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



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

PostPosted: Mon Sep 10, 2012 8:37 pm    Post subject: 2V vs 4V - db4 owner help & hint Reply with quote

hi all,
I have a wonderful idea but I have some (a lot) of doubts!!!

I would like to change my engine 900ie 2V with a 4V unit....

I need your opinion regarding a couple of question:

-the external dimension of the cylinder is the same?
-the rear fork fits exactly?

thanks
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waggy



Joined: 26 Sep 2011
Posts: 277
Location: Northern Ireland

PostPosted: Tue Sep 11, 2012 8:50 am    Post subject: Reply with quote

I seem to recall from some duc forums that 4v's have been fitted to aircooled ss frames, the major mod being altering the frame cross member over the rear cylinder head. The mod being easier on the monster frames as it is a different design, with the area above the rear head being free.
I think the db4 has a frame member across the rear head, which might give problems.
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GeeKay



Joined: 29 May 2009
Posts: 1767
Location: West Yorkshire

PostPosted: Tue Sep 11, 2012 10:19 am    Post subject: Reply with quote

which 4-valve engine are you thinking of using?
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bimototo



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

PostPosted: Tue Sep 11, 2012 12:37 pm    Post subject: Reply with quote

in my opinion the best will be the st4s 996cc unit but a 748s also will be ok!
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bimototo



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

PostPosted: Tue Sep 11, 2012 12:37 pm    Post subject: Reply with quote

in my opinion the best will be the st4s 996cc unit but a 748s also will be ok!
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Evilchicken0



Joined: 12 May 2010
Posts: 2996
Location: London

PostPosted: Tue Sep 11, 2012 2:15 pm    Post subject: Reply with quote

The 748 engine spe is lower than the bigger motors unless you go for the SPS or R versions.

As for the engine swap itself, I wouldn't do it. Yes you'll get more power yada yada but in this case the Bim is designed for the engine and to go that far changes the idea of the bike, (getting the most out of an underpowerred engine). If the 4v motor was just a different head on the original one then yes do it, but it's also watercooled, I think it will loose the value of the bike.
If you still want to do it though have a look at the Suzuki TL1000S engine
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oily



Joined: 05 Apr 2008
Posts: 4788
Location: worcestershire

PostPosted: Tue Sep 11, 2012 2:53 pm    Post subject: Reply with quote

I wondered if someone would spot the obvious.......
If your going to all the trouble of an engine swap, use a Japanese engine engine...TL1000 Laughing
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bimototo



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

PostPosted: Tue Sep 11, 2012 3:50 pm    Post subject: Reply with quote

with a ducati unit the frame bolting are the same!

and, ok that italian police is not so clever but I don't want to risk so much
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waggy



Joined: 26 Sep 2011
Posts: 277
Location: Northern Ireland

PostPosted: Tue Sep 11, 2012 4:39 pm    Post subject: Reply with quote

what about staying aircooled and going with a more modern 1100 duc engine instead.
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bimototo



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

PostPosted: Tue Sep 11, 2012 5:46 pm    Post subject: Reply with quote

the ds engine is my second choice because the second spark plug of the rear cylinder is just in front of a piece of a frame, there was a guy that race in desmochallenge and he has modified the frame with a hole and I DON'T WANT TO DRILL THE FRAME!
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waggy



Joined: 26 Sep 2011
Posts: 277
Location: Northern Ireland

PostPosted: Tue Sep 11, 2012 8:03 pm    Post subject: Reply with quote

maybe the 1100 evo engine could work, as i believe it has single plug heads.
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Tue Sep 11, 2012 11:00 pm    Post subject: Reply with quote

Very Adventurous of you Bimototo, why not go for a 900 carbie version with a 944cc kit, gas flow and polished heads ST2 cams, and modify the tank to take FCR41 Keihin Flatslides and K&N Cone filters.

That then is no change to the frame, suspension linkage, swingarm etc, minor electrics, and will fit in frame and bodywork. Average 90bhp at the back wheel. And you get to keep the crank
Have you had the exisiting one Dyno'd?

Dont forget it is a light bike, too much too light? Who Knows?

I can put you in touch with Cristian Lanzano if you like, an Italian lives in rimini who races a modified DB4 as a track bike. Perhaps you know him?

Pm me your email address and I can send some pictures of his bike and contact details obviously, he speaks Italian. Nice fellow
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bimototo



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

PostPosted: Tue Sep 11, 2012 11:16 pm    Post subject: Reply with quote

Smile

I know Cristian very well, I've been in his garage last year for see the bike!

my idea is to reach 100hp or a little less, but I prefer to reach them with a stock unit due to affidability and fuel consumpion!
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Tue Sep 11, 2012 11:41 pm    Post subject: Reply with quote

Affordability is the Key to it all, can go on for ever ever when you start.

Say Ciao to Cristian and Gracie mille. I bought his DB5R from him, and am most happy. Small world Eh?
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Desmo_Demon



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

PostPosted: Wed Sep 12, 2012 6:29 am    Post subject: Reply with quote

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
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