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Discussion Starter #1
Hi Everyone,
I'm not the most mechanically inclined person in the world and my knowledge of motorcycles is very limited, but I'm fascinated with 1970's era bikes and so have chosen to learn through youtube and others advice to restore a 1971 Suzuki TC 125. I thought it would be a great bike to get my feet wet with and have started the restoration project, but I've already ran into a stumbling block. My bike is suffering from low compression (90psi) and so decided to pull the cylinder case and do a top end rebuild on it, but... after pulling the top part off reveling the piston head, I can't seem to find any lower bolts to remove the bottom half... can
anyone help guide me how to remove this? Is it just pulling the one phillips bolt shown in the picture because it's kinda stuck (I've sprayed it with WD40 and just waiting for it to loosen).

Thanks,
Jeff


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American Legion Rider
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WELCOME ON BOARD, and...

We are a friendly site here. Well, most of us.

Good luck with that dang Phillips screw. I do hope you are
using a JIS screw driver on that type of screw. A Phillips
screwdriver could get you in trouble.
 

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The cylinder head bolts probably also hold the cylinder to the case and once the cylinder head is removed, there nay be some hidden bolts made visible. It is a very easy job, have fun:)
Sam
 

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There were probably four bolts you removed to get the head off. There should be four studs protruding from the cylinder. At the base of the cylinder is a gasket with goop on it. That goop is keeping the cylinder stuck to the crank case. The studs may also have some corrosion between them and the cylinder. With a soft large whacking stick ( hammer ) whack the cylinder upside the head. Smack it on one side. Maybe put a block of wood against the side so you do not bust a fin. Tap at first. It should pull free fairly easily. The phillips head screw should not prevent the cylinder from moving. It may be a plug. The lower gasket will probably rip apart. Not a serious problem. Put the piston at TDC when you remove the cylinder. When the cylinder is about an inch or so up, put a rag around the con rod.

Report back on the condition of the piston, rings and cylinder bore.

UK
 

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Discussion Starter #6
Hi UK,
I was very surprised that the piston was in pretty good shape. Just needed to clean up the dried oil on the top, but the sides looked clean and without scratches. The rings seemed very loose and I was going to order new ones. I noticed the .5 stamped on the piston head so I have ordered the +.5mm rings to match. Cylinder bore to me seemed in good shape as well. I did notice that when I added a small amount of oil into the spark plug hole (before I removed the head) it was leaking out the exhaust gasket and so have ordered new gaskets for that location and for the lower cylinder mount as well. Here are the pictures, let me know if you see something that I don't... I'm pretty new to this kinda stuff, but Youtube is amazing for learning.
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As I said, the 4 cyl head bolts also held the cylinder to the case:)

Fit the new +5 oversize rings into the cylinder and make sure there is 'END GAP,' look the term up on Google or YouTube.

Note ring locating pins if they are used!

Use some 'wet and dry' very fine grit sandpaper on the inside of the cylinder to remove built up 'glaze,' and gently sand down the bright and shiny spots in the cylinder before reassembly.

A new exhaust gasket should always be used.

Sam
 

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Wot Porky said above.
You can also snap an old ring and use it to clean the piston grooves. With your finger nail, check for any lip at the top of the cylinder. The piston looks good. The cylinder bore could use cleaning as Porky has described. We would often give them a slight scratch with a honing tool. Your local machine shop can do that and offer advice on the bore. But again, wot Porky said will do.

UK
 

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Discussion Starter #9
Your advice is great, thank you! I don't think I would have known about sanding the inside of the cylinder to remove the glaze, great info.
 

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Ace Tuner
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Along with removing the glaze you should work to get a 45 degree angle (sanding "pattern") on the inside of the bore.
It's called a crosshatch. The correct crosshatch pattern will help the new rings break in and also hold oil to lube the piston skirt.
A higher tech way would be to use a ball hone, with oil, attached to a variable speed hand drill (running slow-ish) and working the hone back and forth to achieve the 45 degree pattern. (A 60 degree pattern makes for a slower break in period, either will work).
Either way be sure to scrub the bore with dish soap, running water and a stiff hand brush to remove the sanding/honing grit.
Just be sure to get oil on the bore after scrubbing because it will try to rust faster than you can say ... oops.

S F
 

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Discussion Starter #11
OK Guys, I honed the cylinder wall and the top end rebuild is complete.

Now... the engine starts up, and the foot pedal seems to "Click" through the gears (I can hear at least 2 gears click), but the clutch handle is soft and the clutch won't engage. I replaced the clutch cable and is attached to the rocker arm which seems correct, any idea what might be causing the clutch to no engage? Could it be the clutch rod?

Any help would be appreciated.
Jeff

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Ace Tuner
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Not real familiar with '71 year models but there is, or should be, a ball inside the engine case at the rocker arm deal that works with the rod. Sometimes that ball gets lost if anybody has had that stuff apart.
If the ball is in place and the clutch is correctly assembled then possibly you just need to adjust the rocker arm / lever thing.
You can see the adjuster (slot in shaft) and the lock nut behind it in the pic.
Another possibility is that the arm on the screw adjuster is 'off' by a notch. That may not be possible depending on how much space there is for movement in the area.
Thanks for letting us know how it's going. Please keep us informed.

S F
 

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Discussion Starter #13
Good advice! Before I go tearing into the clutch, I will remove the rocker arm and see how it is manipulating the push rod. I did notice the lock nut you mentioned is very loose.
 

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Discussion Starter #14
Well, I did notice that the rocker arm needs to fit into the spindle that touches the push rod, and I don't think the arm was connected right. I've now made the adjustment and tried riding again with no luck. Then I decided to try the hi/low gear that this particular bike has (4 on dirt and 4 on pavement...see picture). When I put the gear shifter to the front position... nothing happens and the bike won't move. If I hold the clutch in and move the shifter into the back position, then, the bike will jerk forward a bit, and I can ride the bike and all 4 gears are engaged and work fine. I'm not familiar with the hi/low gear and not certain how to fix it... anybody have experience with this kinda thing?

The picture above shows the inside of the case and the inner workings of the shifter (I noticed the nut with the washers is loose and not certain if I should tighten it down or if it needs to be loose to work)

Jeff

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