Intek 40 Series Pushrod Length vs Adjustment Range

[Dave_C]

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.

 

[Tiger Small Engine]

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.

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.

 

[Dave_C]

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?

 

[StarTech]

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?

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.

While using this modified test I found several engines with lower cylinder damage that would have no shown up on a standard leak down test.

 

[Tiger Small Engine]

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.

 

[kbowley]

I have seen and repaired this issue countless times in my shop from mice building nests beneath the cooling shroud. Buy a new head, gasket kit, and pushrods if you want it fixed properly. You can try driving the guide back down with a correct-size socket, but it won't last. A new head will be around two hundred, pushrods, twenty-five, and a gasket kit around twenty-five. It isn't a hard job, just a bit time-consuming removing everything to get it done. For me, roughly 2.5 hours of labor. For me to do it for someone runs around four hundred to four fifty, including an oil change.

 

[justin@justintime]

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

 

[Peva]

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:

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?

 

[Peva]

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

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.

Started thinking: Standard ambient air pressure is 14.7 psi. But that can't be it. Suddenly the words "stoichiometric" and "O2 sensors" popped info my mind from years ago - so I internet-searched those terms, and - voilà! - 14.7:1 is the ideal stoichiometric air-fuel ratio.

The mind us a terrible thing!

 

[justin@justintime]

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?

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.