how much pressure is normal in the crankcase?
 

i am sooo dang close to getting this thing running, but i keep finding more and more stuff... got spark with the old harness bits, and the new cdi... throw some gasin the tank, no bang...pull the carb cleant he jets out because they were clogged shut...try again... still no bang...next on the list, check the valve clearances...intake valve was wwaaaaayyyyy too tight... i backed it off a full turn to get it to .05 tolerance...try again...still no bang, but it sounds like it may be trying (had one kick over 3 revolutions, but that was it...) as i crank it over with the e start, i notice a good bit of air coming out the crankcase vent...i am thinking i may have some serious ring issues if theres a good bit of air there?

any ideas? also, turned out that the old cdi is still good... i get spark with that too...LOL oh well... i am waiting on my new harness to show up, but i can get spark now, i wanna hear it run...i am fearing the worst though that it will need rings minimum... gotta figure out how to drop the engine out of the frame soon to see about puling the head and getting a look deeper inside this thing... >:(>:(

moral of the story... if the seller says itjust lostspark, dont always believe him... :crazy::crazy:

Please remind us; what bike are you working on?

Oops sorry, shineray xy200, 200cc pushrod motor, seems lifan based...

Thank you for the reminder. :)

I think it's time for a compression test. ;) I use an inexpensive, yet effective compression tester I bought at Harbor Freight. :)

http://www.harborfreight.com/quick-c...ter-95187.html

I was going to do so last night, but it would appear that my HF compression tester doesnt have the appropriate adapters for the smaller spark plug hole. Mine only fits standard automotive sized plugs... Guess i gotta look for the proper adapter...

Spud, that link teleported me to Kato's shop.

Was this what you meant, Spud? http://www.harborfreight.com/compres...kit-66216.html

BB, I've never tried to measure the pressure in the crankcase, but I would expect it to be a noticeable amount. It should inhale / exhale as the engine is turning over, but that might be interpreted as exhaling only. it would be interesting to attach a vacuum / pressure gauge on a healthy four stroke to get a baseline. Hmmm...

If i put my finger over the vent, theres no vaccum, only pressure...thats what leads me to believe the rings got fried.... It also looks like theres not enough oil in the case, which may have contributed to to rings going....i would like to see if i can find an adapter for my compression guage to check for sure though....

I don't think you can feel the vacuum on a crankcase vent although I have never tried. They just seem to gently blow.

Some oil dripping is normal too.

A thumb makes a usable cursury compression gauge. If you push as hard as you can, choke off, throttle wide open and crank the engine it should smartly blow your thumb off no matter how hard you press. This will suggest the compression is over 100 PSI.

Oops! :hehe: I fixed the link in my original post. ;) No, that's not the compression tester I own. Here's the link to the compression tester I use on my bikes; it has the proper adapter for the Zong. :)

http://www.harborfreight.com/quick-c...ter-95187.html

The tester i have isnt listed on thier site anymore, but it was half the cost of all the other ones....i need to find an adapter and see....LOL im sure i can fine something...

got the right fittings for the compression gauge, checked compression, made a whopping 60#....well, tore into the top end, and that suckers rings (exceot for the oil rings are SHOT....top ring was cracked, both combustion rings are STUCK in the piston...oddly enough, the bore is spotless...not a single scuff or scratch.... will be good as new with a basic hone, and a new set of rings....

http://i662.photobucket.com/albums/u...ps0f613915.jpg

http://i662.photobucket.com/albums/u...psde182df6.jpg

Good work, BB. :tup: I think that's the first time I have heard of a cracked piston ring. :wtf:

You can certainly get piston rings from Taobao. In fact, a new piston is probably quite inexpensive, as well. :)