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I have one of those motorized bikes. I got it as a gift and it was used. I went to torque the head bolts one day and found out the studs were glued in with that weld stuff(brand withheld), and one had broke loose. I decided to rebuild the engine and got a new engine case, new rings and new cylinder.

My question is this:

Since I bought the cylinder and rings new, should I hone the cylinder. I kind of thought since its from the factory, or where ever (Online) that it probably didn't need it. I DID see cross hatching inside the cylinder. So I went ahead and put it back together, but it seems like I have no compression. Its VERY hard to start.

What do you think I should do?

Can anybody help?

Thanks for your time and effort, skintech

DucatiKiller
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skintech
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    Have you actually done a compression check, or are you just guessing? I'd suggest you might if you haven't. Also, how did you go about breaking the engine in? – Pᴀᴜʟsᴛᴇʀ2 Sep 03 '16 at 20:27
  • I have done a comp test and its at around 90psi (using the home made one I have), pluss its still under break in because I have such a hard time starting it its been ridden like 3 times for about 5 min each. Also I have to turn up the idle just about all the way and give it throttle just to keep it going. – skintech Sep 03 '16 at 20:43
  • Do you have any specifications for what the pressure should be for a regular engine of this type? – Pᴀᴜʟsᴛᴇʀ2 Sep 03 '16 at 20:58
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    My thinking is, 90psi should be more than enough compression to run your motor ... I'm wonder if there is something else going on? – Pᴀᴜʟsᴛᴇʀ2 Sep 03 '16 at 21:04
  • No I dont. Sorry, when I got the bike it was a gift and it was used so I didnt get any manuals or anything. – skintech Sep 03 '16 at 21:04
  • I dont really believe in my home made comp tester, Also, I have to peddle to get the motor turning, But when I tested it, just to see if it had ANY comp, I used a drill to spin the crankshaft and simulate peddling, And as far as I KNOW, the bike motor would be in normal running condition(set-up) if it had the old rings and cylinder on it. It should run, and I can get it running, its just really hard to start it.(Probably because its still being broke in)I would think with new rings and cyl. It would fire right up, buit it doesnt,. – skintech Sep 03 '16 at 21:13
  • so was I supposed to hone the cylinder when it was right from the store,before putting it back togather? – skintech Sep 03 '16 at 21:15
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    Try this ... squirt a small amount of automatic transmission fluid in through the spark plug hole. Rotate the piston back and forth in the bore for several times (10-12 revolutions). Then throw the spark plug back in and see how easy it will start. The tranny fluid will allow you to get some extra compression right off of the bat (wet cylinder vs dry cylinder). You'll get a little bit of white smoke out of it, but it won't hurt anything. You're looking to see if it will start easier. Make sure the spark plug is completely clean/dry upon insertion. – Pᴀᴜʟsᴛᴇʀ2 Sep 03 '16 at 21:18
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    If it does start easier, I think your compression ideas might be on par. If it doesn't, I think you've got other issues. I'd have you do this first so as to not cause you to have to tear it all down again and incur new gaskets to put it all together again if you don't have to. Secondarily, I do believe you should have honed the cylinder before you threw it back together ... I know I would have, followed by a very good cleaning. – Pᴀᴜʟsᴛᴇʀ2 Sep 03 '16 at 21:20

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