Walbro 255 for a bike??? I have it running, but something is up. FUEL TECH GUYS ITT

Shift518 Automotive
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More ducati issues.

starts hard choke on, need a blip of the throttle to get it to fire, wait a few MINS to warm up, back off choke and it wants to stall, gotta hold a higher idle to keep it running, throttle input and it runs like crap with crappy throttle response. Keep in mind this is EFI. Trieed to ride it around the lot, and it stalls out at full engaugement of the clutch, no matter how long you slip it out to get rolling.

When I got it back together, the tank smelled like kero or something odd, not gas. I emptied it the best I could when it was stored, but a little was still sloshing around. I put new gas in and a week later as I was putting the rest of it together, the gas turned turned cloudy looking. I emptyied some last night and it looks like straight cloudy pee, like after you drink a few energy drinks. Smell if off a bit again too. Put a fuel pressure gauge on it, and only got 31 psi (suposed to be 3 bar or 43.5 psi).

Dumped the rest of the fuel and pulled the pump sock and filter, all in tank. Pulled the sock off the pump inlet, and a little bugger of rusty looking gunk was right there. about 1.5mm dia or so. not alot but still not good. Put air to the inlet and gently shot a bunch more crap out of the pump, again brown looking crap. not a ton, but a bit of crap came out. took the fuel filter off and turned it around and shot it out too, a TON of brown crap came out, looks like someone used brown spray paint on the wall I shot it on.

Put the pump back in, no filter, and got 35psi now. still not enough. Pump is probably bad. $280 for a new Ducati pump.

So I grabbed a Walbro 255 off the shelf and plumbed it in the tank, no filter yet. put it on the bike and put the T gauge by accident on the reutrn line (1am not paying attention). Key on, for a blip up to about 10psi, and instantly dropped to nothing while the pump runs. Pump primes, but sounds like its bogging down a bit. sounds a bit odd to me. Switch the T for the pressure gauge to the feed side. Key on, pump sounds the same, and the pressure pegs the gauge at 100+psi and doesnt move. Key off and the pressure instantly drops to 42psi (about what it should be for the FPR) and holds dead steady, like it should. Key on, I can see a faint flow of return fuel in the tank from the return outlet, def not 42 psi worth though. (I think this is my problem).

I start it anyway. Choke on, fires the instant I hit the button, no throttle at all needed. 10 sec into warm up, choke completely off and it hold idle like a champ. Instant throttle response, and cleanish (need a power commander for open pipes and pod filters instead of air box). You can crack the throttle as fast as you want and it wont want to die out. I didnt get to ride it, way too loud for 1:30am!

So, is the pump too big? I have heard of people running them on bikes for turbo setups and such, with base FPR 3-3.5 bar or so… so i doubt its too big. fuel lines feed and return are the same as cars I installed these pumps on in the past, so volume and flow I doubt are an issue to cause the back up of fuel and high pressure. Or with all the crap I blew out of the old pump and filter, maybe the FPR is gunked up and not flowing enough volume when it opens to control the pressure. what do you think?

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3 bar fpr

bosch oem pump 160l/h operating pressure of 3 bar

one of the best write ups I have ever read on a specific car or bike. answered everything to a T!

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choke on efi bike?

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yeah, mechanical valve on the throttle body and linkage to slightly raise the mechanical idle. probably changes the enrichment table for the injectors at start up too.

After reading that link, and many others it sounds like my hunch about the clogged return line or pressure regulator is going to be the culprit. Not enough flow and the pressure is backing up. OR, the 255 VS 160 l/h is sending too much volume, but thats a long shot since many other people use these pumps, or other car pumps in-lue of the ducati original when they fail.

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when I get to the shop ill pull an old 3 bar off a 1.8T rail on the parts shelf, see if it fits in the housing on the bike, and take some air to the fuel lines and blast them clear if they are obstructed. if that doesnt help, then the 255 just feeds too much fuel for the return to vent back and maintain pressure.

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Nothing I can add, you’re on the right track!

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thanks for the encouragment buddy!

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So this is what its like to be in your head for 15 minutes…

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Plus rep ^ :rofl

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jesus christ

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LOOOOL +rep!

Yes my son.

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Well, I found a clog in the return and blasted out the FPR and the return lines. Ran new feed and return line, new fuel filter and tried it. Now the 3 bar reg is pushing 3.5 bar through the system close enough for now. The top looks dimpled in, like someone peened it to get a bit more pressure. Which with open exhaust and intakes, Ill leave it for now until I get a PC3 and tune it.

BUT

Tthe damn thing still stalls with the clutch fully out. It fires up perfectly, idles perfect. snappy throttle, and feathering out the clutch is normal. Its just the last 15% of the lever at full engagement where it stalls out. Feels like the clutch chatters and causes it to stall.

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Does this ducati have a dry clutch?

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Yes my friend, dry clutch. 9Kmi on the bike/OEM clutches. 16-25K they say they last.

Update.

fuel system works like a champ. so that problem is solved.

The thing still freakin stalls at full engaugement. Pulled the clutch rod and its straight, and slides fine, cleaned and greased it. Pulled the clutch pack and everything is in there as it should be, pressure plate seated correctly, springs all tqd as they should be.

Clutch pack condition.

The steels dont look warped, no signs of excessive heat, no grooving on the faces. Frictions are thin, but they have a bit left (they arent that thick to begin with) min spec is 2.8mm, ill check that when I get there tonight.

The teeth on the plates are slightly worn, but nothing crazy. The basket looks worn, some of the faces where the plates ride are grooved a bit, not nothing horible. What everyone says is it takes alot of wear to cause problems, and excessive wear usually causes drag, not so much engaugement issues.

The engaugement point is rather far out there on the lever. The only thing I can think is that they are worn to where it has so much distance to slip in the friction zone on the clutches throw, that once it get to the engaugement point its like a light switch, and locks up then stalls the bike. Which makes sense with the long-ish lever throw and the chatter I feel. (i know dry clutches chatter a bit but I dont remember it being that bad the mile I rode it prior to taking it apart). I just have a hard time beliveing that this motor cant grunt its way trough the engaugment. I need a stand to get the tire off the ground and try to enguage it free spinning. straps on the swinger to the lift arms would work but we have a car for a motor swap sitting on it atm.

Electrical. I really find it hard to believe thats the cause. The only things that are odd are. the nutral switch i think is worn and wouldnt show nutral, switch works, but I think the nub on the shaft on the trans is not contacting it enough. So its not hooked up/grounded out right now. In other words the bike thinks its in gear the entire time. I tried it ground out and not and it still stalls the same.

Kickstand switch, doesnt seem to do shit either. up or down, with or without the nutral switch grounded out, motor still runs. Which is odd, it should cut out with the nutral switch as it sits now (not grounded AKA in gear).

And the nail in the coffin, there is NOT a microswitch on the clutch lever. So the bike has no idea where the clutch is in its travel.

I am stumped, but suspect the clutch is worn and giving crappy engaugment.

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So this is a total left field no experience guess. But with the kick stand switch not working Properly does the bike just assume its down and kill the motor when it starts rolling?

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could be that for sure.

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I would look into the kick stand switch. Check the whole harness with that circuit. Who knows what could have got stretched/pinched during diassembly or re assembly. Im sure you of all people would becareful about that, but maybe other people have worked on it as well?

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http://www.desmotimes.com/clutch.pdf

nice write up on how it all works. i am reading it now.

looks like I am getting a clutch kit, basket minimally.

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Here is the thing too. There is no speedo hooked up, so the bike has no way of knowing if its moving. I have an aftermarket display, in place of the mechanical speedo and tach that was stock. Also when you do a wheelie (speed sensor is on the front wheel) when it stopped, IF the speed was hooked up and monitored somehow by the ecu it would be dangerous if it was allowed to cut the motor. So I dont think it was/is ever electronically monitored. The motor is esentially “dumb” to any actions on the bike, as far as i can tell wiring wise. The ECU, is actually an injector control module. Air temp, throttle pos, coolant temp, injectors, rpm and I think thats about all there is really (not even sure it has a cam/crank sensor). its open loop fueling, no maf, no 02… just air temp, tps and coolant temp changes the fueling. as far as I know.

I redid the entire harness (for better or worse) to tuck it and move everything around under the tanks and tail. So ofcourse thats allways an unknown. but I took my time and every wire matched when I put it back together, soldered and shrink tubed.

Any bike I ever rode or worked on, if the bike is in gear, and the kickstand goes down, it cuts out instantly, dont even have to move or let the clutch out. Or if its in nutral, stand down running, if you kick it in gear it stalls out. BUT what I dont get is how come this kickstand switch has 4 wires??? I didnt look into that enough yet.

I dont know if it assumes its down if its faulty.

Rtrac… hows your nutral & kick stand work on yours? Its like I mentioned above right?

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Can I ask why you put such a large pump on this bike? That thing has to be bypassing some serious fuel into the tank.

Definitely just bypasss the stand switch and see what happens(just as a test, repair/rewire before actually riding if retaining the stand). does this bike also happen to have a layover switch that you may not have positioned correctly?