Been working all summer on restoring my '77 Gs750 and through all the work I've done it still seems the engine is responding sluggishly.
My #4 cylinder is intermittent, sometimes cutting out entirely and the plug is looking oil fouled. On the highway it'll feel like the engine's tugging at me occasionally and any more than about 1/2 throttle isn't accomplishing anything. To make matters worse it seems I can't go any higher than about 5500 rpms without aggrevating the problem.
And here's the weird thing:
About a month ago, I decided to take a 400km trip and before I left I swapped out the plugs for new ones (and gapped them). For the first 100km or so the bike was running like new: took off like a bandit and higher amounts of throttle were accompanied by the power you'd expect. The only issue was as it ran better, it started to leak oil... pretty badly.
By the end of the 800km round trip, I had gone through about a liter of oil, lost the power, and cylinder #4 was back to cutting out. Thankfully the oil hasn't leaked any more since then, but checking the plugs regularly shows that the new ones are looking exactly like the old ones did (#1 carbon fouled, 2, 3 fine, 4 oil-fouled).
This has gotten me thinking that my issue could be a compound of a couple of things:
1. I'm fairly certain the oil leak was simply old gaskets. Checking after I cleaned the engine, it appears the head gasket and one of the crank-case gaskets are the culprits. I don't think it's the cause of the power loss but when the engine was running well I think it might have gotten hotter than usual and caused extra leaking.
2. Valve clearances are off. I'm thinking that the reason #4 is mis-firing could be from low compression.
3. Worn points, bad ignition coils (both are original), and generally weak spark in general. I think the brand new, clean plugs were compensating for my weak ignition system and once they had worn in it went right back to how it was.
Anyways, can anybody confirm or deny my suspicions? Just don't want to start ordering parts or taking apart the engine until I'm warranted in doing so.
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