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Problems on starting

#1

S

shadow_fi

Hi all,

I have old Briggs and Stratton engine lawn mower, model with aluminium tank. I had this lawn mower for free and fixed its carburetor. Also I changed oil (old oil was like mix of diesel and oil.. very thin)(I used this time 15W-40 Super HPD oil because I've heard this machine smoked like hell..) and tried to start it.. But that was with the plug in extremely hard to do. First time rope braked, then after I fixed this "rope", I could get it running, but it run rough, shaked.

Flywheel is on its right position. On copression, valves are closed tightly... But, I've noticed when there is going to be compression, exhaust valve opens for a little bit.. When the piston is in the middle, and closes right after. I thought it's compression release system, to make it easier to crank it. Can it be true? On this kind classic engine, I didn't saw this compression release system... I think so..

So, what could be problem? Too short valve? Problems with camshaft?

P.S.
Sorry for bad English, I'm writing from Finland.


#2

Fish

Fish

Many of the older engines had an extra little hump on the exhaust cam lobe to make for easier starting.

I am guessing that you are trying to start a pushmower engine, it will yank back and break ropes if you try to start
it without a blade on the mower, or else switch over to a cast iron flywheel, as the blade acts as 1/2 of the flywheel
on pushmowers.


#3

S

shadow_fi

Fish said:
Many of the older engines had an extra little hump on the exhaust cam lobe to make for easier starting.

I am guessing that you are trying to start a pushmower engine, it will yank back and break ropes if you try to start
it without a blade on the mower, or else switch over to a cast iron flywheel, as the blade acts as 1/2 of the flywheel
on pushmowers.
Click to expand...

Hahaha! I had that in mind, but.. Yes there is no blade. I try tomorow with blade. Hope it isnt dangerous to motor, coz had it running without blade for 20mins... Stupid me....

Thanks dude.


#4

Fish

Fish

shadow_fi said:
Hahaha! I had that in mind, but.. Yes there is no blade. I try tomorow with blade. Hope it isnt dangerous to motor, coz had it running without blade for 20mins... Stupid me....

Thanks dude.
Click to expand...


No, it won't hurt anything, except your hand every now and then.


#5

G

gregjo1948

shadow_fi said:
Hi all,

I have old Briggs and Stratton engine lawn mower, model with aluminium tank. I had this lawn mower for free and fixed its carburetor. Also I changed oil (old oil was like mix of diesel and oil.. very thin)(I used this time 15W-40 Super HPD oil because I've heard this machine smoked like hell..) and tried to start it.. But that was with the plug in extremely hard to do. First time rope braked, then after I fixed this "rope", I could get it running, but it run rough, shaked.

Flywheel is on its right position. On copression, valves are closed tightly... But, I've noticed when there is going to be compression, exhaust valve opens for a little bit.. When the piston is in the middle, and closes right after. I thought it's compression release system, to make it easier to crank it. Can it be true? On this kind classic engine, I didn't saw this compression release system... I think so..

So, what could be problem? Too short valve? Problems with camshaft?

P.S.
Sorry for bad English, I'm writing from Finland.
Click to expand...

Your English is fine! You are correct about the compression release. When setting valve clearence, with spark plug out, rotate the engine and check the valve gap in several places to be sure it's right. If the exhaust valve gap is too much it will crank very hard when ti comes up on compression and can kick back sometimes yanking the rope from your hand, even breaking the recoil sometimes. gregjo1948


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