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Discussion Starter #1
Hey guys, do you need to remove the engine to replace a head gasket on the Scrambler 1000? The service manual mentions that the cylinder head is accessible by removing the upper right-hand frame support.

I'm away from my ATV right now so I can't check to look for a couple of weeks.

Thanks!

ACCESSIBLE ENGINE COMPONENTS
Components serviceable with engine installed:
• Flywheel
• Alternator (Stator)
• Starter Motor / Solenoid
• Cylinder Head / Valves
• Camshaft / Camshaft Carrier
• Rocker Arms
• Water Pump

TOP-END SERVICE (ENGINE IN CHASSIS)
The top-end of the engine can be serviced while the
engine is mounted in the chassis. A removable upper
right-hand frame support allows access to the valve
cover and cylinder head.
 

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Discussion Starter #3
I ran into a problem during the rebuild. I ended up getting to the head gasket with everything still in the frame. Not bad at all. But I CANNOT get the timing right now that I am putting everything back together. I have the TDC flywheel mark lined up and the camshaft/sprocket are vertical with the two sprocket marks flush with the cylinder head. (According to the service manual, this represents TDC for Cylinder #1). After I put everything back together and rotate the crankshaft, the pistons hit the exhaust valves.

Any ideas on why this is?
 

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My first thought is the camshaft is 180* out - second thought is the piston is not at TDC

Use a soda straw inserted through the spark plug hole to verify the piston TDC position and check to see that the flywheel mark is aligned with the engine case seam - with that done, verify the cam sprocket pin it on top of the cam base circle
137963
 

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When installing the camshaft and carrier you have to get the crank at TDC for the mag side and then rotate the camshaft in the direction of travel so the pin is at the 10:00 position to get the cam lobes turned down before the carrier is tightened. Then rotate the cam clockwise to the straight up position to install the sprocket and chain with the marks level with the head. Then install the tensioner.
Let me see if I can attach the diagram.
scan12446252.jpg

scan124514348.jpg
 

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Discussion Starter #6
Thanks for the input guys! I have the head off right now so I will verify that my flywheel mark is truly at TDC. I think the 10:00 position will be helpful. I did not do that the first time.

I'll let you know how it goes!
 

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Discussion Starter #7
I'm not crazy am I? My crankshaft timing mark looks like it is set to TDC for piston #2. Isn't it supposed to be for the MAG piston (piston #1)?

IMG_20200402_185043.jpg
IMG_20200402_184318.jpg
 

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It may or may not actually have TDC stamped on it but roll around till you get the front, mag piston up and then look for a mark.
 

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Discussion Starter #10
The only "mark" I see when MAG cylinder is at TDC is this gap in between the flywheel marks. (See attached picture - The white mark on the flywheel is just from my camera flash)

Either way, I made my own mark ? and this is definitely going to solve my problem with hitting the exhaust valves.
IMG_20200402_195646.jpg
 

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There ya go! There's always more than one way to skin a cat. (y)
Hmmm... I was just looking back at the pics latebird and I posted from the service manuals. They both show TDC being with the second tooth down from that gap lined up on the parting surfaces of the crankcases. Scroll back up and check it out.
 

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Discussion Starter #12
It looks like Polaris used a new Flywheel part number in 2017. The old part number (4014005) is still shown in the 2018 service manual. The new part number (4015703) does not have the TDC marking and looks very different from the 4014005. The only mark on the new flywheel is the one from my pictures above and it does not line up with anything when the MAG cylinder is at TDC.

Any ideas on how to properly set the time without a mark? I would hate to guess using the plastic straw method and be off by a tooth.


4015703 (2017 & Newer).jpg


4014005 (Pre 2017).jpg
 

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Discussion Starter #14
Ok guys, final post. I found the mark for TDC. When the MAG piston is at TDC the flywheel mark is vertical. I didn't see it because I didn't remove my gas tank but there is a red paint pen mark at the vertical position.

Polaris needs to update their service manual to show this change to the flywheel. It cost me 2 exhaust valves and left a mark on my piston from rotating it by hand when I followed their method.


IMG_20200403_191534.jpg
.
 

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Discussion Starter #16
I bought it used and the coolant was dropping very slowly. I had white smoke coming out of my exhaust so I expected a head gasket. The smoke went away after cold starts but if you really gave it gas it would shoot a little white smoke even after warming up.

The head and block were both flat (checked all directions using feeler gauges a machinist flat edge) and the head gasket didn't look bad either. So I'm going to re-assemble this weekend and see how it turns out!
 

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The flywheels are different and not designated as interchangeable - you should use the flywheel that matches the stator you have. Manuals are fraught with errors. It's the job of the technician to know how to check and verify assembly. The plastic straw method of finding TDC is more accurate than the flywheel marks and builders of high performance engines use degree wheels and dial indicators to set cam and spark timing timing factory marks be damned.

I guess I don't understand - why are you replacing one flywheel for another? A secret performance upgrade?

The flywheels are completely different. Part # 4015703 is $330 and 4014005 is $485. I don't have them on hand to compare, but from the pics one looks to be a larger diameter than the other. The 4014005 is a Shinlin while the 4015701 is not identified, but may be Ducati.

For my own sanity and future reference, I would like to know if they are comparable and interchangeable.
 

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Discussion Starter #18
I'm not replacing the flywheel. I was just saying that the service manual for my 2018 atv shows the wrong flywheel. 2017 and newer use a different flywheel. If you follow the service manual to set your timing, your timing will be way off.
 

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OK - I follow you now - I got lost because I don't use the manual to set timing - I just rebuilt a Triumph Speedmaster 865 with a 270 degree crankshaft (#2 piston reaches TDC 110 degrees after #1) - it was a challenge as the book does not specify which piston is to be at TDC. The flywheel is on the right, the cam timing marks are on the left and the camshafts rotate the opposite direction of the crankshaft. I got it right on the first try, but as I bolted thing up, it didn't look right. I couldn't help but wonder what possessed the engineer to design it with that amount of parts and complexity. I guess it's 'engineer wars', each one tries to make the design more unique than their predecessors and in the process they forget about those who have to service it when it fails. In today's atmosphere everything is designed to last a 'lifetime' and then be disposed of. The lifetime is not that of the owner, but of the lifetime of the device.
 
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