B&S 35 classic, easy pull, hard recoil not starting, advice?

[Mechanima]

Hi,

I am trying to "recommission" a small push mower with a B&S 35 classic engine.

This was laid up without oil or petrol.

I have petrol and oil in now, have left it 48 hours to soak through.

Now the cord pulls very easily and smoothly (I am left handed and it has to be pulled with right hand), little puffs of smoke come out of exhaust after a couple of pulls, and it nearly catchs, but it doesn't start, and the closer it gets to starting the harsher the recoil.

I do not really know what I am doing but am eager to learn, I have a feeling it is a very tiny problem and anyone who did know what they were doing would start it in seconds. :smile:

 

[Briana]

Hey there - WELCOME to LMF!

I moved your thread to the Small Engine & Mower Repair Forum. :smile:

 

[Mechanima]

Thanks :smile:

 

[Trcustoms719]

Hi,

I am trying to "recommission" a small push mower with a B&S 35 classic engine.

This was laid up without oil or petrol.

I have petrol and oil in now, have left it 48 hours to soak through.

Now the cord pulls very easily and smoothly (I am left handed and it has to be pulled with right hand), little puffs of smoke come out of exhaust after a couple of pulls, and it nearly catchs, but it doesn't start, and the closer it gets to starting the harsher the recoil.

I do not really know what I am doing but am eager to learn, I have a feeling it is a very tiny problem and anyone who did know what they were doing would start it in seconds. :smile:

Do you have the tools do do a compression test?
You might have a stuck valve from it sitting without oil in it.
Have you checked for spark?

 

[Mechanima]

I don't know if I have the right tools to do a compression test...what would I need? (i have a lot of tools for various reasons).

Definately a spark because of the little puffs of white smoke out of exhaust as it gets close to starting.

One odd thing is that the oil I put in is still clean and clear. I didn't leave it sitting up myself, I got it that way.Everything was dry and the dipstick and (brand new) spark plug were practically welded in. So a stuck valve makes a kind of clueless common sense to me.

 

[Mechanima]

Well I did some intensive googling, worked out that I do not have tools to test compression AND that getting the head off is not a big deal...also, I *felt* the compression was wrong right away (a sort of hiss as it was pulled that felt and sounded to high pressure, so I opened an engine for the first time in my life (BIG THRILL :biggrin and sure enough upper valve (outlet?) was well stuck so I sprayed it with WD40 and gave it a sharp tap with hammer and a rubber handled tool. This freed it, so I sprayed in some WD40 and put it all back together.

First couple of pulls had a worse recoil than ever but it feels better and seems to be settling...I am beginning to suspect plug is bad (I had to destroy the brand new one to get it out and this is one out of spare engine, could be in any shape - though it looks ok).

Can't get a new plug till at least tomorrow.

Any more enlightenment?

 

[Trcustoms719]

Well I did some intensive googling, worked out that I do not have tools to test compression AND that getting the head off is not a big deal...also, I *felt* the compression was wrong right away (a sort of hiss as it was pulled that felt and sounded to high pressure, so I opened an engine for the first time in my life (BIG THRILL :biggrin and sure enough upper valve (outlet?) was well stuck so I sprayed it with WD40 and gave it a sharp tap with hammer and a rubber handled tool. This freed it, so I sprayed in some WD40 and put it all back together.

First couple of pulls had a worse recoil than ever but it feels better and seems to be settling...I am beginning to suspect plug is bad (I had to destroy the brand new one to get it out and this is one out of spare engine, could be in any shape - though it looks ok).

Can't get a new plug till at least tomorrow.

Any more enlightenment?

See.., a compression test would have told you the valve was stuck without having to take it apart.:laughing:
Did you clean the carburetor real good yet?
If it's been sitting over a year the carb could be dirty.

 

[Mechanima]

True...but it wouldn't have unstuck it (and I wouldn't still be high on being a person who has *GOT INSIDE* a real live internal combustion engine :biggrin.

Left stand a while it started to cough and almost start, which sounds a bit like my regular mower when the carb needs a clean out.

Also, I think some of the hard recoil could be because I have been pulling the cord too enthusiastically, now it is free it seems to try and "catch" at a very light pull.

Rain stops play for now, but my next move with certainly be to clean out the carb, unless it starts.

 

[Trcustoms719]

True...but it wouldn't have unstuck it (and I wouldn't still be high on being a person who has *GOT INSIDE* a real live internal combustion engine :biggrin.

Left stand a while it started to cough and almost start, which sounds a bit like my regular mower when the carb needs a clean out.

Also, I think some of the hard recoil could be because I have been pulling the cord too enthusiastically, now it is free it seems to try and "catch" at a very light pull.

Rain stops play for now, but my next move with certainly be to clean out the carb, unless it starts.

Ok, keep me posted.

 

[Mechanima]

It finally stopped raining for a while...so...time to get the carb off...except it is this strange little plastic thing with a primer bulb that doesn't make sense compared to the mikumi carb I clean out on my regular mower...so I googled to see how to clean it and found that they don't need much cleaning and there isn't anything you can strip...BUT...the diaphragm gives problems...

I had to practically dismantle the mower to get the carb off (providing a learning opportunity in terms of coil gaps later :confused2: ) and found that there was a spare piece of old diaphragm somehow stuck in with the gasket (did not seem helpful) and the actual diaphragm had been torn off one of the screws, probably while fitting it. Not in a functional area, but it would definitely interfere with the seal and tension.

Invested 5 euros in a new diaphragm and gasket from ebay, and tried to seat the old one better to see if it helped, or even changed anything.

Had to mess around resetting the coil gap a bit...

...then nearly died when it finally sprung into life

No fluke, it is now starting on the first light pull reliably. I will replace the diaphragm because it will not hold long like that...but my only worry now is that the engine seems to be racing. It has a governor and idle spring, not screws...don't think it is the throttle because it won't shut down even at the lowest point manually...

Any ideas?

PS Only starts on first pull when warm...still troublesome to cold start at all.