1979 Yamahopper Motor Cylinder Head

Hope someone can help me.

I think I overtightened one of the cylinder head studs. How do I get a new one?

Also, When I take off the stud nut, should both the cylinder head and cylinder slide right off? The cylinder head comes off easily, but the cylinder itself seems to be stuck on.

Can anyone help me with these questions?

Thank you,

Re: 1979 Yamahopper Motor Cylinder Head

Jack Rutherford /

You most likely need to remove the exhaust bolts to pull the cylinder off. I assume you did that. So the cylinder has probably "fused" to the case because it has never been removed. Try soaking the base of the cylinder with some penetrating oil like WD-40 and then tapping (yes, gently tapping so you don't break any fins) the cylinder with a rubber mallet and perhaps you can persuade it to come off.

I'm not sure if you are saying you need new cylinder head nuts or studs.

Ok, I guess you need a new stud. treatland carries them for the qt50. (edited)

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

Thank you Jack for replying to me so quickly.

Would you recommend changing the Cylinder, cylinder head, and piston or can they just be removed and cleaned?

If you would suggest changing it all, would you go to a 60cc kit and do I have to change the carburator or anything else if I upgrade to a 60cc kit?

Thanks in advance.

Re: 1979 Yamahopper Motor Cylinder Head

Jack Rutherford /

check your compression and/or inspect piston, cylinder and rings for damage, scoring, excessive wear to determine if you need a new cylinder and/or piston/rings. Does the bike run? Does it run well?

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

I haven’t been able to get it to start yet. I’ve changed the charge coil, cleaned the carburator, and will be changing the left and right crank seals. Just waiting for them to arrive.

I have a new battery and a couple of the signal lights don’t work and neither does the headlight for which I’ve ordered a c70 Honda one with the light bulb adapter thingy.

I sure hope I can get everything working. I’ve been working on it for a month, and I still can’t get it to run.

Re: 1979 Yamahopper Motor Cylinder Head

Jack Rutherford /

measure compression if you haven't and check for spark

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

I'll have to get an air compression tester tool as I don't have one. The spark plug is new, but it might not be the right one. It fits but...

Hey, Jack are you Churnioz26 on Youtube? If so, your videos are EXCELLENT. I'm so grateful for them. I wouldn't be able to do the things I have been without them. So thanks a bunch!

Do you ever do any on changing the cables and how to fit the dang things back through the whole in the frame of the bike that descends from the handle bar? I would love to see one of those. What does the choke cable look like inside the carburator? Would you have a picture of what is SHOULD look like? My spring is so compressed that I don't think the choke is even working. The cable doesn't allow for the spring to be relaxed at all.

Thanks again.

Re: 1979 Yamahopper Motor Cylinder Head

> Anne Brown Wrote:

> -------------------------------------------------------

>changing the cables and how to fit the dang things

> back through the whole in the frame of the bike that descends from the

> handle bar?

Trick : When removing a cable that runs through the frame , tie a long enough string to the cable end before you pull the old cable out . Long enough so the string hangs out both ends of the frame when strung through . Once the old cable is out , untie the string . Attach it to the new cable and pull it through ... ;)

Re: 1979 Yamahopper Motor Cylinder Head

Wire coat hanger has worked for me too.

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

Thank you P D and live evil for your help. I appreciate ALL the help I can get.

Re: 1979 Yamahopper Motor Cylinder Head

Jack Rutherford /

Since you don't have a compression tester yet. Try this.

Have a friend help you. Take the spark plug out and hold your thumb over the spark plug hole. Have your friend kick start the bike. If the compression is strong enough, it should push your thumb off the hole fairly easily. If it does, you should have enough compression to start the bike.

To test for spark - take the spark plug out of the cylinder, keep it in the boot, hold the plug tip against the cylinder head, turn the key on, and work the kick start lever. Turn out the light or dim the lights and watch the spark at the tip. It should be consistent (keep sparking throughout the time that the engine turns) and blue. It's often easier to do this with the help of a friend as well.

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

I don’t have anyone to help me test for compression. I tried to do it myself. There seems to be compression or air that comes out if I put my thumb over it, but I don’t know if it is strong enough. I changed the crank seal on the left side and tried starting the bike and it still won’t start. I also changed the headlight for the cw50 one, and it still won’t go on. What the f..... I am SOOOOOOOOOOOOOOOO frickin frustrated. Why the dang won’t it start?

Please someone help me with the light situation and getting this f..... thing started. I have spent weeks on this with absolutely no improvement. If there is not enough compression, what do I have to change?

Thanks

Re: 1979 Yamahopper Motor Cylinder Head

Anne Brown /

The headlight assembly is a C70....not cw50.

Re: 1979 Yamahopper Motor Cylinder Head

Maybe one of the auto parts stores has a loan a tool program .

See about using a compression tester , so you have a good idea of what you're working with .

If the motor has poor compression and you're sure there are no leaks at the head gasket , you should pull the head and cylinder to inspect the piston , rings and cylinder wall .

Re: 1979 Yamahopper Motor Cylinder Head

Jack Rutherford /

The C70 headlight will work. You just need to drill 2 small holes through the qt50 bezel and the get 2 small screws, nuts and washers to marry the headlight and bezel together.

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