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Help Troubleshooting Lumpy Running When Hot - '06 SM 610

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Good morning (AEST) Thumpsters,

I need a bit of a hand troubleshooting some symptoms on my 610. I've had a solid scrounge around but haven't recognised any discussion online that quite matches the problem. This is really more of a technical/general question than a 610-specific one, so if anyone can easily palm me off to some existing discussion or site please feel free to.

The bike has a fresh top-end, which has been appropriately run-in, and I've been through a tank of fuel on the bike. Standard jets (to the best of my knowledge) and pipe. Runs very well generally, but does have a noticeable stutter at constant throttle in low to mid range. Other than that there aren't noticeable performance issues, except it seems when the bike gets 'very' hot.

It hasn't seen any hard riding since the rebuild, but a couple of times now when the motor feels very hot it starts to run rough, and will often stall when coming to a stop. It also becomes quite hard to start and I have to keep the throttle a touch open when standing to prevent stalling. Overall it feels like it's struggling or 'stiff'. The fan doesn't kick in, but it has in the past so I assume it is working but the temp isn't high enough. The amount of heat coming of the bike feels too much to me, but that's not empirical.

Do you think you could help a bloke out and point me to some troubleshooting steps I can take to track down the issue?

I think the main thing to note is that it runs very differently at what I would call operating temperature (say after a 3 min warm up and 10 riding) compared to this "hot" state - which feels altogether different.

Really appreciate any thoughts on this.

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I would take off your carb and find out what jets are in it. Then compare to what is stock and what others are running. If your fan is not running much, then it is not overheating, so that leaves valve clearances and carburetion (including intake manifold leakage - make sure the plugs from removed emissions junk are back installed). Also make sure your exhaust header gaskets are not leaking, but probably not the issue here. Your valves could be off or things have settled in. They can be hard to adjust properly and take more than one attempt until you get the knack.

Edited by K7MDL

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Thanks K7MDL.

A bit of further info-gathering has lead me to notice that after hard braking the bike tends to stutter and almost always stalls, which would indicate fuel problems I suppose. I momentarily thought that the spark plug could be involved, especially due to the apparently relationship with heat - i.e. it takes a good 10 minutes before the 'hot' symptoms start to show up.

I'll troubleshoot in the order of least effort, I suppose - plug, check valves, check jets.

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Replaced the plug with an NGK CR8EIX which made a big difference to what was a deterioration in running. I still feel the bike gets gradually hotter and hotter until it feels uncomfortable, so will do valves next, then check my jets.

The new plug has made a big improvement and I actually don't know how old the previous one was - P.O. installed. The electrode didn't look too bad... I don't really know enough though.

For those listening in, how do you think the old plug looks? I hadn't run it at any particular revs for a constant period in order to check properly - this is just it pulled out after the last ride.

6983776555_2a8422c62a.jpg

6837654806_7c91dfec52.jpg

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Hi,

that looks OLD and tired / sooty too from overfuelling,

the plug should be a "resistor-less" model for the e-start bikes.( NO "R" in the number = B8ES)

I had the 410 2001 model,

I believe yours is still VERY similar,

the valve clearance on the 410 and 610 of that era were VERY fussy about clearances,

mine was REALLY rich with just the standard running -in wear,

back to std. clearances and all was A1 again,

BEWARE..!! the e-start bikes have different clearances to the left kickers..!!

I'll let you look-up the correct values...,

Charlie

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Thanks Charlie,

I think the plug is right for the bike though - from what I understand it's the de facto replacement plug for the 610 (according to the ever reliable internet).

I did also find this catalogue. If you go to page 29, you'll see the listings for the 610, showing the CR8EIX is the appropriate Iridium plug. Hopefully that covers it.

Re: the valves, I think that'll be the next thing for me to check. The rich running could've been from the terrible old filter which I recently replaced. Either way I think I'm getting closer to eliminating the original symptoms.

Start with the simple things, I suppose!

Dave

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Jetting by using the color of the plug (at least in the USA) really does not apply anymore because they mess with the fuel so much here.

My initial thought would be to pull the choke out a small amount when your stuttering occurs and see if that helps. Repeat with the hot start.

It is extremely possible that you may have a needle with too little taper, which at about 1/8 or 1/4 throttle does not deliver enough fuel, but the pilot circuit (pilot jet in combination with the pilot needle setting) may be too rich.

In 2006, at least in the USA, they had the jetting all messed up to pass road emissions, but no idea how they were delivered in Australia.

I don't have time to visit this site much anymore, so I may not see any further questions you may direct my way...

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Thanks Coffee, appreciate the help.

I feel that although the plug made a difference, the issue overall is gradually worsening. I think my next steps are:

  1. Check for air leaks around the carb using carb cleaner.
  2. Check/adjust the valves.

I did get the fan switching on recently after a long idle, which might indicate I'm wrong about it running 'too hot'. It just feels that way but I could be reading too much into it.

I'm not very sure-footed in these things so approaching it all a bit sheepishly.

One major symptom which everyone might recognise is that with slow, constant turning of the throttle from idle up (in neutral) the bike will only rev up to a certain point, after which any throttle movement (say from 3/4 onwards) has no effect other than to change the exhaust tone to have more of a "worw" to it.

Would that indicate a lack of fuel to accompany the additional air at full throttle?

FYI: The bikes in AU didn't ship with any emissions stuff, but who knows what the P.O. did with the carb, and/or whether there's blockages/wear.

GB

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Just thought I'd post a follow-up to this topic.

Since the last update I've:

  • Been advised it was running very rich from mechanic and realised it was using a lot of fuel.
  • Replaced jets with stock, as we had no idea what previous owner may have done/replaced. Replaced main, idle, starting, needle jet, needle.
  • Replaced throttle position sensor on advice from mechanic though this was probably overkill.
  • Replaced spark plug.

Bike came back running much better, the "hot" problem had gone.

Since then it's developed a pretty bad mid-range stutter/misfire.

Happy days! :banghead:

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