Al.Fisherman
New Member
I went on a simple 7 mile ride to go and from right.........i my motor went dead it had gas my carb is set stock and i changed the spark plug ..........now it wont start at all it just makes this horrible screeching noise like bad breaks on a car
Remove the spark plug, with the clutch out, rotate the rear wheel and see if it's still makes the same sound.
Ruby478
Member
i changed the spark plug cause it was completely burned white , i took it for another ride earlier it'll turn over but when i engaged the clutch to start it, it wouldnt start i checked my cdi thats fine, im so afraid cause i think blew my piston it wont even idle or anything it just screeches and dies like it wants to start but it just cant; and keep in mind it was working fine hours before . im thinking of just ordering a new 66cc motor from pistonbikes.com
GearNut
Active Member
A white colored spark plug is a sure sign of a lean mixture. The state of tune on the carburetor is not supplying enough fuel to the intake air charge. A lean mixture will destroy an engine given enough time. Tear down the top end and take a look at the cylinder and piston. Norm has shared a guide with us on how to do that if you want or need guidance.
http://motorbicycling.com/f39/bicycle-engine-tear-down-391.html
Depending on what you find, it may be much cheaper for you to just replace the top end rather than get a whole new kit.
http://motorbicycling.com/f39/bicycle-engine-tear-down-391.html
Depending on what you find, it may be much cheaper for you to just replace the top end rather than get a whole new kit.
Al.Fisherman
New Member
Hopefully it's just a blown head gasket.. pull the head.
Al.Fisherman
New Member
You can make your own, but I don't. I keep spares around. Most engines come with 2 and I use one. Please don't forget to mill your head before you install a new head gasket. Milling the head, copper kote on gasket and proper torque solves these blown gaskets. I blew a head gasket on my first build...never again with the above.
I mill both the cylinder and head on every build. I do it as it comes out of the box. I just happen to have a roll of DA paper. I stick a sheet to my garage window and go to town. Remove as little as possible to get a good surface. If too much is taken off you may need to double up on the head gasket to keep the piston from hitting the spark plug.
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GearNut
Active Member
A sheet of 250 grit sand paper on a thick or at least strong piece of flat glass.
The use of flat glass in fairly important as you need the perfectly smooth surface to work the head and cylinder on. You can use the self adhesive round sheets of sand paper as used on an electric sander such as what Al.Fisherman uses, or duct tape a regular sheet to the glass. Use mild pressure against the sand paper, moving the head or cylinder in a figure 8 motion. Every 5 cycles or so, turn the head or cylinder 1/4 turn so as to not favor one area and accidentally sand a low spot into it.
The use of flat glass in fairly important as you need the perfectly smooth surface to work the head and cylinder on. You can use the self adhesive round sheets of sand paper as used on an electric sander such as what Al.Fisherman uses, or duct tape a regular sheet to the glass. Use mild pressure against the sand paper, moving the head or cylinder in a figure 8 motion. Every 5 cycles or so, turn the head or cylinder 1/4 turn so as to not favor one area and accidentally sand a low spot into it.
Ruby478
Member
i dont have anyway of getting aluminum or copper sheets to make gaskets......what if on the fly i used the aluminum from a coke can and traced my gasket on that and stamped it out or used permatex ultra copper ht rtv for my head gasket?........or maybe a paper gasket coated in rtv?
GearNut
Active Member
You could try to use a coke can as a gasket although it is a thinner material and will bump up the compression ratio a little (possible benefit). Some folks have had them work fine for hundreds of miles, others have had them fail quickly. Do not use any kind of RTV silicone on the head gasket, no matter if it is ultra copper or ultra kryptonite or whatever.
Copper Kote gasket dressing can be used with very good results.
Copper Kote gasket dressing can be used with very good results.
Ruby478
Member
ok heres what i did and im freaked if i messed up.......i sanded the head right but i sanded the ring that meets the bottom and creats a cirlce like indent is the gasket.......i did this to make the two set flat on each other and they do......
after i did that i made a new gasket of the can lol......and sealed it on both sides with rtv for extra protection ..........hows this so far or do i have to buy a new head?
after i did that i made a new gasket of the can lol......and sealed it on both sides with rtv for extra protection ..........hows this so far or do i have to buy a new head?
Al.Fisherman
New Member
It may work, but RTV is not the item to be used. The only thing that I'd ever use on a non coated metal gasket is Copper Cote or Permatex 80697. They sell it in auto stores..I buy it in the spray can.
Now you can take the head off again and scrape off ALL of that RTV product.
Gasket sealers have their place but only those made for sealing a cylinder head should be used.
Plain old silver paint(not spray) will work better than most things. Paint it on heavy and let it dry slightly before assembling. Use a torque wrench, tighten to 110 inch pounds.
If you're using those chrome acorn nuts make sure they are not bottoming out before they are tight against the head. Preferably you should toss them and replace with shouldered hex nuts. The acorns are pretty but can be a source of problems.
Tom
Gasket sealers have their place but only those made for sealing a cylinder head should be used.
Plain old silver paint(not spray) will work better than most things. Paint it on heavy and let it dry slightly before assembling. Use a torque wrench, tighten to 110 inch pounds.
If you're using those chrome acorn nuts make sure they are not bottoming out before they are tight against the head. Preferably you should toss them and replace with shouldered hex nuts. The acorns are pretty but can be a source of problems.
Tom
Al.Fisherman
New Member
I feel that (if it is a 8mm stud) that 110 inch pounds is kind of light. Of course I replace all hardware with 8.8 metric (grade 5 USS) as my cylinder studs with lock nuts, 8 mm will take as high as 204 inch pounds (17 foot pounds), I use 150 the first time and 175 if I ever need to go into it again, which I haven't. I use Copper Cote, but in the past have aluminum paint as well, on the old chevy heads. The last engine that I bought and just got the parts in yesterday were 8x1.0 studs and not the 8x1.25.
Al.Fisherman
New Member
It should be ok, but running it will tell. Just coat your metal head gasket well. I'd use a few coats of sealer on both sides. On a stock gasket I use two coats.
I've never had one leak @110, Al and you have to keep in mind that regardless of the stud/bolt hardness you're still threading into an aluminum casting on the bottom side.
But, as we've said here hundreds of times; "whatever works for you". Everyone should read the suggestions given then make their own decisions based on common sense and experience.
And yeah, the old aluminum paint trick dates back to the flathead days. I learned it from an old dirt track racer/engine builder who said the paint should be old and ready to harden. He used to have a can with the lid left loose and he'd scrape off the surface skim and use what was under it on head gaskets. They never leaked either
Tom