This is driving me nuts. When my 1995 gtx (657 motor) goes to the lake,....it runs super for about half an hour or so (give or take...I don't use a stop watch),..but then it turns to crap...Either won't run at all....or runs crappy after that. It has gotten worse as time has went on.
When it runs good....it really does run awfully good. But how can it decide to puke on me after a half hour.
I was thinking maybe the gray fuel lines...(but I have always ran non ethanol fuel in it)..so I started to replace them,..but they looked new inside and acted new. So I did not change all of them. I pulled off the carbs..thinking maybe the fuel filters were crap from the previous owner. The fuel filters also were nearly perfect with very little junk in them. So, I just blew them out with compressed air and put them back.
I checked my compression. (This is just a basic compression tester I have had for at least 30 years...nothing to brag about.) The compression reads around 129 or 130 in each cylinder. It seems to me that my really old js550 is around 115 or so..but still runs. So I can't figure out where to go next. I know a new motor should have close to 160 psi compression,..and this is quite a bit lower. But..for some reason I had always thought 2 strokes had to get down to 100 or so before they need a rebuild. Maybe I'm wrong on that one. I haven't done a top end in quite a few years...but thanks to nephews wearing out dirt bikes....I have to help do a top end every now and then.
Does anybody have any ideas on this one????? My brother in-law has an HX (has a 720) and he tells me his also runs for about a half hour before it takes a dive.
One thing,...I do NOT have much of an idea on RV valves, how they work, etc.,... so.. can this type of thing happen due to Rotary valves being amiss?????
When it runs good....it really does run awfully good. But how can it decide to puke on me after a half hour.
I was thinking maybe the gray fuel lines...(but I have always ran non ethanol fuel in it)..so I started to replace them,..but they looked new inside and acted new. So I did not change all of them. I pulled off the carbs..thinking maybe the fuel filters were crap from the previous owner. The fuel filters also were nearly perfect with very little junk in them. So, I just blew them out with compressed air and put them back.
I checked my compression. (This is just a basic compression tester I have had for at least 30 years...nothing to brag about.) The compression reads around 129 or 130 in each cylinder. It seems to me that my really old js550 is around 115 or so..but still runs. So I can't figure out where to go next. I know a new motor should have close to 160 psi compression,..and this is quite a bit lower. But..for some reason I had always thought 2 strokes had to get down to 100 or so before they need a rebuild. Maybe I'm wrong on that one. I haven't done a top end in quite a few years...but thanks to nephews wearing out dirt bikes....I have to help do a top end every now and then.
Does anybody have any ideas on this one????? My brother in-law has an HX (has a 720) and he tells me his also runs for about a half hour before it takes a dive.
One thing,...I do NOT have much of an idea on RV valves, how they work, etc.,... so.. can this type of thing happen due to Rotary valves being amiss?????
