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Firing on one

 
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri Jun 15, 2012 5:15 am    Post subject: Firing on one Reply with quote

Took the db4 for a spin up the mountain on Wednesday and the bike ran fantastic. Rode into town today (about 30 klm's) and by the time i got there it started running a bit sick. By the time i left town to ride home it was like it was running on one cylinder. Had to ride all the way home like that. Got home and pulled the plug leads off one at a time and sure enough, the front cylinder isn't firing.

Hope to get time this afternoon to delve a little deeper and find 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
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Uros



Joined: 22 Aug 2011
Posts: 37
Location: Slovenia EU

PostPosted: Fri Jun 15, 2012 7:32 am    Post subject: Reply with quote

Holy moly, I had this morning a very similar experience, only I'm sure it is a consequence of a defaulty fuel pump (mine leaks a little fuel so I ordered a new one). It felt like it's been running only with one cylinder... Shocked and had also some misfires. All the chicks turned their heads though... Cool Cool
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Uros



Joined: 22 Aug 2011
Posts: 37
Location: Slovenia EU

PostPosted: Fri Jun 15, 2012 7:35 am    Post subject: Reply with quote

I'm almost sure you just have a dead spark plug or some spark cable issues...
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Fri Jun 15, 2012 8:32 am    Post subject: Reply with quote

Suppose its back to the old swopping over of cables, coils, etc to see if the outage swaps over to the rear cylinder. I had an intermittent problem with the rear, it checked out ok on the tester etc, as was still passing current, but only just, and strangely when you unplugged the electronic tacho it was fine again, I would try that first, may sound odd but pull the electonic plug (white) from the back of the tacho and fire it up again, there was an outage or bad earth somewhere and when this was disconnected both cylinders were back again...
More "bonding" time I suppose courtesy of Italian electrics Laughing

I just hope that its not one of the pick ups from the left side of the crankcase, as to pull those (and they do go from time to time,) its pull the left hand crankcase cover off, after draining the oil. But on my Db4 and will be yours also, theres one allen key bolt above the front sprocket that you can get at but not pull all the way out. And then when you pull the cover off theres a weld on the front left engine frame mount that stops the cover coming off, and you can't spin it round either as the splined gearlinkage shaft coming out of the crankcase is still captive at that point, thus it would be drop the engine time Crying or Very sad

Evidently you'll try everthing else first. There are resistance tests and values in the DB4 workshop manual for all of these circuits so check those levels first. I recall?? I emailed the PDF documents to you??
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Fri Jun 15, 2012 8:39 am    Post subject: Reply with quote

Uros wrote:
Holy moly, I had this morning a very similar experience, only I'm sure it is a consequence of a defaulty fuel pump (mine leaks a little fuel so I ordered a new one). It felt like it's been running only with one cylinder... Shocked and had also some misfires. All the chicks turned their heads though... Cool Cool


If it'll only run up to 70mph then yeh theres ones cylinder "missing" there are temperature probes for the exhaust headers to check, or the old trusty "spit" on the pipes to tell if they are waarming up, or a wet rag and see if it "steams"
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Uros



Joined: 22 Aug 2011
Posts: 37
Location: Slovenia EU

PostPosted: Fri Jun 15, 2012 9:01 am    Post subject: Reply with quote

2bims wrote:
If it'll only run up to 70mph then yeh theres ones cylinder "missing" there are temperature probes for the exhaust headers to check, or the old trusty "spit" on the pipes to tell if they are waarming up, or a wet rag and see if it "steams"


Oh no no, it runs like a rocket, it just coffs and misfires on startups at green lights. When it gets its breath it goes ordinarily- like a crazy woman that is:). Only the first 20 metres it feels like a one cylinder bike. Like I said, I'm sure it's the fuel pump... Rolling Eyes
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri Jun 15, 2012 3:01 pm    Post subject: Reply with quote

I pulled the plug out, earthed it and wound the engine over and no spark. Checked all the connections, all looks good. Swapped the coils over, still no spark at the front plug. Swapped the plugs and voila, spark. Cleaned the non-sparking plug and got some spark but very little.

Just so happens that i've got new plugs on order so should be an easy fix. I am curious as to what makes a spark plug foul though? Is it possible that it's running too rich?
_________________
'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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Uros



Joined: 22 Aug 2011
Posts: 37
Location: Slovenia EU

PostPosted: Mon Jun 18, 2012 10:11 am    Post subject: Reply with quote

brian wrote:
I pulled the plug out, earthed it and wound the engine over and no spark. Checked all the connections, all looks good. Swapped the coils over, still no spark at the front plug. Swapped the plugs and voila, spark. Cleaned the non-sparking plug and got some spark but very little.

Just so happens that i've got new plugs on order so should be an easy fix. I am curious as to what makes a spark plug foul though? Is it possible that it's running too rich?


Hah! Told ya! No, there can be no real reason for the spark to go out. Usually it just gets tired to work and dies. Of course, if you have the original spec spark! (If you changed the spark with a different spec, then you should go back to the original right away on both cylinders.) You should become concerned if it happens again in a short period of time. Otherwise, this is just ordinary nineties-motoring stuff.

For the record, I tried the iridiums from NGK with same specs and the bike misfired on every occasion. I went back to the originals,...voila,...perfect again. So, don't change sparks! Stick to the originals.
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Tue Jun 19, 2012 1:04 am    Post subject: Reply with quote

They are the original spec Champion RA6HC plugs. The previous owner said that the plugs were'nt very old and i've only put 1500 klm's on it since i've owned it (since mid March).

My new plugs should turn up this week so i'll see how they go. The new ones are the same spec Champions.
_________________
'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: Tue Jun 19, 2012 6:15 am    Post subject: Reply with quote

Uros wrote:
brian wrote:
I pulled the plug out, earthed it and wound the engine over and no spark. Checked all the connections, all looks good. Swapped the coils over, still no spark at the front plug. Swapped the plugs and voila, spark. Cleaned the non-sparking plug and got some spark but very little.

Just so happens that i've got new plugs on order so should be an easy fix. I am curious as to what makes a spark plug foul though? Is it possible that it's running too rich?


Hah! Told ya! No, there can be no real reason for the spark to go out. Usually it just gets tired to work and dies. Of course, if you have the original spec spark! (If you changed the spark with a different spec, then you should go back to the original right away on both cylinders.) You should become concerned if it happens again in a short period of time. Otherwise, this is just ordinary nineties-motoring stuff.

For the record, I tried the iridiums from NGK with same specs and the bike misfired on every occasion. I went back to the originals,...voila,...perfect again. So, don't change sparks! Stick to the originals.


...........


Last edited by deebee4 on Tue Jun 19, 2012 5:54 pm; edited 1 time in total
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Tue Jun 19, 2012 6:15 am    Post subject: Reply with quote

Uros wrote:
brian wrote:
I pulled the plug out, earthed it and wound the engine over and no spark. Checked all the connections, all looks good. Swapped the coils over, still no spark at the front plug. Swapped the plugs and voila, spark. Cleaned the non-sparking plug and got some spark but very little.

Just so happens that i've got new plugs on order so should be an easy fix. I am curious as to what makes a spark plug foul though? Is it possible that it's running too rich?


Hah! Told ya! No, there can be no real reason for the spark to go out. Usually it just gets tired to work and dies. Of course, if you have the original spec spark! (If you changed the spark with a different spec, then you should go back to the original right away on both cylinders.) You should become concerned if it happens again in a short period of time. Otherwise, this is just ordinary nineties-motoring stuff.

For the record, I tried the iridiums from NGK with same specs and the bike misfired on every occasion. I went back to the originals,...voila,...perfect again. So, don't change sparks! Stick to the originals.


I use the NGK Iridiums DCPR8EIX and before that platinums D8EVX the last 6 years without problems. They last long.

Weak spark is most of of the time a result of other problems. Don't assume the worst (like the pick-ups) but just make sure the whole iginition wiring system is in perfect shape. You'll be surprised how many bikes run with oxidated connetors around the coils and in the grey multiple connectors that are supposed to be water proof. In Italy when it's not raining maybe....Wink

I had misfiring and total collapse of the performance from 7.000 rpm onwards. That was cured completely by renewing 70% of the ignition wiring system (used 2,5 mm2 wherever I could reach), renewing spark plug cables and spark plug cap (again no resistor types).
Also I made a modification: replaced the Kokusan iginition boxes for the old Bosch BTZ items (which were brand new...). Never had iginition problems again and better starting.
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Thu Jun 28, 2012 11:22 am    Post subject: Reply with quote

Gave the db4 a cleanup today and then pulled all connectors apart to make sure they had no water in them. Checked that all the connectors were clean and put a little electrical spray on them. Gapped the new plugs and fitted them. Bike started and ran fine. Very smokey for a few minutes but i'm guessing this was the result of running about 30 klms with the front pot not firing at all. Fairing will go back on next week then out for a spin.
_________________
'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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