What have i done?

It started off by changing the plugs. The old Iridiums had done 70000klms and were taking longer to warm up. I put in some NGK standard type plugs and it was much better on start up.
But I began to notice some drive train slop caused by a very small miss in the engine at a constant speed, mainly 100-200 rpms either side of 2000rpms. On acceleration it would go away but there was a very slight hesitation before it pulled strongly.
A few days ago I lifted the tank after syphoning the fuel out. I had a feel around the wiring making sure all the spark plug leads and coil wires were properly connected at each end.
While the tank was in the vertical position I started the engine and had it running. It seemed to be running no worse than before ,then it cut out. I thought maybe it had run out of fuel ,so I put the fuel back in.
I got it started but it runs like crap , maybe on 2 cyls or sometimes 1 cyl and the engine check light is on. Some irregular small black puffs of smoke
I had another go yesterday. Its difficult to start, you have to give it some throttle and hold the throttle at 1700 and them it begins to run a little better. It seems to be going through its normal cold start cycle of high idle then coming down to around its idle speed of 900. But it gets slower and slower.
I originally had a tune boy tune. But I have ordered a cable and will try and nut out the tuneecu when it gets here.
Ive tried disconnecting and reconnecting the battery

Any ideas out there?

I have an 07 Classic with 16000 miles. Earlier this year I thought I would replace the plugs just for fun and to get more familiar with things. I bought a set of NGK DPR7EA-9 at the dealer. After properly gapping them and lovingly installing them I started the engine and it would barely run at all. I think it was down to one cylinder at one point. I checked and rechecked all the low and high voltage connections and found nothing unusual. I finally just took my losses and put the original plugs back in and everything was fine again.

I know that's no help, but I'm just saying I experienced problems after a plug change, too.

BTW, I also have quite a bit of drive train slop. Never had any tuning or throttle balance. I'm hoping throttle balance is the answer for my problem. I hope you find your answer and I'm also looking for your results.

Throttle body balancing can be done with a Tuneboy (or TuneECU I presume). That fixes surging at low throttle settings.

I think that you may have inadvertantly loosened one or more of the spade connections to the coils, zimtuff.

Visually inspect each and recrimp nice and tight if necessary. Coating the connections with some dielectric grease is not a bad idea, either.

atomsplitter said:

Throttle body balancing can be done with a Tuneboy (or TuneECU I presume). That fixes surging at low throttle settings.

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I think I have 2 problems, that maybe one of them and will check soon.

TriumPhil said:

I think that you may have inadvertantly loosened one or more of the spade connections to the coils, zimtuff.

Visually inspect each and recrimp nice and tight if necessary. Coating the connections with some dielectric grease is not a bad idea, either.

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How tight do they have to be? The ones on the outside for 2 and 3 cyl feel as if they could be tighter, but I feel they should work as they are. I somehow feel it is a coil problem.
Is there a test for the coils using a test meter?

cold start video. https://youtu.be/byC7OmeqYhc

Not certain of your Rocket's vintage, but on Roadsters the fuel pump, EMS and cooling fan relays are all the same so it is easy to swap them around to trouble shoot. Just mark them first before you start changing them all around. In my case and at least one other here it was the fuel pump relay.
If memory serves, here in the States the relays are an Echlin AR294 or equivalent and are available at any auto parts store.

Most of the problem was a loose vacuum hose on the air tube. Still have to sort out tthe rough idle etc. Still the occasional missfire and engine light is still on. Can you only clear a fault by plugging in a computer?

zimtuff said:

Most of the problem was a loose vacuum hose on the air tube. Still have to sort out tthe rough idle etc. Still the occasional missfire and engine light is still on. Can you only clear a fault by plugging in a computer?

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Most ODBII code readers can clear the engine fault light.