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S65 carb woes
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<blockquote data-quote="Sams65" data-source="post: 189714" data-attributes="member: 12820"><p>Apologies for the lack of activity as of late - finally getting back at it.</p><p></p><p>While the head head was off, I did a fluid leak test by pouring gasoline into the combustion chamber. The valve seats started seeping almost immediately. (this was with the springs installed) Here's the weird part though: With the engine assembled, using an actual leak-down tester, it only registered about 1-2% leakage. (this was on a cold engine) These are with brand new parts (head and both valves) The head was NOS and had some surface rust on the seats which I cleaned up with WD40 and a scotchbrite pad. So not sure if some micro-pitting could have contributed to the leaking?</p><p></p><p>Not sure what to make of this - I have a local shop that can cut the valves/seats for a reasonable price so will likely take that route.</p><p></p><p>In the meantime, I'm looping back around to the carb... After test running the engine and removing the intake tract (from carb to head), multiple drops of raw fuel came dripping out. Contextually speaking, if compression was poor, or spark was weak/mistimed, I would assume the engine wouldn't be able to light <em>such</em> a fat mixture. We're talking a lot of raw gas making its way into the combustion chamber. (unless I <em>also</em> have an air leak <img src="/styles/default/xenforo/smilies/cautious.png" class="smilie" loading="lazy" alt=":cautious:" title="Cautious :cautious:" data-shortname=":cautious:" />)</p><p></p><p>And with liquid gas sitting in the intake, the logical place would be to look is up the path to the carburetor. No?</p><p></p><p>Speaking of carbs, another part I just realized that was never replaced was the slide. I've tried a couple of them, but both used. I would assume worn out slides usually lead more towards a lean condition, but I might order a new one just to rule it out.</p><p></p><p>To recap:</p><ul> <li data-xf-list-type="ul">Compression tested around 135psi (cold) / leakdown numbers OK<br /> </li> <li data-xf-list-type="ul">**With head removed / solvent test: valve seats <u>do</u> leak**<br /> </li> <li data-xf-list-type="ul">Spark timed correctly to F mark, advances at two lines (II) mark on flywheel</li> <li data-xf-list-type="ul">Points gap in spec</li> <li data-xf-list-type="ul">Carburetor: All parts *<u>except*</u> for throttle slide replaced</li> </ul><p>This is starting to get stupid. Thanks everyone for the continued suggestions & help. (and patience)</p></blockquote><p></p>
[QUOTE="Sams65, post: 189714, member: 12820"] Apologies for the lack of activity as of late - finally getting back at it. While the head head was off, I did a fluid leak test by pouring gasoline into the combustion chamber. The valve seats started seeping almost immediately. (this was with the springs installed) Here's the weird part though: With the engine assembled, using an actual leak-down tester, it only registered about 1-2% leakage. (this was on a cold engine) These are with brand new parts (head and both valves) The head was NOS and had some surface rust on the seats which I cleaned up with WD40 and a scotchbrite pad. So not sure if some micro-pitting could have contributed to the leaking? Not sure what to make of this - I have a local shop that can cut the valves/seats for a reasonable price so will likely take that route. In the meantime, I'm looping back around to the carb... After test running the engine and removing the intake tract (from carb to head), multiple drops of raw fuel came dripping out. Contextually speaking, if compression was poor, or spark was weak/mistimed, I would assume the engine wouldn't be able to light [I]such[/I] a fat mixture. We're talking a lot of raw gas making its way into the combustion chamber. (unless I [I]also[/I] have an air leak :cautious:) And with liquid gas sitting in the intake, the logical place would be to look is up the path to the carburetor. No? Speaking of carbs, another part I just realized that was never replaced was the slide. I've tried a couple of them, but both used. I would assume worn out slides usually lead more towards a lean condition, but I might order a new one just to rule it out. To recap: [LIST] [*]Compression tested around 135psi (cold) / leakdown numbers OK [*]**With head removed / solvent test: valve seats [U]do[/U] leak** [*]Spark timed correctly to F mark, advances at two lines (II) mark on flywheel [*]Points gap in spec [*]Carburetor: All parts *[U]except*[/U] for throttle slide replaced [/LIST] This is starting to get stupid. Thanks everyone for the continued suggestions & help. (and patience) [/QUOTE]
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