Drilled hole in my gas cap (removes tank vacuum)

[AlexRSS8]

From my experience the bike usually rides with no problems, then experiences the same as running out of fuel all together, with a cough and splatter, then nothing at all. The 70 sounds like it is possibly starved of fuel/air. Depending on where the engine was purchased it may be running the same carby as the 50's which means the engine cannot run to it's full capacity being starved of fuel and possibly air particularly at top end. You could try bigger jetting or better still a bigger carby. As a suggestion Skyhawk distributors have a carby designed with bigger jetting and air flow that seem to work quite well.

yeah probably, but the problems all fixed, this guy can't stick to the same engine for more then a month or 2 max

 

[5-7HEAVEN]

If you install a locking gas cap, you don't have to drill a hole in the cap.

The cap's keyhole will vent the fuel system.

 

[happycheapskate]

Industrial weedeater tank breathers, $5

re: crude fuel gauge. You could be risking an explosion! That is why float-type fuel guages are made of plastic.

Also the wire could be subject to corrosion. If it vibrates in the drilled hole, it could cause static charging/sparking.
I like your creativity though.

I think the tiny little breathers which go on Echo or similar commercial weedwhackers' fuel tanks would fix your problem. There are replacement kits for low prices at any major Echo power equipment dealer or most weeder/yard equipment dealers.

The kit consists of a rubber grommet, a simple small fuel line, and a barbed end mini air filter, and a fuel filter usually (for the fuel line of a weedeater).
If you go to the shop, you can probably get just the breather filter for $5 and hose by the foot.

You could even seal the standard cap holes with something to prevent rain contamination, if you route the hose and breather to a safe enough location. (beware of siphoning or dripping, esp onto the engine)

Mine doesn't seem to have any tank breathing problems (2009 grubee skyhawk.) What type is air locking on you guys?

Since you guys drilled the cap, why don't you make a crude fuel gauge using a stiff long wire and a "Jack-In-The Box" ball?

 

[GTodd]

I have the same problem with gas cap venting. Im going to drill the cap. Older lawn mowers and other stuff had vent holes in the caps. The hole are off set for splash. The safe thing to do is a vent tub if vented properly. GT

 

[Gregoryzim]

If you install a locking gas cap, you don't have to drill a hole in the cap.

The cap's keyhole will vent the fuel system.

Unfortunately not with my lockung cap. The key barrel is sealed and does not pass through to anywhere let aline the tank.
I had to drill a hole in the cone that surrounds the key barrel and to which the tthe cap seal is fixed.

Now the air can flow into the inside of the cone and through the hole in the cone wallbinto the tank.