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Discussion Starter · #1 · (Edited)
I have a new big bore engine, ran for an hour really well, I put it away for a month tried to restart it wouldn't. Finally after 20min of starting it finally ran (perfectly). Next day won't run at all,so put a brand new carb still won't run. Tried a new coil, spark is strong magnets seem to be at the coil when piston is at top dead centre. This engine does not even sound like it wants to fire at all and it doesn't change even using starter fluid any thoughts?
 

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The reeds could be open, or your flywheel has jump the rocket key. Your magnets should be just past the coil at TDC. Have you pulled the plug and checked for a spark?
 

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Discussion Starter · #3 ·
Thanks Outlaw, i know the reeds are good checked them when I changed the carb! So as I was researching this forum I found a thread on having the right distance between the flywheel and coil so as there is not much movement in the coil i just pressed it down and tightened, making sure the coil did not scrape the flywheel and now it just fired up! will check again and report.
 

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Discussion Starter · #4 ·
wow this is confusing it ran for a minute then died. no won't start again, keep in mind it is acting the exact same way with the new carb. could this be a compression issue, engine only has an hour.magnets are just passing tdc.
 

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A brand new engine is a tight engine...Tight engines need a gentle rigerous \break-in procedure to loosen them up the right way...in the beginning youll experience lots of issues,,,Dont trust the carb float is set correctly and you dont have a 43cc jetted carb on a 49cc and vice versa.....

These bikes arent of any stringent quality like japan made stuff so it will take some time,,tools ,,new hardware and loctite to straighten them out...Afterall youre buying a pb assembled by 12-13 year old chinese kids in china....

Pull the sparkplug and see what the plug says.....The flywheel is supposed to be gapped to .020"..new laserprinted cards are only .010"..youll need to double it up to get the correct gapping.......

theres a c-clip on the plunger needle that can be adjusted if needed.....

Id do the petcock mod and upgrade the fuellines/fuelfilter to 1/4" and get a quality NGK plug BM6A gapped to .030"

Good Luck
 

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The engine is Tight and the rings are dragging the wall and not fully seally and creating heat. Run 25:1 gas to oil. Might try to go richer on the main jet or drop the carb piston clip to raise the needle out of the hole, or richer at the low end.
 

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Discussion Starter · #7 ·
Well i have 4 blisters on my fingers from trying to start this bike. I have put a couple of shots of oil in the cylinder to make sure it has not lost any compression. I will try again later, I have already upgraded the fuel line, a separate shut off valve, dual reed valve, better spark plug, it has good spark. Any other thoughts are much appreciated.
 

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Its futile to pull that much ,,,if that thing wont start in 10-15 pulls max then theres a gremlin preventing so............Pull the sparkplug to see if its wet or dry..............My guess would be you need to richen the float adjustment a bit by bending the float forks a lil
 

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Discussion Starter · #9 ·
Well it does start if i put some two stroke oil in the cylinder so i am thinking about pulling the engine and checking the rings and piston. Even though its a new big bore engine with about an hour run time on it. When i pull the spark plug it is wet but that is probably from the 5 minutes of trying to start it haha running out of band aids for my blisters!!!
 

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LOL. good to see you're not giving up so easy.... Thing is with these motors, the more you upgrade it, the more it compress', then the harder it gets to pullstart them. Did you try using some starter fluid to get it to run? and once it fires can you get it to idle?
 

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Sometimes the plug gets too wet and it don't want to fire right. Put a spare dry plug in and try it, check your spark while you have it out.
 

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Discussion Starter · #12 ·
OK thanks EPR & Spacely for your interest, the engine does idle and runs great
but it just won't restart after sitting. When I put oil in the cylinder it will fire but now that is just getting more difficult to start. The plug is wet but that is most likely from trying to get it to start. I have replaced it a few times. I feel that the rings did not seat in the cylinder,(remember this is a new big bore engine) so I have a back up big bore engine i will install, and just buy another big bore kit for this engine. I suspect this because when i turn the engine over it does not sound like there is any compression in the engine but when you add oil it sounds like the rest of my bikes when trying to start . And when i use starting fluid it makes no difference as this always works when you are desperate. It has not started once with the fluid which i fear is washing any oil off the cylinder walls taking away any last bit of compression left in the engine.
 

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French Fries N Cheese
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2-3 pulls on full choke. If it doesent start, put it to half choke, then 2-3 pulls, if no start, put the choke down and 2-3 pulls again. My motor has quite a few mods on it now, and cold starts arent much fun. once warmed though, one pull, hell half a pull will start it. just turns over and starts on it's own... LOL.
 

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Check your head bolts, after you run a new engine and hour or two, you need to check them, not on a stock but 2 pcs head/cyld. The parts exspand when they get hot then the cool. That's happened to me so many times.
 

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Check your head bolts, after you run a new engine and hour or two, you need to check them, not on a stock but 2 pcs head/cyld. The parts exspand when they get hot then the cool. That's happened to me so many times.
funny you say that lol.... my head bolts came loose earlier... pealed the old yamabond gasket, made a new one. Now she needs to settle for a while..
 

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I sounded just like him. The things new and it won't run right,lol. These engine are like a woman w/ PMS, don't know what they will do next,lol.
 

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If your still breaking it in you should be waiting until its cooled down before cycling it back up to operating temperature. This will allow the cylinder to "season" without becoming loose. If its past break in and the plug is wet then try reducing the plug gap a bit. Your coil might be too weak to fire the HC head.

Hugh
SDscooters
 

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That's one of the things that bugg me the most. No one has a hp Cag coil. I don't see how that PBU $80 spark plug wire attached to a stock coil works. If you raise the voltage, you lose amps. It takes like 11amps at 12V to make 1 amp at 110 volts. Oh, you can buy a $350 coil.
 

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That's one of the things that bugg me the most. No one has a hp Cag coil. I don't see how that PBU $80 spark plug wire attached to a stock coil works. If you raise the voltage, you lose amps. It takes like 11amps at 12V to make 1 amp at 110 volts. Oh, you can buy a $350 coil.
 

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Discussion Starter · #20 ·
Hey Everyone, an update on whats going on, I have a great spark on the engine and of course used new plugs as well and no go. So I replaced the engine with a back up engine which has an ada big bore kit and she fired up right away first pull! My fingers were in heaven as my blisters are healing! I have pulled apart the engine and found that there were big score marks on the cylinder wall so its hard to say what happened but it obviously had no chance of seating correctly, I emailed big motor sports and they are going to send me a top end kit to repair my engine, So hopefully it will all work out!

Thanks for everyone's help its great to see!!!

Danny
 
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