briggs 17hp ohv platnium

I have this motor in a crafstmen rider that runs great if you can start it. It will crank over until it hits TDC comp and can't get past it. I adjusted the valves to spec per this site and even went tighter on the exhaust after it still wouldn't get over the hump. The decompression does tip the exhaust valve doesn't it? At what point in what stroke does the decompression come into play? Anyway when I had the valve cover off and the spark plug out I watched the rockers to see if they would move on the comp stroke all the way before tdc and way after tdc and they didn't move at all so is the mechanism shot. If so what a shame because it runs great if you can start it. The battery is new and good. It cranks fast with plug out. Is there a starter available with more torque to overcome the bad acr if thats the problem? When I did adjust the valves I went past tdc about a 1/4 per a older post. Help me understand whats going on. Thanks Fred

Depending on which it has, either the compression release mechamism is broken or your cam is worn to the point that the intake valve is closing way too early in the compression stroke.

I say 'depending' because Briggs used to just grind the profile of the intake cam to make the intake valve stay partly open for a good part of the compression stroke. But in the last few years they have added a mechanical lever/mechamism to the cam to do the valve open/compression release at cranking speed. This moves out of the way when the engine reaches rated rpm, allowing the intake valve to close earlier which I bet helps emissions.

If your valves are in spec., you have good battery cables-they are marginal on some mowers when new and loose their ability to carry current with age- and a good ground connection for the neg. battery cable, You probably need a new cam. If the compression release parts are missing or broken, the only way to get them is to buy a new camshaft.

I am guessing you have the heavy duty starter on there already. Approx. 4" long, top to bottom. Back in the day Briggs used some shorter starters that had less torque, but can be bolted up to that engine.

So you are saying that the intake valve is the one that releases the compression? I always thought the exhaust valve did like on my XR honda dirt bikes. I concentrated on the exhaust valve when I was watching it and didn't see it push on the valve through the compression stroke. If the acr is shot which I suspect do you think by adding another head gasket would work to lower the compression enough so the starter could handle it. It only has a 42" mower on it and I use it to cut aroung trees and such and mow the majority with my Internation 184. Thanks for your response. Fred

This may be too obvious, but are you sure your CCA are up to snuff? I've had the same issue on a Kohler since I went cheap on the new battery. If I let off the key and give her another try she will go. It is getting over the initial hump. I redid the valves on my Briggs flathead twin and I am sure it wouldn't start either but I have a 700 CCA Interstate in that so it goes.

After reading your replies I went out this morning and watched the rocker arm for the intake and could see it move ever so slightly. measuring the clearance as I rotated the flywheel all the way through the compression stroke I noticed that the gap got a little bigger just before the exhaust valve opened. So I tightened it up to .003 and it turned over and over and put everything back together and she fired right up. Just finished mowing with it and it worked great. Thanks for the replies, info and patience....Fred

It depends on the manufacturer I guess. On the single cylinder K series Kohlers their compression release is on the exhaust valve.

It is possible you can find compression release on the exhaust on some Briggs engines too. They have some of them (Vanguard-the better line) made by Daihatsu in the far east.

Some of that may be the nature of that engine. I had same engine in jd saber mower for years and it cranked hard from day one (bought it new). I put a heavier battery in it and found on cold start little or no throttle would let it crank and once spinning pop it into to choke position to fire. Warm start just past idle with throttle. The way mine acted (always started if you knew procedure) the intake valve relief adjustment makes perfect since. Like yours mine ran great once started so I never tinkered with the valve adjustments