New addition, Gyro

[patthesoundguy]

Pull the cylinder and inspect the condition of it and the piston, it could very well need new rings. Check the reeds but I doubt that's the cause of your low compression. I'm guessing you could have worn cranks seals as well. I willing to bet the bore is super shiny when you get it apart. Don't use starting fluid it washes the oil from all of the parts. squirt oil in the cyl before doing the compression test the cyl could have been dry from the starting flud if you used it. The cylinder will tell a lot of the story as a dirty carb won't give you low compression but you should clean it and the tank and screen and the lines, if it has old gas in it. Once fuel has lost its volatility the thing will not run period, unless you squirt fuel in the cylinder or carb.

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[steffen707]

Thanks man, i'll try squirting some oil in it tomorrow and retest the compression. If its still bad i'll pull the cyl head off and snap some pics. How does one test the crank seals to see if those are leaking?

[steffen707]

The previous owner screwed with the idle and air screw. I know the air should be about 2.25 turns out, but any idea on the idle screw?

[steffen707]

Another question. I didn't notice a vacuum line going to the gas tank. I looked on the wikispredia and found this"
Remove the fuel line going into the carb.. turn the gas on.. does fuel flow freely out the gas line?.. No?.. You may have a vacuum operated petcock (if you do there will be another rubber line going from the engine to the petcock).. take this second line off the engine or carb and suck on it and watch for fuel flow out of the other line... If no flow, you must take the petcock off and disassemble and clean it.". I unplugged the fuel line from the fuel filter, and it did not flow freely, I moved the petcock around, but still only dribbles of gas. Is there a screen in the gas tank? I didnt see anything in the in line fuel filter, but i'll try pulling that off as well.

[steffen707]

Putting oil in the cylinder helped the compression come up to 90-95psi

[patthesoundguy]

Take a flashlight and peek in the tank i bet youll see a screen in there. The petcock will have two line comming from it if its vacum operated. If its like the spree which it likley is vacum operated it will be those screens get clogged over the years. Somtimes a bike will run on a full tank but not at half with all the junk stuck to the screen. If you suck on a vac line do it gently too much suction might damage the diaphram and render the vacum side of the petcock useless.

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[steffen707]

It's not vacuum operated, it has an on off reserve manual peacock.

[steffen707]

I disconnected the gas tank, pulled the carb cleaned it, didn't find anything particularly dirty in there. looked like it was just cleaned. I used a new spark plug and checked, it was sparking blue. I put it back together and used some fresh gas connected to a tube and a syringe to feed the carb. I put the air screw at 2 1/4 turns. It didn't start. I varied throttle positions from none to WOT and everything in between. I cleaned off the spark plug a few times with a micro torch. Still nothing. I thought i read in another thread that Bear said some scooters won't even run with a 90-100psi compression. Mine had 75 and came up to about 90-95 after I squirted oil in it.

How do you put new rings on? Do I have to hone the cylinder, do you have it bored .25mm over and use bigger rings? I have no idea. I've only put a new piston in when I put a BBK on my elite, so there was nothing to hone/bore ect.

What do you guys think?

Below are 3 pics from the cylinder. Thanks.

[patthesoundguy]

Go buy a brake cylinder hone and deglaze the cylinder in a 45 degree cross hatch pattern using oil to lube while you do it This is the most important step. You will need new base gasket and a new head gasket. And you will need new piston circlips if you pull the piston which would be a good idea so you can properly clean the piston grooves and clean the piston up. A new exhaust gasket would also be a good idea. After you hone the cylinder make sure to wash it 3 or 4 times with lot and lots of dish soap, dry it as soon as you wash it and oil the bore the second its dry with fresh 2 stroke oil. Clean the piston up with steel wool or scotch brite in the sink.

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[steffen707]

Do I need new piston rings?

[patthesoundguy]

You will need new rings I would think with by the looks of the bore. I de glazed my spree cylinder and cleaned up the piston and the rings and it worka finest kind, but where you are trouble shooting new rings wont hurt if you can get them and i would put new on of it were me. I was waiting for a new piston to show u so i reuseds my old rindgs for a while. It also looks like there is moisture in the cylinder, just from the look of that greyish residue in the cylinder and on the head. And also in the carb the thing you need to double check is the idle pilot circuit. Its a tiny hole in the bowl of the carb and of its not clear it won't idle and may not want to start.

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[patthesoundguy]

If you don't have a ring installer tool be very careful with those rings its easy to break them.

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[steffen707]

If i were to buy a flex hone, what grit should I get? And by 45 degree cross hatch, do you mean honing in forward and then honing in reverse?

[steffen707]

I saw bakaracer suggested a 240 grit on another thread to get the glazing off. Next question, I see bike bandit still has the cylinder head gasket, but not the base gasket. Can I make one out of that paper gasket stuff?

[patthesoundguy]

Base gaskets are easy to make, just pick up gasket paper the same thickness that is on the cylinder now. Sometimes you can peel the old base gasket off with a razor blade after soaking it with oil so you can trace it. Flex hones are the best tool but all you need is an 8$ brake cylinder hone available at any auto parts store or harbor freight. 220 grit is exactly what you are looking for. To get the cross hatch you just need to move the drill up and down slowly and evenly to get the 45 degree pattern. You can reverse a flex hone but brake cylinder hones sometimes will unscrew and come apart when you go in reverse.
Before
After

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