Breaking down, stumbling, backfiring

[BJ]

Bike (2006 86,000kms) was running like shit couple months back and barely made it to dealer shop. Left it there for them to look at. Was going overseas so dropped off new clutch switch and side stand switch for installation. I had previously done filter bypass. Anyway, shop ended replacing new fuel pump and filter. I replaced the teabag couple months back. Plugs are 6 months old. Shop said they sent the injectors for cleaning and advised they adjusted the TPS. Got it back from the shop and they said it was running perfect but I wasn't convinced as it was slightly rough around 3500 rpm. Actually took it back but they said all's good. Gave it a hand full going up a local hill recently and it started breaking down, stumbling and backfiring. Went straight home and there it sits. I am no way inclined to take it back to the shop. I'm on Sunshine Coast so wondering if anyone can recommend a decent mechanic between here and Gold Coast.
Checked heat on all four exhausts at idle and all were heating.
As well, is there anything I can check in the meantime?

[Alan Moreton]

Hi BJ
Sorry to hear you are having problems.
I had similar issues last year or so.  I have an 03 bike with 60,000 miles up.
I was advised by my local dealer to check the obvious connectors etc and he also suggested that the after market alarm / immobiliser can cause similar problems.  (mine is an 03 model so doesn't have the Suzuki one fitted).  I removed said alarm, and the improvements were so marked I took the same type of alarm off my Hayabusa too! (MT375).

However, even then she wasn't as smooth as I remember it could be.  The guys on this forum also suggested I do the repair and clean on the ignition switch which is described somewhere on the forum.  Its fairly straight forward to do.  That seemed to cure the issue at that time.

One other thing - earlier this year, it started to run lumpy again, and shortly afterwards the generator stator failed.  You might want to check out your charging / battery system?  I think that any fluctuations in the electric supply caused by dodgy connections, alarm interconnections and / or charging system faults seem to have an effect on the ECU which results in poor running.

Good luck.  Regards

Chip

[Eric GSX1400K3]

#1: Get your money back from the bike shop you took it to.

Things to check, maybe not in order of preference:
- throttle body balancing between all 4
- check / remove pairs valve and block / blank the covers and line into the airbox and throttle body #3( I think, could be #2, can't remember exactly)
- check vacuum lines interconnecting the throttle bodies, plus the plastic t pieces.
- check plugs are seated and leads are secure, can trim the ends of the leads at the plug end and recrimp into the plug rubber.
- check air filter and replace or clean
- check airbox for cracks, splits or loose connections to the throttle bodies and from throttle bodies to the intake manifold.
- run a bottle of quality petrol injector cleaner into 1/2 a tank of fuel, if the bike has sat for a while, the fuel can gum up injectors.
- check battery (charge it overnight) and measure voltage
- check generator
- check clutch cut out switch up at clutch lever, the connectors can come loose and cause issues.
- check side/centre stand switch, these get filled with road grit and can also cause issues.

Hope this helps

[Hooli]

I had a TPS fail years ago (at about 67k miles), it run perfectly at idle or full throttle but mid throttle it'd cough, bang, stutter, fart, jerk etc etc.

To make it more fun it passed all the tests in the manual when checked, but as everything kept pointing to it I borrowed one on an ex's 14 & tried it before ordering a new one.

What I think happened (I never opened the old TPS to check) is the ferite core cracked so at certain positions near the break the vibes of the engine gave it an intermittent contact so the fueling was all over the place.

[Andre]

These sensors (TPS, STPS) don't have to be broken to malfunction. They wear. I consider them consumables.

[BJ]

Thought I would start with the easy and simple things.
Replaced the plugs and put a new fuel line between the drain and bottom of pump.
The standard line is soft and thin with a couple of bends that I thought that may present a problem with fuel flow so I replaced it with some 8mm high pressure FI line.
Just went for a blast up my local hills and reved cleanly to over 5000 whereas before it was stumbling at 3500.
No breakdown or misfire so that is all positive.
Hopefully it will continue this way.
The plugs removed were pretty black but I'm not sure what they should look like. Advices would be appreciated.
I replaced the plugs about 7 months ago when it was stumbling back then and it did run quite well for while afterwoods.

[Snapey]

I had previously done filter bypass. Anyway, shop ended replacing new fuel pump and filter.

Was the pump faulty?  Did they ask any questions about the external filter before replacing it? Did they contact you for an OK before fitting a $798 pump & filter.

[BJ]

Yep. Apparently the pump had shit it self with metal fragments in fuel line.
I've got a dozen bikes and I really like the 14. It's my round town V8.
Its a keeper so I thought what the hell, fix it. The new pump/filter will see me out.
My attitude with the bike now is replace anything faulty or likely to be faulty in the near future as I don't want to be going over the same stuff time after time trying to locate faults.

[grog]

Good result BJ.

[BJ]

Blocked off my PAIRS today as well. Sort of went the same route as Grog, basically left everything in place but blocked it all off.
I disconnected the biggish hose from airbox and put a rubber cap over the air box outlet.
Put a big bolt in hose that was connected to airbox and secured with a hose clamp.
Had enough slack in the hose on number 3 manifold to fold it and put two zip ties around it to effectively close it off.
Have I missed anything here or done anything I shouldn't have?
Bike is a little smoother decelerating from 2000 tp 1000.
I've got a Yoshi slip-on so no crackle and pop on the overrun to start with.
Spent an hour on the bike today toying with suspension settings.

[BJ]

Did some extensive reading on the owners org last night and discovered that some bikes have trouble running the air filter that has a tube running halfway down. So took the air filter out this morning and ride to coffee shop. NO spluttering backfiring breaking down etc.  Got the cutting disk out and cut the top off the filter which allowed the inner tube to be removed. So put the modified filter back in and the bike went ok with some stuttering around 3000rpm 80k. But if a splitter on constant throttle. Have ordered a genuine filter so will get back with the results. The filter in the bike was only 2 years and 3000 km old.

[BJ]

Following on from my last post. Put a new genuine air filter in and bike ran much better. For a while anyway. Built my self a manometer and did the throttle sync several times. Wasn't particularly pleased with the result so purchased a Carbtune and redid the sync. Surprisingly it was pretty accurate so it's possible that a homemade manometer can be ok. After all this it was still a bit off so I checked the TPS and that required adjustment. I had to drill out the collars on the TPS just a little but eventually got it on 1100. Still not running so good. Eventually got around to testing and setting the STPS and it was out a fair bit. After setting the STPS the bike ran MUCH better and so far has gone cleanly to 6,000rpm. Haven't been past that yet as I've only been on my local roads.
The joy of it all!

[Hooli]

If it gets to 6k it should be fine, the secondary throttles will be open before that (something in the back of my head says by 3k).