20 Most Recent 2002 KTM LC4 625 Sc - Page 4 Questions & Answers

if it is running and not making any noises then I would only consider the piston, rings and liner as a last resort If it has valves , (4 stroke) , check the valve clearance and adjust to specifications as valve stems get longer when hot and if the clearance is not sufficient when cold then a valve will be held slightly open when hot next check the coil and ignition module and the timing

check for a bare wire touching metal .

and neither you should have to as it is a 2015 make , why have you not taken it back for a warranty fix next you would be using a single point plug ( car plug) when it would be better to use a mulit point plug ( anti fouling plug) that is available from good spares shops , motor bike shops and marine shops You mention that it fouls after sitting over night can you comment of the fouling condition( wet , black, oil ,carbon build up etc ) as the information all points to a problem area.

You need 3 thing to make an engine run.spark at the right time ,fuel /air ratio to be correct,and compression.Isuspect you have tight intake valves.The valves are to tight letting compression out.To adj valves take your plug out put motor on tdc compression stroke .intake should be .006 exhaust .008.If this checks out to be ok you may have a fly wheel key that sheared and your ignition timing is off.

Its not to bad .You will need to purchase a shift shaft a shift shaft seal and a primary cover gasket and oil.First drain your oil.Remove your kick starter .Remove your primary cover.Remove entire clutch assembly.You will need air gun or a clutch holding tool to remove the clutch.Once you have the clutch assembly removed yuo can remove the shift shaft .Pay attention to the postion of the shift shaft in relation to the shift drum .Also pay attention to any shims on the shift shaft as that will need to be installed on the new one.Now remove the seal that the shaft was coming out of.Replace the seal install the new shift shaft.Make sure to center it in relation to the shift drum.clean every thing with brake cleaner.clean gasket area .Install the clutch assembly .If you have any trouble with the oriantation of the parts you can look at world of power sports for parts diagrams.Make sure you tighten the clutch hub to the proper torque spec.I would use blue loc tight on the nut as well .If you have a shop do it expect to pay about 2 hours labor max.Plus parts

Brand new ngk plugs are pre gapped but in thousanths .28 to .32 works

These bikes ran hot from brand new.Im guessing that the radiators are in good shape and the water pump is also?If so try running evans coolant.If your riding in a lot of slow speed enduro single track you may want to consider an electric fan available from your local ktm dealer.

Hi im guessing your year to be 1981 or 1982.First if you have not done so make sure your coil is grounded.Next disconnect your kill switch.Next check the primary side of the coil .3 to .5 ohms check the secondary side of the coil 5k to 7k ohms with out the spark plug cap.While your at it check for spark with out the cap.Make sure your kicking it fast as motoplats do not spark below 700 rpm.If all else fails you have a few choices .Vance smith can rebuild yours for under 200.00 usally.You can go with a pvl ignition for around 500.00.Also make sure your crank bearings are tight and your mag side crank seal is not leaking if you smell fuel in the mag cover you need to replace your crank seal good luck

run a compression check to see if it is low. If low squirt some oil in cylinder and rerun. If it stays low possible valve guide problem. If oil fixes compression then the rings are bad.

A backfire is unburnt fuel igniting. Check you have no air being drawn into the engine through a split in the carb rubbers or a loose carb rubber clamp. The easiest way is to let it idle/tick over and spray some carb cleaner around the rubbers. If the engine stutters or stalls then this is where the leak is. An unsealed collector box will cause this to happen as well so check that your exhaust system is correctly sealed and fitted.

replace the throttle spring and take the handle off and grease in there