hi! My speedfight 2 (with sf 1 LC engine block) seems to be a bit out of sync looking at the tuning or something. I had a problem lately that it would start to splutter a bit and keep on smoking in a way it would normally only do when it was still cold and the auto choke would be engaged. I didnt really change anything on the tuning though so that made it a bit strange. The setup is pretty much stock, only put a couple washers between the vario and the restrictor plate to make it go a bit more nippy top end. Setup: 7.5gr weights, 56 jet, the rest is stock. I already replaced the spark cap, spark plug, HT lead, HT coil. That seemed to improve the spluttering slightly. As I have a digital dash from Koso, I can read the coolant temp fairly accurate and it seems it has trouble sometimes reaching over 66 deg. celsius. Might it have something to do with the fact that the outside temp has been around 0 - 4 deg? Last couple of days it has been a bit warmer @ 8 degrees and it seems to reach temps over 72 deg on the coolant but not every time, regardless of the outside temp being stable over the last days. The exhaust tip is a bit wet sometimes, when it does get over 70 deg, that moist evaporates. I have been playing around with different spark plugs, went from a 7 to a 6 which didnt really make a difference, tried to open up the air screw on the carb too from 1.5 even up to 2.5 but above that it would just “aaaaahw” on full throttle and still smoke. What also seems to make a difference, when at a traffic light, if I open straight full throttle, it will splutter, when I throttle it a couple of times quickly to full open and then take off, it almost doesnt splutter. Anyone a clue?
give your air filter a good clean or replace it, check for air leaks around filter and manifold, strip and clean the carb. It sounds like it could be one of 2 things, too much initial air/not enough fuel or vice versa
I just replaced the airfilter element for a similar new one and cleaned the carb about 3 months ago and it still ran fine after that. I’m suspecting 2 things: - as i bought it with a completely overhauled engineblock, i am suspecting that the person that overhauled it, left the thermostat out of the head, it won’t really get up to ideal operating temp (keeps around 65 deg.). It would get much warmer before I swapped the clutch, vario, belt and weights (went from 9gr to 7.5). Back then it was very sluggish and took ages to get up to ideal rpm. Since it now makes more rpm, it pumps around coolant a lot faster, which could make a missing thermostat become apparent. - The oilpump, could it be faulty? It definitely “works” as it seems to need an oil top up on normal regular basis but I remember that the O ring on its driveshaft can start to leak oil into the crank case. The spluttering when taking off seems to be more apparent when sitting idle at a traffic light slightly longer, it will splutter a bit and throw out a puff of blue-ish smoke. Then again, when the thing actually does get to up temps of around 75 deg, the smoking and spluttering is pretty much gone.
Now that you've mentioned the oil pump 'o' ring, it jogged my memory of my second Katana. That had a similar set-up with the oil pump geared off the crank and because that 'o' ring had gone it leaked oil into the crank case and smoked like hell until it more or less emptied itself, but that was after standing for a few days. The off shoot of that was that the plug was getting oily really quickly. It could well be that if your pump seal is shot but you are using the bike every day, then you are not getting the huge oil build up in the cases, but enough to put too much oil into the mix when it's running at lower rpm's. I know the Speedfights and Aerox's can be a bit thirsty with the oil, but that's not really a bad thing on a 2 stroke engine.
