to the OP, yeah,
You can take shortcuts if you want.
But then, many hours later, having not found the problem, you're finally gonna do a compression test, at least on the isolated cylinder, and then if it jumps up and bites you on the nose, you might as well go inside and ask yur wife to kick yur azz. lol.
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Sure, for all we know, the low-speed circuit on one side, may not be working properly and on a dualplane this is gonna affect 2 cylinders on each side, but maybe one cylinder is getting enough to idle on, one is getting none, and the other two are sputtering along.
So I get it, a compression test is NOT gonna find that for you. But if you don't KNOW the compression is even, then will you ever think it's all just an emmulsion-tube issue?
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> I bet most guys are going down the ignition road....... and a few hundred dollars later, it still ain't running any better. Now What? Are you gonna do a compression test yet?
> This engine has 1800 miles on it. Should you be suspecting a Lobe gone bad? Most of us are gonna listen for the tell-tale rocker-gear rattle. But you know, those lifters have a working range of over .085, so it could take a lotta wear before it rattles........ but it will show up on the compression test right away.
> But no, most guys are moving on to carburation. They'll spend several hours on that, come up empty, and borrow another carb; or worse buy one. With no change. So now, you could be into it for lotsa-dollars, and you're still no closer to a solution. Is it time for a compression test yet?
Answer; Heck-NO! that shouldda been the first test.
If you already have a good screw-in tester, it costs you zero dollars.
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BTW
Even with a perfect compression test, with a brand new carb, and ignition system; there's still lotsa things it could be. But by far, the compression test is almost always the fastest and cheapest road to finding a solution, or formulating a game-plan..
>Even after you have a bad cylinder isolated, there are still like, SIX things it could be, not including mystery problems. I mean count them with me;
lobes gone, rocker gear, sticking valves, Ignition, carburetion, and exhaust. That's six.
And then you have mysteries, like water in the floatbowl, wrong float-level, rags in the intake, collapsed mufflers, crossed wires, inductive cross fires, cracked plug insulators, loose primary connections, a bad headgasket, Primary throttle closed too far, Secondary not closed all the way, or throttles not synced to eachother, vacuum leaks, floatbowl internal leakage, and the list goes on. That's like a whole bunchamore.
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Usually, compression problems are gonna be the most expensive to fix; so I start there. Then, if that's where the issue is, then I can give my customer an idea of what it's gonna cost to continue. Maybe the project is already too expensive for the customer, and he pays for just a C-test. But suppose his pockets are deeper, then I can run a few more tests, and broaden the picture. Maybe it gets better, but maybe it gets worse. Maybe I find out the compression problem started out as a detonation problem, and the engine needs to come apart, AND the timing fixed. What if, simultaneously, the carb was lean, and now it needs a valvejob? So then, very quickly the cost has gone from a few tests to a repair estimate of thousands of dollars.
Had I never started with a compression test, How am I gonna tell the customer later that I effed up? I can't afford to ef up like that, and my boss is not gonna be impressed with that bill either.
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Now, I have been a motorcycle tech for many decades, and I get that, that industry is a lil different than is automotive. And nearly every problem on a bike can be traced to a compression issue. So when a bike comes in with certain symptoms, Ima gonna do a compression test, or, you can take it down the road. I fix stuff. I don't put bandaids on gushing arteries.
Same when I do marine work. the last thing a guy wants is to be stuck out on the water ripping on the rope; lemmee fix it right or take it on down the road.
Same with chainsaws; some guys make a living with those.
Now: Pushmowers, that's a different world. I quit working on those many decades ago. We sent those to a retired old guy, who was pretty good at it, and his shoprate was a fraction of ours. Now, I'm the retired old guy in my community, and guess what ............ Hyup, I do a lotta compression tests, which usually ends up with me owning the junker, and them buying a new one. I got 23 pushmowers, three riders, a snowblower, a tiller, and a whole mess of chainsaws/and string trimmers.. I'm thinking of going into the rental business, lol.
