Curious about the engine, :question:

Discussion in 'Motorized Bicycle General Discussion' started by mapbike, Jan 8, 2015.

  1. YesImLDS

    YesImLDS Member

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    This is the one that came on his engine as I got a couple more from the manufacturer and ported them out even more for both of us.
    http://i.imgur.com/P5iDsp5.jpg
    http://i.imgur.com/4wudxRy.jpg

    Currently can't get the picture format to work to just show the pictures, but I might add that even the intake gasket was already matched to the intake shown.
     
  2. mapbike

    mapbike Active Member

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    Thanks for the info on this YesImLDS, I may end up trying one of them in the future because I'm just so curios about it, I'm wondering if it may be a configuration like what Fred calls the "Half Breed" which has the same stroke as the GT5 but uses the same rod and piston as the Type A PK-80 engines, Fred has said that these typically have really good cranks and rods in them and have a good balance, the issue is that the timing is in need of more correction than the PK-80 and has the same typical timing issues as the GT5 engines and needs about 0.060 milled off the deck and the piston ramped on the exhaust to get timing more close to where it needs to be, I think these are the numbers Fred gave, but I could be off a little.

    They may have the rods marker ZAE50 if so that tells that they're the "Half Breed" 38mm stroke engines that have the heavier cranks with extra wide balancers that actually increase the primary crank case compression and thats a good thing actually.

    I'm gonna have to get one eventually, someone else with a pocket full of money here needs to drop the cash on one and pull the top off and let us know what it is.....LOL!

    Map
     
  3. mapbike

    mapbike Active Member

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    Yep I can see hw easy it would be to just slot out the mounting holes a tad from the 35mm center to center to where the normal 32mm center to center will work and then I'd chuck it up in the lather and turn the intake hole out to about 14mm or what ever is needed to be equal or a tad larger than carb throat.

    Nice work YesImLDS looks like those woll work like a champ.
    dance1

    map
     
  4. YesImLDS

    YesImLDS Member

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    I took my drill press and bored out the inside of it using a bigger drill bit on the ported intake seemed restricted in the diameter. The ones that I got from the buyer were slightly wider and the port itself was wider than the one pictured, but they were the same casting I could tell. Must of just been a different batch.

    I think the engine pictured on post 1 isn't a half-breed. When we cracked open my friends he had a type b piston in it. I only know this because as Shan knows I ran a GT5, which he now owns, and compared between the two.
     
  5. YesImLDS

    YesImLDS Member

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    Oh I forgot to mention it also came with 3 head gaskets on and yes I mean 3. 3 THICK suckers. Took two off and ran great.
     
  6. mapbike

    mapbike Active Member

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    well it seems that you have confirmed what these engines are then, at GT5 type with a wider intake.

    did your friends engine run fairly smooth in the upper rpms?

    Thats always a concern for many of us, so many of the older type cranks were so badly balance and untrue they would vibrate you to piecs when they revved up a little.
     
  7. mapbike

    mapbike Active Member

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    wow three gaskets, they didn't want that one to have any compression did they...?
     
  8. Davezilla

    Davezilla New Member

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    That's the same intake my engine came with when I got my kit, I ended up putting it in a lathe and bored it out to 15mm because it's only got a 13mm opening, After it was bored out to size I went in and match ported it to my intake and it works great so I'm still running it. Before I bored it out it was noticeably smaller than the carb's barrel size.
     
  9. YesImLDS

    YesImLDS Member

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    It ran just fine. Probably the same as a regular GT5 kit. Shook like any stock motor would. Which we remedied by lightening the piston. Then it ran great with little vibes.
     
  10. YesImLDS

    YesImLDS Member

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    Exactly. I took a standard drill bit I can remember what size and just used a drill press on it. Then I ported it to be nice and wide. Still quite a bit better of a set up than the welded intake though.
     
  11. YesImLDS

    YesImLDS Member

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    *Guys assembling it* ALRIGHT WE DON'T WANT ANY PINGING AT ALL ON THIS ONE. STACK EM UP BOYS.

    Plus side I got a couple free head gaskets out of it.
     
  12. mapbike

    mapbike Active Member

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    extra gaskets is a good thing...

    yep no pinging with that one
     
  13. Davezilla

    Davezilla New Member

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    Definitely not gonna ping with 3 gaskets up top... I guess they were going for a 4:1 compression ratio or something... but hey, at least ya got a few spares now...

    On the intake manifold, yeah, I got a jug & piston combo from boygeasfast on ebay and that welded intake was just plain horrid to say the least, and not even enough metal there to do a match port. I think I ended up cutting that one up to use for something else, but I kept the flange to use as a template in case I ever decide to make my own, but so far I hadn't had the need to.
     
  14. maniac57

    maniac57 Old, Fat, and still faster than you

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    I got the jug off and mine is still a regular 38mm stroke crank.
    The jug has substantially better "as cast" transfers, but they still have that damn ridge! I'll be porting this one a bit more aggressively since it already has better ports and can use the mods better hopefully.
    The bottom end does look a bit different around the transfer bulges with TONS of room for opening it up but no stroker crank, alas!
     
  15. Davezilla

    Davezilla New Member

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    Sounds like a good start for a high rpm engine... short stroke and lots of room for porting. Can you post a pic of the transfers on that jug you got?
    If you got a good dremel or one of those mini die grinders Harbor freight has, you can get some extra long rotary files for them at browntool.com or yardstore.com I got one that's like 3" long and it reaches that ridge with ease. You can sometimes get these cheap when they have these "grab bag" sales (yardstore.com) on used 1/8" carbide rotary files, I prefer to buy new, but it takes a LOT to dull a carbide burr so the used ones are almost always as good as new.... they have tons of metal working tools at both sites since they're both aircraft structure tool suppliers. I'm sure you'll find a lot of goodies there even if you don't need rotary files...
     
  16. mapbike

    mapbike Active Member

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    Here is a place that has good burrs and they are priced good and made in USA I just ordered some last week and got them a couple days ago.

    these are made in Ohio and they are carbide burrs.

    http://pages.ebay.com/link/?nav=item.view&id=371227755460&alt=web


    just wanted to share this along with the places Dave recommended.
     
    #36 mapbike, Jan 9, 2015
    Last edited: Jan 9, 2015
  17. Davezilla

    Davezilla New Member

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    very Nice... That's another Excellent way to build up a collection of long burrs that can reach into those areas most people have all kinds of trouble reaching... I think I'll make a purchase too... Those long straight ones with the dome tips are what I've duse on mine, but those mine flame tips are also very useful too
     
  18. Davezilla

    Davezilla New Member

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  19. Davezilla

    Davezilla New Member

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  20. mapbike

    mapbike Active Member

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    both of those are nice sets, im gonna get a set of those last ones you listed a link to also.

    thanks for sharing.
     

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