spurdy Posted August 22, 2009 Report Share Posted August 22, 2009 Ok guys, I have a buddy with a stock crank ported motor with 35mm PWKs. I am repeating what he told me cause I wasn't involved in the assembly or tuning process. He just put it back together and was in the process of jetting it. It was hard to start so he was pull starting it. He says it ran good and I think he had it rich with 162 mains, middle clip CEL needle and not sure on the pilot or air screw. Any way, in the process of pull starting it he had it lock up on him. He brought it over tonight and we pulled the motor and split the cases. One of the rods was bent and the cases were full of fuel. It seems he got lucky and the only thing bad is the crank. The bent rod got caught in the counter balance weights and got bound there. Seems no damage to the cases. My question is, could the float not being adjusted right cause enough fuel to flow into the cylinder and not drain out the exhaust fast enough and get trapped in the compression zone to cause this? Are there any other ways this could happen? I am sure it was fluid trapped in the cylinder that bent the rod. Thanks for the help. SP Quote Link to comment Share on other sites More sharing options...
T_Shee Posted August 22, 2009 Report Share Posted August 22, 2009 man the float would have to be doing more than leaking i would think. maybe the little rod fell out that holds the float needle on or something. that sucks for him Quote Link to comment Share on other sites More sharing options...
_Hex* Posted August 22, 2009 Report Share Posted August 22, 2009 yea what happened is that the float on the carb probably is stuck open and the overflows might not be working right so it flooded the cases and the extra pressure goes in the combustion chamber and forces the rod which in turn bends it. Quote Link to comment Share on other sites More sharing options...
spurdy Posted August 22, 2009 Author Report Share Posted August 22, 2009 man the float would have to be doing more than leaking i would think. maybe the little rod fell out that holds the float needle on or something. that sucks for him That's kinda what I thought. It would take a lot of fuel but pulling behind a vehicle would cause aspiration in the engine and that's exactly what the carb needs to flow fuel. Just didn't think it would be able to collect in the combustion chamber that rapidly unless there was so much in the crankcase that it was being forced up through the transfers. SP Quote Link to comment Share on other sites More sharing options...
AKheathen Posted August 22, 2009 Report Share Posted August 22, 2009 a little momentum, and it will shoot up into the chamber. that's how we clear the fuel out of snomachine motors. pull the plugs, and pullit over as fast as you can and it'll shoot a stream of fuel out of the sparkplug holes. if there isn't na overflow in the bowl like stock carbs and it just has the vent lines, all the ful will drain from the emultion tube /pilot strait into the crank. once full, not much speed and it'll pump the fuel up through the transfers and pack the chambers. didn't he check the plugs before pull starting? i bet they were completely drenched. Quote Link to comment Share on other sites More sharing options...
Building my First Posted August 22, 2009 Report Share Posted August 22, 2009 Same thing happened to joe20002 no too long ago. Only his was caused by a leaking float valve, carbs had no overflow, and the fuel was left on. Quote Link to comment Share on other sites More sharing options...
spurdy Posted August 23, 2009 Author Report Share Posted August 23, 2009 Same thing happened to joe20002 no too long ago. Only his was caused by a leaking float valve, carbs had no overflow, and the fuel was left on. But these are Keihin PWKs and they do have overflows. That's what I don't get. At least I think they have overflows. I haven't look at them yet but my PWKs have overflows. SP Quote Link to comment Share on other sites More sharing options...
AKheathen Posted August 23, 2009 Report Share Posted August 23, 2009 for it to be an overflow, it'd have to drain from below the carb bore. otherwise, it's just a vent, or bowl pressure port, when used with altitude comphensation. Quote Link to comment Share on other sites More sharing options...
spurdy Posted August 23, 2009 Author Report Share Posted August 23, 2009 for it to be an overflow, it'd have to drain from below the carb bore. otherwise, it's just a vent, or bowl pressure port, when used with altitude comphensation. Just took his carb bowl off and checked. There is a hose coming off the bottom of the carb that drains from a pipe inside the carb bowl that is below the carb bore. I also checked Keihin's website and this is called an overflow. He is just running a stock petcock. I am surprised that this could flow enough fuel to fill the case that quickly. Then again, I don't know how long he tried to pull start it either. SP Quote Link to comment Share on other sites More sharing options...
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