HELP I'm about to give motor bicycling up..

Discussion in 'Motorized Bicycle Trouble Shooting' started by alienboy366, Nov 16, 2011.

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  1. alienboy366

    alienboy366 New Member

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    I AM FURIOUS. This all started with me wanting to simply upgrade my cns carb to a RT carb from thatsdax. I made a new intake manifold that was offset and shorter than my previous intake. I hook up the carb and begins a high idle. Check for air leaks, none, sealed up joints anyways. Duane at thatsdax suggested a bigger jet size thinking it was too lean at idle. swapped out the 70 for a 75 jet and rode it down the street to warm it up. KAPOW engine starts making knocking sound like Broken - YouTube. It happens if i turn over the motor without the motor on as well. Took of head, plug was darkish slightly wet. saw imprint of one of the piston rings on the top of the cylinder wall but dunno if that has any significance. Now i have a loud as ****, slow, & weak bike. Duane hasn't been able to help much some people have suggested testing for leaks, none.. so WHAT NOW!?
     
  2. linnix13

    linnix13 New Member

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    your engines cooked. sounds like the low end is shot or/and your rings are broken and scoring it up. it needs a complete overhaul.

    probably from an intake leak, to lean and it burned up. just buy a new replacement motor. thats the cheapest
     
    #2 linnix13, Nov 16, 2011
    Last edited: Nov 16, 2011
  3. Tohri

    Tohri New Member

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    You blew a head gasket more than likely.

    If it were me? I'd tear the head and cylinder off the bike, check my head studs and make sure they're not stripped, Lap the Cylinder deck and head mating surfaces totally flat, and make sure you didn't break anything in the piston/Crankshaft area.

    If that turns up nothing: Re assemble engine and reseal. Check your head gasket for damage, torque the whole thing down and check your compression (roughly).

    If it were mine, I'd pull the motor off and give it a full teardown and inspection. And speaking frankly, if you want to own one of these lil devils, you should get used to tearing them apart on a regular basis.
     
  4. Nashville Kat

    Nashville Kat Active Member

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    Sounds like you broke a ring- is the motor new- they can catch a port- you'll have to take the cylinder jug off to see- if a ring broke it has likely scoured the cylindar walls-
    and you'd have to replace the jug, the rings and possibly the piston- sounds worse than it is, but first time sorta a challenge
    don't know how an imprint gets on the head

    heres a thread I asked questions in when I replaced my cylinder head
    http://motorbicycling.com/f52/can-cylinder-body-replaced-without-special-29691.html

    Don't give up! The motors are really pretty simple, cleaner than four stroke and can be fairly reliable when you get it going.

    My thinking is to keep it simple- I think you may have trouble with any longish offset intake- seems to be a lot of nehgative there- Although you've already spent a lot of money you may get better results with a short billet intake - about $18 and I think a regular carb-

    It appears that the 66 "Speed carb" introduced a couple of years back MAY BE RESURFACING with a new name from the chinese- I queried Boygofast about a carb he's selling for $20 delivered that looks like a Speed- his ad says speed in it- and asked him if it was labled "speed" at the top - his answer was inconclusive- other letters at top of body- so I'm still wondering-the body looks like my "speed carb" and not an older kit carb.
    http://www.ebay.com/itm/gas-bicycle...=190490814316&ps=63&clkid=4087498979654954736
    at any rate I have a 66 speed carb and billet intake on my 66 and can't ask for better performance with no hassle

    You may or may not have clearance for a short billet and/or a normal carb- there's also a short billet for CNS- Your air cleaner is MASSIVE- you have clearnce problems- but I think the closer to the motor generally the better the carburetion- The little round kit air cleaneres doesn't look that cool , but serves it's purpose- I generally drill a few small holes in the back to let in more air.

    these little motors just don't suck that hard when you get off the throttle- search other posts here about lonfg offest intakes and I think there's problems.

    If it's making noises tho- probably a blown ring- but maybe not if it still runs- I'd take off the head and pull the jug up- you may need some gaskets or have some extras if you can reuse the old ones top and bottom- you had the top off- how'd the gasket look?

    take a file if you have one- a nice flat one- and file the head surfaces smooth to help the gasket do it's job.

    good luck- and don't give up.
     
    #4 Nashville Kat, Nov 17, 2011
    Last edited: Nov 17, 2011
  5. happycheapskate

    happycheapskate New Member

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    Don't give up yet. If you like what you have, take it apart and see what went wrong. My first engine "blew up." It made a squeaking noise for a bit, then a ring jammed in a port. I hunted around and got a replacement engine, since the bike was already built up. You might be able to just buy replacement parts new or from members.

    In the future, go with the modular rack style kits like a Dax chain drive and a japanese pull-start motor. The engines are serviceable by mower shops and some ATV shops or marine (boat) shops. The kit is simple and self-serviceable. Since they are not permanently attached, you can use a spare engine or move the kit to another bike easily compared to the finicky china girls.
     
  6. Nashville Kat

    Nashville Kat Active Member

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    If you go to boygofast on ebay- a jug is about $25 shipped, a piston and rings purchased separately orr together ma be another 15-18- After doing it once you'll see it's not that complicated and doesn't take long. good luck
     
  7. Nashville Kat

    Nashville Kat Active Member

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