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db4 - Italian electrics or maybe something else?
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Fri Dec 27, 2013 10:17 pm    Post subject: Reply with quote

Well, imho an engine that's not running properly without unusual mechanical noises most of the time only 2 things can be wrong: either the mixture or the spark.

Is it only running badly at slow revs like at idle or only at higher revs over all over the range? Low revs: maybe the carbs are out of sync? High revs: feels like misfiring or just no puff? Even the key contact switch can cause wicked problems, In my switch the contact was burned and slightly displaced. Also the handlebar stop switch can get worn during the years.

First check the mixture: the complete tract from the fuel tank down to the jets in the carbs. Check fuel delivery. If yours still has the vacuum fuel pump test its functionality and look for signs of internal leakage (actating membrane) Just suck on the vacuum hose and if you taste fuel it's shot. You can replace it but also might consider fitting an electric fuel pump like fitted on most Japanese carburetted mulitcylinder bikes from the era before the fuel injection. Like FZR, VFR, ZXR etc. It's a low pressure Mitsubishi mebrane pump, very reliable. Easy to find on flea bay. Works like a charm.

Fuel pump working? check if the fuel reaches the carb float bowls. There might be a stuck float needle inside or another obstruction. Do you have an extra fuel filter between pump and carbs? Also the tiny filter in the T-shaped plastic tube where the fuel hose attaches can get obstructed.

Assuming all's fine (maybe after a correction) fire it up and check if it's only one cylinder behaving badly or both. Slowly twist the throttle slightly up and see what happens. I can't write everything down here so just come back if you discovered something noteworthy.

Spark issues: I had misfiring above 7K rpm, on the dyno it was more obvious than on the road. After the usual checks did not reveal something i decided to replace as much as could reach the ignition wiring with 2,5 mm2 gauge wire. On the fly making every contact surface immaculate. That helped and any misfiring was completey cured, even better starting and idling.
There are 2 pickups in the lh side of the engine, that usually are dead reliable. But you can check them with an Ohm meter while they're still in place. Before doing that check ignition timing with a strobe light and check ignition advance on both horizontal and vertical cylinder. If that's a stable reading nothing wrong with that. If you see different behavior per cylinder swap Kokusan ignition boxes (horizontal with vertical) and see if the other cylinder has the problem now.

My db4 is only used for track riding and I trust when you take yours to track (and is running properly) you'll take it to track more often.

Mine's stripped, no lights, and some modifications (like usual 944 HC kit, 41MM FCR, lightened interior, open 2 into 1 Akrapovic and brake upgrade, amongst more fiddling...Wink
I've improved my lap times last season with it and plan more progression next season.

Now she's waiting to be prepaired for the next season.

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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Sat Dec 28, 2013 12:03 am    Post subject: Reply with quote

Thanks for taking the time to pen a long reply deebee, that great info. I've previously done quite a lot of what you suggested. Mine seems to be an intermitent problem. Sometimes it runs fine and i can do a long run without so much as a single hiccup, idles, starts, pulls, and runs just fine. But the next time i go out it'll start missing and then deteriorates to a point where i can hardly keep it running. When it's playing up it will still run ok in the mid to high rev range.

Being an intermitent fault, makes me think that it's electrical. I' guessing if it were fuel related it would run sick all the time. I've got too many half done jobs at the moment to be able to spend time on it.

I'll give an update when i get around to having another go at it.

Thanks again.

P.S. Nice pic of you on the track mate Exclamation Wink
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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
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Sat Dec 28, 2013 11:39 am    Post subject: Reply with quote

UR welcome. How long ago was it since you cleaned out the carburettors? It could well be that a small particle/deposit in a float bowl clogs up your idle jet now and then. Just take them off the bike and clean them meticulously. Take them apart, after writing down the settings (like idle mixture screw xx back from fully closed), remove float bowls, jets, vacuum membranes etc etc. No need for splitting them or remove the choke leverage. With carb cleaner (or brake cleaner on non plastic/rubber parts) clean them out. I usually spray brake cleaner through jets from the opposite direction to remove any deposits. Check float needles that could become sticky.
Maybe the bad running at low revs is caused by one flooding carb because a float needle doesn't close completely (dirty?), at high revs that's usually not a problem because it asks for more fuel anyway. Your symptom of the engine starting to die on you might be an indication for that.

Then after everything is nice, clean and dry put them back together again. Use a little clean bearing grease on the sealing rubbers in the float bowl and around O-rings on the float assembly so it slides in nicely and sets itself. Check float heights, I made a tool for securing the float assembly from an old float bowl. I don't use it anymore (FCR's, you know) so if you want that I'll gladly send it to you. Now you can synchronise them perfectly too.

You might also consider putting in a Dynojet stage 2 jet kit, now it's taken apart. Or just put in a set of FCR's (tough with the stock fuel tank but still possible) or Mikuni TDMR40's that will adapt easily with the stock throttle cables and stock fuel tank.

Intermittent electrical issue? That's got to be a faulty contact or a broken wire somewhere. When it's running badly you might turn the key switch back and forth a few times and see if that helps. Or actuate the cut out switch a few times and see if that makes a difference. Electrical would mean worse running at higher revs because of the increased vibrations and increased need for a good spark, imho.

Troubleshooting is often a matter of elimination of possible causes, but it's better not to eliminate randomly, but to work in a structural and analytical
way. Really no offence to you, Brian. But I've seen "proffessional" mechanics spending hours on "random search expeditions" resulting in the discovery of a minor problem (a $ 0,50 solution) and many hours of labour charge on the bill. That pisses me off when I hear someone tell about that.

How was the track day with the SB6? High speed track the SB will be a blast but on a more curved track the db4 is almost unbeatable through the twisties. Post pictures!

Cheers.
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Sat Dec 28, 2013 11:03 pm    Post subject: Reply with quote

I had the carbs apart last year and i think that i cleaned them fairly well. I plan on pulling them apart again to double check. I wasn't sure what to set the float heights at when i put them back together so i left them how they were (can't remember what they were set at). The idle mixture screw was another one i wasn't sure on so i adjusted them to get them running best, i think they ended up around 2 turns out.

I've also heard that the needles can wear badly on these ducs due to the vibration? This bike has got 23000 klm's on it and most likely the original carbs/ needles. I was thinking about just buying a new set of carbs and putting them on as i can get a new set from a guy on ebay that 2bims put me on to.

So... i recon i still haven't found the original problem. when i balanced the carbs it ran a lot better but i still have this intermitent problem of when it runs bad, it runs BAD.

I did a fairly good job cleaning all the electrical connections and applying dielectric grease too. But i haven't looked at the key switch or the kill switch. I'll keep working away at it when i get the time.

The track day went fabulously on the sb6 and theres some pics in a thread in the bimota chat section. I'm looking forward to getting the db4 on the track as i recon it'll be fun to ride being so light.

Thanks again Very Happy
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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
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CNC



Joined: 19 Jul 2013
Posts: 256
Location: Slovenia

PostPosted: Sun Dec 29, 2013 9:04 am    Post subject: Reply with quote

deebee4 wrote:
If yours still has the vacuum fuel pump test its functionality and look for signs of internal leakage (actating membrane) Just suck on the vacuum hose and if you taste fuel it's shot. You can replace it but also might consider fitting an electric fuel pump like fitted on most Japanese carburetted mulitcylinder bikes from the era before the fuel injection. Like FZR, VFR, ZXR etc. It's a low pressure Mitsubishi mebrane pump, very reliable. Easy to find on flea bay. Works like a charm.


Deebee could you help me with this one... I have M900 with membrane pump and I would replace it... Do you have any link for this Mitsubishi pump?

Thanks!
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Sun Dec 29, 2013 12:28 pm    Post subject: Reply with quote

CNC wrote:
deebee4 wrote:
If yours still has the vacuum fuel pump test its functionality and look for signs of internal leakage (actating membrane) Just suck on the vacuum hose and if you taste fuel it's shot. You can replace it but also might consider fitting an electric fuel pump like fitted on most Japanese carburetted mulitcylinder bikes from the era before the fuel injection. Like FZR, VFR, ZXR etc. It's a low pressure Mitsubishi mebrane pump, very reliable. Easy to find on flea bay. Works like a charm.


Deebee could you help me with this one... I have M900 with membrane pump and I would replace it... Do you have any link for this Mitsubishi pump?

Thanks!


Hi there, it's a pump like these: http://www.ebay.de/itm/Benzinpumpe-Kraftstoffpumpe-ZZR600-ZX600E-/281235548960?pt=DE_Motorradteile&hash=item417af1eb20
http://www.ebay.de/itm/VT-600-Benzinpumpe-PC21-/191017697756?hash=item2c798ac1dc
http://www.ebay.de/itm/Kawasaki-ZZR-1100-D-ZZR-1100-C-Benzinpumpe-/251412943137?
http://www.ebay.de/itm/Kawasaki-ZX636A-ZX-636-A-ZX6R-Benzinpumpe-fuel-pump-/301053916673?pt=DE_Motorradteile&hash=item4618363601pt=DE_Motorradteile&hash=item3a89611121

So plenty for sale.

+ of the pump on switched +, - on mass. If you want to you can have it switched by a relais. I've fitted a fuel filter between pump and carbs.

Good luck!
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Corona



Joined: 26 Jun 2008
Posts: 118
Location: Norfolk

PostPosted: Sun Dec 29, 2013 10:38 pm    Post subject: Reply with quote

Just a though but I had a similar problem on the wife's er5, turned out to be a spot of corrosion on the kill switch contacts and the connector for the ignition switch wasn't that great either. Also check for any greening or corrosion where the wiring is terminated into a crimp as it's hard to spot as all is well one day and not the next, connections to the coils on the loom side are also a favourite niggle as well as the reg/rectifier wiring going to the battery. Durite connectors look pretty robust but the japo spade ones used for power will fail, like all things Japanese they just don't last.
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CNC



Joined: 19 Jul 2013
Posts: 256
Location: Slovenia

PostPosted: Sun Dec 29, 2013 11:58 pm    Post subject: Reply with quote

Deebee thanks... I get the picture... I'll fish some and try out!

Thanks again!
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Mon Dec 30, 2013 12:59 pm    Post subject: Reply with quote

I think i'll have another (beter) look at the electrics before i splash out on the new carbs. Thanks
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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
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri May 02, 2014 6:17 am    Post subject: Reply with quote

Anybody ever experienced a dodgy CDI unit on a db2, 3 or carbed db4? I'm still having the same trouble with this db4, seems to foul the plugs and miss and fart and carry on.

I can get a good 2nd hand CDI fairly cheap so thought I might get it to at least eliminate that as a possible cause.
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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
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Fri May 02, 2014 8:12 am    Post subject: Reply with quote

No Brian...cant say I have........and thats on 4 separate Ducs with 900 motors..........My DB4 had similar...and it was cured by simply unplugging the tacho...as it was causing the rear cylinder to cut out....

Other than the usual things you may have tried...plug caps, plug leads? How healthy is the spark when you pull the plug and ground it and crank the motor?

A likely cause that gives the same effect on fouling/poor running...poor fuel/starvation/electrical....is the crank sensor pick up feeding the HT packs and coils...if a bad connection...worn crank pick up...it gives the same issues re poor starting, bad spark...fouling plugs due to intermittent start...I have that issue with my DB1....started with poor running, popping/banging...fouling of plugs etc..and its now down to No spark on either cylinder...Boo Hoo......... Crying or Very sad
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri May 02, 2014 10:42 pm    Post subject: Reply with quote

I have to make some time to have a good look at this thing. Too much stuff going on not enough time. It seems to be my front jug that doesn't fire properly or fouls. I've pulled the bodywork off again now so will get to it as I get some time. I just bought a box of 10 x RA6HC plugs, so that should keep me going for a while.
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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
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri May 02, 2014 10:44 pm    Post subject: Reply with quote

I really need to change the belts on this thing too before I do too much more. Any preference of belts?? I've seen gates and dayco belts available.
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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
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SpikeC



Joined: 20 Aug 2013
Posts: 450
Location: Portland, Oregon

PostPosted: Fri May 02, 2014 10:58 pm    Post subject: Reply with quote

I installed a set of California Cycle Works "Exactfit" belts, they are highly regarded hereabouts. I have heard from one who should know that the Gates belts are not quite close enough for these motors.
Acquiring them where you are may be an issue, tho........
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2008 Bimota DB5R
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Sat May 03, 2014 8:43 am    Post subject: Reply with quote

Well, as long as you're using the red printed kevlar reinforced belts (Gates/original Ducati) you should be fine. Never heard of one fail within its service period. I last discovered a tire "bogger?" stuck on the outer side of the belt that had been flattened by the tension rollers. No harm done. Yes I run mine without the belt covers.

The white printed Gates belts have a less good reputation, but aren't hardly used nowadays.
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