Grubee GT5 w/high compression head issue

Discussion in '2-Stroke Engines' started by Matts22366, Jul 2, 2015.

  1. Matts22366

    Matts22366 New Member

    What's up guys, I just bought a GT5 pro kit and it came with a high compression head, and I was reading "Jaguars" posts on some mods that must be done to prevent det. What are those mods? Also what are some mods that should be done first CDI, exhaust, carb????

    thank u much,

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Whatever kit you bought from gasbike was not made by Grubee.

    Grubee has not shipped any kits to the USA for a long time and
    they do not have a business relationship with gasbike.
  3. KCvale

    KCvale Motorized Bicycle Vendor

    Absolutely correct.
    Gasbike hasn't had any real Skyhawk anything for a couple of years, they just continue to use the name, just like they still call their EPA illegal 66cc engines 80's.

    Don't get me wrong here...
    I don't want to see gasbike go away as they import hundreds of things I often need, but the new actually good quality stuff from the YaunDong (Skyhawk) factory are headed to the US now and beside a couple of vendors like I am working towards being a supplier of good cool stuff I like myself.

    I know, way off topic, but what the heck, relevant 1st hand facts ya know?
    I generally wouldn't even dip my toe into in a lake of uncertainty but I am weighing my options for authorized parts supply with actual real support as I kinda do that now for free, but everyone has to eat ;-}
  4. Matts22366

    Matts22366 New Member

    Ok well my question was an I going to have a problem with the high performace head will it damage my motor, should I buy a new CDI ???
  5. jaguar

    jaguar Well-Known Member

    yes, with high compression you need the Jaguar CDI because its retarded timing matches the higher compression.
    get a gauge and make sure the cranking psi is not more than 135psi.
  6. Matts22366

    Matts22366 New Member

    I understand ase what about those product, does it have switches for different retard/advance settings? Also are u familiar with the kit I got, it's the GT5 kit from, and it comes with a high comp head So my question remains what CDI should I buy, your jag that's $75 or do I have another choice as far as a performace CDI goes? Also what other MODS should I do first to obtain optimum performace for example, different carb, jetting, exhaust...... What should be first?

    Attached Files:

  7. butre

    butre Well-Known Member

    keep in mind, jaguar makes the jaguar CDI and is trying to sell his product. his CDI is certainly a good product that will improve engine life, but running a different CDI such as the HD Lightning or Rocket CDI or even the stock unit isn't going to kill your engine. there are plenty of racers using the stock CDI with compression figures exceeding 170 PSI. of course, they're killing bearings and rings much faster than most people, and the cylinder plating only needs to last a few miles.
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Just a note about the gasbike GT5 engines, they are not real GT5's.

    Grube Skyhawk GT5 engines are made in the Yuan Dong engine factory and gasbike can't buy them.
    Like their fake GT2 gastank frames, they are just using the good name.
  9. kjp123

    kjp123 New Member

    I noticed some of you are ill informed as far as what grube does with those warehouses full of years past models meant for US shores that could not get shipped here due to ever changing EPA regulations . they find loopholes , list them as " off road use only" and leave off the ID plate , they then wholesale these older grubees to companies here with an agreement that they NOT sell them under the official grube name , for example : sells the grubees with 38 mm stroke , long rod , type b piston , exaust ports are 40mm , but the intakes are 32 mm, also bicycle Motor Works sells them too , the guy that runs kings and gasbike got in trouble years ago with grubee for selling older , non tagged motors under the grubee name
  10. gary55

    gary55 Well-Known Member

    First off neither of the heads you are showing are high compression heads. The gt 6 head with the converging fins is a 6cc head. The same as a stock slant plug head. The gt5 round head is a 8 cc head and requires cyl. decking to maintain stock compression. Mzmiami's latest round head is 6cc, but the earlier ones were 8cc so who knows what the latest ones from gasbike are. Don't believe what you read. CC the heads yourself before making any assumptions or modifications to the cylinder. About the only way you will know for sure what head you will get is to order American made like a Fred head/Cr machine.
  11. Street Ryderz

    Street Ryderz Well-Known Member

    Actually it seems you may be ill informed as to whats what,The Grubee engines are produced in lots with an extra percentage to cover defective parts and pre sold prior to production.In this day and age and especaily the Chiness no one goes into production to sit on the product.In 2010 when the epa changed it's rules for importers to be responsible for meeting the standerds set out by them along with the manufacture things changed and grubee commisioned Jin Ling to produce their star fire line and the supper rat and mouse engines to be able to ship to N.A. under China Gas's epa clearence.Then Jin Ling witch is the parrent company to what is now known as Zeda technoliges started making engines on their own first using the older style case halfs then implemented suttle changes to make it their own.Jin ling is parented by China Gas do you see where this is going? This is from Grubee's old website,
    As of 2010 until present day Sept 2012, YuanDong SkyHawk is the only EPA certified 40CFR-1051 supplier in China. via Importer on Record, Nationwide Access in Van Nuys, Ca. EPA requirements starting in 2010 have both the US importer on record and the China engine manufacture both involved in EPA certification. Meaning the EPA certification process has changed and now involves the US importer who must be responsible to EPA as well as being responsible for what the engine manufacture does. Before 2010 EPA had no way to legally enforce their rulings at off shore bicycle engine factory locations so in this way EPA has control by making the USA Importer on Record totally responsible. This can be a good change but without clear communication from EPA officials and a trusted contracted fiduciary agent in China this new process is unthinkable and not very workable.
    China GAS plays an important role as fiduciary agent and licensed exporter. EPA Certification for bicycle engines can no longer be obtained in China as was done in years past. This new process of having both the engine and importer approved is time consuming and very costly, approx. $25,000 to $30,000 for 190 hour lab test plus EPA filing fees and your involvement time. Conversely a 4 cycle lawn mower engine can still be EPA certified in the name of the China OEM manufacture who made it. WARNING: Do not order 4 cycle engines from China kit suppliers, only buy these engines direct from Huasheng the engine manufacture. HuaSheng 4 cycle engines should not be shipped with bicycle installation kits due to having the wrong class of EPA COC. Chinese gate keepers do not understand EPA laws and will tell you anything you want to hear to get your money then go silent.
    BEWARE: It has been noticed that some unscrupulous importers in the USA are still bringing in the 2 cycle bicycle engines EPA certified as lawn mower replacement engines which only requires simple Class 90 certification. EPA officials have repeatedly told us this is totally illegal and they plan to stop it. Laws without enforcement can be worst than no laws at all. The fact is unscrupulous test labs as well as some unscrupulous Importers have falsified test records to enable this to happen. So beware if you run across this situation. Contact EPA enforcement division for latest details.
    To this date Sept 2012 StarFire factory has not gained a WD partner in the USA willing and able to pay the cost of obtaining EPA 40CFR1051 certification and take total responsibility. This means the StarFire line is open to the first qualifying IMPORTER willing and able to perform. Let it be clearly understood that No SuperRat or SuperMouse shipments can go to the USA until a 2013 EPA COC for 40CFR1051 has been issued. Contact EPA enforcement and compliance at 734 214-4100 and 202 564 2063 for latest details.
    The engines Gas bike and others sell are Not older grubees The factorys that were commisioned to make the engines make suttle changes and did their own production run with no epa certification and offered them to the public for offroad use in N.A. with the vendors taking the chance that the shipment may be seized.
  12. kjp123

    kjp123 New Member

    Acually , i do know that ,
    In talking about motors built between 2008 and 2014, there are tons of unmarked grubees around being sold as "jett" "jeet" or black stallion , they are grube motors , minus the id plate , all of motor kits are all grubee , the upgraded carbs are yaung dong cns carbs , the cylinders are easy to identify as well
  13. kjp123

    kjp123 New Member

    They were shipped in parts bro , thats why half the time the heads blow , unless the vendor knows what hes doing
  14. kjp123

    kjp123 New Member

    I bought from gasbike, 3 motors from fastbike , one from bmw
    All five were grube motors , the rods on all 5 motors were ZAE 80
    Not very common either , but a grube for sure
    Last edited: Oct 12, 2017 at 2:45 PM
  15. Street Ryderz

    Street Ryderz Well-Known Member

    Fastbikemotors engines are low pin piston and short rod not a Grubee engine.Jet engines also not a Grubee they also use the low pined piston and short rod I've had many of them here at my shop, Zoom bicycle engines in B.C. Canada sell these they too self labled them currently.And they were shipped overseas as a complete bottom end and the top end in a seperate box in the same package as again I had received many that way.All Grubee engines since 2010 have long rod, high pinned piston,wider front mounts and the cylinder is almost 1mm taller.
  16. kjp123

    kjp123 New Member

    No they are not
    Fastbike sells short stroke long rod motors. , i got one in front of me from gasbike , same rod same everything , ill take the head off and take a pic
  17. kjp123

    kjp123 New Member

    These are the black motors i got from fastbike , i bought 3 , all black all same rod , gas bikes was a silver jett i ordered, but recieved a silver motor identical down to the rod as the motors i got from fastbike.hardware, transfer ports in the cylinder were angled , long clutch arm , they all had a 32 mm intake and a 40 mm exhaust
    Con rod on all of them was the same
    ZAE 80
  18. kjp123

    kjp123 New Member

    Fastbike black , rod ZAE 80 , short stroke , long rod , 32 intake 40 mm exhaust port FB_IMG_1507842139482.jpg FB_IMG_1507842139482.jpg
  19. Street Ryderz

    Street Ryderz Well-Known Member

    Z-L & ZL Rod = 40mm / Type A Piston – PK Type (Caged and Non-Caged) *

    ZL E80 Rod = 40mm / Type A Piston – PK Type *

    ZL40MM Rod = 40mm / Type A or B depends on cylinder – Overcut journal = junk.

    Zeda 80 Rod = 40mm / Type A or B depends on cylinder – Overcut journal = junk.

    FM80 Rod = 38mm / Type B Piston – GT5 Type *

    F80 Rod = 40mm / Type A Piston * Use #2 B w/ 41mm tall cylinder – GT5 Type

    ZAE 50 Rod = 38mm / Type A Specialized crank setup.= 38mm / Type A Piston – PK Type *

    ZAF80 Rod = 38mm / Type B Piston – GT5 Type *

    No Mark Rod = 40mm / Type A Piston – PK Type (Caged) *

    SX-OP = 111.47 mm (Overall) ?????

    ZAF 60 Rod =

    ZAE 80 = 40mm / Type B Piston – GT5 Type * Double check piston!

    ZMN = 38mm / Type A Piston – Halfbreed type * Always double check

    JSF50 =

    CY Rod = 38mm / Type A Piston – Halfbreed Type

    ZAF 50, ZAF 60, and ZAF 80. The higher the number, the longer, and therefore heavier. You can run a pk piston in a gt5 as long as the con rod has z-l on it or zaf 50 not the zaf 60 though and yes the jugs are different the biggest visual difference is the gt5 usually has a tapered transfer port window.

    The A80 engine uses a long ZL rod that is counter sunk at the bearings and is not heat treated. This engine uses a type B piston

    Grubee Skyhawk GT5SR Super Rat Angle Fire 66cc/80cc
    Front mount diameter (40mml/1.57in)
    Rear mount diameter (32mm/1.26in)
    Integrated CDI Ignition Coil
    Timing key way cut at approx. 3:00 TDC
    17mm Crank – Larger key way @ magnet
    6203 Crank Bearings
    Z-L 115mm / 40mm Stroke
    Type A Piston – Top end con rod needle bearing – 10 x 14 x 13

    GT5A and Super Rat 66cc use the same piston.

    66/80cc Piston #2
    Only compatible with the Flying Horse Bike Engine Kit*

    Piston Measurements:
    Height: 49mm
    Width: 47mm
    Skirt Width: 19mm
    Skirt Height: 5mm
    Piston Pin Port: 5mm
    Height from Skirt to Piston Pin: 5mm


    66/80cc Piston #4
    Compatible with most Grubee Skyhawk Bicycle Engine Kits*

    Piston Measurements:
    Height: 50mm
    Width: 47mm
    Skirt Width: 23mm
    Skirt Height: 10mm
    Piston Pin Port: 10mm
    Height from Skirt to Piston Pin: 5mm


    66/80cc #5
    This piston fits most 66/80cc Flying Horse, Mega Motors, and RAW* engine kits.

    Piston Measurements:
    Height: 50mm
    Width: 47mm
    Skirt Width: 19mm
    Skirt Height: 11mm
    Piston Pin Port: 5mm
    Height from Skirt to Piston Pin: 7mm

    Bearing Reference:

    NTN 6202LLUC3/5C

    Malossi racing top end con rod needle bearing – 10 x 14 x 13
  20. kjp123

    kjp123 New Member

    The silver " jett " i got from gasbike was exactly the same motor , same rod , except the exterior was beat to sh*t , inner parts and cylinder was fine, fastbike even sent me a yd carb