P216g with 80 PSI on front cyl

[TC10284 113]

I just started working on a 416H that I bought a year or so ago. I checked the gov. ball spacer since the flywheel was off already, and it was fine (plastic type with extended tab, not broken). I put the ICM and the flywheel back on. I first wanted to do a compression check before I attempted fixing the jacked up wiring that someone did. It's not too bad really - someone put a toggle switch on for the starter. And I'll have to fix the red wire on the main connector that someone clipped and connected with a wire nut. Real geniuses, I swear...
And repair the PTO safety switch wiring. 

 

Anyway, the main question I have, before I bother doing all this, my compression check showed 80psi on the front cyl and 90psi on the rear cyl. I have not bothered adjusting valves or anything yet. It has 751hr on the meter, so it's past due and probably never been done before. 

 

According to the P216g manual, the minimum is 75psi. 

 

The tractor is in good shape otherwise. I didn't get the model number, but it's probably a 97 or newer - my guesstimate.

 

What do you think? Mess with it or no? 

Edited July 22, 2022 by TC10284

[TC10284 113]

73423 

96 50th anniversary edition. 

[lynnmor 7,813]

If there is some valve clearance adjusting won't bring up the pressure.  Since the compression is near the minimum specification, i would pop the heads, check for loose valve seats, decarbon and then have a look at the cylinder walls.  If there is evidence of excessive wear then measure the bore.  If you are satisfied with the bore, then pop the valves and grind them along with the seats.  I have freshened up valves and brought the compression up to new specification.

[TC10284 113]

37 minutes ago, lynnmor said:

If there is some valve clearance adjusting won't bring up the pressure.  Since the compression is near the minimum specification, i would pop the heads, check for loose valve seats, decarbon and then have a look at the cylinder walls.  If there is evidence of excessive wear then measure the bore.  If you are satisfied with the bore, then pop the valves and grind them along with the seats.  I have freshened up valves and brought the compression up to new specification.

 

I may as well. I'm going to have to remove the engine anyway to tighten the oil drain. It's pretty loose and probably causing the oil buildup I see near there. 

 

I have a valve removal tool. When you say "grind", do you mean using a wire brush on a bench grinder? 

 

Does this look like a decent caliper? 

https://www.amazon.com/VINCA-DCLA-0605-Electronic-Fractions-Conversion/dp/B017KUC6XQ/ref=sr_1_2_sspa?keywords=bore+caliper+measuring+tool&qid=1658533688&sprefix=bore+calpi%2Caps%2C96&sr=8-2-spons&psc=1&smid=A1JAAL829ACROK&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyMjFIRTNTTlZYQzRHJmVuY3J5cHRlZElkPUEwMTE5NjExM1BCSkJBOUdTR1Y4OSZlbmNyeXB0ZWRBZElkPUEwNTI4Mzc2QUc4UDNKSTQyOEE3JndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

[lynnmor 7,813]

1 hour ago, TC10284 said:

 

1 hour ago, TC10284 said:

I may as well. I'm going to have to remove the engine anyway to tighten the oil drain. It's pretty loose and probably causing the oil buildup I see near there. 

 

I have a valve removal tool. When you say "grind", do you mean using a wire brush on a bench grinder? 

 

Does this look like a decent caliper? 

https://www.amazon.com/VINCA-DCLA-0605-Electronic-Fractions-Conversion/dp/B017KUC6XQ/ref=sr_1_2_sspa?keywords=bore+caliper+measuring+tool&qid=1658533688&sprefix=bore+calpi%2Caps%2C96&sr=8-2-spons&psc=1&smid=A1JAAL829ACROK&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyMjFIRTNTTlZYQzRHJmVuY3J5cHRlZElkPUEwMTE5NjExM1BCSkJBOUdTR1Y4OSZlbmNyeXB0ZWRBZElkPUEwNTI4Mzc2QUc4UDNKSTQyOEE3JndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

A caliper of any quality is not a good tool to measure a bore, a telescope gauge together with a micrometer is better and a bore gauge is good.

 

I see that you don't understand the valve grinding process, you should look at a number of Youtube videos to gain knowledge. 

 

Example of valve grinding video.

 

I use Neway tools to cut the valve seats, here is a video showing the process.  I don't agree with some of his ideas but you will get the idea.  For example the reason for cutting the three angles is to get the seat the correct diameter and width, performance is secondary because it naturally will be better when the work is correct.

 

You might want to have a shop do this for you due to tooling cost and lack of experience.  If a shop offers to just lap the valves, find a different shop.

 

If you do pull the valves, put new seals on the intake valves.

[ineedanother 1,668]

8 hours ago, TC10284 said:

Anyway, the main question I have, before I bother doing all this, my compression check showed 80psi on the front cyl and 90psi on the rear cyl. I have not bothered adjusting valves or anything yet. It has 751hr on the meter, so it's past due and probably never been done before. 

 

What do you think? Mess with it or no? 

Are you concerned about the compression? My point with that question is that you could be looking for a problem that might not exist. Compression checks are finicky. If you used a different gauge and did the cylinders in the opposite order or under different conditions and compared them to what you have stated, I suspect that your findings would confound you. If you aren't concerned with a loss of power or something related to a possible loss of compression, put it together and do what you intend to do with it. I could be off-base but I don't follow what problem with engine performance you're chasing.

[TC10284 113]

11 hours ago, ineedanother said:

Are you concerned about the compression? My point with that question is that you could be looking for a problem that might not exist. Compression checks are finicky. If you used a different gauge and did the cylinders in the opposite order or under different conditions and compared them to what you have stated, I suspect that your findings would confound you. If you aren't concerned with a loss of power or something related to a possible loss of compression, put it together and do what you intend to do with it. I could be off-base but I don't follow what problem with engine performance you're chasing.

 

My concern was going forward with repairing all the wiring and other misc issues if there was already a "pre-existing condition" of low compression. I recently made the mistake of doing that on a 520H, only to find out the rear cyl only had ~30psi, the front one was good (can't remember the exact number). And now that I think of it, I may dismount that one as well and pull the rear head. 

 

Also, I don't have multiple compression checkers, but I did the check a few times to confirm. Release pressure, retest. 

But since I need to dismount the engine to tighten the oil drain tube on this 416H, I may as well just pull the heads and try to grind the valves/replace the seals.

 

I have also ordered a telescoping gauge set and micrometer to see the bore size. 

Edited July 23, 2022 by TC10284

[Tuneup 1,452]

Hey there, TC - you talk like you know what you're talking about so we can assume you tested it with the throttle wide open. Lots less than 75 psi if not so...

 

Oh, can you trust your compression gauge? I decided once to 'splurge' on a Harbor Freight model instead of my old hold-it-down model from the 70s and thought it was time to rebuild the old Honda CB. read: 80 psi, actual 140 psi. This might be accurate in Beijing but not for me! If you trust your tools, clean the combustion chambers and run it under load for a while - mow the lawn. Perhaps it will improve with a little ring exercise? Good luck!

[TC10284 113]

13 minutes ago, Tuneup said:

Hey there, TC - you talk like you know what you're talking about so we can assume you tested it with the throttle wide open. 

 

Hardly...

I wish I knew a lot more about small engines and how to take them apart/put back together successfully. 

[Bill D 2,247]

28 minutes ago, TC10284 said:

 

Hardly...

I wish I knew a lot more about small engines and how to take them apart/put back together successfully. 

Be sure to run your compression check with the throttle wide open and the choke open.  75 psi is about the best you'll get with the throttle at idle or the choke closed.

[TC10284 113]

Thank you both. I'll give that a try. 

[lynnmor 7,813]

Nearly all small engines with governors open the throttle plate when stopped.