Bimota Forum

[brian]

[2bims]

Jeeso yeh its a mere 10 kilos shy of the combined weight of my Db2 and Db4, does it have a reverse gear?

[2bims]

Just as a quickie Brian, I got a reply from "Bob" of bimotaSpirit in the US, saying he had original copies of the DB4 owners handbook. I think you got the same link also, but what price did he quote you for the handbook? He's told me he has some but didn't give a price. Perhaps he would give a better price for 2? I'm waiting to hear a price and confirmation that it is for the carbed version and not the ie injected one.
Maybe theres a chance of a deal

[brian]

[2bims]

Hi Brian, you still up?? Isn't it late there, I think you have an email or 2 re Db4 parts, handbooks etc, cheers

[brian]

[deebee4]

[brian]

Ok, i'm running out of ideas here. The db4 is still not running properly if at all. It just splutters and backfires.

I've never had much to do with carbs and never had much luck getting them to run right but i've stripped these, cleaned them, checked everything twice and found enough info on the net to set them up enough that it should at least run.

The only thing i haven't done yet is replace the plugs which i will do next week when i can buy some. I still think it's got to be something that i've done because it was running better before pulled the carbs to clean them. It would run reasonably well when riding but just wouldn't idle very well.

Things i've now done -

Stripped and cleaned the carbs. The carbs look fine.
Set the float height at 14mm.
Set the pilot screws at 2 3/4 turns out.
Replaced the air filter.
Checked and cleaned all of the electrical connectors.
Cleaned battery terminals and starter connection.
Bypassed the fuel vacuum switch as it wasn't closing anyway and i thought it may not be letting enough fuel through.
Checked fuel tap - good flow through filter.

Any ideas are welcom, thanks.


_________________
'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

[oily]

Have you got enough cylinders?

_________________
SB6 mk1 (project mega light, big bore)
Sb6 mk2 ( Big Bore)
Sb6 mk2 ( Restored)
Sb6R fighter
Sb6 or Sb7 WANTED

[2bims]

If the needles and jets are worn it would not idle so well, but have you tried adjusting the idle screw situated midway between the carbs? Can't be reached with the bodywork on though, but tank the seat/tank cover off and lift the tank and down inbetween the carbs it should be accessible. Large Philips head screw with a big spring clip behind it. Try it full turn in from what it is, and a full turn out from what it is, Other than that, theres the coils and pick-ups on the left side of the crank. Try out the header pipes to make sure they are tight. Mine were when I bought the DB4, but a shake down run, sure shook a few things loose

[2bims]

Even if you haven't any spare spark plugs I'd pull them out and have a look at the colour of them anyhow, and check the gap, should be 0.6mm. The firing end cap should be a brown, tan or grey color. If its not and its something different let me know what, i.e. dry, black sooty, or Wet Oily deposits or blistered white insulator/glazed electrodes

[brian]

Plugs are dry and black. I cleaned and gapped them, put them back in and still runs the same. Carbs back out. checked carb to manifold rubbers, no signs of cracks or perrishing, good condition. Checked headers, ok. Double checked fuel delivery, looks ok. Seems to be fuel to me. Starts and runs for a few seconds then misses and backfires. Why does it backfire... no idea.

This is doing my head in! I'm missing something here.
_________________
'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]

[2bims]

[brian]

Went back to it this afternoon. Stripped carbs again, re-assembled and set float levels to 14mm. Set pilot screws to 3 1/4 turns out this time. Put the carbs back in the bike, still running rough and backfiring. Running better in mid range but wouldn't idle well. Changed pilot screws to 3 turns out. Ran better when hot, still some backfiring. I had been runnig with the tank hung up and a long fuel hose direct to carbs. Put the tank back on with original fuel hose asnd filter which i had earlier confirmed that i was getting fuel through. Tok bike for a test ride. Died in the driveway, back to the shed. Fitted new fuel hose with no filter. Bike ran again. Took for a test ride up abd down the road, still coughing and backfiring.

On the 3rd run up the road it suddenly cleared and pulled like a train. No more backfiring or missing at all. Pulls good, runs good, idles good.

I think the fuel hose was 'a' problem but not 'the' problem. Still not sure has happened but is now running perfect.

I'll put all the fairing back on next week and take it for a descent ride when i can. Happy again.

DeeBee, no pump at all on mine, just a tap and vacuum valve on bottom of the tank then straight to the carbs. I've bypassed the vacuum valve as it doesn't seal anyway. Thanks for the links too.

2bims, my next trick was going to be to buy the NOS carbs from italy! I still might buy them anyway, for 100 euros they're pretty cheap i recon. I'll still put new plugs in next week and give it an oil change.
_________________
'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