Eagler's Nest

Engines => 2 Cylinder => 1/2 vw => Topic started by: Jeff XL79 on February 15, 2025, 05:33:19 PM

Title: Timing mark check?
Post by: Jeff XL79 on February 15, 2025, 05:33:19 PM: Is there any way to check the crank to camshaft timing marks without splitting the case?

I've got an engine that will only run on one cylinder. I bought the airplane finished with a full case better half. The #1 cylinder will fire and run if the mikuni choke is left on. Cylinder #2 has poor suction on the carb inlet and it is drawing a pretty good suction on the exhaust as I hand prop it. It's like the timing marks are off quite a bit.

The previous owner said he could get it to run but claimed the oil pressure was high and it started leaking oil badly. I cleaned and polished the pressure regulator pistons and bores and got the oil pressure to stabilize at 30# when it was running on the one cylinder. That was one problem fixed but now I suspect he got the timing marks way out of whack and compensated by giving the 009 distributor a major misalignment just to get cylinder 1 to fire. I've got fuel and spark to #2 but like I said the timing seems way off.

So, is there any way around splitting the case? I don't mind doing it because I want it to absolutely be correct by the book but just wanted to make sure there wasn't a way to check.

Thank you eaglers.
Jeff
Title: Re: Timing mark check?
Post by: Kamcoman77 on February 15, 2025, 06:46:57 PM: Put the piston at TDC on the compression stroke and check the valve clearance. If it is around 0.004" to 0.008" the cam to crank is OK.
Title: Re: Timing mark check?
Post by: CHARLES DEBOER on February 15, 2025, 11:39:14 PM: Eight or nine years ago I had a bent valve lifter push rod that was due to bad heat treating or lack of heat treating. It would run on only one cylinder.
Title: Re: Timing mark check?
Post by: Jeff XL79 on February 16, 2025, 06:52:01 AM: I will check both suggestions. Thank you.

I was able to see the timing marks using a mirror and my cheap endoscope. The marks line up every two rotations. I'm baffled but there has to be a reason that's fairly simple.

Update: when #2 is at tdc the valve gap is 6 thousands. I'll check the mushrooms next.

Jeff
Title: Re: Timing mark check?
Post by: Kamcoman77 on February 16, 2025, 07:44:43 AM: Camshaft turns at half speed of crank. Cam gear twice as large as crank gear. Turn crank twice, camshaft turns once.
Title: Re: Timing mark check?
Post by: Dan_ on February 16, 2025, 12:40:03 PM: Maybe you could do an actual compression test on both cylinders... But they should feel the same doing the "armstrong" compression check propping it.