I don't know what the hell I've done wrong, but something's gone decidedly pear-shaped! Just finished changing my spark plugs after spending what seems like an eternity wrestling with the bike trying to get around the frame to reach them from above (took tank and airbox off instead of trying hopelessly to access them from the front like last time), and somehow I seem to have turned my bike into a non-runner! The ignition still works fine, but the engine's backfiring a lot, sounds very clunky and won't tick over, with or without the choke. I should have seen something like this coming, everything I touch mechanically turns into a disaster, but I've got work tomorrow morning and I'm at a loss to know what I've done to it!

You sure you've put it backtogether properly?? and the plugs are seated correctly?
Is it backfiring out the exhaust or spitting through the carbs?

Have you tried adjusting the tick over screw in an attempt to make it tick over?

Are they correct plugs for your bike... I don't know what effect the wrong plugs would have, but if you need it fixed fast for 2moro then you could put the old plugs back in till next weekend if they're not totally knakerd?

Or dare i say it... public transport argghh! lol

did you remove the coils/HT leads?
did you put them back in the right way. they have to go to certain plugs or it aint gonna work.
i paint mine different colours as i remove ONE at a time.

can you post the part number from the end of the spark plug box that you used....

I thought I'd put it all back together properly, it seems to be backfiring from the exhaust. They ought to be the right ones for the bike (CR8EH-9), I identified them by code number via the Haynes manual when I was buying them. As far as the leads go, I'm not 100% certain they're in the right ones, I just assumed that as long as every cylinder had a plug in it properly it'd just work, never really occurred to me that the leads had to go into specific cylinders. Would that cause the backfiring then?

Ok, crisis averted! Went back out, took the tank and air box off (again), swapped the leads round a few times and eventually got lucky. Bike's running as it should be again and I feel quite embarrassed for making such a daft assumption. Not been a totally bad day though, bought a paddock stand yesterday so I finally managed to clean and lube my chain up, and even better, I had a fiddle with the speedo and seem to have finally got it reading correctly.

Spudiator wrote:I thought I'd put it all back together properly, it seems to be backfiring from the exhaust. They ought to be the right ones for the bike (CR8EH-9), I identified them by code number via the Haynes manual when I was buying them. As far as the leads go, I'm not 100% certain they're in the right ones, I just assumed that as long as every cylinder had a plug in it properly it'd just work, never really occurred to me that the leads had to go into specific cylinders. Would that cause the backfiring then?

what causes your engine to back fire is that you placed the spark plug wires in the wrong place. every spark plug wire, or high tension wire, HT, deliever specific firing sequence when the crankshaft is rotating.

so, if you place the HT wire in the wrong spark plug, you will have an early or late ignition in your combustion chamber that makes your bike makes a back fire.

go check again your haynes manual, and hope you can see how the HT wire are placed to every spark plug accordingly.


.

tip for future...

get 4 bottles/colours of nail polish
strip tank/air box off as usual
dab a blob of 1 paint on one lead and on to the coil where it screws in to.
do that for each HT lead/coil
remove coils from bike.
duct tape the rubber skirt out the way.
only pull ONE HT lead off the spark plug at a time. when you fit a new plug fit the HT lead back in.. and so on.
re-fit the coils and use the paint to match up which lead screws in to which coil.
at this stage i start the bike to make sure its all ok, let it run for a few seconds. switch off.
tank/air box back on.

done.

Good points LP, I always was a bit of a disaster when it came to self maintenance! I cringe sometimes at some of the utterly ludicrous cockups I've made on bikes in the past! Still, least it's done now.

we all co-ck uk at times, no one is invincible. i did a dozy the other week with not tightening my calliper bolts.

I've gotta say actually, I'm amazed at the difference the plugs seem to have made. My bike's gone from feeling pretty sluggish with the acceleration to suddenly feeling like a little rocket. Still feels a bit sluggish starting off but I'll get to that in due course.