Maybe the crank seals are bad, allowing it to suck air instead of fuel. Also look for an air leak at the carb gasket and crankcase joint. It may have had a leak in the crankcase all along.

This I feared. The two carb gaskets are new and the mating surfaces are in good shape. The four crankcase bolts are tight. So...

Is there a way of testing the crank seals? How about using grease to temporarilly seal the leaks? Or would it get sucked in instantaneously?

Are there any other posible leak points other than the two crank seals, crankcase half seal or a small block porosity or crack? Would a worn throtlte shaft cause the same symptons? It has a small amount of play.

Never having done one, spliting the block without a procedure is really asking for trouble . Where do I find procedures for a 1988 S21BSN F motor? All I have seen online refers to way older D series or F100-300 motors. The literature seem to end in 1984 and does not include the metal Walbro carbs.

If I could only find that web link...

Radar

Don't freak out yet. There are a lot of possibles here. If you do have to change the seals, there is very little disassembly required. You have to take the engine off the deck for the lower, and you take the flywheel off for the upper. The chance of an air leak in the crankcase is somewhat low.
To get to the starting point for the adjusting collar for the governor, just click it clockwise until the spring tension holds the throttle wide open with the engine off. From there you adjust as needed.
Have you checked the exhaust ports and muffler for carbon build-up?
Yes, a loose throttle shaft can cause lean running, and since your mower is post-compliance, I don't think you have a mixture screw - maybe an altitude adjustment?

How do you remove the seal without spliting or damaging the aluminum case? If possible it might be a good idea to put new ones on as I undestand that they a relativelly cheap. The lower seal in particular operates in a horrible environment: sand, stones, sticksÂ.

The piece that does not seem to fit the puzzle is that it was running before the CDI died (BO = Before Overhaul) Yes BO it started hard but it ran and ran fast once the initial couple minute warmup period. So something must be different AO (After Overhaul) as a result of my rebuild that makes it not run without choke. This does not nessecarily point to the seals even though they may not be in the gratest shape. Just maybe. Could be carb or governor related. Or missassembly due to lack of clear pictures, experience or working with the machine on the ground and me in my wheelchair. No longer with 20/20 vision!

So what is the killer culprit? Being a novice on LBs, I looked at the 4 crancase half bolts and immediatelly thought of evenly torquing them tight. I contemplated it and evetually could no longer resist. I first checked to verify they where tight. Nothing turned, no damage done. No here is where I may have screwed up. The serated lock washers make the bolt hard to turn so just seeming tight does not necessarilly mean they are. Locktite may have resulted in more evenly torqued bolts had LB spent the extra nickel per block. On a head gasket practice used to be that you back off one headbolt at a time and evenly retorque. Way back when it was recommended. So that is what I did to just a fraction of a turn tighter than where I started. Evenly of course. I thus cannot rule out the crankcase seal even though the halves probably never separated. If a gasket is used in particular it might. Now if they are bonded at the factory with a semi pliable adhesive such a Yamabond, no way. Great stuff if you never tried it. Holds up to vibrations on Yamaha bikes and Outboards where two highly machined aluminum surfaces must be mated leakproof such as on gearboxes and crankcases. Great Stuff! In a pinch has many other uses. Just bring lots of greenbacks when you go to the Yamaha dealer for the 6-8 Oz tube. Properlly closed lasted me ten years. Online...?

What you going to do,
Novice

SaxMan1,

You commented: "To get to the starting point for the adjusting collar for the governor, just click it clockwise until the spring tension holds the throttle wide open with the engine off."

? At what throttle setting? I recall vaguely that it effects the spring tension of the governor. I could assume ÂOFFÂ and at the ÂSLOWÂ throttle setting.

You might have heard this before. My ME professor's first lessons went something like this (Prof. E N Stevensen?): When you ASSUME, you make an ASS out of U & ME.
So let's not ASSUME.
Thanks for all your help,

Radar

OOPS!
Took a peek at the governor spring & the trottle end was caught under the plastic governor washer. I probably went too far CCW at some point. A little rebending and...

Saxman, About your governor adjustment procedure. It did not make much difference at what throttle setting it was set. More or less just a couple of clicks difference.

Man am I thrilled! It started the second pull & now runs like it never has before. From the starting point RPMs seemed just a little on the low side using my ear. Particularly at the slow throttle setting. So I turned the collar a few clicks CW from the starting point. I also tweeked the altitude conpensator screw in about 1/8-1/4 turn. NOW it starts better & does not seem to need a few minutes warm up period before loading at either throttle setting. I might even start liking LBs.

I belive from day one that the entire time the with hard starting problem may have been due to too wide a gap, a marginal OEM CDI or both. The gap is now set at a tight .010".

You were also dead on about the leak. I think I reused the carb to intake gaskets at one point a long time ago. With two new gaskets & CDI it NOW starts & runs better than the ever. I might even splurge for a new governor spring since I am not sure about the correct bends & angles at the throttle end of the mangled spring. I am a little concerned that the end might come off with use!

On the other hand It sees so little use it might take years! My wife only mows 2-3 times a season whether it needs it or not. It is kind of imposseble mowing myself from a wheelchair. Ironic, I can actually say: Man I wish I could mow. My lawn has gone from one of the best on the street, ORGANIC & ALL, to a close runner up for the worst lawn. On the bright side, at least she does mow 15- 20 minutes 2-3 times a year! The rest of the lawn has now reverted back to a pasture state. Thinking of getting a goat If I could only get my wife to feed it the kitchen scrapsÂ.

Of course I could not have done it without your help.
It would take a SaxMan to make a LB sing!
Thanks a million,
Radar

Wow. Glad you got it going.