Bimota Forum

[brian]

OK... I think i may be finally getting to the bottom of this.

I put my timing light on the plug leads and the front cylinder lead seems to be not firing every few seconds. The rear cylinder also seems to miss every now and then but probably only every couple minutes.

At first ithought it might have been a problem with the timing light but i've tried it on other bikes and it flashes rythmically and flawlessly.

So my question is... is it more likely to be coils, ignition modules, pickups or a combination thereof. Can i test any of these components?

My other option is to find someone with a known good electrical sytem and start swapping components out. It's getting expensive to keep buying parts that turn out NOT to be the problem.
_________________
'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

[deebee4]

[deebee4]

[2bims]

Hi Brian..........its is sounding more like the crank pick-ups are failing.......you can test the continuity of the crank leads with a multimeter as DeeBee4 suggests........to replace the crank pick ups though on the DB4 its left hand side crankcase off though..........and due to the splined front sprocket shaft and a weld on the front engine frame mount...the let hand side crankcase cover wont come off without the engine being dropped....as you cant rotate the cover to cover the weld on the underside of the front frame mount........I had a similar intemittent issue on my Db1.......put it down to carbs...so stripped and cleaned them...wasnt any issues...changed plug caps and leads and plugs.....would run but then backfire miss etc.....down to the stage now where theres no spark on either plug and apparently this means faulty crank pick-up which is where I'm now at with this bike.......they gradually give up the ghost giving poor spark on occassions until such time they just give up the ghost altogether..........

[brian]

Thanks deebee and 2bims.

I'll do a bit more troubleshooting and try to test the coils etc.

I'm planning on dropping the engine before too long anyway, to change the belts and do the valve clearance. So I'll replace the pickups while the engine is out.

Cheers,
Brian
_________________
'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

[deebee4]

[Corona]

I have a PDF copy of the manual covering '91 to '96. It is 190 MB, I also have a copy of the DB4 parts list which is only about 2 meg. If you require these I can send you copies.
That looks like a hell of a spanner frenzy deebee

[deebee4]

[brian]

I took the db4 to a Ducati mechanic that i met through track days. He tested the crank pickups and ignition coils etc. The pickups resistance was very low, one was lower than the other but both only aroung 1/2 the resistance they should read. He said that the original wiring in these Ducs is poor when new and where the wires go inside the case to the pickups gets cooked over time. So this confirms what you guys have said anyway. Also both ignition coils measured well out of spec as well.

He said... 'So that's bad news', and I said... ' No, that's very good news for me as i can now fix the problem instead of replacing parts that are not the problem
_________________
'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]

Not much else it could have been by this stage though, as i've checked or changed most other areas that it could have been.
_________________
'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]

So moving forward, I'll be doing the 'split' thanks to the idea from deebee. I've ordered some new belts and will get my Ducati mechanic to do the valve clearance while i've got the engine out of the frame. And must not forget to replce those pesky crank pickups while it's out too.
_________________
'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

[2bims]

Glad to hear that you've finally got to the bottom of the issue Brian.....Crank pick-ups intermittingly failing do produce all the issues same as if theres bad fuel, blocked carbs, failing Coils, ignition packs, bad plugs/leads etc...as evidently they aint producing the spark that they should be.........Can you get the bits that you need OK over there?

[brian]

[2bims]

This man in Italy still has the full set for sale at 150 euros.....complete with stator and drum

And possibly cheaper postage at 15 euros as the states is mega bucks for postage nowadays...

http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=271551508256&fromMakeTrack=true&ssPageName=VIP:watchlink:top:it

[Garynuttall]

cant help you on the electrics but have had same problem with tachometer on my db5r - now sorted - jumped from 120 to 160 then down to 80 - was all over the place......... - the pick up is nowhere near the front - its on the back wheel and held inplace by a tiny grubscrew that goes through the frame and keeps the sensor in place - ideally it should be a bout 2mm away from the heads of the dic bolts which are magnetic and send the reading to the electrics - check that the screw isnt loose or gone completely - in addition the conmnectors to the dash are very sensitive and while some may work in the same unit others are not communicating - - separate it - its only one - blast with compressed air and fit back together ...........good luck
_________________
Loveitalianbikes