Hi all,
I am attempting a repair on my Makita lawnmower which has a B+S 675Exi engine. I believe that the flywheel key is the culprit for difficult starting/rough running and therefore have taken it apart to access it.
I have bought the special (and very expensive) tool that supposedly both acts as the flywheel puller, and holds it in place to remove the bolt. I have tried the strap wrench method and as you can see this has just caused the fins to shear off as I tightened around them. I have therefore bought a replacement secondhand flywheel off Ebay. This repair is not going well...
Now that I thought I had the right tools, I cannot for the life of me work out how the tool works to hold the flywheel securely in place whilst I remove the nut. The bolts just drop down loosely into the two holes. They don't actually secure into anything underneath. The instructions say hold the bolt in place with a wrench, but I'm just holding onto a loose bolt!
Is anyone able to tell me what I'm missing, or best way of holding the flywheel in place? My other issue appears to be that my blade rotates around the spindle freely so I can't jam it from underneath. Was going to try and fix that after I've sorted this problem.
Thanks
just curious to ask: what made you think the keyway/woodruff was the problem with timing?
while it can happen, it's actually quite rare to see a keyway fail and slip.
there are a few things you can do to diagnose a slipped or sloppy keyway.
lock the flywheel down (anchor the blades so they never move)...the try and move the flywheel...if it slips back and forth...yup...that's your problem...
but sometimes a flywheel keyway is smashed and the doesn't actually move...it's just OFF in timing.
so then to do a better way to diagnose is to perform a timing light test. There are some youtube videos that explain how this is done. What you need to know before doing a timing light test, is where the ignition timing phase begins on your particular machine...paint or mark on the flywheel where that specific spot should happen. Like for instance on my kawasaki v twin (FR 691V, a very common mower engine), the magnet on the flywheel will be just right before it lands on the leading arm of the coil. One can prove this by moving the flywheel to top dead center for that cylinder..and to the other if you have a twin cylinder.. It's an easy concept and process to determine where ignition timing should occur. But you will need to consult with the specs on your specific engine to find out where that ignition timing mark SHOULD BE> if the woodruff key has smashed or slammed the timing will be off...so you have to know where the timing SHOULD BE PER SPEC. Then make that painted mark and go about shooting a timing light to it off the coil high tension wire. IF the timing mark is not correct, then yes, the flywheel is probably off. Some other symptoms when shooting a timing light is that the mark seems to vary back and forth...this would also indicate the keyway has smashed or slammed and that under load the flywheel is shifting back and forth under load. (this is particularly a thing with multi cylinder engines...where ignition pressure in one cylinder will overcome another weaker 4 stroke cycle in the other cylinder and this creates torque on a weak or damaged keyway..thus the flywheel moves...and the timing marks also moves with the timing light test.
a timing light is a very useful tool...especially in these small engines where timing is fixed and not variable, versus something more complex like variable timing or electronic timing/ignition. The vast major or mower engines are fixed timing systems....So this makes timing light test very easy to accomplish. Kind of like using a compression test set and a leak down test set, you can really get a pretty good idea about the condition of the engine overall by shooting a timing light. Brand new, most engines will shoot a really consistent steady mark on both cylinders...and it that timing mark should be exactly where the specifications indicate OEM in the area where the magnet approaches and meets the leading arm of the coil.
so a timing light might be a better idea to diagnose if you really have a flywheel keyway problem. It would save alot of time and frustration versus pulling the flywheel. It's just not that common a problem.
which raises the next question: since you know it's not the keyway...what is the root cause of the poor performance ? Have you determined what the problem is? just curious