FH72IV 25 hp Kawi valve adj.

[hayboy]

After allot of reading, I still don't see the difference between adj the valves @tdc on compression stroke or some saying let piston go about 1/4 past tdc. Which of the valves is on top? Intake or exhaust? My engine which has almost 500 hrs has been getting a little hard to turn and a lot of people say its valve clearance. Before I do anything they check around 10/13 thou each. Would this much clearance cause hard turning. Thanks for looking and helping an old guy just trying to do a little maint on his JD445 that he loves so much.

 

[Rivets]

I have always taught my students to set their valves 1/4" past TDC on the compression stroke. This makes sure that the compression release mechanism is no longer in play and you don't have to worry about an improper setting. For your engine, both the intake and exhaust clearance should be between .004-.006 of an inch. This manual might help you out.

http://www.mymowerparts.com/pdf/Kaw...SAKI-SERVICE-REPAIR-MANUAL--99924-2078-01.pdf

 

[7394]

Agree with Rivets, & to your loose clearance, that should not make it hard starting, it will make the timing a lil late, but also make the rockers clatter.

 

[hayboy]

Thanks When I crank on it today I will probably be listening for a dragging starter, bad news. A OEM starter will be close to 200$ with tax or shipping. He's closed now, but we had a great starter shop in Columbus, MS. Reasonable rate and great service, but had a stroke and shut him down.

 

[7394]

Bummer about your starter shop guy. Have you shopped around for better price ? Internet search ?

 

[hayboy]

May have lucked out. Valves adjusted, bat post cleaned, new set of plugs, cranked a good bit better, something I can live with if it don't get any worse. Some one needs to open a repair shop in our area, my friend was covered up and I would believe he made good at it. Almost everyone, except the city dwellers, has at least one tractor and piles of older autos hanging on. We are fast approaching the age of if it breaks, go buy new, and it cost. Thanks

 

[cpurvis]

Camshaft lobes consist of what we call a base circle, acceleration ramps, and the raised portion, commonly referred to as the 'lobe' although it's just a portion of the entire lobe.

Valve clearance needs to be set with cam in a position so where the maximum clearances exists between the valve stem itself (flathead) or lifter (overhead valve), which will be when the lifter would be riding on the base circle of the camshaft lobe. Ideally, you'd like to set clearance when the peak of the lobe is 180 degrees from the lifter. Piston TDC is not that place.

Fortunately, there's an easy way to determine the right place.

If you look at an end view of a camshaft, you'll see the intake and exhaust lobes are separated by approximately 90 degrees. A picture would truly be worth a thousand words here, but if can visualize this, you'll see that when the exhaust valve just starts to open, the lifter for the intake valve is approximately directly across from the peak of the lobe, the perfect place to set its clearance.

You'll also see that when the intake valve has just finished closing, the same thing is true for the exhaust valve.

Neither of these occur when the piston is at TDC. At TDC, both valves are about 45 degrees of cam rotation from their ideal position. Does it make a lot of difference? Probably not, but .001" on a .006" clearance is a 16 percent error...so why not do it right?

Summarizing:

Rotate crankshaft in normal direction until the intake valve has just finished closing. At that point, set the exhaust valve clearance.

Continue rotating crankshaft in normal direction of travel until exhaust valve has just started to open. Set the intake valve clearance.

 

[Carscw]

Camshaft lobes consist of what we call a base circle, acceleration ramps, and the raised portion, commonly referred to as the 'lobe' although it's just a portion of the entire lobe. Valve clearance needs to be set with cam in a position so where the maximum clearances exists between the valve stem itself (flathead) or lifter (overhead valve), which will be when the lifter would be riding on the base circle of the camshaft lobe. Ideally, you'd like to set clearance when the peak of the lobe is 180 degrees from the lifter. Piston TDC is not that place. Fortunately, there's an easy way to determine the right place. If you look at an end view of a camshaft, you'll see the intake and exhaust lobes are separated by approximately 90 degrees. A picture would truly be worth a thousand words here, but if can visualize this, you'll see that when the exhaust valve just starts to open, the lifter for the intake valve is approximately directly across from the peak of the lobe, the perfect place to set its clearance. You'll also see that when the intake valve has just finished closing, the same thing is true for the exhaust valve. Neither of these occur when the piston is at TDC. At TDC, both valves are about 45 degrees of cam rotation from their ideal position. Does it make a lot of difference? Probably not, but .001" on a .006" clearance is a 16 percent error...so why not do it right? Summarizing: Rotate crankshaft in normal direction until the intake valve has just finished closing. At that point, set the exhaust valve clearance. Continue rotating crankshaft in normal direction of travel until exhaust valve has just started to open. Set the intake valve clearance.

This is how I have always set my valves.
Only it is best to turn the engine counterclockwise. As to bypass the compression release valve.

 

[bertsmobile1]

Ditto , ditto and double ditto.

Setting both clearences at the same time is just plain lazy and very very easy to get wrong.
Setting one at a time always works.
valves clattering make alot of noise and many engines designed to be used indoors have long opening and closing ramps to reduce this clatter.

Early cams had the compression release on the exhaust.
The EPA nazis made the companies move it to the inlet.
so doing one vlave when the opposite one is open is the only way to make sure if you do not know what the cam profile is.

 

[Rivets]

You do it your way and I'll do it mine. Either way will get the job done right if you know what you are doing. When you are teaching how to do it, you follow manufacturers instruction and then can adapt to personal wishes. Nothing lazy about it and I don't know how you can get it wrong, unless you go to fast, or don't know how to feel a feeler gauge.