Help getting a motor to TDC - John Deere Gator Forums
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post #1 of 12 Old 01-03-2019, 04:38 PM Thread Starter
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Help getting a motor to TDC

I have the valve covers off and would like to adjust the valves to 0.006" but I can't get the pistons to TDC. Bumping the starter is not a solution. Taking the from of the drive system was a thought but I am stuck at the front drive shaft roll pin. Another thought was to remove the starter and use the flywheel teeth to bring it to TDC. Does JD have a special tool to turn the motor? I am stuck and frankly frustrated that JD chose to "stick it to" the average guy when it comes to simple procedures like this.

John in OK
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post #2 of 12 Old 01-03-2019, 05:20 PM
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I have zero idea as to which motor you're working on, but can you see the flywheel when taking the starter off ?? if so, can't you use some sort of pry bar to advance it to TDC ?? Maybe put it in gear and turn a drive wheel until it's where you want it ??? I'm just thinking out loud !! On a V-8, we'd use a socket and breaker bar on the nut screwed into the vibration damper. It has to be not that difficult unless I'm way off base !! Let us know when you score a solution. Craig
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post #3 of 12 Old 01-03-2019, 06:15 PM
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How about accessing the drive clutches and rotate the primary (drive) clutch.
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post #4 of 12 Old 01-03-2019, 09:24 PM
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To adjust valves it is not important to be exactly at TDC, only that the lifter is on the base circle of the cam. Use the EO/IC method.

Starting with cylinder No. 1 with the valve cover off, rotate the engine until the exhaust lifter begins to move upward. This is the point at which the exhaust valve is opening (EO), meaning the piston is through with the power stroke, and it’s about to begin the exhaust stroke. At this point, the intake valve is closed and the lifter is on the base circle of the camshaft and can be adjusted.

To adjust the exhaust lash, turn the engine over until the exhaust valve has completed its lift cycle and the intake valve begins to close (IC). Now, the exhaust lifter is on the base circle because the piston is finishing the intake stroke and about to begin compression. Set the lash on the exhaust valve and you’re done.

This needs to be done for each cylinder.

Can use the starter to bump the motor to the desired position since the exact position is not needed.

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Last edited by 200mph; 01-04-2019 at 06:37 AM.
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post #5 of 12 Old 01-04-2019, 10:01 AM Thread Starter
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Thank you all for your help.

As it turns out, the engine in the RSX850I is from an Italian maker. There is zero access to the crankshaft on either end. The only way to turn the engine slowing is to remove the front cover of the engine coving the centrifugal clutch system. After frustration from two local JD dealers, I called JD corporate and spoke to Amy. Amy sent me to a dealer in WI that helped me and they don't even see a lot of these machines! Sorry the picture is upside-down. The cover in the pic needs to be removed, but that won't happen without removing the front drive shaft. WHO COMES UP WITH THIS SHEET?!

Now I am struggling with the "spring pin" removal on the front drive shaft yoke. After I get the "spring pin" out, I am sure that the yoke will be seized to the output shaft and need much persuasion to come off. b 200mph, thank you for your detailed break-down of the EO/IC method. I will use that plan, but I still need to get access to the primary clutch system to turn the crank.

Also, I thought there may be a special tool with the starter sprocket on a 3/8" drive socket... No deal. I would make one if I could find a bad starter to tear apart.

John in OK
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post #6 of 12 Old 01-04-2019, 12:23 PM
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Help getting a motor to TDC

Quote:
As it turns out, the engine in the RSX850I is from an Italian maker......John in OK

Yes the engine is made by Piaggio, perhaps a foreign motorcycle shop in your area would be able to help you?

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Last edited by Bradhill; 01-04-2019 at 12:26 PM.
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post #7 of 12 Old 01-04-2019, 02:29 PM
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Quote:
Originally Posted by polymerjohn View Post
Thank you all for your help.

I will use that plan, but I still need to get access to the primary clutch system to turn the crank.
Perhaps I missed the reason why in one of the posts... Why can't the starter be used to bump the motor over to adjust the valves?

A remote starter switch can make this job easier to do. It's also helpful to removing the spark plugs and disabling the ignition are added safety steps and can reduce the power required to turn the motor over.

Example of remote starter switch for reference: https://www.walmart.com/ip/Equus-Pro...Clips/48206851

Since you appear to be the first, perhaps you can document some of the steps to help those who may reference this thread in 5 years.

Good luck!!!

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post #8 of 12 Old 01-11-2019, 07:23 PM Thread Starter
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I have made some progress. I have (5) pics I will post. I will try to get them in chronological order. It all started with the realization that I need move an entire cross-member of the frame out of the way to simply get the valve cover off the vertical cylinder. Fast forward to got that done and now I can't move the engine to TDC. The starter kicks over 4 to 5 time with each turn of the key and bumping it simply did not work. Tried the start/flywheel approach - no deal. Now the clutch housing cover needs to come off. That's where start...
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post #9 of 12 Old 01-12-2019, 05:49 AM
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It's enough to make you switch to snowmobiles where you just lift the hood and the clutch is easily accessible.
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post #10 of 12 Old 01-12-2019, 08:05 AM
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I must be missing something. There is absolutely no reason the motor needs to be at TDC to adjust the valves!!!

Follow the EO/IC method and the exact position is not needed. This is a very common method when checking valve lash on race motors (drag racing) with radical valve timing and lifts, not to mention minimal valve/piston clearance. It's common to have two momentary switches (one on each side) so the motor could the motor can be bumped around while watching valve motion. Again it is NOT important to be at a specific crank rotation, such as TDC. The lifters only need to be on the base circle of the cam.

I do want to thank you for creating such detailed photos to support your work. I'm certain others will find these helpful in years to come. Great Job!!!


You may want to rethink, not adjusting the valves unless otherwise recommended in the workshop manual. Mechanical lifters normally require some valve lash and minimal clearance can cause the valves not the seat completely once the engine warms and thermal expansion takes place. Then again, I'm not certain what type of lifters are used in the motor. Therefore minimal or zero clearance may be ok.

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Last edited by 200mph; 01-12-2019 at 08:15 AM.
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post #11 of 12 Old 01-12-2019, 06:19 PM Thread Starter
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200,

There is absolutely NO WAY to turn the engine over to get the crank/valves to move for the EO/IC method or any method. I tried many times with the key to bump the starter and it was simply impossible to be sure about what is happening to the valve train especially with one set of eyes. Strangely, the starter turns it 4 to 5 times automatically with just a simple quick key to start motion. I removed the starter and the flywheel is too deep in a small hole to be of use moving the crank. If you get after one of these machines you will see how frustratingly they are put together. Even the technicians at (3) JD establishments had very little useful information about the RSX 850i.

I elected to leave the valves alone for three reasons and I did spend a good amount of time debating with myself about messing with the valve train. 1.) The engine ran well for 1200 hours. 2.) It was PM and not really a complaint about how the engine was running. 3.) It must have left the factory with "tight" valve clearances. So if it's ok with those that built the engine, then who am I to mess with it. The valves certainly didn't get tighter after 1200 hours. With the alignment marks lined up there was clearance on both intake and exhaust valves.

Here is my final "what the fick?", (maybe). I have drained the oil from the crankcase and want to put oil back into the engine. The "geniuses" at JD/Piaggio have a remote plastic oil tank with a cap/dip-stick. Put the oil into the remote tank, NOT THE ENGINE!? I am entirely uncomfortable with this type of setup. The tank is polymer. I am a polymer chemist and I understand most types of polymers. This is a very stupid design! Just plain stupid! Honestly, after my work on this machine I will NEVER purchase a JD product. This kind of engineering is what puts equipment in junk yards long before they should be.

Thank you for your help, Thank you much.

John Delaney
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post #12 of 12 Old 01-12-2019, 06:28 PM
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You have my sympathy with that engine!

Hope it continues to perform satisfactory as it sounds like they make it way to difficult to repair.

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