The LC4 is a strong RTW platform. Before you get into the middle of nowhere, I would carry a spare intake rocker roller tip and both water pump bearings and a water pump seal. If you ever find both intake valves become looser, the rocker arm roller is failing. If you suddenly find the coolant is going down a little bit each day and there is no leaks, your water pump seal is failing and the coolant is draining into the crankcase oil. Don't forget to unplug the brown wire at the CDI box under the right side cover if your getting low grade fuel. You don't want to detonate the motor to death, 1000 miles from the closest KTM dealer. A lifetime of adventure is just around the corner, enjoy the trip and good luck!!
Hey Paul, Stock jets for the low flow head(smaller intakes) are main 142.5 idle 45. Jeedle raised one notch. Fuel screw set using this procedure. Open for fastest idle, close until idle breaks down, go to center of that movement, close screw 1/4 turn. 48 mpg with premium gas, 17/42 gearing now(16/42 for Russia-Mongolia). Pulls from just off idle cleanly to redline, spins the tire in every gear. Likes life at 4000+rpm's. Open airbox, stockfilter, SXC Comp muffler with pre muff eliminator pipe. bill
went to start the bike today after its sitting for a few days, did the exact same thing, did not turn over, pulled in the decomp lever and let it spin a few trimes and then closed it...tried again and it fired right up, did this three times in a row and instant fire everytime with no throttle or choke...i guess its a learning curve for me and the bike... on the battery test no significant drop in volts and steady charging when running just waiting on Derek to get back to me so we can review jetting and float height for my set up, i'll reference Bills 142.5/45/1 notch as it is completely different set up than mine
Bill has the smaller valve engine where the carb came with a smaller mains from the factory... The stock jetting on the 640 hi flo was 152.5 / 45 / 3rd notch... This jetting is not far off with the stock set up... I added a better flowing exhaust with a quiet core [no airbox mod] and bumped up to 155 with good results at sea level... A lot of guys that also crack open the airbox will bump up to 157.5 or 160 if they run without the sparky/restricter... With your setup and considering the elevation you plan for I would start at a 155/45/3rd notch and make sure your float level is ballpark as per manual... The mains are an easy swap through the bowl plug without removing the carb... With the starting difficulties your describing, I would recommend that you replace the battery right off... Using the decomp lever to help roll the engine past compression is something that normally should only be needed on occasion and not every time... I have dealt with the same thing twice as my battery aged and lost it's backup push... As soon as the new battery went in the engine turned over with much more gusto and started with ease.. With your bike being near new I would assume that your auto decomp, starter motor and sprague clutch would all be in prime condition which leaves only a poor battery and jetting as causes to your starting difficulties...
With the starting difficulties your describing, I would recommend that you replace the battery right off... Using the decomp lever to help roll the engine past compression is something that normally should only be needed on occasion and not every time... I have dealt with the same thing twice as my battery aged and lost it's backup push... As soon as the new battery went in the engine turned over with much more gusto and started with ease.. With your bike being near new I would assume that your auto decomp, starter motor and sprague clutch would all be in prime condition which leaves only a poor battery and jetting as causes to your starting difficulties...[/QUOTE] You probably have already eliminated this cause but is your auto decomp working? Maybe the cam has worn down. Do you hear the audible "click" when you kick the bike over. Best answer is the battery as mentioned above.
You are correct Derek, I am a gas miser. Would you say a half turn too lean? bill Paul, I have the LOW FLOW engine so my jetting is meaningless for your machine. How to set the float height and adjust the fuel screw are something we can share, I have a crazy way to set the float height where I attatch a piece of old fuel line to the gas inlet spigot and blow while raising the float with my finger(carb body with float hanging), when the air leakage stops and the float is level/parallel with the carb frame, I call it good. Works for me. Works when I am far from hearth and home. bill
The procedure I recommend when gas analysis is not available is: Adjust fuel screw to 2-½ turns out from lightly seated. Start the engine, let it warm up and ride the bike around until it's hot. Using the idle speed screw, lower the idle speed below the factory spec. Adjust the fuel screw so that the strongest idle is achieved. You will notice there is a threshold where it becomes rich enough (enough turns out) to run strongest, beyond which no change is noticed. Adjust the idle mixture screw ~1/8-1/4 turn out from this threshold. Adjust the idle speed back to 1400-1500 rpm. If I was setting the bike up for economy or knew it would see much higher altitudes at times, I would not add the ~1/8-1/4 turn out from the threshold. I don't know how many turns away from your method either of these would end up. The procedure I recommend: Preset the tang on the float setting tool to the desired height. Set the tool's width just wider than the width of the floats. With the carburetor in your hand with the downstream side facing your palm and your forefinger holding the base of the cage tightly against the body, rotate the carb so that the float tang just just touches the needle's spring-loaded plunger. With your other hand, hold the float height tool onto the carb body, making sure it is square to the gasket surface front to back (side to side is taken care of since the tool straddles the floats) and so the tang lines up with the point on the float that is farthest away from the body. The tool's tang should just touch the float but not depress it. Flip the tool 180 degrees to check the other side of the float. If the other side is different, you can decide whether to use the high side, the low side, or an average to set to. The stock height is 14.7mm, but I found that 640LC4s tend to run richer toward the bottom of the rpm range at all openings, which is exacerbated by the larger main jet that is required when opening the airbox. I therefore recommend using 16.7mm when the airbox has been opened. A main jet one or two sizes larger should be installed to go along with this change. Regards, Derek
Your SXC will become a very trusty friend. I wish I could tag along on your adventure. Some spare parts that I would suggest for the very reliable LC4 is both water pump bearings and seal and a spare intake roller follower. If you find your coolant is slowly going away and you have no external leak, rebuild your water pump. If you find both intake valves are loose, your roller follower is failing and needs replaced. I think the LC4 is a perfect bike for RTW work, it should be a fun trip. Good luck.
Apologies if this has already been mentioned/dealt with but, have you considered swapping your regulator/rectifier for a mosfet type? I know RoninMoto's (post above) 690 stock has failed. That's the second one on his bike to go.
you know i have thought about it, on my XT it was a known failing point so i carried a spare, and it never failed, but after seeing Noah and his issues i am seriously considering your point i have been so slammed over the last few weeks i haven't even been able to get to the bike to finish the last few loose ends that i need to deal with, i'll add this to the list