SV650S (K4) - Misfiring Mystery

[maviczap]

Have you checked to see if the fuel hoses arent trapped or squished under the tank

Make sure there's no tiny cracks in either the fuel or vacum hose. if its dying when you slow down, or roll off the throttle, then there maybe a fuel issue.

I had a car that did this, turned out to be a perished hose.

[maviczap]

Also worth checking the rubber caps for the vacum take off's haven't perished and letting air in.

Thanks guys. Appreciate the feedback.

So I checked all the electrics I could today. My TPS was perfect and STP sensor is (now) perfect. Checked for faulty electrics on the TB's and didn't find anything. My fuelling system seems to all be in spec so far as I can tell. The hoses look fine although they're due replacement. Nothing was trapped when I rebuilt it all again this afternoon. Everything was cleaned as best as possible and lubricated. It was amazingly smooth thanks to the STP adjustment but...

The bike died again in my way home tonight. Not on/off the throttle but steady. Same symptoms: cutting in and out, unable to idle reliably, sounded horrible, jerky. When it did idle, the idle speed was up from 1300 to 15/1600 and if you touched the throttle and let it return to idle it would die. I'm at a loss now really. Ignition coils? Alternator generating the sparks? Dead ecu? Dead injector (I didn't manage to get the injectors checked today for resistance and input voltage but on my way in it seemed fine)?

Any help is greatly appreciated! I'm going to ride it tomorrow until it occurs again and then get it straight to my mechanic. Took it to him last time and it didn't miss a beat.

One other thing. Noticed a fair bit of white emulsified oil in one of my crankcase breather hoses but not the other. Something to be worried about or not? No white gunk anywhere else in the oil system, just the breather.

Thanks all.

EDIT: PS. If my vacuum balancing caps were leaking, surely my bike wouldn't be running super rich like it always has? It's rich even after several dyno runs and ecu maps...!

[Mr_Chin]

I'm with Mavic on this. You are assuming the vacuum caps are in good order based on richness - check them. I had all the symptoms you described, and it was actually my scottoiler vacuum attachment that was cracked and leaking air. Just my ten pence worth.
Chin

OK. I'll check them today. I do have a scotoiler but its effectively brand new so I'd be surprised if it was cracked or leaking already. I'll check the caps too. Question. I got a throttle body synchronizing gauge which came with rubber tubing to attach to the vacuum points. Is it a feasible idea to use some of the spare rubber tubing to make new caps? Would it stand the heat? I'd have though so given you sync the TB's at temperature but would value a second opinion.

Thanks all!

[maviczap]

Originally Posted by The RAM

OK. I'll check them today. I do have a scotoiler but its effectively brand new so I'd be surprised if it was cracked or leaking already.
Thanks all!

Just make sure it was fitted correctly

I fitted it myself so I know it's good. I double checked the fitting on the oiler this morning before I went out and it's properly jammed on right on to the throttle body, so no leaks there. Even hard to twist it's so snug! Haven't had chance to check the caps yet but the bike is a bit warm for that right now! Still hoping it'll play up so I can take it round to my mechanic whilst it's misbehaving.

Anyone any thoughts on the butterfly's not moving smoothly? And using the carb sync tool pipes to extend my vacuum points?

Thanks again.

100c temperature difference between front and back down pipe. Just got it to the mechanic now. Rear is 220c, front is 320c! Been given an ancient Honda Doze-ville to keep me going while they try to fix it.

I knew something was wrong with the fuelling but that's crazy! Duff injector?

Extend the carb sync points by all means, there used to be a kit abailable to do this.

Yeah, I know Bibio used to do them. Just wondering if I might cannibalise the tubes I got with my gauges. Maybe when I get my bike back. I'm fascinated to see what the find given what's going on.