installed puch head and it runs bad.....

Discussion in 'Performance Mods' started by borntofli, Apr 3, 2013.

  1. borntofli

    borntofli New Member

    ht 66... Installed a puch 70 hi hi head w/ 2 head gaskets... I can get it to run but barely....

    Too low of compression?? ( swithch to 1 head gasket)..

    I switched the jet from 70 to 66 and it would run better.... still super bad...

    It wont run or start w/ choke on at all....

    What are your thoughts on what I should change...??

  2. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Its funny because I had the same problem! When I compression tested the Puch head with 1 gaskets I got really high compression readings. I tried stacking about 4 or 5 head gaskets and it got a little better but still not as good as a slant head (currently using). If you look at the Puch head and compare it to the slant head you'll notice that the Puch head has quite a bit less area for fuel in it's dome. I suppose this could also be a culprit. Just my 2 cents.
  3. borntofli

    borntofli New Member

    Maybe it works on some engines and not others... others have had success......

    Im not giving up yet....
  4. geebt48cc

    geebt48cc Member


    Are you serious?

    Well, I'm not using a gasket at all, just good Indian sealer. Anyway, it's about the same as my stock milled slant head, just maybe a few pounds of compression more. The very BIG improvement I've found, is the engine always run cooler!!

    Now, bike fires first half turn of wheel.

    Attached Files:

  5. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Oh man that setup looks SMEXY!
  6. jaguar

    jaguar Well-Known Member

    Make sure the piston hasnt touched the spark plug and changed the spark gap.
  7. geebt48cc

    geebt48cc Member

    Hey there Jag,

    Yeap, everything clears well. Very good compression, I just wonder what the 50cc Puch head on this 66cc would of been like? The reason I say that, is really this Puch head is not much difference than stock milled was. But still, worth it running much cooler. See, some people have talked so much about using up to two head gaskets, in order to even get the bike to row start? This 70cc head, is about same as original milled................(and that with out head gasket)
  8. jaguar

    jaguar Well-Known Member

    actually I was asking borntofli
  9. geebt48cc

    geebt48cc Member

    No, No, I'm not trying to cut in here. I was just firing some stuff out here. Carry on........................:)
  10. borntofli

    borntofli New Member

    The problem is the piston is hitting my spark plug....
    Either 1 more gasket on the spark plug, or one more head gasket....

    I think i'll try the plug first...
  11. Fabian

    Fabian Well-Known Member

    Jaguar is on the money :wink:
    I've tried various high compression cylinder heads and i've had metal to metal interference on all of them with anything up to 3 head gaskets. One cylinder head required 4 head gaskets to clear an NGK B6HS spark plug.

    The other thing to note is that the cylinder head will walk around on the cylinder and find it's natural position if your engine uses 6mm head studs and 8mm stud holes in the cylinder and cylinder head.
    Sometimes the natural position of the cylinder head is offset from the cylinder and because of this the cylinder head combustion chamber will walk it's way into contact with the piston, initially making a sound like detonation then an ever increasing metal to metal rattling sound, even if using 3 or 4 head gaskets.

    Placing 6mm to 8mm sleeves over the 6mm head studs fixes the problem.

    In such a situation you start chasing an ignition/compression problems because it sounds like detonation. I have wasted countless hours of my life doing this very thing, only to find out the real cause of the problem.
    Last edited: Apr 12, 2013