Ct70 engine seized?

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Ct70 engine seized?

This is a discussion on Ct70 engine seized? within the Z50, CT70 and JDM Monkeybikes forums, part of the General Talk category; I just bought a 1980 Ct70, the guy that I purchased it from told me that it had sat for 5 years because he had ...

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    Ct70 engine seized?

    I just bought a 1980 Ct70, the guy that I purchased it from told me that it had sat for 5 years because he had lost the key but was running well when the key was lost he finally found a key and tried to start it and couldn't and decided to sell it, I bought it thinking that I could clean the carburetor and get it going, upon further inspection I think the engine is seized it will kick over but it is pretty stuff to do and I don't think when I do kick it the piston is moving, what would cause this and I'm not really sure where to do next any help would be greatly appreciated!

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    T Bolt USA's Avatar

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    Likely rust in the cylinder
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    It could just be your clutch slipping. It's a common problem. Try kicking it slower, just spin the lever with your foot, rather than kinda jumping on it.
    If you put regular car oil in your motor, it will cause your clutch to slip...contaminate the friction discs to the point of needing replacement. You HAVE to use the correct 4 stroke motorcycle oil, or a acceptable substitute.
    If you're trying to get your bike running for the first time, try putting it into 2nd or 3rd gear and pushing it around in circles. That'll get your motor spinning, sparking, and sucking fuel if it's going to.
    Clean and set the points, then check for spark. Points are a common problem too. They have to be CLEAN and gapped to about .015-.016 inches.
    Last edited by kirrbby; 06-16-2017 at 04:08 PM.
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    5 years in storage is certainly long enough for the cylinder to have rusted too. You could start by putting a little WD-40, or something right into the spark plug hole. It could be just enough to allow your piston to start moving.

    Either way, even if it's seized, it's repairable. Not a huge deal. It's unlikely that it's badly rusted.

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    Ok last thing :--)
    Try kicking it over with the spark plug out. If it still isn't turning the engine over, the piston is likely seized.

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    So I have put some wd 40 in the cylinder and let it sit for a while and there has been really no change, as far as pushing the kick starter down by hand it's way too stiff. I also tried pushing around while in gear and it's locked up pretty good. I pulled the fuel lines to see what they looked like and there was some sort of goo that hard hardened in there and it was solid so I'm thinking it may have sat longer than he said. Is it possibly that it's not rust that has locked it up and some other goo that could be in there?

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    davmo's Avatar

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    could be some goo. An old method of un-seizing if not significantly rusted is to put ATF transmission fluid in the cylinder through the spark hole, let it sit several days, and hit it with a heat gun or a heat source that doesn't use an open flame several times during the wait. A hot plate several inches below the cylinder will work well. Empty the fluid out of the cylinder, put the bike in fourth gear and push forward. If it is just goo it will come loose this way. If it doesn't work,it is probably rusted enough to need a bore job and rings. The other thing to note is whether the flywheel turns. It is directly attached to the crank and will tell you if the piston is moving. You can sometimes use a strap wrench to turn it, breaking it free.
    Last edited by davmo; 06-16-2017 at 08:18 PM.
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    Is the flywheel on the left side of the motor?

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    Quote Originally Posted by Bearlakemonster View Post
    Is the flywheel on the left side of the motor?
    Yes....
    tmas

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    So if I am able to get it freed up will it need a rebuild? If so or if I can't get it to free up what is the best "kit" for a rebuild, also will I just need to do the top end or will I have to mess with the crank as well?

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    Theres lots of replacement cylinders and heads you can buy. Its cheap

    I would not wast time soaking the cylinder to free it up. Pull the exhaust off first then remove the top end.

    http://planetminis.com/forums/#/topics/233057

    You may want to inspect your valves & seats or cross your fingers and hope there ok. Its also good to clean your carb and check your points.

    How is your fuel tank? You may want to clean it out and add new fuel lines and filters.

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    I have seen some kits that come with a new head would recommend that I go that route? What kits are good and who should I stay away from if I going to do the top end I was thinking that I would go with the 88cc big bore.

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    Also if I go with the 88cc do I need to get a bigger carb?

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    If you decide to go with an 88 kit, just buy the Tbparts that includes the race head as it will also come with a new carburetor. It's much cheaper to buy it all at once as a kit.

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    Quote Originally Posted by Bearlakemonster View Post
    Also if I go with the 88cc do I need to get a bigger carb?
    You can use the kit below and rejet your stock carb.
    tmas

    https://tboltusa.com/store/tbparts-v...81-p-1439.html

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