Bimota Forum

welshlamb · Posted: Mon Apr 12, 2021 4:18 pm Post subject: Recommissioned DB2

OK. First run in 18 months following recommissioning. Everything is connected back up. Fresh fuel, Plugs and battery. Turn ignition key: neutral battery and oil lights come on and fuel pump primes carbs and then stops after a few seconds. Hit starter button....nothing! Have jiggled kill switch a few times but no difference. Is that a likely fault before i take the switch apart?

Collective genius of the forum sought!
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Not as many bikes as I would like and already too many to keep up with!

welshlamb · Posted: Mon Apr 12, 2021 6:47 pm Post subject:

Please put collective genius on hold (at least for now!)

Found one connector not fully pushed home.
Once properly secured (Doh!) now turning over but not firing. Will quit while I’m ahead for the day. Battery on a top up overnight. Will then check fuel, and spark. Fingers crossed.

Starting up is the worst part after a rebuild/recommissioning. Doesn’t matter how brill the design or brill the execution, if the motor doesn’t start its worth didley squit!!
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Not as many bikes as I would like and already too many to keep up with!

2bims · Joined: 03 Apr 2010 Posts: 7294

My Ducati 900ss scared the life out of me....Fully rebuilt evey nut and bolt....frech fuel....checked all lights horn etc...new carbs...uncle on standby with fire extinguisher....pressed the starter button...and.....Ruddy fired into life without even cranking...scared the crap out of me....running from first prod....

Spark?....HT leads on plug caps can corrode...unscrew pug caps and retrim to make fresh copper ends....Is the fuel on....sounds like so because the ticking of the pump has stopped meaning the carbs are charged....kill switches can be problematic.....killing when not in kill position....try with some rubber insulated pliers....and cross the brass terminals on the starter solenoid.....

Re kill switch...it will still crank if not working or swtiched off...but wont start....I do have 2 new spare ones...but for you...play swapsies with other bike...ONLY...I mean ONLY...change over 1 thing at a time......have you got the coil packs on the right cylinders?...CT packs wired incorrect....so timing and spark are out?

brian · Joined: 22 Aug 2011 Posts: 3789 Location: Australia

Electrical issues can be a challenge. Just work your way through things one at a time to eliminate things as you go.
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'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

welshlamb · Posted: Sun Apr 18, 2021 10:08 pm Post subject:

Fresh fuel, pump working. Plug gaps reset as a tad too wide. Checked i wa getting a spark. On FULL choke it eventually fired . Doesn’t like coming off choke. I have read on the Ducati forum (yes I know!) that pilot jets often get bunged up. Will put some carb cleaner through the system tomorrow and see if that improves things. After It warmed up I did have a a slight drip from the oil filter so gave that a tweak and seems OK now. Brakes work and so does clutch (a relief after all the pain of bleeding them and fitting a new rear brake master cylinder.)

Thanks for the suggestions above.

Going in the right direction. Hope to get its clothes on this week!
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Not as many bikes as I would like and already too many to keep up with!

2bims · Joined: 03 Apr 2010 Posts: 7294

Low idle jets it sounds like...had it with a friends DB4....with brake cleaner it fired right up....shot down the spark plug holes.....but would only run if revved over 4K....low idle jets were blocked....which DB2 as in what carbs are you talking about?

brian · Joined: 22 Aug 2011 Posts: 3789 Location: Australia

Agreed.... pilot circuit has a blockage by the sound of it. unlikely that carb cleaner will clear the blockage. Most likely the pilot jets as they have VERY tiny holes through them. Usually need to poke a wire from a wire brush through to clear or carefully with a small jet drill. Your carbs would benefit from a full strip and ultrasonic clean. Be sure to always synchronize (balance) the carbs after having them apart.
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'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

brian · Joined: 22 Aug 2011 Posts: 3789 Location: Australia

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'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

welshlamb · Posted: Wed Apr 21, 2021 9:02 pm Post subject:

MMMmm. No joy today trying to get it running below 1500rpm/smoothly so carbs coming off for a deep clean. Will advise!!
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Not as many bikes as I would like and already too many to keep up with!

welshlamb · Posted: Wed May 05, 2021 11:15 pm Post subject:

Carbs have been ultrasonic cleaned. All jets and passages blown through . Reassembled with new seals o rings and float needles. Float height set at 13mm, air screws 3 and 3.1/4 turns out from full in. New fully charged battery.

Bike turns over but wont fire! At least before carb service it ran on full choke.

Petrol pump working, all fuses OK, Will check spark at plugs tomorrow and go from there. I must be missing something but at present not sure what.

Watch this space.
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Not as many bikes as I would like and already too many to keep up with!

atomibart · Joined: 11 Apr 2011 Posts: 126 Location: France

Did you check if oil arrived to the carbs ?

2bims · Joined: 03 Apr 2010 Posts: 7294

Pull vertical plug.....and spray Quick Start or Brake cleaner down there.....connect up and fire.....doing to both cylinders best but not always necessary......Did it yesterday to someones DB4 that wouldnt fire.....he tried for 10 minutes and nothing.....Some Holts Quick start and fired first prod and then pulled fuel through and ran....and then restarted and restarted.....

welshlamb · Posted: Thu May 06, 2021 10:59 am Post subject:

Checked fuel level in carbs using the clear pipe on drain outlet and its within 1-2mm of where it should be. Checked spark using the old plug out and hold against casings method. Looks like good spark.

Will double check gap and try some 'starter magic' as 2 Bims suggests. After that I';m a bit stumped as its got a spark, fuel and compression.

Mmmmmm!
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Not as many bikes as I would like and already too many to keep up with!

welshlamb · Posted: Thu May 06, 2021 6:02 pm Post subject:

PROGRESS. on 3rd try with the 'Cold Start' spray she roared into life. I adjusted the throttle stop and she started up without choke 4 or 5 times. (OK Steve its your choice of cakes when I visit next!)

Q/. What rpm should I be aiming at for idle? at the moment its just over 1000rpm after a minutes running, much lower and the charging light flickers.

Also has a bit of exhaust popping at idle.The pilot screws were reset at 3 turns out (horiz cyl) and 3.1/4 (vert Cyl) after the clean/rebuild. (Pretty sure these are Ducati 900s settings although this sint given in Haynes manual!). They were set at 4 and 4. 1/2 turns out when disassembled.

Q/. Does anyone know if DB2 Bimota settings were different. Old skool teaching (if I remember correctly) was to turn the pilot screw for fastest idle and then adjust throttle stop screw to the correct level. It would be nice though if anyone has a note of the pilot screw settings they have found/used
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Not as many bikes as I would like and already too many to keep up with!

brian · Joined: 22 Aug 2011 Posts: 3789 Location: Australia

I’ll check my notes when I get back to the shed for my DB4 settings which should be close (although we are at different ends of the planet). From memory my DB2 junior pilot screws are around 3 1/2 turns out.

My DB4 still popes a little at idle, mainly when cold. Double check that you don’t have a leak on a header or elsewhere on the exhaust system. Popping can be caused by air being sucked back into the exhaust and igniting unburnt fuel
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'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