Rebuilt engine hard to turn over, but then loosens up?

unioncreek

Active Member
Joined
Sep 5, 2016
Threads
13
Messages
65
  • / Rebuilt engine hard to turn over, but then loosens up?
Bob
B&S i think also makes motors for the John Deere mowers sold at lowes i have one with only 300 hrs
One Guy said he had one that was smoking and using oil and he put T4 rotella 15 w 40 made by shell have you heard of this or tried it?
Mine had 140 hrs. I run Mobile Delvac 15/40 in my truck so I tried that still used almost as much. Even tried 50wt the last oil change that didn't work either.

I've overhauled the engine. The rings were shot. A leakdown test on cylinder #2 was 100 % and #1 was about 20%. A new connecting rod fixed the hard to turn over problem. I've ran it for over an hour since the rebuild starts right up and no smoke.

Bob
 
Last edited:

unioncreek

Active Member
Joined
Sep 5, 2016
Threads
13
Messages
65
  • / Rebuilt engine hard to turn over, but then loosens up?
That's .004-.006 on both valves on the Briggs OHV twins...per Briggs and Stratton.
The singles are .003-.005 intake and .005-.007 exhaust. Both adjusted at 1/4inch past TDC of compression stroke for each cylinder.
B&S repair manual states 0.005 on both intake and exhaust.
 

TobyU

Well-Known Member
Joined
Jun 1, 2014
Threads
0
Messages
430
  • / Rebuilt engine hard to turn over, but then loosens up?
B&S repair manual states 0.005 on both intake and exhaust.
Their official chart states .004-.006 and.005 is right in the middle so that's all good too.
Kohler has a similar controversy but it's actually worse because the numbers don't fall exactly in the spec range like the brakes does. For their Kohler courage engines you can look at two different Kohler branded shop manuals and fine two different specs but in all reality either one will work because they are all close enough.
I've done a lot of these rigs overhead valve engines and what a lot of people don't realize is they are not like automobiles where the valve seat erodes and the valve goes further down into the margin and less the tip stick out further so they get tight. This is what used to burn valves on cars when they got out of adjustment because valves cool when they are closed so if they don't close all the way because they have not enough lash of clearance, they will burn.
These overhead valve Briggs engines always wear loose. I believe it's because they don't get nearly the hours of use on the actual valves themselves to wear like a car would and they're also not used at extremely different temperatures but I think the biggest reason is the material on the rocker arms is just such a soft not hard metal that it wears away where it rubs onto the hardened button cap on top of the valve stem which does seem to be very hardened and long-lasting without anywhere and also wears where the push rods ride into the hole on The rocker arms.
It doesn't take much wear to give you a couple of extra thousandths.
So typically when you pull one of these engines apart that's 6 or 8 years old and has never been adjusted when it's supposed to be .004-.006 you will find it's far more often around .012.
That's three times and saying it this way sounds like a lot but it doesn't make much difference on the exhaust valve. When the intake gets loose enough you lose your ACR action which causes it to be hard to crank over and that happens sometime around the .010 mark.
 

TobyU

Well-Known Member
Joined
Jun 1, 2014
Threads
0
Messages
430
  • / Rebuilt engine hard to turn over, but then loosens up?
Bob
B&S i think also makes motors for the John Deere mowers sold at lowes i have one with only 300 hrs and it started smoking and using oil
How many hours was on your before you overhauled it
One Guy said he had one that was smoking and using oil and he put T4 rotella 15 w 40 made by shell have you heard of this or tried it?
I know thats not the problem you have but thought you might help solve my problem.
It seems the B&S motors are sorry engines
I cn,t even find anyone to overhaul mine they claim they don,t have the equipment to bore the block but i wouldn,t think wirth only 300 hours it would need boring what do you think?
Here's the deal.. Briggs had a number of their early first generation you could say in tech v twins that were wiping out the rings and under 100 hours. They replaced quite a few under warranty but you really had to keep after it and go through the proper channels but by quite a few I mean numbers and certainly not percentages.
See, most people in a large part of the country only put between 25 and 35 hours a year on a mower and some less than that so the mowers get pretty old pretty quickly with not many hours so people don't realize that the engine should still be like a baby at 4 to 5 years or even 10 years but that's kind of a different story and the reason I think they no longer put the hour meters on most of them like they were for a long time because those things became so cheap.
Regardless, the problem with these was all about air filtration or lack thereof.
There can be other reasons and things that are not quite the most typical but for the most part he will only find worn out rings and smoking and using old engines on the ones that have the oval D shaped hole with the flat rectangular air filter. You won't find these problems on most of the round air filters.
These early ones and some of the second gen ones too even though they thought they fixed it allow dirt to bypass the air filter and go straight down the plastic d-shaped hole of the intake. You can spot it pretty often bye simply looking down there even without a flashlight. Or use a your finger or a paper towel. You will get this dirt colored residue sometimes it's excessively thick like it's been spray painted.
This simply destroys the rings and probably not too good in the cylinder walls either.
The funny part is none of this ever happened with the singles!
Why aren't they just the same engine but half or whatever and I'm saying this because plenty of people had air filtration issues with the singles even if the filter wasn't bypassing. People run these things for years sometimes without any air filter and they still don't wipe out the rings!
This is what has surprised me. Even if a twin is sucking that much more air even double the air how does it magically suck more dirt in than one cylinder would sucking half as much air. Shouldn't the dirt per cylinder be the same? Shouldn't a single running without an air filter suck a lot more dirt in than a twin with just a leaky air filter?
I can't answer all these but the known problem is with the twins with air filter bypass problems. There's no known or acknowledged issue with any of the singles.
Oil will help some but it's no magic bullet cure. Most people don't start their riding lawn mower when it's under 60 degrees so you can go by a straight weight 40 or even straight weight 50 if you want. 20 w 50 does better than 15W40 and so does a straight 50 weight normally or even a 40 weight.
O'Reilly carries Valvoline VR1 racing oil in all of these weights except the 15W40 because that's a diesel formulation.
You can also do what I think is the best thing for them and get some of the restore engine treatment.
It's one of the few products on the Walmart chemical automotive shelf that has not gone up in price!
Experiments B12 has doubled in price, Marvel's Mystery Oil has gone crazy and stable is up 20 or 30% but the restore is still sitting there with the four six and eight cylinder treatments the exact same price they were 8 to 10 years ago.
Read the back because you don't want to put a whole can in but I believe it says you can go up to 20% of your oil capacity.
You can actually go more like 25 to 30 and not be concerned I've done it lots of times.
You have to remember that one of these engines only holds about 53 to 56 oz of oil. And that depends on whether they have a spin on filter or not which they've also started to delete because they're trying to save money and lawnmower engines never needed a spin on filter to start with because it's not going to increase engine life because none of the failures are lubrication problems other than people not checking the oil and they're not having enough oil in them.
The whole oil filter thing and fully pressurized lubrication system was all about marketing!
So basically I'm saying put 10 to 13 oz of this stuff in with your oil and keep running it and keep your oil topped off..
It'.
This stuff is the only additive snake oil if you will but I've ever seen actually work for all consumption and compression with exception of the really super thick honey oil thickeners which works because they're super thick but we all know that.
This stuff seems to work and it's only like a thinner oil maybe 20 to 30 weight.
It certainly can't hurt one that's using oil so I recommend trying it on those and the most part check your air filter to see if dirt is going down the intake tube.
 

gtman

Forum Newbie
Joined
Feb 18, 2013
Threads
3
Messages
8
  • / Rebuilt engine hard to turn over, but then loosens up?
I didn't read the whole thread bit it sounds like your classic failed decompression feature when starting , hard to start when the engine is on the compression stroke
 

TobyU

Well-Known Member
Joined
Jun 1, 2014
Threads
0
Messages
430
  • / Rebuilt engine hard to turn over, but then loosens up?
I didn't read the whole thread bit it sounds like your classic failed decompression feature when starting , hard to start when the engine is on the compression stroke
True, and it's been a while for this thread but I believe it was a twin he was working on and those don't have the compressor release spring and finger and weight built into the camshaft like the single cylinders do.
 

gtman

Forum Newbie
Joined
Feb 18, 2013
Threads
3
Messages
8
  • / Rebuilt engine hard to turn over, but then loosens up?
True, and it's been a while for this thread but I believe it was a twin he was working on and those don't have the compressor release spring and finger and weight built into the camshaft like the single cylinders do.
wow, I just noticed how old this thread is. lol
 

TobyU

Well-Known Member
Joined
Jun 1, 2014
Threads
0
Messages
430
  • / Rebuilt engine hard to turn over, but then loosens up?
wow, I just noticed how old this thread is. lol
Heck, this was nothing. Some of the threads get revived years later but that's okay because it keeps people finding them when they search on things especially on the forums that have been around a long long time and that way people learn things.
 
Top