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| Ktm 400 exc 2009 won't idle!! And backfires. Help please https://www.trf.org.uk/forum/viewtopic.php?f=36&t=22859 |
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| Author: | mancchair [ Sat Nov 19, 2016 11:08 am ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
Personally I think you have water in your fuel, you need to remove the float bowl drain screw on the bottom of the carb with the fuel off then replace once it has emptied out, if this solves the problem temporarily then it proves the theory, you will then need to drain the carb and tank completely let them dry out and then replace the fuel, all this can be done yourself quite easily without the need for specialist equipment or knowledge 
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| Author: | smokinrider [ Sat Nov 19, 2016 11:09 am ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
Popping on the over run and poor idle is a clear sign there is an issue with the pilot circuit. Deceleration popping is a lean idle mix. It all points to clean the carb the jets and the pilot fuel screw. Don't change jets yet as if it ran ok before then they are likely to be right. Once clean set up the pilot screw and idle. Link to follow with basic carb setting procedures. Sent from my iPhone using Tapatalk |
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| Author: | smokinrider [ Sat Nov 19, 2016 11:14 am ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
http://www.duncanracing.com/TechCenter/ ... etting.pdf Two stroke based I know but principles are the same just pilot screw is a fuel screw (4t) (in for lean out for rich) not an air screw(2t)(in for rich out for lean). Check carb rubbers are sealed and crack free as well and that exhaust header is sealed properly. Once you've eliminated the carb and put a new plug in it, then delve deeper and check valves. Sent from my iPhone using Tapatalk |
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| Author: | mancchair [ Sat Nov 19, 2016 11:52 am ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
I can't see the point in cleaning the carb again when this has already been done and the problem still exists, that is without solving the most likely cause of dirt in the carb ie dirty water in the fuel  Also the tuning of a kehein fcr carburettor is s very complex procedure, not for someone new to spannering a ktm
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| Author: | Joel [ Sat Nov 19, 2016 1:07 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
Hugh Cleary wrote: Greetings, I note that you have called yourself "shall we say non mechanically minded", if this is the case then I have to ask should you really be fiddling with carburettor parts, etc,  Carburettors are expensive items, relatively delicate parts and easily damaged so I would advise you not to play around with it. Similarly valve clearance checks and re-shimming can be tricky if there is nobody there to guide you  As described I can not see it being a problem with the tank breathing but to check you simply run the engine without the fuel cap in place, if the engine stops then you know that the cap is not the cause of the problem. I note that your 'name' is a black colour which indicates that you may not have joined yet, if not then join up and check out your local Group, they will be best to advise you of a trusted technician in your area or somebody with greater experience might offer to take a look and guide you on the practicalities. TTFN Hugh. Just pull the breather pipe off the cap and run it...but my money is still on the valves...have you ever had them checked and how long have you had it ?how many rides etc... |
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| Author: | JoeThomson [ Sat Nov 19, 2016 1:56 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
My money is "all in" on valves. Sounds like exhaust valves are too tight, when the engine warms up there is no clearance for the valve stem to expand into, it lifts the seat giving the backfiring described. Said backfiring overheats the valve stem even more burning the valve & exasperating the problem to the point the engine dies and won't start. I would definitely check the valve clearances first and if adjustment doesn't solve the problem it could be time for new valves. I've heard of valve stems necking, eventually dropping a valve into the cylinder if you keep running in this condition (very bad) FYI the KTM recommendation is to check the valve clearance every 30h on a 350exc which is generally what I do, they do get tighter over time as the valve face wears |
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| Author: | Joel [ Sat Nov 19, 2016 2:31 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
http://youtu.be/-6i2-TxVKYg Loads of these on Yous Tubes...it ain't hard to do,some maths involved...but very satisfying when done...you don't need a whole shim kit..just the ones you need...max 4 sometimes less...also,can you please report back when it's 'sorted' as to what it was...info is king. |
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| Author: | Hugh Cleary [ Sat Nov 19, 2016 2:46 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
Greetings, A cylinder leak down test will confirm the clearance problem, it does not take long to carry out such a test on a single cylinder engine. If the valve clearance do require adjustment then make and keep note of when you adjusted them and by how much, this way you know how often and by how much over a period of engine running hours. If you are having to make large adjustments often then the cylinder head should be removed for closer examination. Remember that engine running hours are not the same as riding hours, the running hours are longer I still think that you need to find somebody more qualified and knowledgable to help you, but that's just me erring on safety for you and the engine. TTFN Hugh. |
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| Author: | ChrisC [ Sat Nov 19, 2016 3:03 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
I had similar symptoms recently on a honda, started fine from cold but wouldn't tick over popped and banged at mid throttle would cut out, sometimes it would restart others it wouldn't. Turned out to be a duff spark plug |
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| Author: | Blacklightning [ Sat Nov 19, 2016 5:29 pm ] |
| Post subject: | Re: Ktm 400 exc 2009 won't idle!! And backfires. Help please |
mancchair wrote: I can't see the point in cleaning the carb again when this has already been done and the problem still exists, that is without solving the most likely cause of dirt in the carb ie dirty water in the fuel Also the tuning of a kehein fcr carburettor is s very complex procedure, not for someone new to spannering a ktm I think we need to ask ourselves how do we know the carb has been cleaned, original post doesn't confirm? And if it was the garage who did do it, how did they do it and to what end result quality? Seems odd to me that on collecting the bike from the garage you had to adjust the idle screw to get the bike to fire - what did the garage have to say about the fact you had to do that? Seems odd. Bike was running when it when in.....and I assume it was ridden home and so ran immediately after the service once you'd adjusted the idle screw. And appears worse after sitting for a month and a week after? Can't personally see how valve clearances would have closed up whilst the bike has been sitting for a month and a half. Bike sitting idle, with fuel in it, points to carb and fuel first off to me. Then the HT firing circuit including plug. However, it could of course be the main bearings.....  One of the best pieces of advice is to know your own limitations on bike maintenance - there will be folks around in the TRF local section who will know what they are about and will likely be willing to share their knowledge and experience. If the bloke who shows you strips a carb on the trail and pust the parts down in the mud - maybe find someone else. If you really are not sure what you are doing - then don't. Get someone who knows to watch you do it and teach you - then you'll know. Overtightening a spark plug can be serious, undertightening a spark plug ditto - missing off a plug washer can cause problems, mis-fitting a plug cap can cause bike not to run, taking things apart and putting them back together in a different order a challenge. It's all logical and can be easily learnt - if you want to - join the TRF and its one of the benefits you'd likely pick up. It is a very satisfying feeling to resurrect a dead bike out on the trail and enable it to be ridden home. Amazing what a few cable ties can do.... Carbs are wonderful scientific instruments and the slightest spec of dirt can cause a problem - and a spec of rust can be worse as it likely wont break down - and can ebb and flow with the fuel level change giving intermittent faults - carbs should be kept spotlessley clean inside in my view. Poking at them with sharp instruments can damage mating surfaces, a scratched pilot screw can upset the idle so certainly don't go about it with a knife, scraper, or anything sharp and pointed. Best of luck - keep us posted. Cheers StuartM |
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