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Discussion Starter #1
Hi guys

Having some minor rough running issues with my 660. Started with the auto decomp ticking last year on idle and after having replaced that i was hoping for the ticking to stop but it has not.

It is better than it was but still not 100%

Starting it up is perfect normally first kick and it fires up, but after turning the choke off it will make the headers glow after a couple of mins of idling....but riding is fine no glowing metal!

I have had a play with the carb which made it much better but still not perfect. I have a new pilot screw and idle jet on the way and I'm going to blast it with carb cleaner....not sure what else it would be? I suspect its running lean on idle and not knowing when the carb was overhauled last thats my first step.

Any help would be great.
 

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Hi mate,

I had exactly the same with my 660, basically what you described. Tried every carb setting under the sun, had it dynojetted to try and cure it and it seemed to run okay for a while.

About a week later it grenaded, completely shit itself, cost me 2 grand to fix it :eek:

Welcome to the forum :D
 

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Discussion Starter #3
Did you ever find the cause of the problem before it exploded? I cannot think what else could be the cause but bad a bad carb or timing is slightly out causing the cylinder to get hotter than normal?

The Cam was replaced by a KTM dealership but i can't say I'm happy with them. Over filled the engine oil, didn't loctite the bike back together so was missing bolts when i got back, striped out one of the sump threads that i have just repaired with helicoil to name a few things.
 

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Discussion Starter #4
Update

Blasted the carb with cleaner and compressor today, replaced the pilot screw and idle jet and its MUCH better! Still a little lean when i first start it but after a run it ticks over perfectly....no glowing headers and no auto decomp ticking.

Took it to a local specialist who seemed to know them very well and he said its the quietest 660 engine he's heard and i shouldn't be worrying about the motor but he did suggest the carb properly dismantled, cleaned and new needle installed etc as the manual says every 200 hours. Bike has done 6000 miles and in the past two years of me owning it has not been done so i would say its due.

So worried about the engine detonating with fewer and fewer 660's around I'm trying to keep mine alive! I have no intention on selling it!
 

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Update

Blasted the carb with cleaner and compressor today, replaced the pilot screw and idle jet and its MUCH better! Still a little lean when i first start it but after a run it ticks over perfectly....no glowing headers and no auto decomp ticking.

Took it to a local specialist who seemed to know them very well and he said its the quietest 660 engine he's heard and i shouldn't be worrying about the motor but he did suggest the carb properly dismantled, cleaned and new needle installed etc as the manual says every 200 hours. Bike has done 6000 miles and in the past two years of me owning it has not been done so i would say its due.

So worried about the engine detonating with fewer and fewer 660's around I'm trying to keep mine alive! I have no intention on selling it!
Mechanic said the same about mine, it's when they go quiet they go boom. The engines are naturally noisey and rattly. The conrod expands and the crank spreads which makes the engine go quieter, then boom, bits of case everywhere. Sort that fuelling out quick on a dyno and get that engine split and looked at
 

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wazza........stop it

nice bike fella

mine had done 24k, and i hadnt renewed the carb internals
 

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Discussion Starter #9
I'm trying to look at it for what it is...a single cylinder thumper. And as they go these LC4's are very good motors and generlly very reliable. I don't know what to do for the best. I asked him to have a listen to the motor for a second opinion because i thought it was actually a little rattly....but he said it sounded very normal to him and is guessing that the KTM "specialist" may have over tightened the valves and that wouldn't surprise me.

I do plan on splitting the engine down and doing a rebuild over the winter while its sat in the workshop....hopefully i can sort out this minor issue I'm having and get another summer out of it!
 

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Welcome to the mad house. Don't listen to wazza - they only blow up every now and again:)
I had a few issues with the carb on mine and eventually found my problem (after I replaced the whole carb).
They can run a bigger idle jet - think standard is 45 - I run a 50 and it's sweet (48 is available and would maybe split the difference). With the FCR carb there are loads of variables and maybe a dyno run would be best but at the same time the jets, needle and adjustments are quite easy to get to so you can buy a handful of jets and give it a try.
I wouldn't recommend changing everything at the same time - concentrate on one area. BTW ref mentioning the needle - only the idle jet will be working at tick over - not the main/needle.
stick in - when they are running good they are a great bike.
 

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Discussion Starter #11
Thanks for the help.

Its only recently its been running rough....when i had the cam replaced to solve the auto decomp i was expecting the annoying ticking to go away and even though its much better i know thats somethings not 100% but its trying to diagnose it!

Again the KTM dealer said that it would never run smooth on idle because its got the titanium akropovic system......simply told him thats a load of crap because it used to run sweet!

i replaced the idle jet with a 45 and thats what was in it originaly and it used to run sweet. Just strange how after a run it will sit and idle perfectly with no decomp ticking and no hot exhaust . Seems that once everything is hot it runs perfect.

Like i said eventually i will split the engine and overhaul it just so i know its 100% but its not needed just yet. Its only done just over 6000 miles.
 

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Ahh. When you boil it down a bit - I think the idle jet thing was maybe a bit of a quick knee jerk. you hear the word lean or weak and jump straight to the carb (and they are fiddly carbs).
Looking for a root cause though:
bike was running sweet
went to shop for new cam
shop replaced cam but generally did a shit job
bike got hot at tick over
better local mechanic suggested - quietest 660 he'd heard
you cleaned and replaced idle jet
still not great.

Given the above - maybe you should be looking at the valve clearances?
Quiet sometimes means tight clearances!
If the original shop didn't torque bolts, stripped threads, etc. Maybe they didn't do a good job of the valve clearances.
There's loads of threads (on other supermoto forums too) - on how to do it correctly. give it a search - one i like was a thread index on the LC4 (on SJ forum I think?). It's not a huge job and is quite quick/easy to do.

keep at it.
 

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Discussion Starter #13
It seems to be better after some minor adjustment. Once i have ridden it for 10 mins there no more clicking from the auto decomp.....

I have noticed that when giving it some power the clutch lever point changes....i think it may be the plate that prevents the main shaft bearing from slipping out is worn and causing the clutch to move in and out with the pressure and thats got me thinking maybe due to that having some play its having a interferance with the smooth running of the cam?

Only one way to check so will be doing that soon.
 
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