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Discussion Starter #1
First motocross bike in 16 years, does this ktm 125 sx sound ok, thought the engine seemed abit to noisy. any helps appreciated

 

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Ktm's have got noisy clutches, that might be what you can here. I doubt anyone will be able to diagnose much accurately from that video. I'd take the flywheel cover off and give the crank a wiggle and maybe even take the head and barrel off for a look at the crank and top end if you don't know it's history. It's better than waiting for it to detonate.
 

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Agree with Nick, difficult going by that. They are noisy engines when new. I see it is a 2016 on bike, the power valve is much noisier than the old system on the pre 16s. Do you know its service history, bearing in mind a lot of sellers fib about piston changes? How does it perform?
 

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Discussion Starter #4
i dont know its full history, its a 2017, said to be never raced and a new piston 8 hours ago. had cr 80, 125, 250, 500 and a few others back in the day, its been a while granted, quite impressed with these 125s

edit: id say it performs well, suspension needs setup, and sometimes alittle boggy when pulling away, apart from that, quick
 

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I dont hear any intimidating noises, but as the guys said its difficult to judge. My 300 sounded much worse and it still runs fine. The wafer thin engine covers may be a reason too why the newer bikes sound very loud...
 

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Sounds just like my mates 16 TX, they all seam a lot noises than the old Jap stuff, mine scares me at times, but I never find anything wrong, starter excepted.


Sent from my iPhone using Tapatalk Pro
 

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Does it go when you pull the clutch in/out? The 300’s sound like a cement mixer until you pull the clutch in... or put it on the pipe. :D

How does the modern 125 feel compared to the older 2T you had?
 

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Mind you'll have to check the jetting as the ambient temperature becomes cooler. When hot and jetted correctly these bikes rip right off the bottom. You'll have a Mikuni, which aren't as good performance wise (compared to the Keihin) - your handbook will give you base figures for your jetting. The AER forks are pretty good as is the shock as long as you have the correct spring for your weight. Did you get a fork pump with the bike? They often come up on ebay as you get a freebie one with the 2019 bikes. Our only problem with the 16 on 125s was the magnet liner in the stators (new part for 16 on)breaking up on both bikes. Over £350 for 2 new ones which hurt. Symptoms were the bikes just wouldn't pull. Other issue is the silly bar clamp system - if you bend it on track, even with a minor off, that's your day done. We don't use that system. Keep the rear linkage needle bearings greased, they can seize quite quickly and pull the swing arm bolt a few times a year to grease it up. We do our pistons every 15 hours. Cracking good bikes which are pretty bullet proof. Try and change that crappy gear lever for an oem. The splines are very soft and as it becomes loose on the taper shaft the temptation is too keep tightening it until you break the bolt which is then a nuisance to remove. Enjoy it, they are good fun. Bob
 

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Oh, meant to say you could maybe check your reeds sometime. They don't last long on some 125/150s and become chipped at the corners and don't fully close. Def a bad move by KTM. We use VForce4Rs because of this.
 

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Discussion Starter #12
:rotflmao:

had someone listen to it, no expert, seems to know abit. he thought maybe main bairings? what are you guys paying for rebuilds.
 

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Hmm. However, since you don't know its history, it could well be over 2 years old (KTM bring out their next year bikes in the July of the preceding year) with lots of hours on it.
 

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Discussion Starter #14
Done another 3 hours , not blown up yet, time to have a look over and service.

removed the side casing to check for play , no in and out play , side to side, or up and down.( was unsure what way to check , so checked all )

Does both sides need to be checked ?

It has the Keihin carb fitted, in the process of striping it to clean up , going to check reeds.

Picture added of side I checked.
 

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You're looking for lateral movement on the crankshaft and yes you need to check both sides otherwise how will you know? It's easy to miss if you're not exactly sure what you're looking for. I was chasing a noise on my old 200 a few years back, checked the mains and they seemed ok... I was wrong, both sides were fucked, but I managed to miss it first time that I checked. Small particles come away from the bearing before it lets go completely and can make a mess of the piston, barrel, big and little end, meanwhile the bike keeps running, but with a strange noise.
 

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Discussion Starter #18
Ok mate , will try again. I noticed some sand has got in on the clutch side , through the bottom of the case/gasket. I wonder if that’s related. I’ll give it another check, then I might try find someone local for another opinion
 

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Discussion Starter #19
does anyone know the torque settings for the 17mm nut on the stator cover ( one in picture ) it was suggested that the stator maybe scrapping, causing the noise. buzzed the 17mm off but i dont have a puller that will fit. dont want to just buzz the nut back on lol

think its time to get the opinion of an expert
 

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60nm, but you need a tool to hold the rotor. We use one of these old clutch basket holders, like mole grips, which have 2 pins on the ends of the arms which fit into the rotor (same idea as the 2 pin tool you get with an angle grinder to tighten the blade holder). Why not invest 12 quid on a rotor puller? You can then easily pull the rotor. I covered in another thread that we had rotor issues on both 2016 125s. The really thin metal sleeve which covers the magnets in the rotor had broken up into loads of small pieces in one of the bikes while the other was loose and rattling about. These sleeves mesh with the rivets you can see and are held in place with glue. When it comes loose, there is enough space between the rotor and crankcase for the liner to move away from its meshing point towards the crankcase where it rubs away then breaks up. I tried gluing the complete one again but it immediately let go as soon as we started the bike. These rotors were new for 2016 and obviously had some quality issues. Worth a look, it's an easy job to do yourself. The crank has a woodruff key so the rotor can only go back on one way so you can't mix up the crankshaft positioning sensor. If I could post photos you would see what I mean as I still have the parts but I can't. Bob
 
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