If it's open to the atmosphere, it needs to be closed off. Find another dipstick, pipe plug or something to use as a stopper. The crankcase needs to vent somewhere. Older flatheads had a cover & foam gasket. Newer OHV engines have a tube usually (off the valve cover or somewhere else).
Is this a "new" to you bike, or have you had it a while? As CC said, it could have been cast with this hole not open & used in a different application. Let us know what you find out!
Is this a "new" to you bike, or have you had it a while? As CC said, it could have been cast with this hole not open & used in a different application. Let us know what you find out!
Definitely appears to be part of the casting to be used as an oil filler hole. Some engines I've seen have both forward facing and rear oil fill holes with dipsticks. The Coleman CT100's that we own have Hisun motors and they have both forward/rear facing holes, but only the front is threaded and mated to a dip stick. Since the rear hole was never drilled out, the engine is sealed off. The depth of the hole is probably .5" deep before your finger touches the cast aluminum which seals off the hole.
Your engine may be the same. Try sticking your little finger down the hole to see what you feel. Does it stop and you feel a flat top? Or does your finger go all the way through to the crankcase? Do you feel threads on the inner diameter of the hole? If you haven't inspected it closely yet, I'd start there. If it's threaded, you can order a dipstick and you should be in business.
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Your engine may be the same. Try sticking your little finger down the hole to see what you feel. Does it stop and you feel a flat top? Or does your finger go all the way through to the crankcase? Do you feel threads on the inner diameter of the hole? If you haven't inspected it closely yet, I'd start there. If it's threaded, you can order a dipstick and you should be in business.
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This is probably obvious and you most likely already planned on doing this but......Since the bike is new to you and there's no way of knowing how the previous owner cared for it, I would change the oil before running it, most especially if that oil fill hole is indeed open and is missing the dipstick. There's no way of knowing what may have contaminated the oil or what condition it's in.
As far as replacing your carb is concerned, if it's fouled up, you might consider running some Sea Foam through with a fresh tank of gas to clean things up. I swear by this product and it has worked like magic for me in the past. If that fails and you still feel the need to replace the carb, you might consider disassembling and cleaning the one you have now with carb cleaner. Rebuild kits are available which come with diaphragm, gaskets, jet, etc. The kits are usually pretty cheap. Compare the cost to that of a new carb and see which is the more economical way to go. Some folks probably would prefer just to install a new carb and not have to deal with the hassle. Personally, I like to tinker with such projects, so I tend to prefer that route.
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