bike misfiring at around 25mph

[aj1soad]

so i decided to give my bike a proper clean using in these steps, WD40, de greaser, autoglym car shampoo, then once dry i gave it a coat of WD40. took the bike for a spin and mainly in 3rd gear when im doing around 25mph and give it some power it misfires like water has gone into something. once im doing 35mph or more it runs fine. when i first noticed it i came back home and gave it another coat of WD40 and it seemed to have made it worse.  ive changed the plugs and ive dried the rubber part that goes onto the plugs and its still doing the same. any idea what i could have done?

[Lez72]

When you shampoo'd it how much water did you use when you rinsed it off. Did you hose it down ?

[aj1soad]

I probably used half a bucket of water with 1 capfull of shampoo and yes I rinsed it with a hose

[Fazerider]

Have you checked the spark plug well drainage holes are not blocked?

[aj1soad]

I didn't even know there was a drainage hole. The spark plugs were dry when I checked them again today. Where about are the drainage holes?

[darrsi]

Look at the fins on the sides of the engine and you'll notice a hole in the middle, that is the drainage hole from the spark plug area.
You need to get something like wire or tubing to poke up it to make sure it is clear to let water out. If they're blocked water just sits around the plugs, which if aren't tightened properly can work it's way into the block, and will also rust the outer plugs.
If possible get some compressed air up it.


It's always a good idea to used compressed air to blow around the spark plug area before removing the plugs anyway, otherwise any crap that is sitting next to the plugs will drop into your engine when you remove them, which you really don't want.
Especially if your drainage holes are blocked, as you'll get leaves and general dirt accumulating there.
You can get cans of compressed air on Ebay for a few quid each.

[darrsi]

Make sure your spark plug caps are properly screwed in to the HT leads, you say you dried "the rubber parts" but there's a chance you may have undone them.
The rubber caps have a screw in them that literally screws into the middle of the wire of the HT cable.
Unscrew one of them and see what condition the inner cable is like, if it looks a bit ropey cut about 5mm off the end of the wire with some cutters then start afresh by screwing back into the middle of the new wire, making sure they're screwed in firmly, don't over do it.

[aj1soad]

Thanx for all the replys. I'll have a look when I get home. By the rubber parts i mean just the part that goes over the spark plugs. Would wd40 make it worse if there was any in the leads?

[darrsi]

WD stands for water displacement, it will get rid of any water.
I still reckon the caps need looking at, or you can even replace them with NGK ones, only around £12 for 4.
Originals are £52 EACH.

[caretaker]

if there is a short somewhere, fire it up in pitch black. you may see some sparking