I have an old 28D7070123-01 11.5HP engine on an MTD riding mower. When I try starting it, the flywheel only turns part way then stops. I also hear a wheezing sound that sounds like pressure being released. I tried starting once with the sparkplug removed and the the flywheel rotated normally. I removed the cylinder head and rotated the flywheel by hand and it turns smoothly and the valves seem to work. From some internet research I think it might be the compression relief part, but I can't find one in the parts manual, and I'd really like to be sure before taking the whole engine apart. Does anyone have any advice for diagnosing it?
Is it compression relief or something else - 28D7070123-01 11.5HP
- Thread starter MowSlow
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Do you Know your battery is good?
With the head off, rotating the engine by hand look at the exhaust valve on the compression stroke, it should bump open a little, then close.and then open when the piston comes back up on the exhaust stroke.
With the head off, rotating the engine by hand look at the exhaust valve on the compression stroke, it should bump open a little, then close.and then open when the piston comes back up on the exhaust stroke.
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Mower King
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I know what you meant.....
A lot of the flat head engines didn't have camshaft based compression release mechanism. they used a cam lobe that held the valve open just a little longer than normal that operates like that all the time. I would check valve clearances and see if they are too wide or not. Most of the L head engine normally close the gaps from seat and valve face wear and will float the valves causing low compression not the issue that you are having.
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ILengine's right, looked at a picture of the Cam, disregard my previous post.
Can you recommend a link with good instructions on how to do that? Most of the stuff I find online is for overhead valves
Mower King
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If it's a Flathead, most flatheads, you take the valve cover / breather assy off, that is where the lifter meets the valve, there are no push rods. That is where the lash is measured and it is not manually adjustable like a OHV.
When I used to build Flathead racing engines for racing go-karts, I use to file the end of the valve to get the proper measurement but, I didn't care about the lash, I cared about when the valves opened and closed in relation to TDC, on a degree wheel!
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not your specific engine but a good guide on what to do what you'll need
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can you spin the top of the valve in the seat? place your thumb in the middle of them and try to spin them back and forth.