748 /853 Stalling Problems

[blairjw]

Hello -
Posting for a freind who hasn't signed up yet... I talked to him tonight, he asked if my 748 "stalls"... We talked the problem through... does it happen in one gear? (nope) idle (nope) acceleration (once) deceleration (once).

He says' it will last for about as long as it takes to roll to a stop, It has always restarted.

Searched the archives... low battery, loose connections, TPS...

Anyone ever come across this?

His;
98 748/853... unimap chip, lightweight flywheel

Blair

[RI749]

Could be a lot of things. Where does your friend live?

[bubbazenetty]

Have him check the TPS setting.

[blade625CT]

Hey guys this is my old bike. Let's help this guy out.

This cutting out problem is new to the bike [bike never did it while I had it]

I set the TPS, and hit 150mv dead nuts [of course it could be off 2-3 few mv due to accuracy of the meter] So I wouldn't think that's it. But that is far better than the 14mv it was off when I checked it originally...and it ran then.

I had, however, set my idle AFR to about 13.7:1 [using a lambda meter w/bosch sensor...and the CO trimmer in the ECU] the last time I was out riding/tinkering with it. I set it to that on the advice of another racer, and it really made a nice difference. BUT, I set it while the bike was good and hot and never had the opportunity to start it again from cold until the day Todd picked it up [and it was a bit difficult to start] it was also a damp raining day when they came to get it...and I had never started the bike in the rain either....

Do you guys think electrical? or fueling?

The only time the bike ever failed to start and run for me was when a dry break [quick disconnect] failed at the track. It failed in an unusual way, in that it quit passing fuel...so I had low fuel pressure and the injectors wouldn't fire.

I finally, after much testing, discovered the problem and replaced the QD. So unless that happened again [doubtful] that shouldn't be it.

It has a fresh fuel filter, so that shouldn't be it either.

[SeanFromTX]

Rainman was lookin' out for me and told me about this thread. Sounds like the same problem I'm having and aint figured out yet. With that said, I'll describe the symptoms I'm having so we can collaberate on a resolution. I have a 1999 748 with ~16K miles. The only engine mods I have that could contribute to the diagnosis are; Termi slip-ons, JHP air filter and a FIM chip. I have CF intakes so the inline air filters no longer exist.

1) I'll take the bike out for a ride. The symptoms do NOT happen immediately.

2) It seems to take at least 20-30 minutes before it occurs(this is a guestimate).

3) When I approach a stop sign/light and pull the clutch in, the motor goes to idle, but dies within a few seconds. During those few seconds it's very erratic. I can blip the throttle to keep it running until I need to go, but it's a pain in the @$$. If I wanted a TZ250, I would have bought one.

4) I've also experienced another unwanted behavior that I believe is related to the stalling while stopping problem.

5) While riding down the highway, my 748 will start to surge/stumble around 5-5500 rpm. When this occurs, I can pull the clutch all the way in and the bike will stall. I let the clutch out which immediately "bump" starts the engine. When it occurs I can get on the gas and ride around 6-6500 rpm and the bike will recover from the condition. It can get pretty annoying.

- Because the issue was intermittent, I went with replacing the fuel filter first. I also replaced the spark plugs and cleaned the air filter. I went ahead and replaced the high pressure hoses as preventative maintenance because I had given a guy an 85 mile ride because his had split. My fuel sending unit broke around the collar so I had to replace that because the fuel would leak. I had both the 6 and 12K services performed by my local Ducati shop and it's always ran fine when I've picked it up.

I hope the extra information aids some of you knowledgeable folks in determining what the problem is. I haven't posted up because I have an absolutely bullet proof ZRX1200R that never let's me down. I really cannot afford to hand it over to the shop for stuff like this. I do bite the bullet at the maintenance intervals as I believe I'm getting some value out of that.

Thanks Mr. Bill !!!

My fingers are crossed,

[blairjw]

Thanks both Seans'

From what I have found problems associated with the TPS manifest themselfs as stalling at traffic lights.

Found some other threads about a white connector behind the battery that seems to have some issues.

We will check it out this weekend...


Blair

[blade625CT]

just want to keep this up top where someone might think of a possible cause/solution.

Blair, let me know how you and Todd make out this weekend, and whether you need a fuel pressure testing rig [i'll lend you mine]

It will allow you to check pressure, and run the bike with the tank off on a side stand. It hooks directly into the QD's between the tank and the TB's

Btw..i'm pretty sure i dielectric greased the connector you are refering to...but can't remember for sure.

[level7]

If you have a sidestand bypass, jiggle that bad boy while in neutral and the engine running.

Early on, I had very rare stalling problem coming up to lights, maybe once or twice. I couldn't tie it to anything but now I know it was probably the side stand bypass someone put on my bike before I bougth it.

It recently got worse, no rhyme or reason, stall/cutout. Then normal operation. Seemed it was fuel related but wasn't. Luckily, my installation of my bar risers brought it to light. All it took was a slight (and I mean slight) tug on the sidestand bypass and voila! stalling/sputtering/dying.

Anywhere someone installed those crimp jumpers or T-taps, double check those. They WILL go bad after a few years especially with the heat these motors put out. This recently happened to my Jeep. I had a alarm put in when I first bought it. Five years later, I had lighting issues. It was the T-taps, some of them worked themselves loose.

[Matt748]

Just bought a 98 748/853, runs like a clock, but now I'm having problems starting it. It either starts or it doesn't, no stalling yet but I only have about an hour and a half on it on 3 or 4 different occasions.
Now I'm familiar with car mechanicals but I know absolutely nothing about bikes, do you guys have any ideas? I took the tank off and wired the fuel pump to a battery and it runs (pump), drained the gas...doesn't look like there's any water...what gives? To be honest I've experienced bad gas before...twice...and this is way too hit or miss IMO.

I searched the archives and heard level7 talking about a side-stand bypass? What is that and how do I know if I have one to check??

Now with the tank off and everything it doesn't seem to have spark, any ideas??

Sorry to bring only ignorance to the table here, thanks for the time, appreciate ANY advice.


Matt

[blade625CT]

No side stand bypass on '98 bikes. So forget about that.

How are you checking for spark?