Misfiring Bonneville

Hi filbay, this is usually a symptom of running rich with SAI in place, the popping is unburnt fuel getting burnt off when it hits the fresh oxygenated air injected just after the exhaust valve's. Maybe your choke/cold start mechanism is a bit sticky or not fully off ??

 

Removing the AI usually cures this, which you've done.Have you bunged some different pipes on? You might need a different map

 

So, just to be clear, the problem is backfiring and generally misbehaves (????) - is this on the throttle or when on over-run with the throttle closed?

 

I had this a couple of weeks ago, ticking over and just stall's, spitting back, not really bad but enough to be a nuisance, used all the fuel, got another tank full from the same BP garage and not missed a beat since!
Could be you just got a bad tank of fuel?

 

Ah have you tried swapping coils round ? I rebuilt my motor, put higher compression pistons in, the left hand coil failed, the higher compression was too much for the sparks to jump the gap on the plug, it ran like a bastard when throttle was opened up, only came on as the engine reached operating temperature, cold and restart was good again. New coil solved it !

 

Also try just starting it and riding straight away, too much choke is not good

 

I would've tempted to put the old plugs back in and see how it runs. You may have a breakdown on one of the plugs. I've had this problem before myself and found bike misbehaving on light throttle but under plenty torque/acceleration ran fine.

 

Take it out on the road and give it a good thrashing.
I have learnt with my Bonnie EFI that the choke can be virtually pushed straight back in once the engine has started no matter how cold the weather and mine sleeps outside.
My method of starting:
1) Choke fully pulled out and no throttle whatsoever
2) 5 seconds later push the choke in to the first click (1/2 choke) and a light touch of throttle for a few seconds
3) 30 seconds max push choke fully in and throttle on/off to ensure engine response for 3-4 seconds
4) Engine will now run on idle while I get all my gear on.

As suggested earlier you may be leaving your choke on for too long which is too rich and flooding your engine.
If that does not solve it do as Tigcraft has said and change your plugs, there is every chance a new plug could be faulty, it may spark when out of the cylinder but not under compression.
Then look at plug leads, plug caps etc. Changing only one thing at a time until you eliminate the problem.

My bet is that you are keeping the choke on for too long, and I hope it turns out to be that easy a solution for you.

Just as a final note, no matter how many miles I have ridden or how warm the engine is, if I stop for fuel for example, I always have to pull the choke out to restart the engine, only for 1-2 seconds but I do have to do it.

 

That's worth knowing, I will try that.
What is your verdict on carbs opposed to EFI ?
I must admit every bike I ever owned was carbs, it is something that I understand and can work on.
The EFI is a bit like magic to me and I'm not a particular lover of jiggerypokery and electronic mapping etc.
(Probably my Luddite inheritance from the area I live in)
I had planned to remove the SAI but have read conflicting information on re-map or not after removal.
At present she runs like a dream, bit of popping on deceleration but I have opted to leave well alone for the time being.

 

What sort of cost are we looking at on the EFI ?
I do ride pretty steady all in all and I don't really want to be spending big bucks on something that I might not fully benefit from.
I appreciate your feedback in helping me understand this a little better.

 

£108 doesn't sound bad if you get all the improvements and can remove the gubbings.
What about the ECU free download that is regularly mentioned ?
Do you recommend removing the Lambda sensors as well ?
Cheers

 

Cheers for that HT
Yes my bike has the standard silencers fitted and they are in good nick.
I have actually visited the TTP site before and recognised it once I brought it up.
Certainly given me food for thought, your experience of it all is more than helpful.