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Build a Bultaco TSS from scratch

Discussion in '2 smokers' started by blaine.hale, Feb 21, 2012.

  1. spokester

    spokester Long timer

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    :clapWow, you guys are super-ultra-awesome!:clap

    :baldy This thread has rekindled my intense self loathing for having turned a mint OSSA Wildfire (230cc) into a dirt bike back in 1970. :baldy
  2. PSchrauber

    PSchrauber Long timer

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    Beeing a kind of a Bultaco fanatic too for me there could be more pic's sent! :evil
  3. DieterDDP

    DieterDDP Adventurer

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    Hi Bultaquista's,
    Very-very interesting thread indeed. I just bought a TSS 350 replica with AJR 4LS shoe brake. The former owner said it was built by Romero bros of Barcelona but - obviously - I have no proof of that. It has a Metralla Mk2 (Kit America 250cc) engine with Pursang cylinder (possibly 350cc) and Amal 40mm carb. Frame is still a mystery. The bike is being tested and prepped by a 2 smoker wizard in Belgium as we speak. It has so much compression it wanted to fire up but we couldn't bump start it. Have a look at the photos and plse tell me what you think. I still need to have a lefthand gear shift conversion and I definitely need a muffler to race it overhere in Belgium. Any tips welcome for this LH gear conversion and muffler! The rear brake will move to the RH side where the brake actually is. Thanks in advance. I will let you know what the test results are... bult25812.jpg bult25814.jpg bult25818frame.JPG image_2.jpeg
  4. knudln

    knudln Been here awhile

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    Interesting looking bike. It's not a TSS350 replica though, as yours has a single downtube frame and sideport, five speed derived engine. The TSS350 has a centerport four speed Bandido derived engine with a five speed box. You don't have a Metralla engine, as your bottom end has the shift shaft extending through the left side of the case, which only came on later model Pursangs, etc. The difference between a Kit America and standard Metralla engine are the cylinder, head, pipe and carb, so you don't have Kit America parts if a 350 cylinder somehow got mated up to your bottom end. Do you have model #s on the engine or the steering neck of the frame? The frame looks like a somewhat modified Pursang unit. Looking forward to some details.
  5. DieterDDP

    DieterDDP Adventurer

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    Hi Knudln,
    Engine# PM2303173 and frame# 14200005BS. I've talked to a Swiss Bultaco specialist today. He was telling me later Metralla engines had the shaft exiting on the left as well. Seitz.us site states: "Metralla Serial Numbers by Year of Manufacture (Courtesy of John Somerville): (1300 units) 23.02.201 - 23.03.500 = 1967".
    Regards, Dieter
  6. knudln

    knudln Been here awhile

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    Even more interesting. A model 23 (mk2) Metralla engine starts with M23xxxxx; it would not start with PM. Could the number be 203, and not 230? A model 203 (and I think model 142) Metralla would have the shaft exiting on the left. If it's really 23, then the #23 right side case may have been matched with a later (#135 on) left side case. The serial # on the frame is not a standard Bultaco #, but perhaps it is a #142 Metralla with modified #'s, or a special build from Romeros. Pretty bike any way you look at it.
  7. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    Left-side shift Metrallas had enclosed chains, so the left crankcase half, side cover, and shift shaft were different than your bike's.

    [​IMG]
  8. knudln

    knudln Been here awhile

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    Ah, forgot about that. Actually, all 250 Metrallas had enclosed chains. Must be a later Pursang(#135 -) left side case.
  9. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    The "P" alpha prefix before the M was nothing uncommon, and indicates that it's a 250cc engine. "PM2303173" would be an appropriate serial number for a Metralla MK2. But that is quite clearly not a '67 engine, unless it's got mismatched case halves.
  10. knudln

    knudln Been here awhile

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    The "PM" alpha prefix was not used on early (60's) Bultaco engines to the best of my knowledge. My Metrallas all start with M23. I don't recall when PM was first used, I would guess early 70's.
  11. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    The frame number is perhaps even more interesting. 142 is the Metralla 250 GT, which makes sense. But "14200005BS" - did it not start with a letter? The very low serial number, the BS suffix (?) and the lack of a letter at the start makes me wonder if it was a special factory project of some sort.

    75-GT.jpg
  12. Tanshanomi

    Tanshanomi Your Favorite Uncle Supporter

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    I will certainly defer to the man who's owned them. All my Buls have been either early 4-speeds or later, mid-'70s-on.

    There's one obvious answer here: the bike was stolen at some point and the serial numbers were deliberately altered.
  13. DieterDDP

    DieterDDP Adventurer

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    bult25812crop.jpg
    I tried contacting previous owners but no luck. Traced it back to an auction in 2010 where it was sold as a TSS 350 replica of 1965 as part of "The Valencia Collection". "The bike formed part of a large collection of bikes from a big car collector in Valencia . He was not familiar with bikes and had purchased this bike as part of the collection . He did not know anything about the history and unfortunately the gentleman who was our contact there has died.", says the representative of the auction house. The buyer of this auctioned bike sold it again: "The previous owner is a mystery to me but is, apparently, a well known collector of Ferraris and other exotica who lives in Valencia close by the AJR concern. There is a beautiful AJR 4 leading shoe brake on the front but I am unaware of any other AJR input. The frame is a single downtube design which, it has been suggested, is from a 250 Metralla GT. The engine does not appear to be from this bike unless it has been modified to take a twin plug head." Anyone aware of a way to convert it to a LH gear shift? I could build it up from the LH shaft but it would almost be hitting the chain.

    Some more photos of engine and frame numbers. Sorry for the quality of the frame number photo but it really says: 14200005BS.

    Attached Files:

  14. snarlyjohn

    snarlyjohn Human money repellant

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    The frame, forks, triple clamps, rear shocks and rear wheel are Metralla GT. I think you'll have to take the top end off the engine to positively identify it but given that it's impossible to bump start I'm guessing it's a 350/360/370. A 10mm decompressor makes starting these much easier.
    It isn't difficult to set up a left side gearshift; I'll put up a photo later.
  15. DieterDDP

    DieterDDP Adventurer

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    Thanks John. I really liked your Bultaco Engine Built Up Notes. I opened the cylinder head and noticed a Mahle piston. 371cc she has. I'll race her with the 500s then. I need to make a kill-switch, add a nice muffler and change the front tyre to an 18 x 1.85. Tips or references for making a kill-switch, muffler and a 10mm decompressor more than welcome.
  16. snarlyjohn

    snarlyjohn Human money repellant

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    The angle of the spark plugs indicate that the engine - or at least the head - isn't from a Pursang. The Pursang heads that I'm familiar with had a trench chamber with both plugs angled from the cylinder axis. The Frontera head had a quadrant chamber with one central plug and one angled forwards, the same as in your photo. Sherpa and Alpina heads had a similar chamber but usually only had one plug and are easy to spot because of the fins trimmed for exhaust clearance on the right hand side. Here are Pursang and Frontera heads side-by-side:
    [​IMG]
    [​IMG]

    Here is a simple way of running a left side gear shift on a late engine with the through shaft:
    [​IMG]
  17. DieterDDP

    DieterDDP Adventurer

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    Thanks John! Is it good or bad that it's a Frontera head? And what are the benefits of an oversquare lay out?
  18. snarlyjohn

    snarlyjohn Human money repellant

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    Something like this http://tyga-performance.com/site/product_info.php?cPath=71_815_816&products_id=2993 will quieten the bike substantially, though there'll still be a lot of noise from the intake and the chamber walls.

    Your local Stihl or Husqvarna chainsaw dealer will be able to supply you with a decompressor valve. If you look at the top photo in my post above you'll be able to see where the heads have been drilled and tapped to suit. You can also see in the second photo where the 2mm hole breaks out into the chamber of the Pursang head. I only drill and tap 10mm just deep enough to accomodate the valve then reduce to 2mm into the chamber. This prevents disturbing the chamber shape too much.

    Generally kill switches connect the trigger or pulse coil wire to ground when you push the button, or in the case of points ignition they ground the points to coil wire.
  19. snarlyjohn

    snarlyjohn Human money repellant

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    The Frontera head is OK, and has a slightly lower comp. ratio than the Pursang.

    An oversquare layout is actually a disadvantage with a two-stroke. As the bore is made bigger the cylinder capacity increases in line with the square of the bore diameter. But the wall area only increases in direct proportion, so with an oversquare engine it can become difficult to get sufficient port area without running into the ultimate porting limit, ie. you can't cut a hole in a hole. On the other hand the shorter stroke helps keep piston speed down so you might be able to spin it up a bit tighter. Providing of course you can give it the port area to do so.
  20. DieterDDP

    DieterDDP Adventurer

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    Tks much! And the Amal 40mm is a good choice?