Help with Valve Adjustment on PT425

[SRB331]

Happy Holidays Everyone!
I'm looking for some guidance on how to rotate the crankshaft to tdc so I can adjust the valves. The manual tells me where to align the marks but on the 425 it seems you would have to lift the engine out to access the fly wheel. Any assistance is appreciated. Thanks in advance.

 

[MossRoad]

What engine do you have?

 

[SRB331]

It's a Robin EH72 with carb.

 

[MinnesotaEric]

Giant strap wrench on the harmonic balancer.

If you have an access plate, you can pop it off and rotate the engine with a flywheel turning tool as well. A shade tree could use a pry bar as well.

My flywheel turning tool says Mac Tools on it, meaning I overpaid for it by about a million dollars, but they all look and work the same.

Amazon.com: Powerbuilt 648455 Flywheel Turning Tool: Home Improvement

Amazon.com: OTC 7206 Multi-Purpose Strap Wrench: Home Improvement

 

[MossRoad]

I'd try pulling the spark plugs, then bump the starter.

 

[SRB331]

Thanks guys. I have no access point on the engine, not to mention the tub makes it pretty hard to get any kind of jacking tool in place. I'm going to go with bumping the starter. One of the members pointed out that if one valve is in the down position (open) the other will be clear of the cam and can then be adjusted. I'll just work my way through the valves.

Thanks for your help everyone!

 

[marrt]

See page 38 of the service manual on the Robin Subaru site. You have to line up the flywheel with a mark on the cylinder. This needs to be done accurately or you're wasting your time (and likely creating a worse problem). I don't look forward to this procedure and will probably pull the engine in order to conveniently access everything.

 

[MossRoad]

You can also use a drinking straw in the spark plug hole and rotate the crankshaft back and forth until you can tell where top dead center is. Just do that by hand, not with the starter.

I guess the issues with this setup is how to spin the crankshaft, since its hard to get to. Can't you see any part of the crankshaft, pump couplings, etc... that you can grab with a wrench and turn?

 

[Gravy]

I've done literally thousands of valve adjustments on a wide variety of engines, and about six on my EH72 before the engine swap. None of the conventional advice and methods apply to the EH72 in a PT. There is no practical way to turn it over by hand or to see any timing marks without removing the engine.

Fortunately, and contrary to popular opinion, you don't actually need to be very precise about being at TDC. The camshaft profile is extremely forgiving. The base circle is evidently close to 180 degrees of camshaft rotation. Just get the piston fairly close to the top of it's travel and it'll be OK.

Pull the plugs, use soda straws to determine approximate TDC, and bump it over with the starter. It will take patience because the starter doesn't like to bump in small increments, but keep at it. If you have to turn the adjustment screw more than a tiny bit to get clearance, you're probably not on the firing stroke. Bump some more and try again.

 

[SwampmanLA]

I know this is all wrong but it worked for me. I just bumped the starter till the valves were seated, slack in the lifters, and tightened the arm down till it was about to touch the valve. Worked great for me and my Robin is singing.