Gravely Tractor L8 Convertible

Hi all,
Up-date on my Gravely L8 Convertible. Have it all torn down again, jug off, measured ring gap. Top ring .026, middle ring .077, bottom ring .062. Removed the carbon at top of cylinder, and need to order valve spring compressor to lap valves again as found some small carbon build up on seat. Probably good reason for not having good compression even through being lapped the first time? Did reset timing as reading manual numerous time found that setting line to dot at TDC can be misleading as we need to be going on the down stroke and not at the very top. Carburetor is being rebuilt with some new hardware. Do understand that these machines are very forgiving as for tolerances, but if you are used to working with tenths and millionths in calibrations, we maybe a bit too critical?
Your commits are always welcome and are of the most importance to me. Thank you!
Bob

Could you post a picture of it ? that is of the
Gravley .





AZpeapicker

Bob,

I love Yesterday's Tractors. I've been on here for about 20 years and have found it to be extremely helpful. I've also bought parts from them and found them to be
high quality parts.

Having said all of that, I noticed that you are working on a Gravely tractor (mower). I'm not suggesting that you do so, but if you need a forum specifically oriented
toward Gravely, I know of such a forum. I also have an L8 Convertible, so I go there often. If you want a forum that is specifically for Gravely, send me a e-mail
and I'll tell you the URL to get there.

Again, I would never disparage Yesterday's Tractor but a forum specifically for Gravely might be helpful also.

Tom in TN

The ring end gaps seem a bit wide.

Rule of thumb, .004" per inch cylinder diameter on compression rings, oil rings about .015 all bores.

Ring land fit is also critical. There should only be about .003" clearance, but, as you say, they are forgiving engines.

Where are you finding information that says to line the timing marks up 3/8" AFTER TDC? It's 3/8" before TDC on the compression stroke in everything I've ever seen.

Ring gap sounds wide. I don't have a manual handy, but sound like you have a worn cylinder bore. Carbon in these is an issue when they get worn.

Love the Gravely's, I've a half a dozen on the farm, and have used them since the 60s.... Your end gap is waco, use 010 over rings and knurl the piston skirt, so it'
doesn't tip. Clean the ring groves completely and accurately measure the side clearance. Rings seal by the expanding gasses getting behind them and forcing them against
the cylinder. If carbon is present, the only sealing is with the ring tension which is not enough. Excess side clearance can be corrected by machining the ring grove
square and installed a spacer, available from ring suppliers. New pistons, like available for the L are much cheaper then "restoring" the original. Pistons are
forgiving for taper, but not out of roundness. Check carefully. If you don't belong to the Gravely Club, you're missing the boat. It's been around for over 20 years
and it's magazine is excellent. Drop a note if you need help or info. Larry
gravely club

(reply to post at 23:44:51 10/25/20)

Click to expand...

How do I send someone my email address without spreading it everywhere?
Bob

Bret4207,
Reading the manual Piston is at TDC use air to make sure. Back off using belt to 1 inch mark, then come back up to 3/8 inch mark. Magneto in place line up lines with one another with fiber collar engaged and .010 feeler gauge for looseness. Tighten down collar coupling with pressure in forward motion.
I have the head off this time when going through the procedure.
Bob

Larry,
I will join up. Thank you! At the moment things look grim as there sure seems to to too many problems that look serious and expensive, hopefully there will be plenty of useful suggestions and routes to take to get from point A to point B.
Bob/Honor Guard Windham, Maine post 148

Thank you, I will plan to join, and am sure there will be plenty of helpful suggestions.
Bob

(quoted from post at 00:05:01 10/27/20)
Bret4207,
Reading the manual Piston is at TDC use air to make sure. Back off using belt to 1 inch mark, then come back up to 3/8 inch mark. Magneto in place line up lines with one another with fiber collar engaged and .010 feeler gauge for looseness. Tighten down collar coupling with pressure in forward motion.
I have the head off this time when going through the procedure.
Bob

Click to expand...

Okay, with the head off, the only way I've ever done it, as both valves start to close you bring the piston up and STOP 3/8" BEFORE TDC. If you were going to TDC a then bringing the piston down you were timing it AFTER TDC. Wrong. You can go to TDC and back it off against the direction of normal rotation but why bother? It's pretty simple to do. If you have it timed to fire 3/8" after TDC then it's no wonder it runs like crap. If you go to TDC and back off you have to go a couple inches backwards and then forward (up) to take care of gear lash. I've done this dozens of times. I don't know which manual edition you have but the older ones made it clear not to go past TDC- past being beyond TDC in the direction of normal rotation.

(quoted from post at 12:26:32 10/27/20)

(quoted from post at 00:05:01 10/27/20)
Bret4207,
Reading the manual Piston is at TDC use air to make sure. Back off using belt to 1 inch mark, then come back up to 3/8 inch mark. Magneto in place line up lines with one another with fiber collar engaged and .010 feeler gauge for looseness. Tighten down collar coupling with pressure in forward motion.
I have the head off this time when going through the procedure.
Bob

Click to expand...

Okay, with the head off, the only way I've ever done it, as both valves start to close you bring the piston up and STOP 3/8" BEFORE TDC. If you were going to TDC a then bringing the piston down you were timing it AFTER TDC. Wrong. You can go to TDC and back it off against the direction of normal rotation but why bother? It's pretty simple to do. If you have it timed to fire 3/8" after TDC then it's no wonder it runs like crap. If you go to TDC and back off you have to go a couple inches backwards and then forward (up) to take care of gear lash. I've done this dozens of times. I don't know which manual edition you have but the older ones made it clear not to go past TDC- past being beyond TDC in the direction of normal rotation.

Click to expand...

Bret4207
Okay, that is the way I had it, and will make sure it is like that when completed and head back on. Thanks!

(quoted from post at 08:40:52 10/27/20)

(quoted from post at 12:26:32 10/27/20)

(quoted from post at 00:05:01 10/27/20)
Bret4207,
Reading the manual Piston is at TDC use air to make sure. Back off using belt to 1 inch mark, then come back up to 3/8 inch mark. Magneto in place line up lines with one another with fiber collar engaged and .010 feeler gauge for looseness. Tighten down collar coupling with pressure in forward motion.
I have the head off this time when going through the procedure.
Bob

Click to expand...

Okay, with the head off, the only way I've ever done it, as both valves start to close you bring the piston up and STOP 3/8" BEFORE TDC. If you were going to TDC a then bringing the piston down you were timing it AFTER TDC. Wrong. You can go to TDC and back it off against the direction of normal rotation but why bother? It's pretty simple to do. If you have it timed to fire 3/8" after TDC then it's no wonder it runs like crap. If you go to TDC and back off you have to go a couple inches backwards and then forward (up) to take care of gear lash. I've done this dozens of times. I don't know which manual edition you have but the older ones made it clear not to go past TDC- past being beyond TDC in the direction of normal rotation.

Click to expand...

Bret4207
Okay, that is the way I had it, and will make sure it is like that when completed and head back on. Thanks!

Click to expand...

It is possible that the mag has been messed with. I had one that was a nightmare until I went through and fixed whatever it was that was messed up. I think it was the timing mark itself, but I had another brand machine that used a similar setup (a Frazer Rototiller) so I may be confusing them, it's been 25-30 years. Once you set the timing, you should see the spark, a good blue one, as the piston comes to TDC with both vales closed. If it's significantly before or after that the marks are off someplace.

(quoted from post at 15:08:07 10/27/20)

(quoted from post at 08:40:52 10/27/20)

(quoted from post at 12:26:32 10/27/20)

(quoted from post at 00:05:01 10/27/20)
Bret4207,
Reading the manual Piston is at TDC use air to make sure. Back off using belt to 1 inch mark, then come back up to 3/8 inch mark. Magneto in place line up lines with one another with fiber collar engaged and .010 feeler gauge for looseness. Tighten down collar coupling with pressure in forward motion.
I have the head off this time when going through the procedure.
Bob

Click to expand...

Okay, with the head off, the only way I've ever done it, as both valves start to close you bring the piston up and STOP 3/8" BEFORE TDC. If you were going to TDC a then bringing the piston down you were timing it AFTER TDC. Wrong. You can go to TDC and back it off against the direction of normal rotation but why bother? It's pretty simple to do. If you have it timed to fire 3/8" after TDC then it's no wonder it runs like crap. If you go to TDC and back off you have to go a couple inches backwards and then forward (up) to take care of gear lash. I've done this dozens of times. I don't know which manual edition you have but the older ones made it clear not to go past TDC- past being beyond TDC in the direction of normal rotation.

Click to expand...

Bret4207
Okay, that is the way I had it, and will make sure it is like that when completed and head back on. Thanks!

Click to expand...

It is possible that the mag has been messed with. I had one that was a nightmare until I went through and fixed whatever it was that was messed up. I think it was the timing mark itself, but I had another brand machine that used a similar setup (a Frazer Rototiller) so I may be confusing them, it's been 25-30 years. Once you set the timing, you should see the spark, a good blue one, as the piston comes to TDC with both vales closed. If it's significantly before or after that the marks are off someplace.

Click to expand...

Yes, Bret4207 there is reason to believe people have been into this Gravely many times and have given up on it because of not taking care of the fine details. Have noticed plenty of wear and believe even the magneto has been changed from the original so anything is possible. I should have been more through when going through it the first and second time, but wanted to not have to purchase expensive parts. Timing marks yes are messed up.
Bob