2008 Ktm 105 Sx
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9 Posts
Discussion Starter · #1 ·
Stator died due to deformed fly wheel. I installed new stator, new fly wheel, set timing with the nihlo piston top height tool to line up stator and flywheel marks. New head orings and torqued properly.
Also repacked the exhaust with FMF 2 stroke packing kit. Then I kicked her, she started second kick and idled about 30 seconds all good, sounded sweet. Then she cut out. And has been impossible to start since, no luck to get her going. She has spark but plug is from last year with low hours, took off carb and cleaned jets and sprayed it out. If I take out plug, it is soaked in fuel. If I take plug out and clean it, and blow out the cylinder with some air to dry it, then replace plug, she will sputter first kick and then nothing and plug is soaked again. Any suggestions to the issue, noting it did run about 30nseconds smoothly??? Is my coolant leaking in at head? Is the plug un need of replacement? Man , I am lost on this one. Thanks , Bill
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2,562 Posts
Suggestions:
- Replace plug with new one. It is not uncommon that a plug will give nice spark while on the outside, but when in cylinder the pressure under compression will stop the spark.
- As motor did run 30 seconds on idle (and just a little throttle I hope??) your setup of stator and timing should be good.
- You might have an issue with the ignition cable/lead and/or the spark plug cap. I have come across a cable/lead that had a small cut in it that got close enough to earth when on the plug in cylinder, but when plug was out and I was checking for spark the cable/lead did not get close to any earth (frame) so would not earth. So I had good spark with plug out lying on cylinder, but no spark while in cylinder.
- I assume that when you kick over the motor with the plug in she feels good and has heaps of compression?
- To check if coolant is getting in to head empty carbi and close fuel tap. Then kick for a short while w/o spark plug. Now put plug back in and get kicking leaving fuel tap closed. If your plug is wet when you take it out check if it is water or fuel. (Taste, smell or try to burn with a lighter)
- Also take off stator cover and have a look incase you forgot to tighten up something properly and that nothing has moved.
If all this checks up OK you might have an issue with the head gasket (the one closest to the piston). It only needs to be a little bit out of place when you tighten up the head and you will loose enough compression for the bike not to want to start. Normally bike starts initially but as the high compression starts beating on that part of the gasket it won't take long before it gets bad enough so it does not do it's job anymore.
Once you checked all this I hope you find the issue. But if not, come back and we dig deeper.
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9 Posts
Discussion Starter · #3 ·
Hey Axem, thanks very much for all the help. We ended up with a new spark plug (a cheap 3 dollar one just for troubleshooting) and it runs A1. I had a $40 Irridium plug that had just a few hours on it, but perhaps the last failing stator killed it with irregular output?
I also took the head off, checked my timing again (was ok) and added a new rubber oring nearest the cylinder (the oring with small outer rings around each bolt). I torqued it a bit more than last time. No more water in exhaust now. We've been out several short rides, running A1, lift up the front tire in 4th for him.
Your suggestions were bang on, and I will remeber for future troubleshooting. I am curious to see how long this 3 dollar plug lasts as well. Best part is getting my 14 yr old computer gaming addicted boy in the garage tearing the motor down to troubleshoot - that's the stuff he will remeber down the road!
Thanks again,
Bill
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high priced performance
good to hear bike is sorted. good to hear your boy is involved in the workings of the bike. good on you sir. good for the boy. save your money on exotic spark plugs. unless your motor is tuned like a violin it is not needed. most riders can foul a cheap spark plug as quickly as a precious metal high priced one. kids are notorious for fouling plugs on properly tuned and jetted motors, so no need to risk any dirt bike budget dollars unless they are really needed. your bike will run fine with standard plug and your high priced plug will not add any power or performance worth the expense. save your money and spend it on more fun stuff.....like premix for more dirt bike riding:grin2:
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2,562 Posts
Thanks!
Cool to learn that you solved the issues!! And that boy working on the bike, priceless! Memories for life! With the added bonus of him learning something, that is always handy!
And I fully agree with @augiedoggie re the plugs. The Iridium ones struggle to handle a motor that is a little worn and not finely tuned. We have been racing at a relatively high level in NZ (a few NZ Champs and more local ones) and I have never found any noticeable advantage from a Iridium plug. I am sure they do what we are told. But it has to be for someone who is riding at 100% and wants/needs to find one more %... And how many of them are there at a local MX track??
You might already know this but anyhow:
- The 85cc/105cc (same bike just a bigger bore and piston) needs their big end/conrod replaced at 80 hours use. You can squeeze some more out of them, but the costs to fix a blown one is always more than doing it before it blows...
- Top racers swap pistons at 12 hours. We have managed well by doing a new ring (we run one ring pistons for less drag) at 20 hours and the piston at 40 hours. If you use twin ring pistons you get more than that out of them, probably 30 and 60 hours?
- KTM's 85cc stators tend to die. You can wait until it happens, or get a spare one that you can easily swap at a race day. (If you never use it they sell well once you guys move up to 125cc) We moved to having 2 bikes, that solved any issues with a bike dying at a race meet 3 hours away first thing in the morning...
Apart from that... keep on top of things, if you notice something that is not right (sticking throttle, spongy brake, clutch issues etc.) sort them before they become bigger and more costly! Make the boy wash the bike and teach him how to oil the chain, check/swap gearbox oil (we do gearbox oil at 5 hours of use) wash and oil air filters and replace them safely w/o allowing dirt in to the carby!!
Feel free to come back to tell us how it all goes for you guys!
Source: https://www.ktmforums.com/threads/105sx-will-not-run-wet-plug-with-spark.129532/
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