New Pk80j 66cc Teardown

Discussion in '2-Stroke Engines' started by 210061741, Nov 19, 2009.

  1. 210061741

    210061741 Guest

    Well i got the new motor on tuesday.
    I promised i'd take it apart and i did.
    I found many things that put big smiles on my face. :detective:
    Got some good pics, i will try to keep it short and sweet.

    If this should be a photo album or some other kinda post please let me know.

    Attached Files:

  2. 210061741

    210061741 Guest

    The Top End

    8 MM Head Studs either Stainless or Crome Plated.

    The piston wrist pin is drilled out a little larger than iv'e seen before and the hole is actually in the center of the pin.

    Standard Needle bearing at the wrist pin, The main bearings have a manufacturer identification mark so i should be able to find out the quality of the bearings easily enough. Chineese / Japaneese
    I'm positive they would use only one bearing supplier so we will assume all the bearings in the motor came from the same place.

    The piston rings are coated with something.... ( I don't know what )

    The piston itself has a Dome shape head which gives higher compression and more surface area for pulling heat out of the motor.

    The piston even has oil holes drilled in the bosses where the wristpin goes.

    It is also marked on the top with a 5 at the exhaust side and an arrow pointing which direction to install it. ( points from intake toward Exhaust )

    Put the piston in wrong and you could land the Ring ends and Pins in a port which would sooner or later break a ring.

    Also the ring locating pins are at the intake side of the motor which helps with the problem of loosing a pin caused by a large exhaust port.

    The jug is very well engineered. A little of casting flash was in there but other than that it is looking good.

    The exhaust port is up high and the transfer ports sit a little lower than the top of the exhaust port.
    It is also shaped very nicely not just an oval going just about straight through the jug.

    The intake port is quite low and very nicely angled toward the top of the piston. It is also clear of the piston skirt at TDC.

    Both ports taper from large outside to smaller toward the cylinder. "PERFECT"

    All of the ports are very large and have some very distinctive angles going into the cylinder.

    I really like the porting in this jug. Seems to lead me to believe this will be a top performer.

    Even the transfer ports have a nice widened port at the cylinder walls.

    Hard to get good pictures inside there... too much glare from the crome plating. I think it's crome.

    The slant head itself will need a little working over.
    Several small scratches and nicks in the sealing surface.
    I planned on milling it on the Glass / Sandpaper anyway and that'll all clean up.

    Also there were 2 head gaskets installed.

    If anyone wants a picture of a particular part that isn't shown clearly enough let me know before i put it back together. ( Soon )

    Attached Files:

  3. Dilly Bar Rob

    Dilly Bar Rob Member

    Good to see that this engine indeed looks half decent on the inside (have never had either of mine apart yet-knock on wood).

    I thought that the PK/zoombicycles engines were of the "bottom of the barrel" variety (based on a report from Don Grube about the factory where they are assembled...), I guess you can't believe everything you read.

    So it has a needle bearing on the wrist pin? I thought that all PK engines had a bushing (at least I was kinda' hoping that mine did-they seem to be more reliable in the long run)...

    Looks like all PK80's come with the 2 headgaskets installed.
  4. 210061741

    210061741 Guest

    The Bottom End

    The ****ershat bearings are 6202 - 2RS. (sprocket shaft)
    Shielded and Sealed on both sides = no lube required.
    I'll still pack grease in the clutch post hole.

    Antother very nice feature, i noticed a thrust washer behind the sprocket and a thick heavy duty rubber seal behind it.
    No more dirty chain from the engine. That bearing is sealed on both sides + an extra seal in front.

    The transfers in the crankcase are nice and smoothe.
    No big step like others i have seen.
    Actually ground my last motor just like it.

    It also has the extra wide 40 mm front mount for large downtubes.
    (no drilling)

    The crankshaft and connecting rod look like the usual but i found out looks are very decieving.

    The only thing i didnt like here is there are no oil holes drilled in the con rod small end. (easy enough to fix)

    Ther rest is allmost unbelievable.

    Standard 5 pc crank with the rough machined flwwheels.

    Until i looked at the big end.

    The crank pin is drilled out hollow
    (helps reduce that extra weight from the heavy 66cc piston assy)

    Now for the grand finally.

    I was checking out the conn rod big end to look for oil holes.
    First i noticed "Hey this thing has thrust washers at the needle bearing"
    I spun the rod around to expose the slit in the con rod for oil.
    To my astonishment this baby dosen't have a caged needle bearing on the big end.:tt1:

    It has Crowded needle rollers. (Awsem) there the best !!! :grin5:

    Now if they were at the piston wrist pin that would be even better.
    But even at the crank thats a bonus.
    Much less slop in the con rod vs my other motor.
    And thoose needles should never fail.
    Wear yes Fail Completly NEVER.
    No more K16x21x10 roller bearings for me.

    The thing about crouded needle bearings is there very hard to assemble.
    Theres no cage to keep the needles from going all over.
    I think thats why most use the caged bearing.
    I've heard assembling a crowded roller is enough to make a grown man cry.

    Also in one of Fabian's post there is a writeup about the better crowded needle bearings. ( that they are the correct ones to use )

    Supposedly only found in old generation StarFire Engines.
    Guess not no more my engine has a production date of 6 / 2009

    I absolutly could not be happier.

    Attached Files:

  5. 210061741

    210061741 Guest

    Dilly Bar Rob

    I believe there are several categories of engines out there.
    Allthough they might all be PK engines. (variation depends on production date)

    Maybe some vendors gets a substancial price break on a Blemished Engine.

    I guess it would depend on there source.

    This one came from Pirate Cycles.

    It is a PK80J Limited Edition Slant Head.

    It reminds me of Grubee famous GT4 Go Sickem.

    As far as Don advertisement. " apparently he was worried for a reason "
    Anyway there were apparent hammer marks in my 6202 bearings of my Grubee

    I didnt see any marks on this PK.

    I would reccoment anyone with the know how to dissassemble ther engine and clean it up before you ever run it.

    There was alot of metal particales all throughout and some sharp enges.

    Other than that this motor is the cream of the crop.

    I hope i can get me a few more.
  6. iron_monkey

    iron_monkey Guest

    What other motors have you observed? Is this the only motor you seen with the special crowded bottom end bearing?
  7. 210061741

    210061741 Guest


    I have a Grubee GT-2B 48cc with about 2000 miles on it.
    Hard miles 6000 / 8000 rpm all day.
    It has taken my abuse very well.
    I bought it cause they were supposed to be the best.

    I have worked on engines alot of my life.
    I have a Mechanical Engineering Degree and a un-buyable 12 years of machining experience.

    Any way i have another thread around here "1500 mile teardown"
    If you wnat to see the pics.

    I have spent countless hours studying every aspect of the HT Motors.
    It is easy for me to see that his PK will run circles around my Grubee.

    Actually i pulled the Jug off the Grubee today cause i decided to use the PK needle bearing at the piston wristpin.

    I orderd a few Sthil chainsaw bearings to replace the standard HT bearings so i figured i'd get some use out of it.

    When i pulled the needle out of the Grubee it fell apart.
    4 needles came loose from the cage.

    It was when i tried to put the PK bearing in the Grubee piston that i realized the Grubee bearing was 10MM wide and the PK was 13mm.

    Obviously i'd prefer the 13mm wide bearing.

    It was a little too big so i filed down the bosses inside the piston to give enough clearence. Put it back together and well see how it runs tommorow.

    I can say one thing for sure.
    I like the quality of the components in the PK much better than the Grubee.
    But thats my opinion.

    Most of the HT's ive heard have K16X21X10 for the crank bearing.
    Thats what the grubee has.

    The crowdede rollers are much better.
    So is this PK
  8. 210061741

    210061741 Guest

    Mann guys i figured you would really like to know what the difference between motors really is.

    Not too much response on this one.

    I put much time and effort into bringing post like this here.

    Sometimes it feels like i wasted my time.

    It would be nice to see you guys add what you have found in your engines.

    Maybe some other opinions would help also.

    I'm not perfect as hard as i try to be.

    So a little help is much appreciated.
  9. sportscarpat

    sportscarpat New Member


    I have just introduced myself to this forum so I could reply to your thread. I read every bit of your post and have looked at some of your other posts as well. You are not wasting your time with your efforts around here. I am looking into a second build and want to find the best and most powerful 2 stroke I can get my hands on without going to the custom tear down rebuild guys. I can do that myself. I have also spent years working on and around engines and feel I know what I am doing. You look to have a great deal of experience, as well. I saw that you were looking at the new Grube "GoSickem" on another thread you started, but now see you went with the PK80. Was this because of availability? I may go with the Grube and buy all the parts and assemble myself as you said in your other post that you could not buy the complete engine in the states due to the EPA. So, in your opinion (which I value), which engine will have more power? Does this PK80 have the wider intake and exhaust ports? By the way, I ported the intake and exhaust on my Grube 80cc and it made the engine much smoother. I also threw on the performance CNS carb and it ran smoother still, a little slower at the bottom end, but smoother and nicer running.
    Thanks for your efforts to keep us informed.
  10. professor

    professor Active Member

    I never knew that the needle brgs. that lacked a cage were called "crowded".
    I am looking at the HTs even though they are not legal here- fascinating design.
    Thanks for the post.
  11. 210061741

    210061741 Guest

    Hey Sportscarpat

    Thanks for the reply. (sometimes i wonder if i dont get too deep into it.)
    My wife says i have OCD "Obsessive Compulsive Disorder"

    I got the PK80-J limited edition Slant head for a few reasons.

    The 48cc grubee GT-2B barley fit in my bike.
    So i knew if i wanted a 80 it would have to be a slant.
    Needing a slant narrowed down what i could buy.

    Then one day wile searching I see Pirate Cycles was getting a shipment of the 4th Quarter Grubee GT-5
    A slant with the new carb and wider mounts and some other nice features.
    When i saw that i E-mailed Justin to get one.

    Unfortunatly when his shipment came in it wasn't what he expected.
    Which is why i was considering the PK.
    That i new nothing about.
    It was easily available to me.
    Justin at Pirate Cycles answered all my calls and e-mails promptly plus i'm on the east coast and took only 2 buisness days to get it via regular UPS.

    So i took my chances just to see what i'd get.
    I wanted the wider mount.
    I wanted a Slant Head.
    The price was very good.
    I planned on tearing it down so i wasn't really worried about anything else.

    All I know about the Grubee is what the Grubee ad said.
    Sounds like a good motor.
    I do know that it has caged rollers on the top and bottom end.

    I was happy when i dissassembled the PK80-J for many reasons i've allready mentioned.

    Especially the Crowded Roller Needle Bearing on the Bottom End.

    There is a post out there that i cant find know that explained which bearings were the right ones.
    I remember the needle count was much higher and wondered how they got so many needles in the cage.
    Now i know.
    There not in a cage thats how.

    I like to run my motors up to 8000 rpm so thoose needle bearings are important to me.
    I orderd 2 (Sthil 028 chainsaw) 10X14X13 needle bearings to replace my piston pin bearings.

    The porting on the PK is huge.
    And the Angle of them looks great.

    Initially i will only be smoothing and polishing the ports slightly.
    I don't think they will need much.

    As far as what is more powerful i really can't say.

    But this PK has all of the things you would find in a performance motor.
    The rest is up to it's owner.
  12. 210061741

    210061741 Guest

    Now that excerpt came from a diff site.

    But i bet there are 23 rollers in that bottom end.
  13. Dilly Bar Rob

    Dilly Bar Rob Member

    here is a link to the "report" from Grube that I mentioned before, just thought I would throw it out here, some might find it interesting to read (I did), there Is also some info on "PK engines" in it that we may find usefull...

    "Engines sales from this "assembly factory" go to the Rico Group, California, Zone 8 RAW engines in California, WildFire in Ohio, and RuiHong in Canada." ....."Engines with PK on box come from this factory. Instruction sheets also are a dead give away for identification." - No doubt that the engines go to even more places then this. "RuiHong enterprises" for example IS & powerking(ebay) &

    Personally I don't think there is ANY difference (quality wise) between the PK kits from different vendors (comparing kits from the same production run/date of course), aside possibly from packing & other minor differences (ie slant head or such). I don't think any vendor would get a discount on a batch of "blemished" engines or anything like that-that would mean that there is actually some quality control going on at the factory, which is doubtfull. I also doubt that any of the vendors could specify that they want a higher quality engine part in "their" kit (lets say the crowded needle bearing for instance). The manufacturer would probably tell the vendor that wanted a change "yeah no problem we fix in next shipment dont worry" over the phone, but in reality either do nothing at all, or holler out of his office window something like "hey frank, when that box of bearing run out you find different bearing to use, these no good".... This approach would of course result in all engines coming from the factory to have a bearing of that type after some point in time....

    I worked in a sweatshop type factory in central europe (czech rep.) for about a year and a half at one time. We made office furniture under the 3M & Franken brand names, also projection screens for french manufacturer "Oray" and others. We made metal shelving units (Raxa, Regalux...) that exported to germany and italy. Stuff from the factory was always labled as "made in france" or "precision made in eu". Quality was very inconsistent depending on how good of a nights sleep the workers had or how pi$$ed they were with the supervisors that day. Nobody cared at all, mainly the supervisors & bosses didn't. There was one guy who's responsibility was to ensure that the nuts, bolts & other hardware we were using was the absolute cheapest available. At one time part of my job was to check that shelving units looked "ok and well packed" whilst I piled them on pallets. I got in trouble for putting too many "bad" ones aside, supervisor said: "Oh if they don't like it they will just send it back (across half the continent....), don't worry about it. " Getting like 1/4 of a shipment back as defective was common. The defecteve units were torn apart, and what appeard good was re-used. Kept everyone nice and busy. After some point I couldn't take it anymore. I had to quit. Funny thing- nobody was ever worried about getting fired end execs. didn't seem to be worried about the company going out of business. The manufacturing prices must have been so low that the companys that ordered the products simply didn't care about the quality.

    Just to give you an idea- if this goes on in central europe just imagine what goes on in china where the poor saps make even less money....

    By no means is this supposed to mean that I have something against the PK engines or their distributors - on the contrary, mine also runs flawless, I am happy with it and zoombicycles services were fast cheap and excellent in my opinion. You wanted response so i just threw some out there :-D

    Good to see that we don't have to pay a "premium" for a grubee. If only PK made a sleeved cylinder engine, that would be my wet HT dream :)
  14. sportscarpat

    sportscarpat New Member

    Maybe I should go back and read your other posts more carefully before I cover the same ground here, but I will ask anyhow. So, if Justin at Pirate Cycles did not receive the new Grube GT5 in his shipment, does he expect them in soon or is he not getting them at all? Were these just the pieces necessary to assemble this Grube engine or were they complete engines? I thought they were not going to be available as complete engines because they would not pass EPA. I could and probably will call Justin, but I am just beginning a second build so the engine purchase is still a few weeks out. By the way I live in California and a lot of the engine suppliers will not ship here. I bought the Grube because I could get it here in California.
  15. 210061741

    210061741 Guest

    Very good points.
    Thats exactly why i took the motor apart. ( Personel Quality Control )
    There was metal debris throughout the engine and some surfaces were nicked up but thats the worst i found.

    What makes me happy is the fact that all the components in the PK are of similar design that you would find in a performance motor.

    Maybe not the 6202 or upper needle bearings.

    But to have the better bottom end, the nicer piston, and proper porting makes this a perfect Foundation for someone like me to turn it into a Real Quality HT.

    Not much Different than what Rock Solid does.
    They have to start with something.

    With the exception to the complete Billet Machined Engine that has a $1500 price tag.

    I could get prolly 20 PK's for that much dough and thats alot of miles.

    Even at 4000 Miles each thats 80000 miles total.

    I hope that $1500 motor goes 80000 miles.

    Any way i love Rock Solids Parts and would love to have a Billet Head and a Ceramic Coated Piston.

    But for the $99 bucks i spent i am very happy with the PK.
  16. Turtle Tedd

    Turtle Tedd Member

    210061741.....a lot of good info you have putting in here..The Turtle says ..thanks
  17. iron_monkey

    iron_monkey Guest

    Funny this isnt advertised, this is actually solid improvement in the technical design of the HT (compared to all the previous hogwash that your brand is better than mine, etc but without having any real difference in the design).

    The HT might actually be quite reliable if every supplier started making them like this; although no engine no matter how good can survive WOT downhill.
  18. Turtle Tedd

    Turtle Tedd Member

    Just ordered another motor for a spare...PK80-J limited edition..pirate cycles...better price for the whole kit than the (moter only) grubee gt2 48cc I am running now.....210061741..thanks again for the effort
  19. iron_monkey

    iron_monkey Guest

    Well, I looked up the factory. Looks like Don Grube apparently tried to shut down exports from it because of shoddy practices and it wasnt complying with EPA.

    Ironically enough you're telling us this engine is much better built than the engines from Don Grubes.

    Also, looks like my engine comes from the same factory as yours, if there is only one factory called 'yongxing'. I ordered mine from Although my engine is 1 year old and the spare upper bearing given to me is 10mm, not 13mm. Looks like they are evolving.
  20. Fabian

    Fabian Well-Known Member

    Hi Rich

    Great to see your teardown pics.

    Wonderful to see that the factory has abandoned using a caged needle roller bearing on the connecting rod big end and converted operations to installing a crowded needle roller setup.

    Just for your information, i have done exactly the same thing by stripping out needle rollers from the cages of two K16x21x10 needle roller bearings and squeezing as many as possible (with clearance) into the connecting rod big end, to make a crowded bearing system.
    It was the only simple and cost effective way of doing things.
    Assembling the needle rollers isn't difficult - just use bearing grease to hold the needle rollers against the inner wall of the connecting rod and slide it over the crankshaft pin.