SV650S (K4) - Misfiring Mystery

[The RAM]

HI all,

In brief, I've had a post here already in which Bibio and a few other members were most helpful. (http://forums.sv650.org/showthread.php?t=215566)

So last Saturday, for the 4th time in 3.5 years, my engine cut out as I pulled to a stop and upon starting up again it wouldn't idle. It kept cutting out and had to be held at 3-4k rpm to prevent it stalling. It was missing like there was no tomorrow and jerking all over the place. Managed to get home in one piece and showed it to another biker across the street and he knew something was wrong and told me not to start it again.

Bike was picked up by a trusted local bike mechanic, taken off and fired up yesterday - it ran like a dream... A customer even commented it was one of the nicest running SV's he'd seen! Problem is, none of us can figure out what the problem might be. Injectors? ECU? Electrical? Up until the point I pulled up at the roundabout, the bike hadn't missed a beat since June when it happened previously.

Oh, and it's also the 4th time I've had this problem, taken it in and it's been perfect. Any thoughts?

(TPS at 1400, TB's sync'd, plugs new in Jan along with oil/air filter and oil.)

Thanks all in advance! :)

RAM

[DJ123]

Checked spark plugs & HT leads? I would also check the HT leads have a good connection at each end too

[Typhon219]

Whats the weather been like each time its happened? Just wondering if its wet and water could be getting in somewhere

[Craig380]

I can only think something electrical. Is the main earth point at the back of the gearbox sound and not corroded, etc? Might be worth giving it a hosing down with WD40 / ACF50

[The RAM]

Spark plugs should be fine. New in January, and given it's the 4th time this has happened, the chances of me having bought 4 sets of duff plugs is nil. The HT leads seem fine and my mechanic suggests so too. He thinks if it was the leads the problem would manifest itself instantly every time I run the bike, not without warning every 6-9 months. The problems with the bike running rich seem to be a part of the problem but right now I'm concerned about fixing this recurring one as it's dangerous when it occurs.

Re weather, it's happened when both dry and wet, always without warning. Bike is running fine and then suddenly not. The last two times it's been totally dry and the bike up to temperature.

Re earthing, what would the bad earth do? I'll look at it when I get it back and go over all my electrical connections. I read recently on this site of a guy with an electrical problem with his throttle bodies. Could it be something similar? Most mechanical people I'm talking to seem to think it's electrical given the spontaneity of the problem. Anyone got a list of things to check in order so as to rule out things one by one?

Thanks all! :)

[Craig380]

A dodgy / corroded main earth could make it stutter and cut out because it creates a higher resistance to current flow that's also unpredictable. My old Suzi X7 had an incredibly elusive random misfire / cutting out problem that turned out to be corrosion where the loom earthed to the frame. It's easy enough to hose down with some WD40, anyway :)

Two other random thoughts - could be worth checking the clutch switch connections aren't furry / corroded, and give the side-stand switch a squirt of ACF / WD too. Just to eliminate simple stuff ...

[The RAM]

So I've got the bike back and the last two days it has been running perfectly. I'm going to keep it running until my next day off on Wednesday and then, assuming the weather is good, strip lots of it down and 'service' the electrics with some ACF50. Here's to it not cropping up again.

On a side note, does anyone know where I can get a new clutch and some cush drive rubbers? I'm trying to eliminate a noticeable clunk from the drive train. Chain is fine, next is clutch as I suspect it's on it's way out, third is the cush drive.

Thanks all! :)

PS. If anyone is in the Southampton area and wants to join in you'd be more than welcome. Payment in biscuits, tea and coffee! :)

[Toooldtodie]

Check rusting inside the fuel filler part of the tank. Could be rain water getting into fuel if it's not draining away properly.
Pipe can corrode inside the tank or the rubber drain hose can get kinked, This allows water to overflow into the petrol giving you Buckaroo performance. Re-filling the tank negates some of this until the water re-settles down to the fuel pump.
Just a thought, happened to me.

[The RAM]

Hi guys,

So it happened again today. Upon deceleration from 70-40mph leaving the motorway using mostly engine braking there was a stutter and then the misfiring started with a vengeance! I've managed to get two videos (please excuse my camera voice!) of the misfiring, tacho and the TB linkage upon throttle inputs. Forgive my thinking out loud too. This is immensely frustrating for me that this is still occurring.

https://www.youtube.com/watch?v=1QBvmopY-8g

First, you can hear the misfiring most clearly at the beginning of the first video. The longer I ran it the more it seemed to settle and fix itself.

Second, notice the revs bouncing by themselves at around 30 seconds. I wasn't moving the throttle at all and it bobs up and down by itself around 2000 rpm.

https://www.youtube.com/watch?v=isgPeslCMKk

Third, on the throttle body linkage video, shouldn't the STV move consistently throughout the rev range? I'm no mechanical expert but the fact it moves a bit, stops and then opens fully seems odd to me. What's even more odd is at 30 seconds or so when the engine picks up a lot with fractional input and the STV doesn't move at all! Is this right? Would certainly explain the fact that the bike is running so rich if the STV's are limiting the airflow...!

Please forgive me if I'm being a noob. I just want to sort this ASAP!

[Toooldtodie]

Could the throttle be snagging on the hoses exiting the air box?

[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.

[The RAM]

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

[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. 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]

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 :)

[The RAM]

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. :)

[The RAM]

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?

[AlexAdams]

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

[The RAM]

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.

[sev]

I had a problem on my curvy that caused it to cut out completely randomly. Last time in the third lane on the motorway. Took it to my Suzuki dealer and they couldn't find anything wrong then when they were going to phone me to collect it the mechanic took it for one last test ride it cut out on him in the middle of a very busy roundabout. it turned out to be a problem with the connector in the rear of the seat with the ecu hope this might be of help

[The RAM]

Thanks Sey. Will bear it in mind. I'm popping round to the garage to see how things are going tomorrow morning.

Did anyone have any thoughts on the temperature difference between the two exhaust pipes?

[AlexAdams]

Did anyone have any thoughts on the temperature difference between the two exhaust pipes?


Given the random occurrence it's not a blocked injector because that isn't going to clear then block again so points to ignition issue, electrical as everyone has been suggesting. I would replace both coils or at the vry least check/clean their connections possibly try and find a friendly breaker who'll let you test a different pair. . . if not they're pittance 2nd hand and the forum isn't plagued with dead coil issues so they're unlikely to be faulty.

[The RAM]

Rang the garage this morning. Nothing found yet... I'm beginning to run out of ideas as to what it could possibly be!

[The RAM]

Given the random occurrence it's not a blocked injector because that isn't going to clear then block again so points to ignition issue, electrical as everyone has been suggesting. I would replace both coils or at the vry least check/clean their connections possibly try and find a friendly breaker who'll let you test a different pair. . . if not they're pittance 2nd hand and the forum isn't plagued with dead coil issues so they're unlikely to be faulty.

I'll see what the garage is up to and find out what they've checked today.

My thing with the injectors is whether it's stuck open slightly/leaking, not shut as the bike has had chronic running rich issues since I bought it. The usual sequence is: new plugs, runs fine for a few (9-12) months, dies, I replace plugs as they're black and fouled, repeat.

The other thing in relation to that (if you've watched the two terribly shot videos in my original post) was the operation of the secondary butterfly valves. They seem to move a little, stay stationary as the engine revs up toward 7-8k and then go wide open. This doesn't strike me as normal as I'd have thought the engine needed more air as the revs climb, not less. I'm no mechanic, but surely they should open consistently as the revs climb?

Thanks as always.

[The RAM]

Update from the garage. Compression check. Rear =145/150, front ~50........!!!!! I'm going in to check the figures on Monday morning as they don't work on Saturdays but if they're that bad... Gee... Apparently the air was leaking through the exhaust so its the exhaust valves. Will have to wait and see. If its valve regrinding then the head is going to have to come off.

The guy did say it was amazing that my bike was even running and I'd not be surprised...! :(

RAM

Edit: I guess it'd explain the mega smell of fuel on the overrun and some/all of the running rich problems!

[maviczap]

No compression no bang, so thats why the fuel isn't burning.

Oh well its an answer

[The RAM]

Yeah. I'm hoping it's not true as fixing it will be expensive! But it does make sense. If the valves are open then all the fuel will be dumped into the exhaust, hence richness and black plugs. Will update on Monday when ice seen it ams hopefully photographed/video'd it.

Thanks as ever.

RAM

[Toooldtodie]

Thanks for the updates.
It's all really useful info to help all the fellow millionaires who subscribe to this forum! It is a shame you have to bear the cost for this, but we are all grateful to you for sharing.
Just think of the sweet running machine you will have...

[The RAM]

My pleasure. I'm off to the garage this morning so hopefully I'll get some video/photo updates and then upload them this evening.

RAM

[The RAM]

So in short, compressed air blown into the front cylinder at TDC escapes out of the exhaust significantly. So, they're going to remove my exhaust header pipe (try as the studs are seized!), poke the camera in and look at the valves to see if there's any damage or carbon fouling. If so, it looks like the head will be taken off, cleaned, and the valves reground... (£££££....). They're also going to check the valve clearances as it appears it's been far too long since they were done. Suspect the rear cylinder will be fine. Hoping it's just badly set valve tolerances as that's the easy and cheaper fix. But I feel that might be wishful thinking...

I'm definitely no millionaire, and this has come as I'm wedding planning, but it's all part of life! Fun, fun, fun!

RAM :)

[Corny Gizmo]

Good luck matey, if it helps I dont think valve clearences could cause the issues your having, Its sound like your timing is out.

[timwilky]

Good luck matey, if it helps I dont think valve clearences could cause the issues your having, Its sound like your timing is out.


Ehh!

Clearance is an integral part of the valve timing. Too little/no clearance will result in the valve closing later, opening earlier or at the extreme never fully closing . This could result in damage to the valves/seats etc.

[Corny Gizmo]

To this extent though? I dont know 100% but I didnt think it could cause this much trouble thats all.

Ignore me, im crap at explaining haha

[The RAM]

Well I'm about to head to the garage to find out how it is as I was last there on Monday. Update coming hopefully soon enough, maybe even with photos if they took them like I asked. :)

RAM

[The RAM]

So here's the update as promised. First is of the top of the head, no problems there. The valve guides and seals are all fine thanks goodness!!
http://s12.postimg.org/h62o19zs9/Aog6_TKuis_i_Jp_ZAt_Pvtul_Fh_Oz1k_Wm_QPtc24_Zsv_II 2x1_Z.jpg (http://postimg.org/image/h62o19zs9/)

The piston reveals the problem quite clearly. Some pretty horrible carbon fouling there. It's not catastrophic but it's still pretty bad.
http://s12.postimg.org/qf4ube8o9/Ahc_NSbk_ISqri_JSW7v_EE8_OQXh_Jdlgsj_AJ62_Gv1_ZJn_ C2_E.jpg (http://postimg.org/image/qf4ube8o9/)

Valve seats after being lapped and ground. They're waiting on getting a new pair of valves as two had suffered some moderate damage. The head is going to be ultrasonically cleaned before being put back together.
http://s12.postimg.org/8y0qga7vt/Am_Be_Xr_T59k_FUa6_w_Md60_Iy_Pgzk_H1u_AV7b_DHd_Qa_ TJj_TCW.jpg (http://postimg.org/image/8y0qga7vt/)

Just to top it off, that's one of my engine mounting bolts. As you can see, Swiss cheese and utterly ruined, just like the thread in the case below. looks like a helicoil job to me.
http://s12.postimg.org/6s6fls4fd/Agj_PTq_Oj_VEply_Uq5_Eq_TEMBDG2_DCoj6_Hv_O5_i_CJer _CWv0.jpg (http://postimg.org/image/6s6fls4fd/)

http://s12.postimg.org/vb8h338tl/Aji_OH68_NVXa_Yfbqw74_T3c3_DRQj_ZLu_Bkh_Q9_Yy02_My _B_g4.jpg (http://postimg.org/image/vb8h338tl/)

Bill so far, £425. 4 hours labour at £55p/h plus parts with another 3 hours labour to go. My wallet is crying as I was paid yesterday but nearly all of it is going to go on this repair... Fun times.

Conclusion? The previous owners of this bike really didn't care about it...!!!

PS. I'll hopefully get the before photos from the mechanic at some point so you can see the difference. Also, the valve tolerances were within spec. I'm grateful that I didn't have a more significant failure before now!

[maviczap]

The engine mounting bolts do that. Mr Suzuki didn't use any grease on assembly.

Weird about the valves getting damaged?

[The RAM]

Yep. Very bizarre but not much I can do now. Looking forward to getting it back. Was due to get it this week but their supplier only sent them 2 valve stem oil seals, not 4... Now waiting until Monday or Tuesday to get it back. Hoping beyond anything it's fixed! Maybe then I can figure out how bad the fuelling actually is!

[The RAM]

Hi guys,

So an update on the bike. Got it back this morning. Aside from feeling tiny compared to the Deauville, it's run exquisitely. Pulls amazingly through all the gears and is smooth as silk.

That is, until on the way home from the climbing wall tonight it threw an FI light and the revs stuck at 4.5k. Restarted at the lights using the kill switch and the light disappeared. Would have grabbed the code but didn't realise a restart would wipe it. Any thoughts? Or do I need to wait to see if it does it again and grab the code before proceeding further? Bear in mind that the bike has never thrown a code in the 3.5 years I've had it, so presumably it's a result of the work I've just had done.

Thanks.

PS. Compression on the front is now 150psi. Spot on really. The final cost was £512 for: Front head off, 4 new valves, lapped, head ultrasonically cleaned, piston cleaned, valve checks, new stem oil seals, new gaskets, (used my castol oil), coolant, tb sync and sensor position checks, frame bolt thread repair and mount repaired plus labour! They took about 4 hours labour off just because...!!! Amazing.

[Corny Gizmo]

I think that a good price considering a valve clearance is quite pricey on its own.

Weird issue throwing a code, could just be something loose...

[The RAM]

C28............. :( :( :(

So I've managed to get it to throw the code twice more and finally got it. Am I basically sunk with the problem? Could a loose connector cause that? Or is it a case of new TB's?

Man this sucks...

RAM

[The RAM]

C28............. :( :( :(

So I've managed to get it to throw the code twice more and finally got it. Am I basically sunk with the problem? Could a loose connector cause that? Or is it a case of new TB's?

Man this sucks...

RAM

EDIT: And for some reason I can't see my last post. Doh! Sorry if this is a double post.

[Craig380]

Hi, C28 is the secondary throttle valve actuator. Could be the connector - unplug it and replug it in.

It could also be the actuator needs calibrating (kind of like doing the TPS), see this thread: http://forums.sv650.org/showthread.php?t=99650&page=2

[The RAM]

Figured it was the actuator. If you're referring to checking the secondary butterfly sensor, I calibrated that to as close as possible to the values as I could a few weeks back whilst I was investigating the problem initially. Some filing of the metal ring insert in the mount was required but I got it pretty darn close. Spent a long time doing that too. I'd be surprised if it had changed because of the head work I had done on the front cylinder. I will double check though, and I'll check and clean the connector too.

Thanks. :)

[The RAM]

Sorry to resurrect this again but I thought some folk might like to be updated.

Figured out today that the FI light seems to come on above a certain RPM figure, somewhere in the region of 8-10k. Doesn't seem to matter which gear I'm in, though I've not tried it in neutral yet. I accelerate up to that RPM range and as I begin to roll off, on comes the FI light. Resets upon a restart, as always.

I'm getting the fuelling checked next week as I know the bike has been leaned out to try to compensate for the rich fuelling whilst it was broken. I'm interested to see what it comes back as now compression is good.

RAM

[Toooldtodie]

Sorry to resurrect this again but I thought some folk might like to be update.

RAM

No need to apologise. This is exactly why we rely on the forum.

In fact, thank you for keeping this thread updated. Please continue. :thumright:

[The RAM]

Hi all. Finally to close this off, it turns out the secondary TPS was a bit out after all the work and was unable to go through the full motion of movement. Still, glad it's all done. It's been checked on a dyno and it's still fuelling pretty rich but nothing extreme. Maybe one day I'll save up enough to buy what I need to sort it. There was a funny moment when it came off the dyno reading 90+bhp!! I thought, "Who's nicked my bike and taken it to JHS...?!" :D

Still, time to start saving up to sort the horrendous rear shock. It's phenomenally 'lazy' and isn't what you would call fun! :)