lawnmower wouldt run

[m_c]

I wouldn't be stripping anything until I'd given it a decent run to see if the smoke clears after some use. It also lets you establish if it's worth the effort of even attempting a fix.

 

[jimbo84]

Ha, “vintage barn find mower, lovely patina, untested. Ideal for upcycling”
It’ll make a fortune!!

More than when it was new knowing some people

 

[Memmeddu]

got a decent mountfield lawnmower given supposedly only the starting chord and spring gone . took the top off filled it with fuel and used a socket on the rechargeable drill to run it . would it hell start cleaned the carb out new plug nowt sent of for a new coil just in case and just the same . took the plug out stuck me finger in and no compression . checked the oil and none in hardly . topped it up and checked again good compression plug back in tried starting and off it went. great ive scored . yea till it started smoking and filled the garage with blue smoke .its an oil puffer so 18 quid down on bits and a few hours wasted ohh well was worth a try

Did you check valves and rocker arms adjustments?

 

[brightspark]

Did you check valves and rocker arms adjustments?

haven't looked at it yet been busy working today. just debating to take the head of it if I can be bothered at the mo I will look though

 

[gaz1]

ha mine works and at 8.50 to get it up and running again no problem just needed a new diaphram at that

 

[brightspark]

well got to the bottom of it sort off, took the head off cranked it round the inlet valve opens and closes same with the exhaust valve but when its coming up to the compression stroke the exhaust valve slightly opens and closes so something amiss that operates the valves looks like its cream crackered as the whole lot would need to come to bits hardly think its worth it

 

[Pete.]

Yeah I've seen that. Did you check the clearance via the little cover?

 

[Cobbler]

Is that some sort of decompressor for starting BSpark? I know some mowers have some arrangement with valves, but never seen one to know how it works.

 

[Ton-up]

I believe that a lot of Briggs exhaust valves do not close completely for that reason

 

[brightspark]

Yeah I've seen that. Did you check the clearance via the little cover?

will investigate as I never noticed or looked elsewhere on it

 

[brightspark]

Is that some sort of decompressor for starting BSpark? I know some mowers have some arrangement with valves, but never seen one to know how it works.

no it looks a pretty simple set up just a brake and kill switch on it

 

[Pete.]

will investigate as I never noticed or looked elsewhere on it

You gotta take off the heat shield then the exhaust then under that is a small cover that looks like it should never be removed. Remove it and all you'll see inside is the pushrod and valve tops.

Pic here:

https://www.outdoorking.com/forum/u...eak-on-briggs-stratton-quantum.html#Post60621

 

[gaz1]

this ones mine

 

[Dev]

While doing a bit of research into a crack-pot idea I had I found this https://repairlawnmowersforprofit.c...ggs-and-stratton-35-classic-lawnmower-engine/ which mentions white smoke as a result of tipping it on its side.

Remediated by letting it run for a while...

 

[andymfell]

what you are seeeing is the action of an extra small lobe on the exhaust part of the camshaft, it only has any real effect when starting although it works on every other revolution ( cam rotates at 1/2 engine speed) the action is so slight that when runnung at 3000 rpm it has no effect on the power output

the correct way to check for compression on a briggs engine is to rotate the flywheel the opposite direction to normal and if it bounces against compression it is OK

 

[ukracer]

what you are seeeing is the action of an extra small lobe on the exhaust part of the camshaft, it only has any real effect when starting although it works on every other revolution ( cam rotates at 1/2 engine speed) the action is so slight that when runnung at 3000 rpm it has no effect on the power output

the correct way to check for compression on a briggs engine is to rotate the flywheel the opposite direction to normal and if it bounces against compression it is OK

Is that why a briggs starts on the second pull usually?

 

[andymfell]

Is that why a briggs starts on the second pull usually?

first pull gets the fuel flowing thru the carb jets and into the cylinder

 

[ukracer]

first pull gets the fuel flowing thru the carb jets and into the cylinder

I recently purchased a SP550
Ultra Easy Start but after the winter sitting it would not run without easy start being used two or 3 times.
So I purchased a carb and a service kit advertised for 550 but neither fits
It appears to be a Quantum engine.
So what on earth is going on I do not know.

 

[tom2207]

I recently purchased a SP550
Ultra Easy Start but after the winter sitting it would not run without easy start being used two or 3 times.
So I purchased a carb and a service kit advertised for 550 but neither fits
It appears to be a Quantum engine.
So what on earth is going on I do not know.

run a tank of 2t through it , and never look back

 

[Matchless]

Is that some sort of decompressor for starting BSpark? I know some mowers have some arrangement with valves, but never seen one to know how it works.

Nothing new, several of my 1931-33 Matchless singles, D80, CS, D5 etc. have a half compression lever that operates on a second small cam ground behind the main exhaust cam, it lifts the inlet valve a bit just before compression, actually runs quite well with the lever on, just sounds a bit off colour and lacks a bit of power, cannot tell you how I know that...………………… bitch to kick over if you don't use it!