get a socket onto the engine mounting bolt if you use the larger diameter bolts. This is because there will not be enough clearance between the frame and the engine bolt head/nut. I've heard of people cutting down the outter diameter of a socket to make it fit. If you wanted to try the 4V engine, chances are, the best engine for the swap would be a '99-'00 ST4 with the 916 engine as the one that may be the easiest.

If you go to that extreme, though, I'd probably opt for a 749 or 999 Testastretta engine so you don't have to worry about the flaking rockers on the Desmoquattro engine.

As for the DS1100 (or 1000) engine in a DB2, the guy from Sweden is in the process of sticking one in his DB2. He goes by Redtop....red.....red-something. Off the top of my head I forgot the name he goes by. Real name is Lars.....I'll go look it up.


Edit - Lars Soderman a.k.a. Redtop. He's on this forum but not very active. This is part of his blog from when he bought his poorly abused DB2...

http://bimota-db2.blogspot.com/search?updated-max=2006-05-18T21%3A00%3A00%2B02%3A00
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Desmo_Demon



Joined: 19 Sep 2011
Posts: 240
Location: Easley, SC, USA

PostPosted: Wed Sep 12, 2012 11:31 pm    Post subject: Reply with quote

duplicate.....
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Last edited by Desmo_Demon on Sat Sep 15, 2012 5:04 am; edited 1 time in total
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Speedmade



Joined: 27 Mar 2012
Posts: 76
Location: Minnesota, USA

PostPosted: Fri Sep 14, 2012 4:23 am    Post subject: Reply with quote

Here's a DB2 I found on the internet in that past. No idea who owns it.
Check out the rear cylinder head. No way the standard suspension still fits there.


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Desmo_Demon



Joined: 19 Sep 2011
Posts: 240
Location: Easley, SC, USA

PostPosted: Sat Sep 15, 2012 5:10 am    Post subject: Reply with quote

Speedmade wrote:
Here's a DB2 I found on the internet in that past. No idea who owns it.
Check out the rear cylinder head. No way the standard suspension still fits there.

Well, looks like it is possible. Wink

I can't tell which heads are on the bike from that picture. For the ST4 heads, the middle rocker pin cover has five bolts vs. 4 bolts for the standard height heads. I would guess there isn't a head-to-wheel clearance issue. I would like to see a close-up of the rear cylinder head. I wonder if that part of the frame rail is modified (along with the suspension), or if they may have shaved the top of the head a little if there wasn't enough room to stuff it in there. From that picture, it does look like the head goes about half a cam gear past the rail, though.
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bimototo



Joined: 03 Jan 2012
Posts: 167
Location: between Imola Mugello and Misano

PostPosted: Sat Sep 15, 2012 5:47 am    Post subject: Reply with quote

Desmo_Demon wrote:
Speedmade wrote:
Here's a DB2 I found on the internet in that past. No idea who owns it.
Check out the rear cylinder head. No way the standard suspension still fits there.

Well, looks like it is possible. Wink

I can't tell which heads are on the bike from that picture. For the ST4 heads, the middle rocker pin cover has five bolts vs. 4 bolts for the standard height heads. I would guess there isn't a head-to-wheel clearance issue. I would like to see a close-up of the rear cylinder head. I wonder if that part of the frame rail is modified (along with the suspension), or if they may have shaved the top of the head a little if there wasn't enough room to stuff it in there. From that picture, it does look like the head goes about half a cam gear past the rail, though.
Shocked Shocked Shocked Shocked
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Desmo_Demon



Joined: 19 Sep 2011
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Location: Easley, SC, USA

PostPosted: Mon Sep 17, 2012 12:16 am    Post subject: Reply with quote

After looking at it again, it looks like the vertical head just barely clears that frame cross member as I think the engine is just mildly tilted so the rail is going right on top of the head.

I wonder what kind of radiator he used and where it is located (up high on the frame where the airbox would be, I would assume.
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Sat Sep 22, 2012 11:31 am    Post subject: Reply with quote

IMHO putting a + 115 HP engine in a db4 chassis will make it hard to ride. Its wheelbase is very short (137-138 cm) and it'll be hard to keep the front wheel down on accelleration. So you can't fully accellerate and this will slow you down... So what's the use of the increased power? Top speed? Again the short wheelbase will make it less stable at speeds over 240 km/h.

Also because of the increase of parts to be put on when you use a liquid cooled engine (hoses, radiators, liquid itself), it'll increase the weight of the bike, making it less handling.

I admit it's a nice challenge to put i.e. a 9xx duc engine in the db4 (a7xx engine is no real use because you can get then same HP output from an air cooled duc engine >900 cc anyway). But you'll have to modify the frame, making returning to the original state a lot harder.

My tricolore db4 is used on track only for the last 6 years. It's got a tuned engine: 944cc Pistal Racing kit, 41mm FCR's with large tapered K&N pod filters on the stock(ish) inlets, ported heads, lightened & rebalanced crankshaft, light flywheel & clutch, modified ignition & wiring loom and all street equipment removed.



The bike's output is estimated 90-95 HP with a dry weight of less than 160 kg. On my home track it's capable of lap times at least 10 seconds faster than I do at this moment. So as long as I can't wring out the bike's performance, creating the need for more power, I'll stick to this package. I'ts proven a very reliable and maintenance friendly bike so far.
Only planned mod for this winter is fitting Carillo con rods, to make the engine even more bulletproof. Maybe a slight increase in performance due to the lighter bottom end will occur.
Also a set of lighter wheels are on my wish list, so I can use the heavy Antera's for rain rubbers.

I would advise every db4/db2 owner to replace the 38z rear chain wheel by a 39z or 40z item. It'll make the bike a lot snappier, because especially with the stock engine, the db4/db2 is over-geared.

AND: don't neglect your front forks!


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Last edited by deebee4 on Sat Sep 22, 2012 9:39 pm; edited 3 times in total
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bimototo



Joined: 03 Jan 2012
Posts: 167
Location: between Imola Mugello and Misano

PostPosted: Sat Sep 22, 2012 12:00 pm    Post subject: Reply with quote

what neglet mean?

so, my bike is now 145kg with oil and half tank of fuel, I know that with all that work the bike runs well, but it's more expensive respect to change the unit.

I've put the bike on dyno for set the PCM and have 73cv at wheel.
In my opinion 120/130cv will be perfect, I use the bike only in mountains road, those power allow to forget the gear.

I have a 41z, and it's ok, max speed 208kmh.
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Sat Sep 22, 2012 9:33 pm    Post subject: Reply with quote

bimototo wrote:
what neglet mean?

so, my bike is now 145kg with oil and half tank of fuel, I know that with all that work the bike runs well, but it's more expensive respect to change the unit.

I've put the bike on dyno for set the PCM and have 73cv at wheel.
In my opinion 120/130cv will be perfect, I use the bike only in mountains road, those power allow to forget the gear.

I have a 41z, and it's ok, max speed 208kmh.


"Neglect" means not take care of, not doing the regular oil changes and inner cleaning.

Wow, how did you get that weight down to 145 kg? Lighter wheels? What did you take off the bike? Please post pictures, I'm very curious. Is yours a db4 ie?

Extra power doesn't mean you can forget about the gear, better go for the torque increase then. If thats the goal: just fit a 1100 air cooled duc engine and you're exactly where you want to be.

41z on a tuned (or 120HP) engine will have the front wheel up in the air all the time execpt at standstill Laughing
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bimototo



Joined: 03 Jan 2012
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Location: between Imola Mugello and Misano

PostPosted: Sat Sep 22, 2012 9:45 pm    Post subject: Reply with quote

hi!
the wheels are stock, I've do all the wiring, taking off all the unuseful think like dash (replaced with a translogic) battery (replaced with a racing battery.uk), rearset, flywheel, airbox, supports, rearbrake tank, clutch drum and basket, oil radiator, belt cover.
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deebee4



Joined: 08 Jan 2011
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Location: Netherlands

PostPosted: Sat Sep 22, 2012 10:01 pm    Post subject: Reply with quote

bimototo wrote:
hi!
the wheels are stock, I've do all the wiring, taking off all the unuseful think like dash (replaced with a translogic) battery (replaced with a racing battery.uk), rearset, flywheel, airbox, supports, rearbrake tank, clutch drum and basket, oil radiator, belt cover.


Please show us your db4! Very curious about your special - lighter - parts, because I would like to save some extra kilograms too.

Of course the best (and cheapest) way to have a better "power to weight ratio" is to have the rider loose some fat........ Laughing

I've seen guys with all kinds of fancy and expensive carbon fiber and titanium parts on their bikes, but they could loose at least 10 kg themselves...... That's what we call "body-tuning"..... Wink
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bimototo



Joined: 03 Jan 2012
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Location: between Imola Mugello and Misano

PostPosted: Sun Sep 23, 2012 2:06 am    Post subject: Reply with quote

I've loose 13kg last year Very Happy
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