briggs timing...firing before tdc??

Discussion in 'High Performance Bicycle Engine Tips and Motorized' started by scratchbuilder, Nov 4, 2016.

  1. scratchbuilder

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    A couple pics of when engine is firing.(I'm thinking). Does the offset woodruf bring closer to tdc for more combustion? The exhaust burn on cylinder looks to me its firing early....? Last pic is jussst before tdc. And flywheel is way past.But, when is spark released?? As both coil legs it the magnet? Help appreciated.
     

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    #1 scratchbuilder, Nov 4, 2016
    Last edited: Nov 4, 2016
  2. Tony01

    Tony01 Member

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    Looks right to me. Typical firing happens around 30deg BTDC. Advancing timing around 6* really boosted my motor a bit in the higher RPMS. I have my 212 advanced 4*, thinkin of doing more.
     
  3. scratchbuilder

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    Thx 01, how did you advance yours?
     
  4. Tony01

    Tony01 Member

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    I just cut the key. I can send you my key if you want, but if you want it now you can do it easily enough with a good enough caliper or 1" micrometer; stock key is .186" wide and every .0055" you cut into a step is one degree, so I cut a ~.035" wide by .075"dp step, then found a .030" shim to put on the other side. When you tighten the flywheel using whatever trick (I use rope in the cylinder BTDC) clock the flywheel forward so it seats on the face of the step and tighten it up. Make sure those tapers are super clean.
     
    #4 Tony01, Nov 4, 2016
    Last edited: Jan 5, 2017
  5. Tony01

    Tony01 Member

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    Here's how it should look. Pm me your address if ya want this key. Is that a Briggs 3.5? You want a high compression head for it too? :D
     
    #5 Tony01, Nov 4, 2016
    Last edited: Jan 5, 2017
  6. Springfieldscooter

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    #6 Springfieldscooter, Nov 5, 2016
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  7. curtisfox

    curtisfox Active Member

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    AWESOME Simple tech , thanks for sharing ..............Curt
     
  8. scratchbuilder

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    Ok guys, at first look I thought the black on the cyl. by exhaust was because it was firing at that point, 3/16 before reaching total compression. Looking again I understand that the top ring is 3/16(the 3\16 is just eyeballing it for discussion)down from top of piston, thus creating a gap between cyl.&piston for the exhaust gases to blacken that area. True??? Yeah 01, I would like the hc head...but this is an engine I got in a 5 bundle deal...it has no mag. I've been swap meet hunting for one. This is a learning work in process... Hey I just watched that eyebrow vid the other day. I will be doing that. I'll try key cutting also. Do you just file it? Yeah 3.5
     
    #8 scratchbuilder, Nov 5, 2016
    Last edited: Nov 5, 2016
  9. curtisfox

    curtisfox Active Member

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    Not to sure but think you can by offset keyways, try AGK.............Curt
     
  10. curtisfox

    curtisfox Active Member

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  11. Tony01

    Tony01 Member

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    Don't touch the eyebrows on that block. On some blocks the deck height is significantly taller than the valve seats and it's a good mod, but on that one if you do even a little bit of grinding you risk getting a loose valve seat.

    Here's the high comp head it's shaved somewhere between .025 and .030", this head with 6* timing advanced and a port/polish job of smoothing the exhaust threads and corners and rounding the inside corner of the intake will make the engine quite a bit more powerful. I have a mag also but you'd need to figure a way to put the plug wire in cause I cut it off to use on my new motor. Head could use some wire brushing in the valve pockets and maybe a good sandblasting on the fins (a couple fins missing)
     
    #11 Tony01, Nov 5, 2016
    Last edited: Jan 5, 2017
  12. scratchbuilder

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    10-4..01 no eyebrowing. I'll practice the porting u mentioned on a spare2hp block. I had 2....but..not paying attention my dremel shaft messed up the v seat. . I'll keep in mind the coil. Can I sand the head down using plate glass as my surface? Also I read bout guys cutting fins off. Seems to me the a critical balance to mess with. Suggestion?? Hey Curt, msrfan thread is wild! Cable op advanced timing...wow.
     
  13. curtisfox

    curtisfox Active Member

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  14. Tony01

    Tony01 Member

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    Yup glass n sandpaper will work that's how I did mine but it was a ton of sweat! I never cut fins off I just broke them trying to get the plug loose with the wrong tools...
     

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