RussN Posted September 23, 2022 Report Share Posted September 23, 2022 Suspect some other problem preventing the engine from starting. The cylinders have compression. Fuel, Air, spark. The three essentials. RussN Quote Link to comment Share on other sites More sharing options...
PazyrykTheGreat Posted September 23, 2022 Author Report Share Posted September 23, 2022 Maybe you're right. I realized that the exhaust port on the right cylinder wasn't puffing out any fuel so I decided to take a look at the carburetor and... blehhh. I gave it a good scrub in the sink to get the gunk out. Quote Link to comment Share on other sites More sharing options...
PazyrykTheGreat Posted September 23, 2022 Author Report Share Posted September 23, 2022 Well she still won't start. I got fuel puffing out of both exhaust ports, spark to both, but I'm still getting really low compression at 75psi on the left and 60 on the right and there are no leaks from the head gaskets. Since the compression pressure jumps when there is oil in the chamber I really think we've exhausted all other possibilities and that it's the piston rings not doing what they are supposed to be doing. So do I need to get new rings or is there something else that I am missing? Quote Link to comment Share on other sites More sharing options...
RussN Posted September 24, 2022 Report Share Posted September 24, 2022 With carb interiors like that, you can bet the gas jets are also plugged and require opening. Also make sure the fuel tank, shut-off valve and associated filter screen are totally clean and clear. And in the correct RUN position. (How do I know that one?...) And I've had visible spark, but a bad coil reducing the spark below ignition level. Replacing the coil brought the engine back to life. On three different Urals since I began riding them in 1998! Food(s) for thought. RussN Quote Link to comment Share on other sites More sharing options...
PazyrykTheGreat Posted September 24, 2022 Author Report Share Posted September 24, 2022 I replaced the coil earlier this spring and the fuel flow looks good and the carb jets are clear. Here's a look at the ring gap. I don't have any gages but I compare it to a ruler and it looks to be about a millimeter which from my understanding is supposed to be 0.25-.05mm. Quote Link to comment Share on other sites More sharing options...
racepres Posted September 27, 2022 Report Share Posted September 27, 2022 for the cost of rings... Ball Hone a new crosshatch and put 10 over rings in...gapped carefully.. the carb looks awefull.. might even need replacement try a Harley coil (they are everywhere) even just to check spark Color (blue) Quote Link to comment Share on other sites More sharing options...
PazyrykTheGreat Posted September 27, 2022 Author Report Share Posted September 27, 2022 I have a Harley style coil on it and the spark looks good. I want to make sure I order the right rings since there appears to be two different types of pistons. Mine is the kind that doesn't have the second set of scrapers around the skirt of the piston and has two different thickness for the compression rings- 1.5 and 2mm. Also what diameter should I get? 78, 78.2 78.5 or 79mm? Quote Link to comment Share on other sites More sharing options...
racepres Posted September 28, 2022 Report Share Posted September 28, 2022 Oddly... I see the scrapers and the expansion ring in that Photo??? I believe I can make out two Thin compression rings...Maybe.. Quote Link to comment Share on other sites More sharing options...
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