- Wed Sep 26, 2012 3:42 pm
#1218
Here is a tip regarding kick starting. We all know how to position the piston just passed TDC aided by using the decompressor. I don't usually have any trouble with the 500 Bullet, however, after rebuilding a high compression short stroke engine recently, I was still getting severe kickback using this method even though the timing was spot on. It occurred so often that I was starting to get too scared to attempt starting the bike as the massive violent kickbacks were starting to damage my knee joint. After some thinking and testing, I discovered that if I continued the full kickstart swing just passed TDC (my normal start position) and then continued slowly down right through the full range to the bottom, there was not another position that the compression TDC position occurred again thus requiring quite a bit more flywheel rotation to get the piston there. You have to remember that from the TDC start position the engine has to spin fully two revolutions to get back to the firing position. In my case I believe what was happening is that as I kicked down, the flywheels spun up but then as my effort stopped at the full swing position, the flywheel still had over half a revolution to go before it could hit full compression and travel passed the firing position. Having an HC piston and superb compression, with the new bore and piston, the flywheels did not have enough inertia to fully meet the effort required on the compression stroke so it was caused to slow down again before the ignition point was reached. The insufficient momentum at this point could not cope with the fuel ignition and consequently the piston was driven back down 4 out of 5 times rather than continue over TDC much to the suffering of my leg and nerves. So, after easing the piston over TDC, I continued to push the kick start slowly down to a new stopping point and made a note of that position. Then releasing the decompressor, and fully returning the kickstart to the top, I slowly continued to move the kickstart down to its full extent. After several tests, I found a start position that would allow the 2nd TDC position to be felt just before the end of the kickstart travel. My thinking was that if I could accelerate the flywheels and piston continuously up to the firing point, the piston would have far less chance of kicking back due to insufficient piston speed and to my joy…it works. Not once did it kick back and most times I can get the engine to fire up first time. So, just to go over the method: Find TDC as per normal with the decompressor but take it further and note the final kickstart position. Return kickstart to the top…Then release the decompressor and check that the SECOND TDC position can be reached just before the end of the kickstart swing. Make a note of the post-TDC setting position and use it every time you kickstart....noting that the kick-starting is done from the top…not the initial setting position. Hope you can understand the method as it would seem likely to work well for other High compression bikes or engines with big bore kits especially the 612cc versions. It might also be useful with standard Bullet engines if you have slight problems with your kick starting strength. Give it a try; it might help if you are having lots of kickbacks (ignition correctly adjusted) certainly worked for me!
