Curious about the engine, :question:

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

  1. frank66

    frank66 New Member

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    mapbike i agree about the gt5 being a great motor aswell as the pk80.

    - the gt5a has the largest frame mounts however so im stuck with the gt5a on my frame.
    - there are the flying horse engines with different pistons aswell. how are they???
     
  2. mapbike

    mapbike Active Member

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    Yeah I have read good and bad on here about the "Flying Horse" engines, I've seen where people have ended up with a GT5 geometry and others have said they got a PK80 40mm stroke geometry... so how the heck do you know what your gonna get....?

    Even though either can be made to be a good running engine if the crank is good and it comes with a cyl/jug that has nice ports that can be cleaned up with minimal work, I would still like to know for sure what the engine is before I ordered one, I'm gonna have a hard time trusting any vendor that will sell me an engine and not be willing to at least know and let me know for sure what I'm gonna be getting.

    Honestly most vendors of these engines and kits have one thing in mind and one thing only...{$$$$$$$}

    Many spend all their time typing up false claims on engine size, hp rating and top speed of the bike after the "simple quick 3 hour build to ride time" that can be accomplished with a few hand tools....LOL!

    Personally, If i have my way all I want to buy is the 40mm stroke engines like dax used to have, I cant figure out for the life of me why he would be ditching those engines..... they are the best of all I have seen and had hands down, smoother and better top speed potential than all others I have put together, I am very disappointed to see dax going to these 38mm stroke engines since out of the box there is no way they can hold a candle to the other "GenIV" 40mm stroke engine he had.

    I know others out there have got to be selling these engines but who are they...?

    I've PM'd Neil Senior (motorbicycleracing) at least twice with no response so I don't know if he still sells them or not or if he just doesn't want to sell them to me...??(Shrug)??

    I'm fixing to put the GT5 lower I have together and see how it performs, it really needs the crank trued up since I can see the counter weights have a little wobble when I rotate it, but the member here that I purchased the lower from said it was a very good running engine when he ran it, so I'm gonna give it a go on one of my bikes that has a terrible running old model BGF engine the will vibrate your fingernails off at above 26-28mph, curious to see what I end up with, it will have a Fred ramped piston and the jug will have some port work like I do on all my jugs, transfers cleaned good and other ports "dee-bird" to help to help the air fuel mix fly in and out a bit better.

    If the vibes get a tad rough at higher rpms, then at some point I'm pull it off take it down and true the crank to get the wobble out.
     
  3. mapbike

    mapbike Active Member

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    OK, here are some pix of four of the several jugs I have that I've set on this GT5 engine lower I have.

    The piston in these pix is a "Fred Piston" it has the nice machined ramps at the transfer port openings, when the stock unmodified piston is used the ports aren't as open as you will see in these pix, the only cyl/jug that still allows the ports to be nice and open is the cyl that has the larger rectangular transfers, the others are the standard GT5 cyl, the BGF 40mm wide intake jug and the PK80/40mm stroke type cyl which is commonly found on ebay, it's what I've gotten in the past from BGF when I ordered a standard jug with 32mm intake bolt pattern. these have fairly good ports that clean up nice but have smaller transfers than the two rectangular port jugs I have and the transfers in the BGF jug are lower and dont open as much @ BDC on the GT5 engine.

    NOTE: The GT5 cylinder is the only one that doesn't need to have the deck shaved/milled for best compression and best squish area for a after-market head like the "Fred Head" or some of the others we have available.

    One thing I will add here is that Fred told me a while back that if I ever need a cylinder/jug deck milled down, all I needed to do was mail it to him with $20 and that would cover shaving the deck to correct height and return shipping, I'm not sure if this is a service he does for anyone needing it but it may be so if someone needs the work done so they can use a pk80 type jug on their GT5 engine I'd say contact Fred and ask him and he might be willing to do that for whomever may need it done since he can do it quick and easy in his shop.
    Here is the link to contact Fred: https://www.shop.crmachine.com/contactus.sc


    Now for the pix
     

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  4. mapbike

    mapbike Active Member

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    Here are some more pix, first set id of the four cyl/jugs intake ports

    Top left is the common PK80 cyl. found on ebay from several vendors.

    Bottom left is BGF cyl. with 40mm wide intake bolt spacing

    Top right is larger rectangular transfer port PK80 type cyl.

    Bottom right is actual GT5 cyl.

    Second pic is of the different shaped transfer ports, the lower right side cylinder is the GT5 that I have started port work on, almost done but need to clean up a bit more and get the shaping matched between the two ports better.

    Third pic with all cylinders in same order is of the exhaust port on each of these cylinder bodies.
     

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  5. cannonball2

    cannonball2 Active Member

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    Great pictorial Map! So sum it up whats the best combo of parts for a good daily driver low/mid range engine and the combo for a high rpm engine?
     
  6. cannonball2

    cannonball2 Active Member

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    Bairdco was kind enough to post this back in 2011 about the Grubee engines. Check out the specs. 38mm stroke, they were purpose built to be. These would be the jugs to be looking for, but how to ever tell if that's what you would get?. Also check out the Super Rat specs. Has 6203 bearings on the crank. HP ratings seem realistic too.

    http://motorbicycling.com/showpost.php?p=270222&postcount=13
     
  7. frank66

    frank66 New Member

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    the super rat? i would wait b4 jumping on that price range.

    there are no 40mm stroke pk80's left then the gt5 setup should be the best stock but my gt5a will be timed higher. once the squish is fixed i see i have no competition. :)
    only question is do i use the gt5 or gt5a cylinder :)

    in theory anyway. this must be what fred is talking about? or did i get it wrong somewhere? :) am i jumping the gun on this?
     
    #107 frank66, Feb 5, 2015
    Last edited: Feb 5, 2015
  8. mapbike

    mapbike Active Member

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    Well, there are so many ideas on this, and I'm not at all a pro at it and don't claim to have even close to the same amount of knowledge on all of this as many on here, but I can tell what I have done and what has been the best for me so far.

    I'm still learning and plan to do a few of the other things that have been suggested in the future like using a degree wheel and getting the port timing set to the best of my ability to where others have said it seems to work the best for them such as Davezilla and a couple others who I can't remember right now....??? have suggested.

    My best current running engine has a cylinder like the one I show in the pix that has the larger rectangular transfers, I just cleaned then up good and "de-bird" the intake and exhaust port, I didn't raise or lower them other than the slight amount that will accur when they are cleaned up and evened up across top and bottom if needed.

    On the engine I speak of I didn't shave the deck, only trued it up on some 320 grit wet/dry sandpaper taped to a glass pane to get it flat for a good gasket seal.

    The piston has ramps filed and finished with Dremel drum sanders on the transfers, the transfer ramps extend 0.60"/aprox. 1.5mm down and taper back about the same amount. they are the exact width of the transfer openings.

    The piston is also ramped on the exhaust port side, it's also the exact width of the exhaust port and at it's max depth down from piston top is 0.40"/ aprox. 1mm

    It has the 6cc Fred Head on it, an NT Speed Carb with jet drillwith #72 wire gauge bit which works good at my elevation with the 100:1 Opti2 fuel mix and my set up.

    The current exhaust is a pocket bike type thath has been modifies a little for better flow and the header pipe is 1" Id exhaust flex pipe and is about 12 or 14" long if I remember right.

    the lower engine is original version 40mm stroke Dax GenIV that has a very good balance.

    This bike will cruise on the flat with no head wind at 46-48 mph with a 32T rear sprocket, I currently have a 34T on it and with the current pocket bike pipe it will cruise at 43-45mph on the flat with no head wind.

    It is running a stock kit CDI which I have found to do anything the "custom made units" will do and actually out performs some of them which I wont call out here in open forum since it always gets a flaming argument started..LOL!

    Main thing I have learned on all my engines since the first build in 2009 is no matter if they're mechanically capable of high rpms or not, is that and easy rolling bike, a well tuned carb and an exhaust that flows as freely as possible is the key to getting the highest rpm the basically stock engines geometry and balance will allow for what I will call a "Common Man Build", I know with more extensive port timing correction work and all that stuff like a correct expansion pipe, correct header size and length blah blah blah...etc one can get even more from the engine, but I like to focus on what I call a "Common Man Build" since that is what 90+% of people who come here will have the skills, tools and finances to accomplish with their motorized bike build or builds that will either be done at the kitchen table, small garage or under a shade tree in the yard.

    My personal fastest build was a bike with 24" wheels, 30T sprocket, Dax GenIV 40mm stroke lower, all the same basic mods as the other bike I listed above but with this one having a Puch 70cc Hi Hi Head, piston ramped the same but with 12 3/16" holes drilled for making it lighter and an RT carb, this bike hit 52 MPH on a slight declining stretch of road and 50.3 on the flat, it had a stock type exhaust pipe that had all the guts removed, was port matched as good as possible to jug port and then had some extra 3/8" holes drilled in end cap and the tiny pipe stinger removed.

    This engine would twist up right at 9000 RPMs, it is retired for now since I got it a little hot and cooked the tension out of the rings, the jug on it was not the large transfer port jug like I listed in the pix earlier either, it was the common PK80 type I got from BGF and I just did a little work to get ports clean as possible for better flow.

    Well, before this gets any longer I'll quit, but this is the simple things I have done to get much better performance on what I call my "Common Man Build" engines, neither of these engines have or had any machine work done on them, all work was done by hand or with a Dremel type rotary tool, some drum sanders, rubber polishing wheels and carbide burrs that can be had fairly inexpensively at two different sources where I have been buying my stuff for port work.

    Links:

    http://www.ebay.com/itm/371249200205?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT

    http://www.widgetsupply.com/category/dremel-sanding-band-1.html

    http://www.widgetsupply.com/category/dremel-sanding-band-0.html

    http://www.widgetsupply.com/category/dremel-sanding-band-2.html

    http://www.widgetsupply.com/category/dremel-polish-rubber-cylinder.html

    http://www.widgetsupply.com/category/dremel-polish-rubber-wheel-square-edge.html
     
  9. mapbike

    mapbike Active Member

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    Problem I remember being a big deal on those "Super Rat" engines is that they have a CDI that is under the mag cover, I remember it being posted here that this was the reason they quick making the engines, these CDI units couldn't take the heat and were very prone to fail quickly.

    Seems I also read somewhere that at least some of the Super Rat engines had 6mm cylinder studs instead of 8mm, BGF was selling some of the Lowers for a while but he doesnt have them listed any longer so they must be gone.

    I think he still has the odd ball rotor listed on his ebay page, but nothing else.

    Seems these were here today and gone tomorrow engines because of all the problems with the CDI mainly.
     
  10. cannonball2

    cannonball2 Active Member

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    Thanks for all the info! You have shared quite a lot. I especially like the "common man" theme!

    Guess what? The internal CDI is back. Maybe the little fan will do the trick.
     

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  11. cannonball2

    cannonball2 Active Member

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    This is a 40mm crank with the ZL rod. Look how close the pin is to the counterweight. Its what is in my FH engine. They seem to be dwindling in supply. These are $20 shipped off ebay. Mine is a fairly smooth engine. There are some cranks with the ZL rod that don't have the two balance? holes, I believe those are older/inferior.
     

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  12. mapbike

    mapbike Active Member

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    Who has those engines and does the cover have a place that fresh air can be brought in without having to worry about getting water in on the mag coil which has been reported to knock them out fairly easy?

    Do the engines have a 50mm spread on the exhaust port studs like the original "Super rat" engines are listed to have had?

    Just asking these questions since I have seen no replacement parts listings anywhere for those engines other than the mag rotor that BGF has listed on his ebay listing.
     
  13. mapbike

    mapbike Active Member

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    The "Red Bat" engine I bought from BGF back in 2009 has that same crank and it has the holes drilled in it, it is the worst balanced engine of all the engine I've had and is the one I plan to retire soon and just set aside, it also has an odd ball bolt pattern for the cylinder studs that is smaller than any of my other engines, it also has 6mm studs instead of the more common now 8mm, the piston in this engine is the low pin type but it is also different than any of the other PK80 type low pin pistons, it is a much lighter casting and it is almost a flat top piston instead of the very pronounced dome piston the 66cc engines come with now, this engine has been a long life dependable engine though, probably about 1500 miles on it without a single internal failure, the reason the vibration is so bad with it is because the crank counter weights have a lot of wobble in them when the engine is spun over, personally I'm a bit shy of these cranks with the Z-L marked rod that have loose uncaged lower rod bearings because the only two engines I have ever had so far that had catastrophic failures both had these cranks in them and what caused the failure was the lower bearing failed and sent a piece of the pi bearing up through a transfer and hung between piston and cyl wall and literally busted the cylinder all to heck.

    Now I still have two of these engines running, but both have serious balance issues one being worse than the other, and one has the Z-L rod on a crankshaft that has the removable cast iron "balancers" on the crank.

    It is possible that I just got two bad ones but so far two major failures out of four engines with that type connecting rod isn't a good average for me...LOL!

    For the same price you can get the ZAE50 "halfbreed" crank with a better rod and a better lower bearing, yeah it's for a 38mm stroke engine but I would trust it for reliability much more than the Z-L with those loose pins between the rod and crank.

    On the engines of mine that failed it looked like not enough pin bearings were used possibly when it was assembled, but I'm not sure how many should have been in there so I could be wrong about that.

    Don't get me wrong, I'm not hating on those cranks, it's just that out of four engines I have or have had, two failed because of the lower bearing breaking up and the two that have stayed together have serious bad balance issues so I'm not personally willing to gamble anymore on them.

    but thats just me.....
    [​IMG]
     
  14. mapbike

    mapbike Active Member

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    Here is a link to gasbike.net

    $259.00 for the "Super Rat" kit... no thank you...LOL!

    Does someone else have this engine now also, since I see the pic you posted shows the engine painted black an with just the simple NT carb?

    [​IMG]
    $259.00
     
  15. cannonball2

    cannonball2 Active Member

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    The black engine I posted is the new Flying Horse Dragonfire. Its kit is $199. That type CDI, unless the Chinese totally screwed up the design is not susceptible to water intrusion. I suppose you could drill a bunch of air circulation holes in the side cover if they haven't provided a means in the design.
     
  16. mapbike

    mapbike Active Member

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    On sale right now for $157.00!!!!

    If someone wants one this would be a good time to pull the trigger on it!

    http://www.bikeberry.com/dragon-fire-66cc-80cc-flying-horse-2-stroke-engine-kit.html

    The specs say this engine has the 202 bearings instead of the original Super Rat engine which used the 203 bearing on the crank ends, so this engine may have all other parts being compatable with standard engines accept the case.
     
    #116 mapbike, Feb 5, 2015
    Last edited: Feb 5, 2015
  17. Davezilla

    Davezilla New Member

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    I saw those the other day when I was doing some online shopping... That's a good deal as long as the ignition has been improved and replacement parts are available if the ignition does get fried...
    I'm thinking they may be exagerating the power output a little, but still a really nice engine and the price is right too... These would make a good "for sale" bike kit if they're really reliable.
     
  18. mapbike

    mapbike Active Member

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    The Super Rat engines were short lived so we can sit back and see what happens with these, at least that is what I will do, I know the standard heads wouldn't work on the super rats, th3 case of course is different, ignition different.

    These may dragon fire ones may be even different than the super rat was, all I know is I have a lot of part to maintain the standard engines and that's what Ill stick with myself.
     
  19. cannonball2

    cannonball2 Active Member

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    When this DragonFire engine came out I began to look for a intergrated CDI that would work with the CG rotor. The rotor is very small and the units I thought of from weedeaters were radiused for a larger flywheel. Havent given up yet. We all know that even the Chinese throw away trimmers have no/little ignition issues and are often left out in the rain on trailers of landscapers. This is the way to go.

    After all this discussion it seems the only way to get a piston to the top 38mm engine is to use the crank with the 114mm FM80 rod and its matching piston. These are I believe Grubee parts. I think my engine in a box is basically a GT5. The stuff looks like Grubee quality. The GT5A/Super Rat? has a different jug, its the one to find. I believe it will have a 50mm exhaust stud spread? If that is the case then it must be design ported for that crank/piston combo since the jug would be a recast anyway. Seems the ignition was the main issue with this engine.
     
  20. mapbike

    mapbike Active Member

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    I have nothing against the super rat engines personally since I have never owned one, but I truly see nothing to gain by having one over the much better balanced engines we have access to nowadays like the dax engines and even the "Half Breed" engines that seem to have better balanced cranks than some of the older designs.

    I'll just stick with what I have the largest selection of parts and pieces for, no reason to make things more complicated than need be for me....LOL!

    since 2009 I've yet to have a single ignition failure and nearly every conversation I have ever seen on here concerning the S.Rat the junk ignition comes upand all the trouble people have had with them, I've also seen where it has been said that the heads like the Manic Mechanic "Ashtray" head wont work on the GT5A/S.Rat engines, I assumed that this is because they actually either have 6mm studs like I remember reading somewhere once, or the bolt pattern is different.

    The "Dragonfly" engines may be a whole new breed with things being even different than the S.Rat was/is, seem Bikeberry say the Dragonfly has 8mm head studs, and says nothing abouit having the 50mm exhaust stud pattern.

    I'm just not to keen on the ignition since there is such a bad track record with then on the S.Rat engines.

    If you get one of those engines keep us posted on how it turns out and what the overall balance is like.

    Map
     

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