GT2A-S in-frame tank frame for MB's

Discussion in 'Frame Mounted Engines' started by KCvale, Jan 13, 2014.

  1. KCvale

    KCvale Motorized Bicycle Vendor

    If you are not familiar with the Grubee 26" GT2-A and GT2A-S unfinished aluminum bicycle frames with a built in gas tank specifically designed for motorizing please get the basics from Grubee's web site here first. & FRAMES.htm

    Here are some pics and specs you can actually use to see what this frame looks like and some specs from the GT2A-S frame for 4-stroke builds.

    (note most images are 1280x wide for detail but reduced here, click the pic links for full size to view)



    Here is more detail on the bottom side.


    And this an extreme closeup of the BB and welds.


    It comes with the fork mounting hardware...


    ... but it does NOT come with any BB parts or a petcock for the gas tank.

    The fuel shutoff petcock from the pre 2014 2-stroke SKyhawk 2.5L tanks work as well as all Skyhawk 4-stroke kits but NOT the newest 2014 2-stroke Skyhawk tanks or most 2.0L thinner HT gas tank fittings.

    It looks like a cool sturdy base for a 4-stroke build (get the other model for a 2-stroke) if you want to customize from the ground up or even transfer everything from a pedal bike to this less than 6 1/2 Lbs. frame that sure seems solid to me.

  2. Barry

    Barry Member

    This is a REALLY great frame. Solid as a rock, super welds and best of all, light weight. Using an HF142 I had a little problem getting the engine lowered enough to keep the choke from hitting the bottom of the tank, just had to rework the mount plate a bit. I'm planning to do another one in the near future trying out 24 X 3 wheels. By the way I did put 3" tires on this one and it worked out great, I hope the **** that stole it is very happy with it.
  3. HeadSmess

    HeadSmess Well-Known Member the BB the large diameter intended for single piece cranks? meh. plenty of adaptors for 3-pieces out there, and or alternatives, such as an eccentric for tensioning a belt driven job...

    and standard 1" tube forks?

  4. KCvale

    KCvale Motorized Bicycle Vendor

    The measurements are on there, 1 1/2" head tube hole so you can use 1 1/8" front fork.

    Yes, big BB hole 51.5mm for 1-piece cranks but as mentioned there are cups to make it 3 piece cranks either sealed cartridge or straight bar.

    If you click the links under the pics you can see incredible (1280x) detail.

    Note you won't get 3" tires on it unless you put them on flat and use a rim no wider than 2 1/2" and then fill the tires because the distance between the V-brake bosses mounts is only 2 1/2".

    About painting...
    Powder coating is usually the best for anything but I am going with the auto body shop around the corner from me for a few reasons.

    I'll know today what that gold 'coating' on the aluminum frame is but it's not primer, the auto shop guy thinks it is the residue from an acid bath.
    In short it is NOT a sealant so you really need to paint the thing.

    This is my 1st GT2 frame for a custom customer build (details here ) and he wants a 4-stroke 3-speed shifter.

    I sent him here to pick a color for a 3-speed wheel set and he went with this yellow rim black spoke set.

    I took a wheel for color matching, the frame, SBP 4-stroke shift kit, and other miscellaneous parts over to the painters yesterday and every part is getting a new car finish so it ought to be a pretty cool canary yellow and black build but I don't want to stray to a specific build, I just had the frame here and took the time to photograph and measure everything so the next guy that wants to build on it has some useable specs.
  5. KCvale

    KCvale Motorized Bicycle Vendor

    I just got off the phone with the paint shop.

    The frames comes acid bathed.

    In short just a couple of coats of rattle can spray paint probably won't hold up well but to each to his own budget.

    Just for cost reference my cost is $300 to paint all the parts I took him (frame, chain guard, 4-stroke shift kit parts and some other smaller parts with 3 coats of primer, 2 coats of paint, and 2 coats of sealer and I can pick them all up tomorrow.

    I'll get the brand names and types of each used but from what understand there are different types of primer for different things and on a build like the one I am doing I'll trust the professionals what what will be show bike quality and durability.
  6. Barry

    Barry Member

    I work in aviation as my day job and am very familiar with this coating. It's actually called a chromate conversion coating, we use a product called Alodine. It chemically etches the aluminum and creates little follicles that make the primer paint coat adhere much better. It also has some corrosion preventative qualities.
  7. Fabian

    Fabian Well-Known Member

    I really like the in-frame tank idea. It's a lot more stealthy.
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Thank you so much for some expert input on what this frame 'coating' is about on this aircraft aluminum frame, it should really help everyone else that comes along after this topic get an idea what this unique frame is all about and what to expect as very little about these frames is known so I am trying to share what to expect for everyone that follows on a build on this frame.
  9. bigbikeseat

    bigbikeseat Member

    I built one with the four cycle . The motor mount was time consuming.
  10. butterbean

    butterbean Well-Known Member

    From what I have heard, if you don't paint the frame, it apparently scratches over time. One member even reported it scratching almost completely off (might have been on the other forum while I was still there). Don't know if it's true, but it's what I've heard.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    I got mine back from the auto body shop yesterday.
    They acid bathed it, put on a coat of some kind of special primer, 2 more coats of other primer, 2 coats of paint, and then 3 coats of sealer.


    I love the open end horizontal dropouts, that is a 3-speed hub and it's getting a 4-stroke jackshaft so some common axle stays will be in order.

    As for the SBP engine mount it dropped right in like a dream.
  12. Bzura

    Bzura Member

    That is one sweet bike! I can't wait to see it completed. I'm thinking about building on of these or using the Phantom frame that BikeBerry has. I just don't know much about that one though. I know that the Grubee is tried & true.
  13. KCvale

    KCvale Motorized Bicycle Vendor