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Discussion Starter #1
Hi everyone. Recently bought a K5 with 20k on the clock. Really pleased with it other than it running quite lumpy at idle and sometimes when I put it in 1st gear from neutral at the lights, it stalls. It has a scorpion can, quickshifter and K&N air filter.

Advice has ranged from adjusting the idle speed, getting the throttle valves cleaned through to fitting a power commander or getting an ECU re flash. The latter being about £400!

Any advice would be gratefully recieved
 

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You should listen to me. No, seriously, listen to
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Check that the idle speed and TPS are correctly adjusted. See 2-14 and 4-20 in the service manual but be sure on both that you adjust the primary throttle/sensor and not the nearby secondary. Check the throttle valve synchronization, the valve clearances, and the throttle valve vacuum hoses. A slip-on shouldn't require a PC or re-flash.
 

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Captain Obvious ... because obviously it’s obvious
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Throw that K&N in the trash, check if it has a power commander, and check the TPS. The lumpy idle is usually because the bike is rich, but it's also pretty much characteristic of this bike.
 

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Discussion Starter #4
Thanks very much for the advice so far. It does backfire when I come off the throttle which I guess is an indication that it is running a bit rich too? I’ll try the idle and TPS adjustment, put a standard air filter in and let you know how it goes!
 

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It can backfire if the PAIR system is left in place.

+1 on the K&N.
 

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Captain Obvious ... because obviously it’s obvious
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Stock. Also, do you know when the spark plugs were last changed?
 

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Discussion Starter #8
Well the guy I bought it off 3 weeks ago said they were done 500 miles ago but..... who knows if that’s true or not! I’ll get those done too 👍🏻
 

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FWIW I couldn't get my bike to run right with my Scorpion can without the tune. It idled like shit and would stall much the same way at barely 8K miles. Mind you it was smooth sailing until I ripped my stock exhaust off. A PC5 and a day spent with the dyno man solved the problem and I've never looked back. :thumbup
 

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Thanks very much. That’s my worry that it’s going to take a Power Commander and a tune to sort it out....the most expensive option. Steve Jordan Motorcycles has recommended a throttle body clean to see if that makes a difference (I guess it won’t hurt) which is happening on Wednesday. I’ll get them to check the idle and TPS adjustments too. Just ordered a stock air filter and will get rid of the K&N.

Is it worth me getting them to change the spark plugs while they are doing the throttle body?
 

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Captain Obvious ... because obviously it’s obvious
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Thanks very much. That’s my worry that it’s going to take a Power Commander and a tune to sort it out....the most expensive option. Steve Jordan Motorcycles has recommended a throttle body clean to see if that makes a difference (I guess it won’t hurt) which is happening on Wednesday. I’ll get them to check the idle and TPS adjustments too. Just ordered a stock air filter and will get rid of the K&N.

Is it worth me getting them to change the spark plugs while they are doing the throttle body?
Throttle body cleans are a scam almost 100% of the time.

Why not do the plugs yourself? It's a very simple procedure with multiple tutorials online. They're going to charge you a very hefty amount for something that can be done in an hour. You're already halfway there by swapping the air filter. At that point you just remove the lower half of the airbox with the 8 or so screws, remove a couple things attached to the bottom of the airbox, boom you can swap the plugs.
 

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You should listen to me. No, seriously, listen to
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+1 on throttle body cleans being in the same category as engine oil flushes for cars. Unless your TB is filthy, inside and out, it sounds unnecessary. If it is filthy, the entire engine likely needs a cleaning.

Changing the plugs is a way to learn about working on the bike. But there's a fair chance that they're OK. Suzuki recommends replacing at 7500 mi/12000 km. You'll need a spark plug socket and a torque wrench unless you use the tightening angle method. Beware of antiseize, i.e. don't torque if you use any.

A PC & tune is appropriate if you're replacing the entire exhaust. But if you're just adding a slip-on to the OEM headers, it shouldn't be necessary. However UK/EU models originally had a muffler with a cat converter and a different ECM. The ECM difference is generally associated with the immobilizer. But there's a possibility that the fueling maps are also slightly different and a PC may be appropriate (that may explain why the Australian models, which have an immobilizer but no cat, got a different ECM). Note that a dyno tune will optimize power at the expense of gas mileage. Also note that, though you can get away with it right now, there may come a time when a removed cat will be a MOT fail (as it is on cars right now).
 

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Discussion Starter #13
It was a throttle balance that they carried out in the end (they said it wasn’t far out anyway). Also did a fuel tweak, checked the air filter and hoses, cleared down old fault codes and checked recalls had been done. All for £68 so not bad and it now runs sweet as a nut! Particularly pleased it didn’t need an ECU reflash which would have set me back £420.
Thanks for all the advice guys, I really appreciate it.
 
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