Are you changing the cylinder that overheated and pushed the valve guide? Did you thoroughly clean the top of engine and cooling fins from debris after it overheated? This mower is 25 years old and has been around the block a time or two.Yes I know there is some adjustment as I'd adjusted it previously when it burped trying to start it (a few years ago, I did not cause this, lol), but I don't know, if after a couple+ decades of wear (maybe around 600 hrs), if 1.5mm shorter is outside a reasonable expectation of adjustment range.
Thanks! I was just reminded that my caliper is only 6", so I had to extrapolate, after beating the old bent pushrod close to straight.The old 690981 which supersedes to 597785 is 6.275" (159.385 mm) in length per my caliper.
Changing the cylinder? You mean a new head? I was hoping to just replace the pushrods, dremel a groove on the valve guide while it's sticking out, that would end up just below the level of the head, put some high-temp red loctite on, pound the guide back down and stake it in.Are you changing the cylinder that overheated and pushed the valve guide? Did you thoroughly clean the top of engine and cooling fins from debris after it overheated? This mower is 25 years old and has been around the block a time or two.
Just out of curiosity are these from Briggs or are they after market? IF form Briggs it does sounds like a quality control issue as Briggs in the past has always been good but ever since the they went bankrupt and the financial investment company took them over I do suspect a lot more items are coming from China.Thanks! I was just reminded that my caliper is only 6", so I had to extrapolate, after beating the old bent pushrod close to straight.
That gives me old pushrod length 159.25mm, two new steel 157.75mm, and oddly the two aluminum are different lengths from each other, about 157.25mm and 158.25mm... gotta luv quality control!
If you cut a groove in valve guide, insert a c-clip into the groove so it stays put. Make sure it is at correct depth of course. You can red Loctite it and peen it also.Changing the cylinder? You mean a new head? I was hoping to just replace the pushrods, dremel a groove on the valve guide while it's sticking out, that would end up just below the level of the head, put some high-temp red loctite on, pound the guide back down and stake it in.
Yes there was a lot of grass muck built up and that has already been cleaned off. I also considered pulling the head, then tapping it and using a set screw as I've seen Taryl and others do on youtube videos, but still trying to decide.
I don’t do this repair this way either for a customer. It is a new cylinder head, clean top of engine of debris, etc.As a professional shop I don't do this to my customers. I warranty my workmanship and if the repair don't hold it bites me in the anus.
Beside grinding on the cast iron valve guide will weaken it. Another option I have heard of is to pull the head drive the guide back in place and spot weld the guide inside the valve chamber as these guides are usually pushed out. Even that I don't recommend. But it is the OP's engine and he can take the risks if he wants to as he can always repair it again if it fails again or replace it. Just note there is no replacement guides.
BTW any beating on the valve guide usually means it will need reaming to correct size.
Just out of curiosity are these from Briggs or are they after market?
Also note the 796632 and 796633 cylinder heads have been superseded a few times. They even at one time came as a set for half the price but quickly changed that back to individual heads out of China. Current heads are 84001918 (#1) and 84001919 (#2) and they are not a stock item from Briggs direct. IE slow boat from China.
If you cut a groove in valve guide, insert a c-clip into the groove so it stays put. Make sure it is at correct depth of course. You can red Loctite it and peen it also.
As a professional shop I don't do this to my customers. I warranty my workmanship and if the repair don't hold it bites me in the anus.
Beside grinding on the cast iron valve guide will weaken it. Another option I have heard of is to pull the head drive the guide back in place and spot weld the guide inside the valve chamber as these guides are usually pushed out. Even that I don't recommend. But it is the OP's engine and he can take the risks if he wants to as he can always repair it again if it fails again or replace it. Just note there is no replacement guides.
BTW any beating on the valve guide usually means it will need reaming to correct size.
Moral of this story is CLEAN YOUR COOLING FINS. Swear this has been posted on here buy one of us.
Technically, by the service manual, the mower shroud is supposed to be removed once a year and the engine and cooling fins checked for debris, to avoid overheating.Okay but as a shop, what would you charge to put the new head on, and presumably clean it out since it is likely brought in with nothing done yet? I figure that's at least a $450 service with parts, right? The mower isn't worth more than that, is a (roughly) circa 1999 Scotts aka Murray, which works fine besides the engine but isn't long term investment worthy. A new head at $190-ish is about the limit. If the other head also needed replaced, it would blow the budget to replace them both.
Grinding on the cast iron valve guide? I'd just put a groove in it for peening around that, to have some purchase on it, or a dimple for a set screw. It looks steel (shiny silver), doesn't look like it would be easy to weaken it. If loctite and staking it, then a set screw doesn't keep it still, I may find some welder to do that. I think the main issue with a set screw will be whether the loctite threadlocker stays set up at the head temperature. It's rated for 450F but since this is a side load, might not slip without it doing its job.
I found yet another alternative which is a machined washer that sits over the casting, under the spring. Here's a video example:
So true so true. On every air cooled engine out there.Technically, by the service manual, the mower shroud is supposed to be removed once a year and the engine and cooling fins checked for debris, to avoid overheating.
Always do visual inspection, lap valves, de-carbon valves, cylinder head, and piston head, and check head for level with feeler gauge on glass. Don’t worry about other cylinder unless it is a problem. Perform compression test to compare two cylinders once work is complete.Before this engine popped out the valve guide, it had plenty of power for mowing.
Should the valves for just this one head be lapped while the head is off, or will this potentially be worse, causing a difference in compression between this cylinder and the other cylinder which won't get the valves lapped?
I realize that best practices would mean lapping valves for both heads, but I'm running out of time, need to get all the work done on the same visit. If all the leaves get too much rain or snow, they're going to mat down and can't be mow-mulched away.
This why you do leak down tests and better yet the modified leak down test when an OHV engine is involved. With low pressure leak down tester you can test all of cylinder condition from TDC to BDC. The tester I have test at 12-15 psi to get full scale readings; therefore I can hand hold the flywheel and can rotate through the TDC to BDC cycle while watching the leak down percentage needle. Also paying attention the air is leaking out in case of a bad valve seal or a blown head gasket.How do you do a compression test on these? I was under the impression that they have a compression release mechanism that's active while cranking, till running higher than a certain RPM. That won't impact the reading?
Yes, the compression release will affect a compression test reading. You are looking for at least 60-70 psi on a twin cylinder with compression release. You are also looking for 10% or less differential between the two cylinders. I sometimes do a leak down test also, depending upon the situation.How do you do a compression test on these? I was under the impression that they have a compression release mechanism that's active while cranking, till running higher than a certain RPM. That won't impact the reading?
That step washer is a clean solution. I was wondering if one or both ends of the spring should be ground shorter to equal the thickness of the part of the washer that it's resting on so the spring is compressed as designed. Or is that over-thinking it?Okay but as a shop, what would you charge to put the new head on, and presumably clean it out since it is likely brought in with nothing done yet? I figure that's at least a $450 service with parts, right? The mower isn't worth more than that, is a (roughly) circa 1999 Scotts aka Murray, which works fine besides the engine but isn't long term investment worthy. A new head at $190-ish is about the limit. If the other head also needed replaced, it would blow the budget to replace them both.
Grinding on the cast iron valve guide? I'd just put a groove in it for peening around that, to have some purchase on it, or a dimple for a set screw. It looks steel (shiny silver), doesn't look like it would be easy to weaken it. If loctite and staking it, then a set screw doesn't keep it still, I may find some welder to do that. I think the main issue with a set screw will be whether the loctite threadlocker stays set up at the head temperature. It's rated for 450F but since this is a side load, might not slip without it doing its job.
I found yet another alternative which is a machined washer that sits over the casting, under the spring. Here's a video example:
I was getting ready to show my ignorance and ask what "14.7" had to do with anything - tried to guess what it might be.I enjoy reading the back and forth on this stuff. Quickly as a shop do it the right way and this only due to save our bum from lack of service and neglect. As a shop for myself that changes his oil uses API rated CH-4 cj-4 or CK-4 oil 20w-50 and cleans his cooling fins id drive the pin in ream the guide and recut my seats and face my valves but I also have the 600 dollars or so in neway tools to do that. As a DIY you don't wanna pay a shop or a head, slam it in do it by feel and do as you please. It'll work just no crystal ball as to how long. Engines are engines they are all the same and they all need to meet the same requirements in order to run 14.7 figure out that number and all engines will be easier to work on heat and friction are the enemy. Your weed Wacker and your Ferrari both need 14.7
Infact from what I can tell I'm the only one that's ever heard of valve spring shims. Again engines are engines there's an odd misconception small engines are in a different category. Yes you want the spring compressed they even last longer that way. Now it is just a small engine yes it will run no it will probably not be a noticeable difference. When I cut valves seats I shim springs on my engines but not so much on customers as I fear faster damage would result in going to far and again it's a small engine cost is the issue not function. These guys getting 6 and 7 grand in RPM achieve this mainly due to (amongst others) heavier springs to reduce "valve float" without the heavy springs they fall on their face at about 4500rpm. The last thing I would do is trim the guide. Pound it in, peen it in, run a drill bit through by hand and wrap a piece of fine grit sandpaper to a stiff piece of wire and hone the guide take a scotch Brite pad to your stem and adjust your valves to spec. The smaller side of spec as you've gone past break in period your 1.5mm will not affect your overall valve lift as your taking it up on the adjuster only way to loose valve lift would be taking the cam lobes down or loose clearancesThat step washer is a clean solution. I was wondering if one or both ends of the spring should be ground shorter to equal the thickness of the part of the washer that it's resting on so the spring is compressed as designed. Or is that over-thinking it?
There is 25.4 mm to an inch, so are you saying they are 1 1/2 inches shorter?Lawn mower has a B&S Intek V-twin 19HP
Model 407777
Type 0137 E1
Code 980422YG
Does anyone know what the spec is for the pushrod length?
It overheated, valve guide slipped, bent one or more pushrods. I got the pushrod part #s, 690981 (steel, exhaust), and 690982 (aluminum, intake).
I was sent a generic kit labeled CT160 (or CTM160, something like that), which is supposed to be the above two part #s but compared to a bent steel exhaust rod that was pulled, the new pushrods look about 1.5mm shorter.
I checked the engine service manual # 273521 and it doesn't spec the pushrod length.
Is there an acceptable range of length that can be adjusted for, is something 1.5mm shorter likely to work okay? I'd just throw it in and try to adjust it but the mower is at my mother's place and I'd like to have viable parts when I get there.
I was only meaning that if you put the step washer in to retain the valve guide, the bottom end of the washer acts as a shim for the spring. Depending on how thick you make that inadvertent-new-spring-shim part of the washer, you could be over-compressing the spring, which may shorten it's life (could yield/weaken or break).Infact from what I can tell I'm the only one that's ever heard of valve spring shims. Again engines are engines there's an odd misconception small engines are in a different category. Yes you want the spring compressed they even last longer that way. Now it is just a small engine yes it will run no it will probably not be a noticeable difference. When I cut valves seats I shim springs on my engines but not so much on customers as I fear faster damage would result in going to far and again it's a small engine cost is the issue not function. These guys getting 6 and 7 grand in RPM achieve this mainly due to (amongst others) heavier springs to reduce "valve float" without the heavy springs they fall on their face at about 4500rpm. The last thing I would do is trim the guide. Pound it in, peen it in, run a drill bit through by hand and wrap a piece of fine grit sandpaper to a stiff piece of wire and hone the guide take a scotch Brite pad to your stem and adjust your valves to spec. The smaller side of spec as you've gone past break in period your 1.5mm will not affect your overall valve lift as your taking it up on the adjuster only way to loose valve lift would be taking the cam lobes down or loose clearances
. Shim the spring if you feel the need I see no need as you haven't changed anything.
I think you had a brain fart,There is 25.4 mm to an inch, so are you saying they are 1 1/2 inches shorter?
Lawn mower has a B&S Intek V-twin 19HP
Model 407777
Type 0137 E1
Code 980422YG
Does anyone know what the spec is for the pushrod length?
It overheated, valve guide slipped, bent one or more pushrods. I got the pushrod part #s, 690981 (steel, exhaust), and 690982 (aluminum, intake).
I was sent a generic kit labeled CT160 (or CTM160, something like that), which is supposed to be the above two part #s but compared to a bent steel exhaust rod that was pulled, the new pushrods look about 1.5mm shorter.
I checked the engine service manual # 273521 and it doesn't spec the pushrod length.
Is there an acceptable range of length that can be adjusted for, is something 1.5mm shorter likely to work okay? I'd just throw it in and try to adjust it but the mower is at my mother's place and I'd like to have viable parts when I get there.
I was only meaning that if you put the step washer in to retain the valve guide, the bottom end of the washer acts as a shim for the spring. Depending on how thick you make that inadvertent-new-spring-shim part of the washer, you could be over-compressing the spring, which may shorten it's life (could yield/weaken or break).
Again - I may be overthinking it. But if you make it 1/16" thick or more, perhaps that would become a spring life factor. Perhaps OK if maybe 1/32 or 3/64" thick. Anyway, with me being OCD, if I were doing it, I would grind the end(s) of the spring to remove maybe 0.01" shy of whatever that thickness is - ounce of prevention kind of thing.
(seemed to want to know the pushrod length)
StarTech said:The old 690981 (pushrod) which supersedes to 597785 is 6.275" (159.385 mm) in length per my caliper.
Could make your own. 4130 tube isn't that much nor is 6061 AL. You already have the ends. Can't be that hard. Give B&S a call and talk to tech about what the specs say.Thanks! I was just reminded that my caliper is only 6", so I had to extrapolate, after beating the old bent pushrod close to straight.
That gives me old pushrod length 159.25mm, two new steel 157.75mm, and oddly the two aluminum are different lengths from each other, about 157.25mm and 158.25mm... gotta luv quality control!