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db4 - Italian electrics or maybe something else?
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Sat Jul 28, 2012 4:14 am    Post subject: db4 - Italian electrics or maybe something else? Reply with quote

I'm still having trouble getting my db4 to run right, or at least, run right consistantly. I suspect that it's electrical but not 100% sure. I think i'll buy some dielectric grease and start from scratch, clean all the connections and apply dielectric grease to everything, including the grounds.

The bike was running ok (not perfect) before i removed the dash to replace the rubber dash mounts. Now it runs very rough, won't idle, coughs ans farts and occasionally backfires. Also, sometimes the indicators don't work and the tacho only works when it wants too.

All of those symptons sound like it's electrical to me, but, there's one thing that sounds like a fuel problem to me. It runs very rough at idle and with small throttle opening but mid to full throttle it seems to run ok and pull ok with no signs of missing or backfiring.

Maybe i have 2 problems? Electrical and a fuel issue?
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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


Last edited by brian on Mon Nov 18, 2013 11:52 pm; edited 1 time in total
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Sat Jul 28, 2012 4:21 am    Post subject: Reply with quote

I have previously cleaned all electrical connections except the ones behind the dash, replaced the plugs (old plugs fouled), stripped and cleaned the carbs, replaced air filter and fuel filter. I've checked all the easy stuff like air leaks and exhaust leaks, battery terminals etc.

I can't work on the bike till next week, so thought i'd post up here to get some suggestions along with what i already plan to do to it next week.

It's frustrating because i've been on a couple rides where it ran fine the whole time and i love it. Then the next time i ride it all i want do is get off and put a match to it because it just won't idle or run right. Crying or Very sad
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Sat Jul 28, 2012 9:07 am    Post subject: Reply with quote

Hi Brian. I echo your issues with my DB4, but now mine is sorted.

Had exactly the same issues, the tacho was always intermittent, wouldn't work then after 10 minutes or so it would work, but also seemed to have a fueling problem.

The mikuni fule "pump" is a simple little bolt on unit under the tank, but is a diaphragm rubber flap type that has a tubed pick-up on the rear inlet tract tube. The brass ferruled connector on the pump could be pulled in and out so evidently wasn't sealing. The air pull from the inlet tube is supposed to suck and cause the diaphragm to flap creating the pumping system. These are about 25squid new, I got mine from a gokart specialist and its an exact match, can send details if you want, as its a cheap fix to try to start with.

The tacho is MORE interesting, as its electronic, i.e. not a spinning wire working off the front cylinder like on early doocatis and as on the DB2.

I replaced my tacho, but this caused an issue as the rear cylinder dropped out. Check if the header pipe is hot or cold after a few minutes running.

It was a simple fix though.....merely unplug the tacho, thats the small white 3 pin connector in the back of the tacho, leave the oil warning light in, thats a separate connector and leave the dash light bulb in, again a separate connector.

It drove the mechanic at Ducati Mcr crazy, but it would appear that somewhere the tacho loom is connected to the rear coil loom, and when the tacho was connected it caused the rear coil to not work, unplug it and it worked, they tried several times believe me, swopping HT,coils, ignition units etc, but the result was always the same, the rear cylinder dropped out whenever the white plastic plug was plugged back in.

I now run without a tacho, at least until the winter when I'll get the rear coil separately wired in and connected with bypasses, and then can have a tacho back.

Just try unplugging the tacho first and see if the rear cylinder fires , if it does fire but is running bad then check the fuel pump. to be honest for the 20 quid it cost me it was a worhwhile cheap fix (and thats for a new one) Theres a thread on here for the part number and then I googled it and came up with a supplier in the UK

Indicators....Is it a rear one that isn't working or front? If a rear one then you can bet its the under the seat connector, the one you have to unplug to take the seat/tank unit off, the wires pull out of the connetor or break at the cnnector point. I had mine pulled and the wires checked and resoldered back in, and is now fine. You have to be careful when disconnecting it to not pull on the wires to pull apart the connector, tricky and tempting yeh, but bound to cause trouble.

Best of luck, and please try the "unplug the tacho" fix first. Easy enough, simply take the frnt cowling off around the headlight no need to pull fairings or such
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Sat Jul 28, 2012 4:22 pm    Post subject: Reply with quote

Heres the spec for the fuel pump if ever you go that way

http://www.saxon-motorsport.co.uk/shop/index.php?main_page=product_info&cPath=24_137&products_id=703
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Mon Jul 30, 2012 1:15 am    Post subject: Reply with quote

Thanks for your replies Steve. I've already ordered a pump as i've thought for a while that the pump is dodgy. I've got one coming from U.S for $27 (au) delivered... cheaper than a carton of grog. I don't think this has anything to do with my current problem though as it seems to run fine in the higher revs.

I'm intrigued by your (and possibly mine) problem with the tacho. Did you have the same problem before you replaced the tacho? The tacho would get it's signal from the coil. I'm guessing that somehow the tacho is causing a dead short which stops the coil working. I'll certainly disconnect my tacho and see if that makes a difference. I think the problem with my tacho is in the connector behind the dash because i never had any trouble with the tacho before i removed the dash. Similarly, i think the problem with the indicators is a connector behind the dash as i never had a problem before i removed it. The problem with the indicators is common to all including the indicator lights on the dash, they just glow very dull but most of the time they work ok.

I think i'll still do the conections with dielectric grease when i get some.

I'll have a play with the bike sometime this week and let you know what i find.

Cheers
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Mon Jul 30, 2012 7:11 am    Post subject: Reply with quote

brian wrote:
Thanks for your replies Steve. I've already ordered a pump as i've thought for a while that the pump is dodgy. I've got one coming from U.S for $27 (au) delivered... cheaper than a carton of grog. I don't think this has anything to do with my current problem though as it seems to run fine in the higher revs.

I'm intrigued by your (and possibly mine) problem with the tacho. Did you have the same problem before you replaced the tacho? The tacho would get it's signal from the coil. I'm guessing that somehow the tacho is causing a dead short which stops the coil working. I'll certainly disconnect my tacho and see if that makes a difference. I think the problem with my tacho is in the connector behind the dash because i never had any trouble with the tacho before i removed the dash. Similarly, i think the problem with the indicators is a connector behind the dash as i never had a problem before i removed it. The problem with the indicators is common to all including the indicator lights on the dash, they just glow very dull but most of the time they work ok.

I think i'll still do the conections with dielectric grease when i get some.

I'll have a play with the bike sometime this week and let you know what i find.

Cheers


My TACHO wasn't working when I got the bike, but I knew that, and it occassionally came on after 10 minutes or so, then went off. I changed for a new one, and thats when the problems came in. So its disconnected again, teeny tiny wires in the connector, so probably a break somewhere
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Mon Aug 27, 2012 10:22 am    Post subject: Reply with quote

Been busy but got some time to work on the db4 on the weekend.

Fitted a new Mikuni vacuum fuel pump. When i removed the clocks i noticed that the connector for the tacho wasn't securely plugged in and locked with the tab. I put dielectric grease on all of the electrical connectors behind the clocks / headlight. Put dielectric grease on every other connector and join that i could find on the bike includung the coil wires.

Took it for a ride and it's definately running better. All of the intermittent elctrical issues mentioned above are gone and the tacho didn't miss a beat.

Still a couple issues that i think are related to carburetor tuning. Still doesn't idle very well and it doesn't like putting around slowly. Even sitting on 100 klm/hr for a period with very little throttle action, after a while it starts to run rough as though the plugs are starting to foul. Give it a good workout through the revs and it comes good again. Some more tinkiering required i think.

Happy for now... i think the main issue (electrical) is sorted.
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Mon Aug 27, 2012 10:27 am    Post subject: Reply with quote

A couple other things that i sorted while i had it apart too...

Replaced the 3 rubber mounts that hold the clocks as one was broken and the other two were very perrished. While i had it apart i noticed that the big ugly bracket that holds the headlight and also the clocks etc was cracked around the base and quite flexable. This had been repaired at some time in the past (previous owner) and was a fairly ordinary repair job. Welded all the cracks and gave it a paint job.
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Mon Aug 27, 2012 10:52 am    Post subject: Reply with quote

Welcome Back Brian, thought you had gone "Walkabout" for a while there, glad to here the 4 is back to the fore.

Took mine out yesterday for 190mile tour around, running fine and on song, no problems to report, well the tacho is still disconnected as if connected it cuts out the rear cylinder, but what the heck Eh?
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Sat Sep 01, 2012 2:10 am    Post subject: Reply with quote

Yeah i've had a lot on lately. Been checking the forum every now and then but not had time to post Wink
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Tue Nov 19, 2013 12:05 am    Post subject: Reply with quote

Well i thought i had this sorted but apparently only temporarilly. It still plays up like a hairy goat but not all the time. Some days it will run perfectly, without a single missfire. But when it decides to play up it really plays up. I rode it into town the other day (about 25klm) and the closer i got the worse it ran. Buy the time i got to the traffic it was a real mission just to keep it running while stopped at the lights, then it would miss and carry on while taking off.

It seems to be low revs and mid range thats the problem, which indicates a carb trouble to me. But it doesn't make sense that on some days it runs perfectly, if it were carbs it should run like crap all the time. Which makes me think it's electrical...

I thought it might be fouling the plugs at low revs to mid range and then clearing in the higher revs. Thinking that there may be an intermittent electrical issue... loose or broken wire, bad connection, bad coil, bad pickup??? I pretty much checked, cleaned everything previously but will have to have another look.

Any other suggestion would be appretiated fellas.

Cheers,
Brian
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Tue Nov 19, 2013 1:08 pm    Post subject: Reply with quote

It'll be because of all those goodies you've been buying for the ZXR....Bimotas get very jealous you know....I treat mine like Multiple wives....if one gets treated then the others also get treated or else they start to play up and go off in a huff....

Is the choke lever/cable sticking on? Give it a lube...this would foul your plugs...I'm assuming you havent pulled either plug yet to check?

Dont know what the temperature is over there Brian...assuming its always warm...but the Db4's came with carb de-icers fitted to the float bowls due to carbs icing up after running and floats sticking etc...basically a feed from the oil lines that feeds around the carb float bowels...my DB4 has one...and theres a lever on the right side to open or close it...but I'll be damned to know what is on and what is off...

Other than this try unplugging the tacho white plug on the back of the tacho...still run mine without it conneted as it was cutting out one of the Coils when connected...

Other possibles are damaged defective plug caps/cables...a cheap enough fix/check...remake the ends by trimming last half inch if you spare length as they corrude at the ends, then rescrew them back on again...
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brian



Joined: 22 Aug 2011
Posts: 3159
Location: Australia

PostPosted: Tue Nov 19, 2013 11:14 pm    Post subject: Reply with quote

Yeah you could be right about the jealousy thing mate... I've got the db4 and the ZXR separated by a couple other bikes but maybe i need to put them in different sheds (oops, only got one shed).

I'll give it another run and then pull the plugs to check them. Choke cable is kinked but definately not staying on. Mine has the oil lines going through the carb bowls toobut it's about 34 deg C here at present so no ice to be seen. I'll check and trim the plug wires, actually i might just replace them. Do these ducs have a pickup coil on the crank???

Not sure when i'll have a crack at it, got a fair bit on as ussual. I was planning on doing a track day in December and taking the db4 but won't until i get it sorted. So i'll have to give the sb6 a birthday and take it to the track instead.

Cheers,
Brian
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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2bims



Joined: 03 Apr 2010
Posts: 6298

PostPosted: Wed Nov 20, 2013 10:20 am    Post subject: Reply with quote

They do have a pick up on the crank, but ypu probably dont want to know and should check everything else first
.
Why?...it means taking the left side crankcase off....and there's a nasty weld /lug on the frame that stops you pulling it off without..... Dropping the engine Crying or Very sad
The sprocket splined shaft stops you wiggling it clear. Also
..
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brian



Joined: 22 Aug 2011
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Location: Australia

PostPosted: Sat Dec 07, 2013 11:14 pm    Post subject: Reply with quote

Well no boubt the db4 will definately have the shits on now. It's been stood in the naughty corner looking on as i pamper the sb6 getting it ready for a nice outing next weekend... track day. It's gunna take me a lot of work to get back in the good books with the db4 after this one i think. Laughing
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Current motorcycles - '99 Bimota DB4 #104, '96 Bimota SB6 #1165, 94 Bimota DB2 J #652, '99 Bimota 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
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