Show Us Your Bul!

Discussion in '2 smokers' started by German Trick, Oct 31, 2012.

  1. m143

    m143 wobbler

    Joined:
    May 22, 2008
    Oddometer:
    115
    Location:
    CT, where riders still decide.
    My forum namesake

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  2. Alpthusiast

    Alpthusiast Adventurer

    Joined:
    Oct 2, 2016
    Oddometer:
    23
  3. Alpthusiast

    Alpthusiast Adventurer

    Joined:
    Oct 2, 2016
    Oddometer:
    23
    Hi Mark, Williams hills pass I see my Frontera on the trailer ...Missed you at this years ride! Alpthusiast
  4. Euromad

    Euromad Been here awhile

    Joined:
    Feb 16, 2010
    Oddometer:
    516
    Location:
    Lower Slobbovia
    1978-bultaco-frontera-250-model-214-0.jpg IMG_20191205_130154.jpg
    Here's a couple of Bul's-The blue 78 250 is a recent acquisition. Needs some love but runs and is pretty complete. It will be an AHRMA cross country bike.
    The '76 360 is a bike I got at mid Ohio. Did some painting and sorting out. While I had the stock bazooka for it, I bought a Pursang pipe for riding.. Much lighter. This one went in trade for a 1970 CZ side piper yesterday.
    Mr. Kairo, m143, Scoozi and 3 others like this.
  5. snarlyjohn

    snarlyjohn Human money repellant

    Joined:
    Apr 1, 2016
    Oddometer:
    469
    Location:
    Australia
    My sweet little Sherpy Derp.. IMG_20191122_095224_1.jpg
    Scoozi, Mr. Kairo, fredz43 and 5 others like this.
  6. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

    Joined:
    Jul 22, 2009
    Oddometer:
    2,885
    Location:
    Heart of America
  7. snarlyjohn

    snarlyjohn Human money repellant

    Joined:
    Apr 1, 2016
    Oddometer:
    469
    Location:
    Australia
    Thank you. Sammy Miller Hi-Boy frame. And Falcon shocks with ultra-light damping that absolutely transformed the bike..
    Tanshanomi likes this.
  8. Rich B

    Rich B Long timer Supporter

    Joined:
    Apr 10, 2010
    Oddometer:
    4,321
    Location:
    Stone Creek, OH
    My final ride of 2019 was in the woods on my Alpina. They are just such a nice woods bike

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  9. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

    Joined:
    Jul 22, 2009
    Oddometer:
    2,885
    Location:
    Heart of America
    I am planning to steal the Husqvarna head swap mod @snarlyjohn came up with. It's a concentric rather than trench combustion chamber shape. I just need to modify it for the Bultaco's slightly different stud spacing, and be very careful about the compression ratio. John, did you skip the head bolt locations furthest outboard in the Bultaco cylinder? Any other tricks I need to know about?

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  10. snarlyjohn

    snarlyjohn Human money repellant

    Joined:
    Apr 1, 2016
    Oddometer:
    469
    Location:
    Australia
    I use all the original studs. The six existing Husky holes are on a slightly smaller bolt circle than the Bul ones, so the new holes break into the old ones forming figure-8 slots. You need to be accurate with your work as the old holes encroach onto the sealing surface and you want to minimise this as much as possible. You can redrill with an end mill or a flat bottom drill and an accurately drilled (and positioned) guide plate. I've only ever used the Husky head on the earlier style barrels where the head spigots onto the top of the sleeve, and haven't had any sealing issues at all. The spigot also locates the head nicely on the barrel, but I don't see any reason why it wouldn't also work with the later gasketed flat top barrels. You also need to cut way some fin material and spot face the nut seats, especially for the two outer studs. I also cut a seat for the decompressor button and reshaped the bottom fin slightly to match the outline of the barrel fins, just for looks. The original Husky hemi chamber shape was retained and I used a squish band of around 50% area, being careful to match it closely to the piston dome radius. Theoretically you could run a higher CR with the Husky head but be conservative - raising the CR with a two stroke rapidly becomes a game of diminishing returns as improvements in thermal efficiency become outweighed by the reduction in EGT and the resulting reduction in pipe efficiency. I've done some back to back dyno testing of different chamber shapes on a 370 engine, with surprising results. The trench chambers as used on the Pursang engines makes just a tiny bit more power than the others, despite being regarded as outdated by some. I'd like to try a trench chamber with a better-cooled head like the Husky.

    Anyhow, once you do all this you'll find it makes no more power than the original on the same tune. Why do it then? There are a few good reasons. One is that cooling is much, much better and you'll be able to maintain full power and WOT indefinitely, unlike the original. With the 350/360/370s especially, once you increase the power output substantially they'll tend to detonate after quite a short period of WOT. Of course you can tune around the problem but it costs power. For me the det disappeared completely with the Husky head and better still it meant the tune didn't have to be compromised so the net result was an improvement in performance. For a methanol engine the head swap probably isn't necessary but with gas it certainly helps.
    knudln and Tanshanomi like this.
  11. specdog

    specdog Perpetual search for roads unused.

    Joined:
    Feb 17, 2018
    Oddometer:
    116
    Location:
    Manitoulin Island
    This is a scan from an old photo from 1995. It's an Astro 360 from I believe 1976. Bultaco got the frame geometry on these bikes perfect. It was stunning just how easy it was to go left on an Astro. In the photo, my Astro was a play bike on the ice, as it had old style, worn studs on it from when I bought it. With the stock bazooka pipe, it was loud. When I say loud, I mean it was really loud. Ice racing.jpg
    Rich B, m143, knudln and 3 others like this.
  12. BackRoader

    BackRoader Life Is A Hiway, Ride It.

    Joined:
    Nov 16, 2007
    Oddometer:
    6,399
    Location:
    WinterPeg
    My first bike. $275.00, no rear brake, no air cleaner..... I remember adding 1 baby food jar of #40 oil to a full tank of gas.
    1966 Lobito, 100cc
    CD787C2D-0E74-436B-92C3-BAB3D0FEF933.jpeg
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  13. staudio

    staudio Time to take a ride.....

    Joined:
    Dec 16, 2008
    Oddometer:
    746
    Location:
    20 Minutes north of the Golden Gate Bridge, CA
  14. Texas Aggie

    Texas Aggie Been here awhile

    Joined:
    Jul 17, 2010
    Oddometer:
    207
    Location:
    Nanjing, China and sometimes..... Dallas, Texas
    WeChat Image_20200125172904.jpg

    Attached Files:

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  15. Texas Aggie

    Texas Aggie Been here awhile

    Joined:
    Jul 17, 2010
    Oddometer:
    207
    Location:
    Nanjing, China and sometimes..... Dallas, Texas
    Got this in December of 1971 new in Dallas Texas. It was just redone by a very talented friend and has a deserved new home as art. Even the fasteners are replated Bultaco OEM.
    Mr. Kairo likes this.
  16. GarageRat

    GarageRat Been here awhile

    Joined:
    Jun 24, 2010
    Oddometer:
    195
    Location:
    Western NY
    70347623_2483802461685671_9014931209486073856_o.jpg
    Mr. Kairo and Rich B like this.
  17. Mr. Kairo

    Mr. Kairo Consequence Management Supporter

    Joined:
    Apr 11, 2012
    Oddometer:
    15
    Location:
    Tirana, Albania to U.S.A.
    IMG_0051[2710].jpg Front.jpg Bul Park.jpg 370 Power Plant.jpg frnot shot (2).jpg
    I'm the original owner of his M181. 80% of the time it runs 100% of the time...... :-) I'll never part with it though.
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