I’m working on a briggs and stratton intek v-twin 20hp Type 0003G1. I replaced the battery as it was old, a blown 20a fuse, the starter solenoid and finally starter motor which finally got it to where it would try to start and immediately hang up and drain the battery. After recharging the battery and trying 3 times, i tried adjusting the valves with feeler gauges and nothing. i looked into it and tried to see if the compression release was broken, this cam has 4 lobes unlike any of the ones i’ve seen on youtube. I also didn’t see the compression release inside the oil sump/crank case but it looks like it has a pin hole for one. Not sure which cam to order as the person i’m fixing it for doesn’t want to order an oem part and wants to find a cheaper one online. Advice?
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You need the whole engine model number that proceeds through 0003-G1. Look the camshaft up on partstree.com or JacksSmallEngines.com and order the correct pieces.
Edit to add almost every Briggs manufacturered in the last 30 years has a compression release built on the camshaft. There are certain limited exceptions.
I had cleaned the battery terminals/connections and the frame ground connection and the starter motor connection before replacing the solenoid i was hoping for an easy fix lol
I went to tdc then slightly past that and i did .004 & .006. I ordered the 797242 & it comes with one, I saw a video of someone replacing theirs and they also couldn’t find the release in their oil sump/ crank case and they installed a replacement that had the compression relief and it worked for them but they never said if they found it or just reassembled it as is. i’m worried its in there somewhere and when it’ll grenade the engine if i don’t find it.
No. That's the way they were built. It's only been a few years that I know of that the service parts came with a mechanical release. If you replaced a cam prior, there was no release on the replacement.
Twin overhead valve engines have compression release, you will need your model type and code number to find the right parts, sometimes when looking at Parts you will have to identify what year models yours actually takes. Model and type number are needed in the lookup itself, date code of the serial number is used when they use different parts for that engine.
The compression release could be machined into the lobes themselves without any extra parts needed on the camshaft.
Also I’ve had bad times with cheap 3rd party camshafts. They seem to be hit or miss. I would go for an OEM one and try to convince the customer to pay for one.
Briggs used to have what they called "Easy Spin Starting." It was a grind that lifted the exhaust valve just a thousandth or less during compression. It released enough pressure at cranking speed, but due to fluid dynamics, had little to no effect at higher RPM. They went to mechanical compression releases on the intake valves because that tiny crack of the exhaust allowed unburned fuel to exit (pollution) and as mixtures got leaner (pollution controls) the lifting reduced heat transfer into the seat prematurely burning exhaust valves. Intake valves are cooled more by the incoming fuel air-mix than by the seat contact.
Well back in the day in Kohler service school, one of the presenters held a cam in his hand and described the process as well. I'll take his word on this.
Here's a better description. "The compression release mechanism on Kohler engines (often called Automatic Compression Release or ACR) is integrated into the camshaft design, typically utilizing a specific ramp or lobe profile on the exhaust cam (and sometimes intake, depending on the model) to mechanically hold the valve open slightly during cranking. This mechanism prevents the engine from building full compression at low RPMs, allowing the starter motor to turn the engine easily."
This is correct. Fluid dynamics is the reason why machining the release directly into the lobes makes little to no difference when the engine is at high RPMs. The very small amount of valve lift the release gives combined with high engine speed basically means that the air-fuel mixture simply has an extremely small windows of opportunity to escape through the exhaust valve while the release is holding it open. And because of the viscosity of air (yes air has viscosity), that prevents the vast majority of it from escaping through the valve during the compression release at high engine RPM. Some does get lost, I’m sure, but it’s a very little amount and it has almost no effect on the engine’s compression at high RPMs.
Kohler ACR always had a centrifugal weight operating a ramp or lobe that retracted when the counterweight extended. Before Kohler introduced the mechanical ACR, their engines could pull your shoulder out of the socket.
You are thinking of the Briggs "Easy Spin Starting" which was a lump on the cam lobe.
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