Experiment leads to INSANITY!

Here's the deal. I decided it was time for an oil and oil filter change. I was running 10w30 but wanted to try something different - so I went to 20w50 thinking it might improve things - what, I don't know, maybe clutch grab or something.

Well, I took it out today and the bike was running like CRAP! I really can't explain it. Huge stutter and occasional backfire just getting to speed in first! Needless to say, I am disappointed. So I decide to colourtune - haven't done it in a while and hey, what can it hurt - right?

So I'm colourtuning and listening to the idle which sounds like it's hunting a bit. I'll have a nice rumble and then a blip, rumble, blip. So colourtuning, I decide just for giggles to pull off the number one plug wire. Guess what happens?

The idle GETS BETTER! WTF! Shouldn't the bike stall or get worse? So I repeat my "experiment" on cylinders 2 to 4. Everytime I pull off a cable, the idle gets crappy and the bike stalls. Pull #1, idle smooths out and bike keeps running!

So now I'm going insane trying to figure out what this is? I haven't synched in a while (cus it's a pain).

Any ideas?

 

I had a car that did that. It had a bent camshaft. The valves weren't closing causing backfiring and a bad idle. Pulled the wire to plug #1 and it ran a smooth as any V7 should.

Maybe you messed up an OHC.

 

Swap the Coil hook-up's to the wiring harness.
See if "This phenomenon" jumps over to #2.

 

I'd try swapping the #1 and #4 plug wires, see if your problem moves to #4. If it does than I'd look at the coil.

If the problem is still on #1 I'd swap that plug to another hole and see if the problem moved.

Since plug 1 and 4 fire together off the same coil I could imagine that a problem with a plug or the coil might effect the other.

Another possibility I can think of is that you are getting preignition on #1 that fights back against the rotation. You could be lean on #1. Could be fuel delivery problem or way out of sync. Don't know what could make them suddenly go way out of sync.

 

You didn't happen to put seafoam through the tank did you? Too much seafoam will cause the bike to run crappy. Did you try some other octain of fuel you normally run? Did you fill up at a gas station you wouldn't. Drain the carbs through the bowl drain and take a look at the clearity of the fuel. Any thing other than clear and you probably got bad gas and a carb cleaning is in order.

 

Update - I put a new plug in and same problem. So I just swapped coils with my Turbo and it seems to have worked. Got a better idle - no blips. So then I started in on synching the carbs - just to tweak it in better cus it still sounded a tiny bit rough.

I did some reading here and it sounds like, for bench synching, that the butterflys are open just a bit - enough to fit a wd-40 tube into. Is this correct? My butterflys are a hair short of shut tight at rest.

I have a manometer but the #3 carb butterfly is shut - no way a wd-40 straw will fit. Or - is the straw just to hold up the butterflys to compare to the other carbs?

 

use the idle screw to open #3 so the straw just goes in between the body and the buttefly with a slight drag. Then adjust the rest of the butterflys to the same spec. as #3 using the sync screws. #3 is the the base line for the rest as it is not adjustable, accept with the idle screw. This should get you close to sync. Dont forget to turn the idle screw back out when you are done bench syncing. back it all the way off then turn back in until it starts to move the butterflys, Then out two turns. This should get the idle close. You may need to back it down once she starts. Good luck. Hope it goes well.

 

To clarify - the WD40 straw is a tool to make sure they are all open the same amount. The amount they are open with a WD40 straw is way too far for proper idle.

Once they are all set the same back off the idle screw untin they are almost completely closed.

 

MiCarl - thanks, that's what I was hoping to confirm. It seemed a bit crazy to have the butterflys open that far at idle but I just wanted to confirm and make sure I don't have some kind of crazy setup!

Thanks again.