This is on a 2002 Toro Dingo 425 with CH25s Kohler, ex-rental, rode hard and put away wet.
It starts, idles and runs fine @ no load ( maybe the occasional miss at full throttle). But when I put it under load it bucks and bawls with heavy misses. To me it sounds like true backfiring (through carb) as opposed to afterfire through exhaust. I can operate smoothly enough at 1/4 - 1/3 throttle but this is not good for a hydraulic drive.
The condition seems to improve slightly with warm-up, esp. in winter, but it's getting worse overall. I did all the fuel things: new fuel pump, new filter, cleaned carb. I didn't think it was fuel anyway because the condition happens immediately when opening the throttle, not like draining the bowl of fuel. Compression is 185, exactly the same both sides.
Can't be spark breakdown due to heat because it happens cold or hot. Choking the carb just makes things worse. The plugs look normal. No smoking or excessive soot in exhaust pipe. Carb governor linkage operates freely. I'm not sure which particular ign. system this has (CDI of some sort?) but the flywheel key is in place and nothing is wobbly there.
At this point I am thinking valve issues. Not burnt but maybe loose seat or bad lifters. Any thoughts from you guys before I take the plunge? Any other checks I can do?
I love that Dingo and really need to bring her back to life.
It starts, idles and runs fine @ no load ( maybe the occasional miss at full throttle). But when I put it under load it bucks and bawls with heavy misses. To me it sounds like true backfiring (through carb) as opposed to afterfire through exhaust. I can operate smoothly enough at 1/4 - 1/3 throttle but this is not good for a hydraulic drive.
The condition seems to improve slightly with warm-up, esp. in winter, but it's getting worse overall. I did all the fuel things: new fuel pump, new filter, cleaned carb. I didn't think it was fuel anyway because the condition happens immediately when opening the throttle, not like draining the bowl of fuel. Compression is 185, exactly the same both sides.
Can't be spark breakdown due to heat because it happens cold or hot. Choking the carb just makes things worse. The plugs look normal. No smoking or excessive soot in exhaust pipe. Carb governor linkage operates freely. I'm not sure which particular ign. system this has (CDI of some sort?) but the flywheel key is in place and nothing is wobbly there.
At this point I am thinking valve issues. Not burnt but maybe loose seat or bad lifters. Any thoughts from you guys before I take the plunge? Any other checks I can do?
I love that Dingo and really need to bring her back to life.
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