Futura stuttering with occasional misfire

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KitchenSync
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Futura stuttering with occasional misfire

#1 Post by KitchenSync » Wed Mar 29, 2017 2:51 pm

Before I once again lift the tank to fiddle with the coils... maybe someone has an idea of what's going on with my 32k Futura?

Occassionally crippling hesitancy when pulling away - I have to wait for the revs to rise before releasing the clutch and sometimes it conks out, other times spits back.

It didn't used to be this way but is consistently behaving like this now. All the coils have been changed, partially replaced the leads and plugs. (the rest are awaiting installation).

I'm getting no warnings from the ECU that there's a problem with the ignition.

I have a new fuel pump on standby. The only time it's ok is when cold, when I crack the throttle open beyond a certain point (then it'll pull like a train). High octane juice does improve it a little bit.

I'll fit the new leads and plugs but I'm not expecting that this is the problem. I've a spare throttle body so could switch the injectors.

Any insights welcome - the old Falco never did this... being generally wonderful and lovely.

Ta

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Dalemac
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#2 Post by Dalemac » Wed Mar 29, 2017 4:34 pm

Check the connector to the fuel pump. I once had an issue where a dodgy connector block was causing it to drop revs when going over bumps and rumble patches. I ended up cutting out the connector and putting an aftermarket one in instead.

I'd also check that the throttle bodies are synced, and that each spark plug is giving a nice strong spark.

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#3 Post by fatboy » Wed Mar 29, 2017 5:31 pm

Have a look at the vacuum pipes from fuel pressure sensor to t/b's,
also check fuel pump relay and all earth conns on the fuel pump wiring,could even be pump itself failing as it gets warm.
Good luck with this, you deserve some !
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KitchenSync
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Guilty as charged (or not charged as it happens)

#4 Post by KitchenSync » Tue Apr 04, 2017 2:55 pm

The old bastard isn't charging...

I've not checked yet - need to bone up on what to measure - but the battery's been bottoming out recently. With all my riding done in the city i just shrugged my shoulders and put it down to the alarm and riding with lights on all the time.

Well last night it was barely able to pull away and starting g was a struggle. Again over a certain RPM it's fine. Having charged the battery overnight it pulls like a train UNLESS I turn the headlight on. BINGO! I surmise that the charging circuit is breaking down so at low RPMs,up to about 3k, the ignition is running off the battery only. With the headlight drawing current there's just not enough to go round.

Now... where's that searchbar... is it the generator or the regulator???

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#5 Post by fatboy » Tue Apr 04, 2017 6:10 pm

Good work on narrowing it down.
On tick over with a multi meter across the battery leads you should be reading 13.75 to 14.25.
Could even be the battery failing to hold anything but a vicious charge, I hate electrical nonsense, too many potential suspects.
Hopefully a grown up will be along soon and tell you how to fix this
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#6 Post by mangocrazy » Tue Apr 04, 2017 7:13 pm

I wasa hoping to be able to link to a really good electrical fault finding thread on A N Other forum, but either I don't have authorisation or the link is broken. If it were me I'd get hold of a modern MOSFET type regulator/rectifier as fitted to later Yam R1, Kawasaki ZX-10 etc. They're a much more efficient type of R/R and don't produce nearly as much heat, while also giving much better regulation and charging.

However I think this thread from a Triumph forum would be widely applicable to our bikes as well:

http://www.triumphrat.net/speed-triple- ... ics/104504

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KitchenSync
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Not the stator!

#7 Post by KitchenSync » Thu Apr 06, 2017 9:09 am

I burrowed my way behind fairings to get the brown plug of death to measure the rotor output.... found it long gone but with one of the connections to be among the worst soldered joints in the history of civilisation. Very warm and maybe only a handful of strands doing the conducting.

Wahey.... get in there I thinks..

Disconnected all the joints - checked the output which was spot on - reconnected them and.....

It's no different. Still stumbling under 3k rpm if the headlight is on.

I've not checked battery voltage with it running yet.

Next: reg/rec check.

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#8 Post by Greg » Thu Apr 06, 2017 9:20 am

How's the battery itself holding up - any sign of over charging?
You don't get a warm-up lap for life...

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#9 Post by KitchenSync » Thu Apr 06, 2017 11:02 am

The battery is brand new... possibly yet another unecessary purchase in the merry game of chasing down a fault!

It's fine, but runs out of steam after a few days if I don't charge it. A bit better now I'm no longer riding with the lights on all the time.

I'll check the voltage with the engine running later. Unlike the Falco the dash doesn't have many features. - not even a trip!

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#10 Post by Dalemac » Thu Apr 06, 2017 3:18 pm

Isn;t there a 'charging wire mod' for the falco? Might be applicable to the fut fut as well? :smt017

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Strangeness

#11 Post by KitchenSync » Thu Apr 06, 2017 6:38 pm

Here's a video of the battery state with and without the lights on. It's almost as if the lights kill the charging circuit!

Voltage almost the same as when not running with the lights on, and what I imagine is normal with them off.

https://goo.gl/photos/8e7mEbkyP1E8f5kEA

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#12 Post by fatboy » Fri Apr 07, 2017 4:51 pm

Well that would seem to point the finger of blame at the lighting circuit, hopefully you will find some obvious horrors, evict the demons, banish the witches....
Or get it diagnosed
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Re: Futura stuttering with occasional misfire

#13 Post by wrenched » Fri Apr 10, 2020 2:49 pm

Probably the first thing I did my RST was to ditch the OE regulator, quite hopeless barely managing 13v. I don't think this was linked to bad running in my case but it at least starts and you can see something of where you're pointing after twilight! The reg I used was Firestorm.

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Re: Futura stuttering with occasional misfire

#14 Post by wrenched » Fri Apr 10, 2020 2:51 pm

Probably the first thing I did my RST was to ditch the OE regulator, quite hopeless barely managing 13v. I don't think this was linked to bad running in my case but it at least starts and you can see something of where you're pointing after twilight! The reg I used was Firestorm. Or ask www.electrexworld.co.uk what they might suggest.

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Re: Futura stuttering with occasional misfire

#15 Post by Rowlrat » Sun Aug 16, 2020 4:40 pm

A direct short to earth will instantly blow a fuze ? Old classics use coils with three ohm resistance V=IR so one coil is pulling 4 Amps normally there are two coils wired in parallel so I think that’s 1/R + 1/R my point is when the lighting circuit is on you may have an additional short that has resistance so draws loads of amps but not enough to blow Fuze🤔
After having trouble with a Guzzi T3 found 3 intermittent faults running pitch black is still a good idea wiggling wire by steering head and he ho a blue flash 👍

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