Bimota Forum Forum Index Bimota Forum
Forum for Bimota Owners and Riders
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  

DB4 Fuel Pump/System Questions

 
Post new topic   Reply to topic    Bimota Forum Forum Index -> DB Series
View previous topic :: View next topic  
Author Message
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Sun Jan 09, 2022 2:12 am    Post subject: DB4 Fuel Pump/System Questions Reply with quote

Working on getting my new to me DB4 back on the road.

Currently there is a fuel pump zip tied to the front cross on the frame. Its slightly more janky then I would have thought.

Can someone shed some light, or share some pictures of how it is all supposed to be installed? I got two pumps with the bike, unsure if one was the original and failed?

Bike has the Corse kit. Without the kit I think the bikes are gravity fed.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)


Last edited by Jaguar on Sun Jan 16, 2022 5:56 pm; edited 1 time in total
Back to top
View user's profile Send private message
brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Sun Jan 09, 2022 12:32 pm    Post subject: Reply with quote

No. All DB4's had a vacuum pulse type fuel pump which is bolted to the bottom of the fuel tank. Fuel hoses connect the petcock to the pump and then pump to carburettors.
_________________
'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
Back to top
View user's profile Send private message Send e-mail
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Sun Jan 09, 2022 5:10 pm    Post subject: Reply with quote

I have that, but there is also an electric fuel pump added.

Was under the impression this was part of the Corse kit, but I do not fully understand why it would be needed.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Mon Jan 10, 2022 11:42 am    Post subject: Reply with quote

As far as i know even the Corse bikes only had the vacuum fuel pump. My guess is that a previous owner has added the electric pump. Not really needed if the vacuum pump is working.
_________________
'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
Back to top
View user's profile Send private message Send e-mail
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Tue Jan 11, 2022 2:43 am    Post subject: Reply with quote

Interesting.
Been reading as many threads as I can find, and you seem correct.

Even found a new vacuum fuel pump in the parts stash that came with the bike!

Ordered the Mikuni replacement for good measure too.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Tue Jan 11, 2022 11:53 am    Post subject: Reply with quote

Good move. I'm happy enough with the vacuum pump. It works fine and is much neater, less clutter and lighter than an electric pump. The less electrics on these finicky things the better!!!
_________________
'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
Back to top
View user's profile Send private message Send e-mail
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Tue Jan 11, 2022 2:27 pm    Post subject: Reply with quote

Yeah the electric fuel pump was not integrated elegantly to say the least.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Wed Jan 12, 2022 9:17 am    Post subject: Reply with quote

Hi Jaguar...you dont say whether the bike runs fine or not.....old addage I follow is "if it aint broke dont fix it".....THis is a mikuni pump that is the same as the paioli units originally bolted to the underside of the tank

https://www.ebay.co.uk/itm/332555807480?hash=item4d6ddeeaf8:g:VfsAAOSwGntahaHK

They have round rubber diaphragms in them that can fail....they work like a tropical fish tank air pump....one of the outlets connects with a rubber small tube to the intake plenum tube on the rear facing vertical cylinder......the cranking of the engine causes suction and operates the vaccum pump......you can easily remove the pump and test it.....suck on one side and see if the other side sucks also

I replaced my paioli pump on my DB4 as it had failed...and a mate did same on his....as the seals had failed....you can pull apart and check...I would say though....one...or the other.....If you have the MotoCorse DB4 version....this has larger flatslide carbs.....is the tube connected from the pump to the intake alloy cranked tube...RHS of bike you can see it.

I would say that an electrical pump "might" be needed to give correct and adequate fuel flow at high engine speeds.....my DB4 occassionally spluttered at high engine speeds.....also....with an electrical pump....it will tick and pre prime the carbs when ignition is on......the vaccuum operated pump will not....it will only prime the carbs when the engine is cranked......electric pumps will tick and then slow the ticking and stop ticking when carbs are fully primed.....Has the bike been stood idle for a long time? with tank empty of fuel? As this can kill the seals in the electric pump also...drying them out...and then when fresh fuel kicks in after 10 years....it refreshes the seals and works for a bit...but then the seals break down....does it have an inline filter after all these pumps prior to introducing fuel into the carbs? If not broken down seal bits will end up in there....

THats my tuppeny worth.....My DB2 has a big bore 944 kit and flatslide Keihin FCR41 carbs....and needs a seperate fuel pump all of its own.....But...does yours work or are you going thru things before a first test??.....Introduce a fuel filter and try....If it aint broke...dont fix it
Back to top
View user's profile Send private message
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Wed Jan 12, 2022 2:31 pm    Post subject: Reply with quote

Bike came to me after sitting for a while, so just going through it with a fine tooth comb. Was told that it was "cold blooded" before it was sitting.

The vacuum pump was not connected at all. The front and rear intakes have the small rubber lines connected to each other and then run to the pump.

The electric pump was zip tied to the front frame cross member. The line were routed oddly.

Basically the fuel system just needs a little love and a proper set up.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Wed Jan 12, 2022 4:56 pm    Post subject: Reply with quote

Does it have Keihin FCR39 flatslides fitted?...If its a corse version it should....they dont have chokes...so yup....take a fair bit of getting going....I have a knurled twisty knob cable into my FCR41's....and I turn it in a couple of turns when starting from cold...and just try to catch the throttle when it fires and tickle it little by little until it revs clean....like starting a 2 stroke after a long slumber.....maybe the diaphragm was not connected coz its seals had failed??
Back to top
View user's profile Send private message
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Wed Jan 12, 2022 6:38 pm    Post subject: Reply with quote

Yeah 39mm.

The vacuum pump that was on the bike had a perished diaphragm.
I assume rather then fix that, they just installed an electric pump.
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Sun Jan 16, 2022 3:45 pm    Post subject: Reply with quote

The Mikuni pump is exactly the same. I ended up using a Mikuni rebuild kit to repair my original pump.

Next question.

I know the line has to go from the petcock to the pump, and then from the pump to the carbs.
Question is. Do I want the exit of the pump to be on the right or left hand side to make life easier. Will spent some time in the garage trying options. Just figured someone knew what it was supposed to be.

thanks for the help
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
Jaguar



Joined: 15 Sep 2017
Posts: 268
Location: Albany NY

PostPosted: Sun Jan 16, 2022 5:55 pm    Post subject: Reply with quote

Petcock mounting question.

It shares the same mount as the fuel level switch, so there are two options.

One:
mount on the "outside" closest to the frame. Could operate it if you really wanted too, but the fuel line needs to be run back towards the head.

Two:
mount in the "center". Fuel line routing would be better, but there is zero chance you would ever operate the petcock.

So what is the "correct" way to route/mount everything?
_________________
Bimota (Tesi 1D 904SR, DB2, DB4, SB6,SB6R, SB8R, SB8K Santa Monica) Ducati (1000SS, Monster S4, 999R) Aprilia (RSV Mille R Haga) Honda (CL125s and 70s Chopper)
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Bimota Forum Forum Index -> DB Series All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group

The Bimota Forum has no official connection to Bimota S.p.A.. We just ride or are interested in their motorcycles and support the brand. All trademarks are acknowledged