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Discussion Starter #1
Good Evening,

I have a 1970 Yamaha DS6 with about 8600 miles.

In the not too distant future, although the engine seems to run well, I'd like to check rings and piston clearance. Does anyone know if I can simply remove the gas tank, exhaust and intake/carbs, remove the head bolts and then slide each cylinder up.

I guess what I'm asking is there enough room to accomplish this or is the frame tube under the gas tank in the way, or do I need to remove the engine from the frame. I have the "shop manual" and at first reading, looks kind of involved to pull the motor, so I'd like to avoid that if possible.

Marty
 

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It will depend on the length of the cylinder and the mounting bolts or studs. Most bikes require the engine to be removed before lifting the cylinders.
 

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Good Evening,

I have a 1970 Yamaha DS6 with about 8600 miles.

In the not too distant future, although the engine seems to run well, I'd like to check rings and piston clearance. Does anyone know if I can simply remove the gas tank, exhaust and intake/carbs, remove the head bolts and then slide each cylinder up.

I guess what I'm asking is there enough room to accomplish this or is the frame tube under the gas tank in the way, or do I need to remove the engine from the frame. I have the "shop manual" and at first reading, looks kind of involved to pull the motor, so I'd like to avoid that if possible.

Marty
Hello Marty!!! Being as how the engine seems to run well, I would advise you not to tear down the top end just yet. There are a few less traumatic tests that can be done to test the top ends sturdiness...

Test 1: Use a compression tester to read the piston/cylinder's ability to create compression.

Test 2: Use a Cylinder Leak Down gauge to test the cylinders ability to HOLD compression.

Those two tests (done properly) will alert you to any need to tear down the top end. Checking the ring and piston gap clearances is usually only done when a rebuild is done. Testing those items on a broke-in engine will just confuse matters and waste your time.

As for whether you need to remove the motor or not? IDK, I'm not familiar with that bike model... But I would strongly urge you to read my post first.:)
 

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Discussion Starter #4
Thanks Much Gentlemen

Getting old now, but in the day with my dirt bikes, I just popped the cylinder, then piston off and measured ring end gap and piston/cylinder clearance and it really wasn't such a big deal.

Yes, the bike runs well, but I was looking for something useful to do this fall/winter and tearing it down sounded reasonable with a bike, purchased about a year ago, with its history unknown to me in its 8700 miles.

A compression test sounds like a fine idea, although I've never done it on a two stroke. A leak down test also sounds interesting and I will do some research on that as well. Thanks for your thoughts.

Marty
 

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Leak down

For the leak down test, you can use:
An outboard motor fuel primer bulb, a gauge, an on/off tap, a hollow plug and some tubing. Probably a diagram somewhere. I have one, but am not sure where it is. Just going by memory.

Unkle Crusty*
 
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