Robin valves

[SwampmanLA]

My 22hp robin has about 700 hours on it and lately I was thinking it was close to replacement time. Hard starting and a general lack of power were causing me to think it was about gone. So before I forked money and time to buy and replace the Robin I decided to run through all the maintenance items I could think of. Cleaned the carb, replaced air filter, changed spark plugs changed fuel filter, and checked the valve clearances. Wow was I surprised at how much slop I found in the lifters. So I reset the clearances and fired it up. It started and ran like new with power I had not felt in some time. All that was really not hard and I admit should have been done long ago. Good news is that the robin is strong again and I saved some money.

 

[MossRoad]

I've heard that about the valves on the Robin several times here in the PT forum. And everyone that does that maintenance is really happy with the results. Makes me want to check my Kohler as soon as it warms up.

 

[ponytug]

I think that valve clearances is an often overlooked service item in engines. I remember changing cars from an engine with manually set valves to ones with hydraulically set lifters- what a difference. (same model, about four years apart in age) It always stayed in peak form. Basically the same engine, just tweaked.

I can't say that it is my favorite service item, but it is well up on the ratio of reward to effort.

The same is true for generators, chippers, rototillers...

All the best,

Peter

 

[MossRoad]

Once I helped a friend rebuild an engine with solid lifters. That was a good education. Mine had hydraulic lifters. And I'd run them out of oil at extremely high RPMs. Without anyone ever explaining the difference, one would never know how it operates. I strongly suggest everyone take the opportunity to tear down a couple different engines sometime in their lives just to see how they work, why they failed, what keeps them going, etc... really interesting stuff that we all take for granted most of the time. :thumbsup: Also, check the differences between two-strokes and four-strokes. Another education worth pursuing.

 

[J_J]

You know there is wear and tear. How about the valve guides, valve seats, do they every wear or pit.

This is some data from the Kohler 25

Valves and Valve Lifters
Hydraulic Valve Lifter to Crankcase Running
Clearance
0.0241/0.0501 mm (0.0009/0.0020 in.)

Intake Valve Stem-to-Valve Guide Running
Clearance 0.038/0.076 mm (0.0015/0.0030 in.)

Exhaust Valve Stem-to-Valve Guide Running
Clearance 0.050/0.088 mm (0.0020/0.0035 in.)

Intake Valve Guide I.D.
New
Max. Wear Limit
7.038/7.058 mm (0.2771/0.2779 in.)7.134 mm (0.2809 in.)

Exhaust Valve Guide I.D.
New
Max. Wear Limit
7.038/7.058 mm (0.2771/0.2779 in.)7.159 mm (0.2819 in.)
Valve Guide Reamer Size Standard 0.25 mm O.S.
7.048 mm (0.2775 in.)
7.298 mm (0.2873 in.)
Intake Valve Minimum Lift 8.07 mm (0.3177 in.)
Exhaust Valve Minimum Lift 8.07 mm (0.3177 in.)
Nominal Valve Seat Angle 45ｰ

 

[ponytug]

Great to have the numbers. Once I start looking at wear in some of those things, I'm replacing the whole set. I guess I'm just lazy; I'd rather go through the exercise of tearing the engine down once, and move on... But everyone is different.

All the best,

Peter

 

[Gravy]

My Robin 25hp is weird about valve clearances. I've been an automotive mechanic since the late 70's, and on nearly every engine that required valve adjustments, the exhaust valves get tight and the intakes get loose between adjustments. The Robin does the opposite. The exhaust valves stay about the same or get a trifle looser, but the intakes tighten up to the point of not quite closing at all, which makes the engine run really lousy at idle.

At 1100 hours, I've just done my fourth valve adjustment. Once again, I'm surprised that the engine will actually stay running at idle. I guess I'm a slow learner