AMF Roadmaster

Discussion in 'Motorized Bicycle General Discussion' started by dracothered, Jul 18, 2013.

  1. silverbear

    silverbear The Boy Who Never Grew Up

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    I can't say that my AMF Roadmaster/Tomos marriage was much celebrated there either. I should never have invited them to the wedding. I think mostly there are different mindsets. One is a kind of reverence for manufactured rides as opposed to ones freely fabricated by the owner. Another is a kind of agreement that the AMF Roadmaster was and is a joke. Anyone who says otherwise is breaking ranks. But the joke is on them. Let them compare their Tomos which is just like the next guy's Tomos, congratulating each other on their excellent taste. And it's OK. We're just made differently is all. Their stock Tomos or Puch doesn't exactly generate excitement on our forum. To each his own.
    SB
     
  2. dracothered

    dracothered New Member

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    Two things I still need to decide on is how many tooth rear sprocket and how to rout the exhaust. So far I haven't been able to find exhaust parts such as the header pipe. :-||

    Would say a 48 tooth rear sprocket be a good choice?
     
  3. silverbear

    silverbear The Boy Who Never Grew Up

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    There are gear calculators on the web, maybe on the forum. Some of the forum members are really good at this stuff, too. One is gearnut and another is aleman. You might try a pm to those guys.

    Don't know about the header other than making one, but no doubt someone on the forum has a lot of know how and experience with pit bike engines... would probably be able to point you toward a source. You might try a specific thread with that question... where to find a header for a pit bike engine to get the attention of the right guys. Good luck!
    SB
     
  4. curtisfox

    curtisfox Well-Known Member

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    If you have to make one. Someone on the forum used a washer with the right size hole and trimed it down,drilled the mount holes,and then welded the pipe to it..........Curt
     
  5. mapbike

    mapbike Active Member

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    Dang Curt.... Thanks for this post, I have been making my flanges from scratch and never even considered that it could be done with a modified washer, I'll have to look at this a bit closer and see if I have the correct size to use this way..... just love the cool ideas like this and as many of us probably do, sometimes I just sit back and think wow...!
    I can't believe I didn't think of that myself... (Head scratching eye squinting moment)..LOL!

    Map
    dance1
     
  6. curtisfox

    curtisfox Well-Known Member

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    Yep always made my own to then i saw it here on the forum BINGO.
    One can also find one that would fit over the pipe you want to use and then weld the pipe in that way form the back. Do a little taper room for weld, then on a sander to flaten..............Curt
     
  7. mapbike

    mapbike Active Member

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    Ill be looking to find one with a hole in it that I can widen to port match to the jug and then Ill find a tubing size that I can heat on that end and create a rectangular shape to match the hole in the flange and then I'll eaitjer braze it are just torch weld with a clothes hanger which works great by the way......
    Yep that is a great idea if I can find the size I need .
    Tahnks for sharing.

    Map
     
  8. dracothered

    dracothered New Member

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    I used the washer method to make the flanges for an intake on another build that needed the carb to sit at another angle.
     
  9. mapbike

    mapbike Active Member

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    Yeah im gonna look in to the washer way, I have all the tools to make any size or shape flange I could ever need, but if I can find the right size washer it would speed up the process for making hese simple intake and exhaust flanges for the HT engines, at least I'm thinking it might speed it up for me, I'll know was I get time to do some comparisons of washers to see how much I'll need to mod them to get a good port matched flange.

    Map
     
  10. curtisfox

    curtisfox Well-Known Member

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    Yep! Been doing it for years. Need some clothes hanger? LOL
     
  11. mapbike

    mapbike Active Member

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    No dont need any more clothes hangers..... probably have a lifetime supply....lol!

    Those plastic ones are really hard to weld with though.......LOL!

    Map
     
  12. dracothered

    dracothered New Member

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    Do you do something about the coating that is on a clothes hanger before you use it to weld with and what kind of strength do you get out of it?
     
  13. curtisfox

    curtisfox Well-Known Member

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    A little sand papper will clean it off,good for general use and is quite strong. Torch welding is basikly the same as tig heat fusion with a filler
     
  14. dracothered

    dracothered New Member

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    Ok I found this on one of those ask a question sites... yea it is most likely for a Honda CRF50 dirt bike, but it should still have some relevance. Tell me what you think and if this make any sense or is a bunch of hog wash...

    What should the gear ratio be on my CRF50 with an 88cc big bore kit?
    It has awesome acceleration very peppy low end. The top end is horrible though. What size gears should I get to even this out?

    That may be Easiest Bike in the world to re-gear for more top end speed.

    Simply "Gear it as High as You Can"

    Stock Sprocket set is 14/37. That’s good for almost 30mph.

    Biggest Front Sprocket commonly available is 17T, Smallest Rear Sprocket is 32T.

    Use a 17T Front x 32T Rear. “That's as High as You Can" That gives you about 42 mph.
    ......................................…
    The Stock CDI Boxes on those things are Rev-Limited at 8500 rpm.
    Any CHEAP Un-Limited CDI will do fine, $20~30. You don’t NEED a $100+ CDI.
    ......................................…
    CRF50 have a relatively LOW RPM power peak at around 6000rpm. That means they pull hard early, then the TORQUE drops off after 6000rpm. This is a BIG part of the reasons behind Your Description of your bike's performance mannerisms.

    It Runs out of Breath at 20mph, then just weakly revs-out to 30mph Limit. The 20 to 30 Acceleration is almost none. Then believe it or Not, a Big Bore Kit makes this characteristic even "WORSE" in a way. It AMPLIFIES the impression.

    The Bigger Motor gives it almost TWICE the Torque so Zero-to-20 gains a Huge Improvement.

    But the Bigger Motor has Bigger Demand for Airflow Volume. So it Runs out of Breathe SOONER and Quicker. By 6000rpm the power peak, Power falls off a cliff.

    Huge Rush of Early PULL from 0-20, Then a Rapid Decline in PULL from 20-30.

    That Wider Spread in Acceleration Rate exaggerates the seat-of-pants impression and
    makes it FEEL Slower than it actually is.

    The HIGHER Gearing will put that Big Bore Kit to work.

    With engine's 6000rpm Torque peak, Stock Gears quit PULLING around 20mph, and engine quits Revving at 30mph. Game Over

    With the 17T / 32T gearing, It PULLS hard up to 30MPH and quits Revving at 42mph

    If you want it to PULL harder past 30mph, You will have to install a "Race Cam",
    Or RE-Index your Stock Cam, which is FREE and easy to do.

    Simply re-indexing cam can extend power peak as much as 1000 rpm or so AND leave enough Post-Peak Power to pull hard Another 1000 revs. That's Pulling Hard to 7500 to 8000 range, which is 35mph to 40mph.

    20mph Stock Peak & 30mph Top Speed vs. 35 to 40 mph Peak & 40 to 45mph Top Speed.

    NOT Huge Numbers in absolute terms, No. But in Relative Terms compared to STOCK,
    It's MORE than HUGE. Not only Actually a Lot Faster, it will FEEL a WHOLE LOT Faster.
    ...............................
    Here's some Numbers on Gearing / Speed.
    Not Perfectly Accurate, but pretty Close.

    14/37 = 2.64 = 29.75 MPH (STOCK)
    15/37 = 2.47 = 31.8 mph
    16/37 = 2.31 = 34 .0 mph
    17/37 = 2.18 = 36.0 mph

    That Range is as High / Fast as you can Go with 37T Stock Rear.

    32T Rear is as 'bout High as you can get for Rear Sprocket.

    Keeping your Current 30mph top Speed in mind, lets see what that 32T looks like

    12/32 = 2.67 = 29.5 mph(Approx Equivalent of Stock speed)
    13/32 = 2.46 = 32mph
    14/32 = 2.29 = 34.3mph ( Stock Front size) 4mph Gain
    15/32 = 2.13 = 36.9
    16/32 = 2.00 = 39.3
    17/32 = 1.88 = 41.8

    Note that I included 2 SMALLER front sprockets in the combos, a 12T & 13T.
    Mostly to illustrate that even going from Stock 37T down to a Higher Geared 32T
    It's Still NOT so High that you cant reach "Stock Gearing" with simply a Front Sprocket Change.

    The Point of that is, It establishes a Range of Gearing Options: From as Low as Stock---what You NOW have to "AS High as Possible" with commercially available gears.
    And You can Cover that entire range with the Least expense & effort by simply changing the Front Sprocket.

    Assuming You'll never want to go LOWER than what You have NOW.
    Using a 32T REAR gives you The Widest range of Options between STOCK and MAX.

    You'll Have your original 14.
    14 x 32 = 34~35mph, up from Stock 30mph

    You Buy a New 17T.
    17 x 32 = 42 Mph, "Highest Possible”

    Your Original 37T Rear, you already have.
    With your new 17T.
    17 x 37 = 36MPH

    Buy 2 new Gears, a 17T & 32T,
    You'll have 4 Combos
    14/37 ---30mph(stock)
    14/32--- 34mph
    17/37----36mph
    17/32----42mph

    Addition of another Cheap Front Sprocket, You can chose a size that'll go LOWER than what You have NOW or Split the Range of your 4 Sprocket Set.

    See the PRACTICALITY & Economy of Using the 32T Rear?
    It's just a better Basis to build your Final Drive ratio on.
    ........................

    Note in the Gear / Speed lists a 1 Tooth change on Front Sprocket is about 2 mph.
    Not near enough, nor worth the trouble.

    A 35T Rear is most commonly available "Higher Geared Rear".
    Actually it's an Oddball, It cannot MAX-out Top Speed potential.
    When paired with alternate Front Sprockets, it Drops LOWER GEARED than You Now have. That "Cheats" you out of some Gearing Options when you exclude the TOO LOW combos. Forget a 35T.
    .....................................

    List of "EVERYTHING" you need

    1-17T Front
    1-32T Rear
    1-Unlimited CDI
     
  15. dracothered

    dracothered New Member

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    Anyone have some input on this above post about gearing?
     
  16. aj502

    aj502 New Member

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    Heh...That was an ugly looking moped...WHich means I like it, ofc...

    Dunno why anyone would be miffed at you modding it.
    Even tho it's prolly fairly rare, it was a pc of junk anyway and not like in the "Gremlin"/"Pacer" junk way...

    Looks cool to me...Nice fab work.
    :)



    -aj
     
  17. dracothered

    dracothered New Member

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    Last year I saw a AMC Pacer that was in real good shape that would be cool to get a hold and do something crazy with if I had some throw away money.
     
  18. dracothered

    dracothered New Member

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    Triple Tree with new steer tube.
    [​IMG]

    [​IMG]

    Still need to run two more welds and then mod the top bracket.
     
  19. dracothered

    dracothered New Member

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    Milled away the lip that needed to go so I can open the hole up to match the new steer tube. Now just a little bit of careful grinding and the new triple tree will be ready to install.

    [​IMG]
     
  20. mapbike

    mapbike Active Member

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    Nice work there draco..

    Map
    reddd
     

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