Need some help please

[Sportsterboy1974]

2003 883R/1200 Conversion (Wiseco),Crane Single fire ignition and coils,Supertrapp 2-1 Exhaust,Kuryakyn Hypercharger.Bought myself this bike today and it ran fine for 80miles until a problem happened that resulted in having to call the RAC out. I was travelling down the A1 north of Leeds in 5th at about 5500rpm when the bike suddenly lost power(like it had dropped a cylinder) and started backfiring,luckily i safely got onto the hard shoulder.The bike sounded like it was missing on the rear cylinder and was fast idling at 2000rpm. No leaks seemed to be coming through the gaskets and it wasn't blowing smoke.I thought maybe a plug had gone down.Mr RAC arrived and pulled the plugs..said the front one looked a bit pitted..swapped them over but still the same rough running and fast idle.He hadnt got spare plugs and his compression tester wouldnt fit the sparky hole's.So onto a trailer and back to Leicester.When i got back started the bike up and it sounded to be running ok again...took it for ride up and down road and all seemed ok but the idle started creeping up again to 2000rpm?The engine does sound very mechanical but then the supertrapps are fairly quiet compared to my last bike's screamin eagles so maybe i'm just hearing what was there before.Just spoke to the previous owner (who sounded surprised about a problem) and he said that the VOES switch had previously had a repair done to it...wandered if this could be the problem?Any suggestions welcome...was a long day..took 2 and half hours before bike got put on trailer! Cheers, Steve
p.s. i'm thinking voes switch,plugs,maybe manifold leak on rear cylinder?

[Hawkeye]

Can't really see what repair to the VOES switch you can do unless it's a broken wire to it or the earth from it.

High tick over sound like could be an air leak on the induction side.

Does it have to do '80 miles' before it happen, just wondering if it's a heat related thing though 80 miles must be an hour to an haour and a half of riding.

Get two new plugs for a start, that way you are starting with something good.

If you run the bike at night it will also show up real easy and spare sparks that may be coming from a bad coil, bad leads etc.

[Sportsterboy1974]

Hiya mate,having trouble getting time to look at the bike at moment..my first port of call is to get some new spark plugs in there.I'll have a look to make sure air cleaner and carb is seated correctly and try and get the bike ticking over at about 1000rpm once warm.Then i'll take it up and down the road and make sure idle doesn't start creeping up again.Checking in the dark is a good idea thanks..i'll have a go at that..should get to have a bit of a look Tues/Weds nite..any other suggestions welcome

p.s. when the problem happened the bike was under heavy engine loading conditions as i was in the outside lane with wide open throttle..i had decided that 80 miles was enough warming!

May be worth having a look at this link re voes adjustment
MKL's Harley-Davidson Sportster 1200 Custom - Adjusting the VOES - Why, When, and How
I'm not an expert. I 've had a 883 1200 wiesco conversion done and I thought i had some pinking mid range, but it could also be something resonating at mid range revs. Seems to go away when bike it nice and warm--- which is the opposite of what you would expect for pinking. Plugs are a lovely soft brown colour and look perfect > I took it back to the dealer and he says in isnt pinking. I wonder whether someting overheated on your ignition system? but I'm not that good mechanically so I may be talking crap. Please let us know how you get on

[Sportsterboy1974]

Thanks for your help everyone...i think i have sorted the bike this evening.Managed to get myself a few hours spare so i stripped off the a/c and carb,checked rubbers,gaskets and manifold for any splits ect(found nothing),bolted it all back on,changed plugs with new NGK's (original HD's in there with front plug looking in bad shape).Started bike up and took off up the road armed with a screwdriver for idle speed adjustment.As the bike warmed up and idle crept up it eventually settled at about 1800rpm with choke right in!I adjusted it down to about 1000rpm and it seemed to settle there no problem.This caused slight popping on over-run which makes me think previous owner may have set idle very high to hide the lean condition?I will do a plug chop when i get chance to see what plugs look like and adjust accordingly (been there before when i staged one'd my first 88 XLH1200).Took the bike for 20 mile run with speeds up to 75mph and fairly hard accelarating once bike warmed..all seemed fine.When i get brave enough (and don't stray too far from home!) i'll see how the bike runs at wide open throttle and giving it some welly..fingers crossed!

[Hawkeye]

I know you said carb rubber mounts were ok but also try spraying wd40 around the joints. Any leaks there will suck in the wd40 and show as smoke in the exhaust. Same goes for and other induction connections

I too use NGK plugs, get them online they are cheap as chips, about £1.80 each.