High Compression Question
- Thread starter massacre
- Start date
Not the pawl.
It probably just isn't the raise in compression. Most likely someone also put in a cam and a flywheel with more advance.
A Big culprit is a cam without a compression release. If you are going to pull start it, make sure you have a compression release. Also make sure your valves are adjusted right. If you have too much lash clearance on the exhaust valve, the compression relief mechanism won't lift the valve enough on the compression stroke.
Advanced timing can cause it to pull the rope out of your hand too. Add advanced timing and more compression and yeah, the rope can get pulled from your hand.
One way to help you start it is too slowly rotate it so you are at TDC on the compression stroke, THEN pull hard and fast.
That gives you and the flywheel a little run at the next compression stroke.
I've had the rope ripped from my hands and thought it broke fingers or tore things in my hand before. No fun. That was a 5 hp Briggs with a cam without a compression release, (SS94 I believe). Anyway, I took it out and put a stock cam in it. No more issues.
Danford1
It probably just isn't the raise in compression. Most likely someone also put in a cam and a flywheel with more advance.
A Big culprit is a cam without a compression release. If you are going to pull start it, make sure you have a compression release. Also make sure your valves are adjusted right. If you have too much lash clearance on the exhaust valve, the compression relief mechanism won't lift the valve enough on the compression stroke.
Advanced timing can cause it to pull the rope out of your hand too. Add advanced timing and more compression and yeah, the rope can get pulled from your hand.
One way to help you start it is too slowly rotate it so you are at TDC on the compression stroke, THEN pull hard and fast.
That gives you and the flywheel a little run at the next compression stroke.
I've had the rope ripped from my hands and thought it broke fingers or tore things in my hand before. No fun. That was a 5 hp Briggs with a cam without a compression release, (SS94 I believe). Anyway, I took it out and put a stock cam in it. No more issues.
Danford1
I am just raising the question, this isn’t in reference to any particular engine.
How does compression = recoil rope getting pulled back? I get why it is hard to pull start with increased compression putting more pressure on the crank, cam can keep valves open longer, etc.
But how does it end up turning backwards it’s confusing
How does compression = recoil rope getting pulled back? I get why it is hard to pull start with increased compression putting more pressure on the crank, cam can keep valves open longer, etc.
But how does it end up turning backwards it’s confusing
It doesn't it just stops while you are still going then smacks the engine as the spring pulls back the handle. I have a couple of 6:1 compression tec hs50's with no compression release and if you try to just crank them over it will hurt you, also will break the pawl or rope over time. Have also broken the shroud. When One of my modded clones had the compression release stuck off it was impossible to crank over. The tecs can be hand started by slowly pulling it over past TDC on compression and then pulling it to start. The heavier the flywheel the better.
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These are two separate causes of kickback. Using a hotter cam that retains the compression release probably won't result in kickback even if the compression is increased.
A cam with no compression release will likely kick regardless of the other parts. Lots of ignition advance can/will cause kick. This is made worse by a lightweight flywheel because there is less inertia to carry through the compression stroke. In extreme cases, an engine may have high enough compression and bad enough fuel to cause spontaneous ignition at cranking speed and that will definitely kick back.
A cam with no compression release will likely kick regardless of the other parts. Lots of ignition advance can/will cause kick. This is made worse by a lightweight flywheel because there is less inertia to carry through the compression stroke. In extreme cases, an engine may have high enough compression and bad enough fuel to cause spontaneous ignition at cranking speed and that will definitely kick back.