Changed belts now backfiring - Vid inside

[mudbutt]

Is my timing off? I have all 3 timing marks perfectly aligned on each of the 3 pulleys.

These are all with the belts on
Pic of upper pulley


pic of middle pulley


Pic of horizontal cylinder pulley


vid of it starting and idling
http://youtu.be/nFUjhsa2UMs


vid of it reving
Ducati backfire - YouTube

was i supposed to do something other than align the 3 pulleys to their timing marks?

I should mentioned that i also pulled the left side starter cover to re-silicon as it was leaking. I also had the spark plugs out just to check them and re-insalled them a little under a quarter turn of tourque with a wrench
I also changed the oil to mobil1 15w50 and used a ducati oil filter. I may have moved the carb adjuster screw on accident no more than a mm of a turn but thought i turned it back to the original spot.

After this vid I pumped out the gas as it was an unknown age and put some fresh 91 in along with some lucas fuel treatment but it is still doing the same thing.

It ran great when i bought it, then i did the above maintenence items and it backfires. Help...

stats that count for now
93 900ss
kehin 41mm carbs
2-1 exhaust
it may have some head work done according to previous owner
stm breather

[va duc]

I wonder if the cam timing was changed via dialing in the cams?

[phil996]

Too many maybe's to make a diagnose.. Start with retracing your steps. most likely a carb issue, but could be 10 other things. Check for air leaks around the manifolds. What did you tension the belt to? 5mm wrench method? hz?

[mudbutt]

Originally Posted by va duc

I wonder if the cam timing was changed via dialing in the cams?

dang i hadn't even considered that the PO's PO may have advanced it a little as its not a stock bike. It was orginaly given to a guy by ducati who raced for ducati in the 90's and the belts haven't been changed since he did all the upgrades and work to it then. Damn...

[mudbutt]

Originally Posted by phil996

Too many maybe's to make a diagnose.. Start with retracing your steps. most likely a carb issue, but could be 10 other things. Check for air leaks around the manifolds. What did you tension the belt to? 5mm wrench method? hz?

yes i tentioned both belts to 5mm. the mani's don't seem to be leaking.

Whats hz?

btw i just added a vid of it idling

[va duc]

I am not that familiar with the electronics on the earlier models, does it have a electronic pick up on the left side, maybe the pickup is dirty or has some sealant on it?, just thinking out loud.

[phil996]

Hz is hertz, the newest way since about 2000 is to use a harmonic gauge to measure the sound frequency of the belt tension. Heres a basic list of more items to check;

1. fuel delivery, lines pinched, routed correctly etc.
2. spark plugs, coils, wires, etc.
3. ignition pickup, sometimes they get metal on them or just go bad
4. Belts, did you get the right ones? I know it sounds weird but sometimes it happens
5. Battery cables, grounds.

Good luck.

Just saw your post about pickup VA. By the way i love your Avatar.

[mudbutt]

Originally Posted by phil996

Hz is hertz, the newest way since about 2000 is to use a harmonic gauge to measure the sound frequency of the belt tension. Heres a basic list of more items to check;

1. fuel delivery, lines pinched, routed correctly etc. should be as i didn't touch them.
2. spark plugs, coils, wires, etc. i'm going to change these tonight as the old ones are from the 90's with unknown mileage. bike has 12k.
3. ignition pickup, sometimes they get metal on them or just go bad I'll check
4. Belts, did you get the right ones? I know it sounds weird but sometimes it happens i got them at a ducati dealer in roseville, CA and the lengths looked identical to old ones.
5. Battery cables, grounds. I'll double check, i did put in a new battery in the middle of all this work as the old one was dead, but all i did was unplug and re-plug.

Good luck.

Just saw your post about pickup VA. By the way i love your Avatar.

My answers are in bolded red above, thanks for your help.
I'll check pickup, but am not sure what it is exactly...? I need to get a repair manual already.

[DuckMan]

Are you certain of the cam pulley position before removing the old belts? Is it possible the horizontal pulley is off 180 degrees? I'm probably wrong but it seems that on my DS motor the mark pointed straight down.

[470four]

Belts look to be fine, if they were the wrong length the engine would have ate itself by now...

Two weeks back I fancied a quick blat on my 400/4, our current winter weather being very mild? I had removed the battery & kept it inside so replaced it in the bike, refilled the tank and got my kit on. It was a pig to start & when it did fire up had a random misfire all up and down the revrange??

Checked everything, still no joy... in the end the girlfriend nailed it when she said "All you did was remove & replace the battery??"

It has Boyer electronic ignition fitted which apparently doesnt take kindly to a bad connection at the battery. Cleaned the terminals back to new, degreased all the terminals with contact/brake cleaner & problem solved... Anti-corrosion agents & even WD40 will leave a film of oil on connectors which wont make a good contact later if rejiggled?

Your bike sounds slow to turn, have you upgraded the starter/battery cables? A big lead from the battery earth/ground to the engine can improve things no end!