220 psi Compression reading. Is this safe?

Discussion in '2-Stroke Engines' started by StrontiumEthics, Apr 18, 2012.

  1. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I ending up getting a new jug and piston, replaced the crappy wrist pin bearing, and upgraded to a Push high compression head. So say the least, I am very impressed with the performance increase. However, today I got my compression tester in the mail and upon testing, after about 4 separate readings I was getting about 220 psi. I did notice that the compression on this engine had increased. These are my main concerns

    1. Is this safe? (im in the process of taking temperature readings)
    2. I'm currently using 87 octane gasoline (normal grade) after using 93 and noticing a big drop in performance.
    3. Spark plug is a light tan color with some oil around the threads.

    Let me know what you guys think. Thanks!
     

  2. You will have to look up the compression your engine should be putting out. 220 sounds a little high to me. Most auto engines run in the 160-200psi range. I would try running it on the 87 octane gas you have been using, but be careful. If you hear predetonation when the engine is under a heavy load, IE pinging, stop immediatly and switch to higher octane fuel. The ping sound is actually a super high pressure wave hitting the inner surfaces of the engine and is very damaging. It is caused when the mixture self-ignites early during the compression stroke, like a diesel from hot temps caused by the high compression, before the spark plug ignites the mixture at the right time. You would notice the pinging most when accelerating hard or climbing a long/steep hill. Hot weather will also make it worse.
     
  3. Al.Fisherman

    Al.Fisherman Active Member

    Depends on what engine you have...if a HT, yes it's too much.
     
  4. jaguar

    jaguar Well-Known Member

    I doubt that tester is reading correctly. If I bring mine close to 150psi then its hard to get enough traction to turn the engine over when starting.

    Those cheap testers are affected by temperature. Best to have the tester between 70 and 80 degrees inside then bring it outside to quickly do the test.

    Does the gauge show 0psi when not hooked up to engine?
     
  5. geebt48cc

    geebt48cc Member

    I even wil say that over 150psi is WOW, for these little china engines............

    Gosh.............! Hello, wrist pin bearing..................
     
    Last edited: Apr 18, 2012
  6. jaguar

    jaguar Well-Known Member

    yeah, even with a replacement wrist pin bearing I don't recommend more than 130psi.
     
  7. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I think the engine temps were running super high so I decided to put another gasket on it which dropped my compression psi to 170.
     
  8. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Thanks for the recommendation. I didn't know that temperature affects them. Now I know. But I actually do my testing inside where the temperature is definitely between 60-75 fah.
     
  9. jaguar

    jaguar Well-Known Member

    170, eh? Mark your mileage now and let us know how many miles it lasts before it starts making clunking noises from play in the bearings. that is, of course, if the reading is accurate. you might take the bike to an auto mechanic and pay him $10 to check the pressure with his more expensive gauge.
     
  10. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    yikes. I actually heard some rattling after today's test run. Does this mean it has messed up my new roller bearings?

    The rattle noise I heard is only when im idling. It smoothness out and goes away when by the time I get low-mid throttle.
     
  11. jaguar

    jaguar Well-Known Member

    Looks like its time to take it apart. have fun
     
  12. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    ahhhh. Do you have any suggestions? Needle bearings? Clutch? I have been doing work with the clutch as well. I really don't want to take this thing apart again lol
     
  13. jaguar

    jaguar Well-Known Member

    Jennings wrote that most production motorcycles cant take more than 175psi and be reliable. We have chinese pieces of junk. Do you think we can get away with that kinda pressure? You ignored all advice. Now ya gotta pay.
    First pull off the ignition cover and grab the magneto with channel locks and see if there is any free play in that left crank bearing. Then do the same on the right side. Then take the head and cylinder off and move the piston to see how much rotary play there is from left to right. Then move the connecting rod left and right to see how much play the lower rod bearing has. There should be no movement in the crank bearings but a little in the rod bearings. Where you have the most movement is where the worst bearing is. replace it.
     
  14. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    So my plan to lower compression is to add another head gasket. That makes 3 head gaskets on my PUSH high compression head. It seems as though per head gasket my compression goes down by 50psi. Thanks.
     
  15. jaguar

    jaguar Well-Known Member

    that will work.
    by the way, it is Puch, not Push.
    you could try an extra base gasket instead. That would make the engine rev higher also but at the expense of low rpm power.
     
  16. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Right! Its Puch. Excuse my disrespect. I think my engine actually revs pretty high already with the mod's Ive done. Im pretty satisfied. I'm trying to find a place where I can order even better quality, and longer needle bearings than what i have. I searched through the forum now and before but was a little confused when I was directed to most sites. I think also that the bearing that I got from treatlands.tv was not long enough. it was 10x14x13. I need at least a 10x14x14 or 10x14x15 because there was a considerable amount of space left over when I checked and compared it to stock needle-bearings.
     
  17. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I added another shim reducing the compression to 135-140psi. I couldn't add another shim because that would throw it down to 110. I also check the needle bearing and it seems fine. I actually switched it out with a brand new stock needle bearing. Checked the mag bearings and they seemed fine.

    I also tuned my Carb while I was at it. Check out the attached pictures of my spark plug. Tell me what you guys think. I thought it looked fine

    And the other picture are the needle bearings lined up. As you can see the shortest one (gilardoni needle bearing - 10 x 14 x 13 - silver competition race version) is shorter (dah) than the stock needle bearings. I figure that this messes with the weight of the crank and also may not disperse force better than the stock needle bearings. What do you guys think?
     

    Attached Files:

  18. pghewins

    pghewins Member

    NO if you havent got compression reduction on start as soon as you let the clutch out at 220 psi the back wheel will just skid either your pressure meter is wrong or whatever but basically what you have at 22o psi is a small hand granade just under your balls if you can ever get it started
     
  19. pghewins

    pghewins Member

    err and how exactlty did you test your compression with hot engine ride along unscrew spark plug screw i tester release clutch all one handed talented guy
     
  20. jaguar

    jaguar Well-Known Member

    I would use that bearing
     
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