Hitting a rpm wall at 7,560, please help getting upset

Discussion in 'Motorized Bicycle Trouble Shooting' started by salorr33cc, Jul 9, 2016.

  1. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    I have a GT5 66cc 38mm stroke engine with 160 miles on it, Run Bel Ray Synthetic oil 32:1 and a little bit of octane boost on Sunoco 93..

    The problem is my motor wont rev past 7,560 rpm at 32.7 mph, have tach and speedo,when I first got the engine I took it apart and cleaned up the cylinder of any casting slag and port matched exhaust to Banana Pipe and intake to intake pipe, I also removed casting lip on transfer ports and widened exhaust and intake ports a hair on both sides,, I did not raise or lower anything,, I believe I got a pretty good motor cause it was pretty clean to begin with not to much to clean up ,, I also case matched the lower end where the cylinder meets lower gasket and case, trimmed gasket then beveled the case edges to gasket and lower part of cylinder jug so its an even flow,,

    using only Banana pipe and stock slant head it 4-stroke like crazy,, under load or hill climb it would run better but still 4-stroking,, running really rich moved needle clip to top and did nothing, so I took a pointed center punch to the left side of main jet hole and tapped it to indent the soft brass fitting and close up hole a little and it worked,, engine ran better... any way to make a long story short I was able to rev out to 35.7 mph and still had more to go but let off due to breaking motor in still....
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

    Joined:
    Oct 8, 2011
    Messages:
    4,484
    Likes Received:
    16
    Jetting, jetting, jetting.
    Until it's broken it, it will keep changing, but once it settles in, THATS when you jet for power.
    Remember, SMALL changes, and never ASSUME what it wants from the sound> do proper plug chops.
    Overly lean jetting melts engines.
    What I do is jet for best power, then back off one size for extra lubrication and durability.
     
  3. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    Octane is a flash retardant. The higher the Octane the less power you will make but too low and you risk pre detonation. I am in the Tucson heat and I am running 87 octane and no ping. We are consistently hitting 43 to 45 on our speedy66.com or Ignite 66cc kit motors on stock 44 tooth sprockets in either of several beach cruiser frames. The mountain bikes are normally about 6 to 7 miles per hour slower with the same kits.
     
  4. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    ok,,,so its nice to hear you talk about your bike on here,,,, but where in your post did you say anything about helping me get past this 7560 wall,,,, thank you for telling me about your bike doing 43 mph on 87 pump gas,,,, i dont believe it,, that would mean your cruising at 12,000 rpms with no sweat,,,,
     
  5. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    Not my bike, bikes I build. Sorry wasn't trash talking was thinking the high octane, and octane boost is hurting you. The numbers i'm quoting are peak not cruising, yes we are seeing over 12,000 rpm. One motor has been over 13,000 now. I don't have a dyno for the small motors so this is all GPS, tachometer, and computer. On the last GSXR 600 we tuned on the ESP dyno in Tucson it lost 5 horsepower even, just by going from 87 pump gas to 93 in an experiment to see if mixing in any of the race fuels could help on a stock tune. It went measurably the other way. Just trying to think your rpm limit thru and my first thought reading the thread was flush the fuel, lower the octane, use one of the synthetic race 2 cycle oils that recommend 40 or 50 to one as long as you have burned enough conventional oil thru to properly break in the rings.
    I'm curious how the bike is doing and hope I didn't offend you I think about fuel, oil, octane, etc etc every day and know you can make huge gains with it and just wanted to see if I could help think it thru.
     
  6. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    Sorry I couldn't see the thread as I was writing. I suck at explaining and asking. I brought up the beach cruiser/ mountain bike because we have identical kits running in mountain bike frames and beach cruiser frames. The mountain bikes are measurably slower in the frames we have been testing and won't spin close to the same RPM. One of the other builders I work with now has a stretched bike that he built an adjustable down tube in. He is running the motor at different angles to the ground and rear sprocket and putting the data together so we can study it and hopefully learn how to maximize the slower bikes a little better. Happy motoring and let us know how the bike is coming.
     
  7. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    Wont let me post
     
  8. sbest

    sbest Member

    Joined:
    Nov 3, 2015
    Messages:
    343
    Likes Received:
    2
    Hey LSR, Nice to hear from you.
    I've hit 41mph on a 44t but there is the wall. It will not go faster even downhill.
    GT5A, ported wider, portmatched stock pipe, quenched head, NT jetted right.
    Pulls hard right up to it, bit of detonation and that's it, no faster.
    Feels like the stock CDI shutting down at 10,000. Ideas?
    How'd you get the ignition to go higher?

    Steve
     
  9. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    hey landspeed thank you for your repl and help,, and i didnt mean to be rude,,,figured out my problem some what i think,,,it seems to be a combination of things,,

    1- I have always run 32:1 in my bikes for 25 years now and never blew a motor, I sometimes go to 40:1 if i know the bike well, but i have never fouled a plug or blew an engine and I am still at the last stage of break in with only 170 miles on it and I am noticing more power and better running each day I take out for a half our or so,,I dont beat my engine I cruise her but crack the throttle every straight away or so for fun and open year up..!!!
     
  10. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    it seems I have caused a lot of issues with my engine,,((FIXED BETTER NOW))) I put an RSE 6cc head on it and I now love it , but probably should have waited to end of break in instead of running the Banana pipe and RSE head from right off the BAT..

    I had run out of gas one day in the middle of no where far from any life forms..lol... but the one house out there i knocked on door and guy with gun said i might have some 2-stroke mix...this guy handed me a metal can with bullet holes in it...lol it was his chain saw mix gas...had no choice to use but this is where my problems got worse..

    it was bad gas and i had mixed my good stuff with it,,,pinging and detonation started,,,tried fixing with octane boost,, no good,,anyway drained gas into clear bottle and let it sit,,, just curious,,, i put 93 sunoco in it and good synthetic oil 4 oz to 1 gallon,,32:1..i also removed the two head gaskets i was running cause i thought my compression was high causing pinging and detonation,, with good gas(no octane boost anymore)) i removed one gasket and started running way smoother , no pinging, and got my power back,,(((((((((( to let you know, bad gas that i drained in clear bottle separated into brown sludge on bottom , then another weird looking swirly oil gas level,, and topped with a watery level of gas,,, anyway was not good gas that i was running........
     
  11. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    3--- I was going thru the 4-stroking blues like crazy , was being told left and right different things to do..!!!! So my NT carb the second one sent to me was all screwed up,, i had raised the needle clip to 5th top position and took my stock .071 main jet and filled with solder and drilled to .063 using micro drills twisting by hand in a jewelers chuck,,.. i immediately noticed i had to use my choke now to start,,(never before had to))) after warm up noticed it ran better at low to 3/4...lot less 4-stroking but had a major dead spot at WOT where i had to back off throttle to make engine run and rev better,,,, HENCE THIS IS WHERE MY 7,560 rpm wall STARTED...!!!!!
     
  12. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    wont let me post this ...why???

    main jet way to small... i micro drilled up more and then more where i am at .069 now with needle in 4th slot,, second from top,,,i have some 4-stroking but gets better with warm up and more miles on bike,,, doesnt four stroke under load or hills
     
  13. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    5---so i also just found out that my magnetto is slotted the key way very sloppy and am almost running at the 12:20 position,,, i am also running the Banana pipe which is tuned to come on at about 10,000 rpm...no good for me,, the pipe has no header section at all,,***************SO LISTEN THESE ARE THE THINGS I AM DOING TODAY AND IN NEAR FUTURE,,, ONE AT A TIME SO I CAN SEE WHAT IS WORKING AND NOT************BUT ANY AND ALL HELP FROM YOU ACTUALLY RIGHT NOW TODAY WOULD BE AWESOME A GREATLY HELPFULL,,, I WILL TRY ALL THINGS AND LET YOU KNOW FEEDBACK******************************************

    6---i am going to try top slot on needle and micro drill up to .070 and either solder low part or high part on needle to thicken or file .05mm off back side of carburetor slide were its slightly slanted ((richen midrange))..

    7-- notched filed top right half of woodruff key and turn magnetto CCW to retard it 5 or so degrees

    8--- i just bought a 2004 RM85 expansion pipe,, mint condition,, going in half hour to have welded on flange exhaust adapter,, should have way better earlier hitting powerband

    9--- install a WALBRO 192 wyk carburetor,,, i fabricated a kit with using the isolator block to keep carb cool and pulse line to tapped fitting in crankcase for switching pressure to run fuel pump diaphragm pump in carb,, also t-fitting setup for fuel return loop system and modified isolator intake and special length mounting screws,,, these carbs are great with no main jets or float bowl,,, and have high and low and idle adjustment screws,,, should run like fuel injection,,had one on my gas scooter and it ran perfect always and NO 4-STROKING,, tan spark plug chop too...
     
  14. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    Going to do walbro mod last......gotta run,,,,,please help...please!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     
  15. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    It sounds like you are on the total right track with each step and you may have more than one small problem and you are addressing the most likely culprits. It sounds like bad gas was a big part of it too. And if water was in the gas it can be tough to get it all out and you end up with un explained hiccups days even weeks later. It sounds like you have a solid technique for pre mix with good products and ratios. Oneodd thing with these motors though is the iron rings/ plated cylinder walls. They really like conventional oil the first few hundred miles to wear in the rings and develop good compression, a high quality full synthetic may keep the rings from ever really breaking in fully.
     
  16. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    Keep us posted as you go thru those steps so we can figure it all out.
     
  17. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    LSR i was looking at my oil..the first gallon of gas i used Walmart SuperTech 2-stroke regular oil at 6oz to a 1 gallon i believe thats 48:1 ratio,,,correct???

    I then one night needed gas real bad and had no oil,, used all the supertech oil as it comes in a 6.4 oz bottle that i used all in first gallon break in gas.. I usually always carry 4oz of oil and $3.00 bucks on me in a side compartment in my book bag that i always strap on when i take the bike out. I always carry the basic tools and mini tire pump and slime no glue needed patches and little survival kit with me, Hey you never know and when you need it and dont have it, it can ruin your day..

    Anyway a buddy of mine gave me some Bel-Ray mineral oil (thats not synthetic RIGHT ?)) I have been using that at 4oz to 1 Gallon of sunoco 93, should be 32:1.

    OK, LSR--- what is the difference between Regular air cooled,, Regular water cooled,, Marine,, Mineral,, and Synthetic 2 stroke pre mix oil ??? Then they even make Oil-Injector oil.. A buddy of mine has an Oliver CP 50cc 2-stroke scooter and it has the oil injector tank on it so he just put straight gas in and that thing hardly uses any oil, i know its got to be running like 20:1,,,crazy

    OK LSR PART 2..----sorry i make it quick..!!

    some guy up here that works on bikes(which is scary) out of a garage run business advertised on craigslist that he carries parts and builds bikes from $700 on up,, (I dont know how people can take a $100 walmart bike and $100 ebay engine kit slap it together and not even cleaning engine casting slag and case and port match for reliability and smoothness reasons and turn around and sell the bike for such high prices $700-$1,200)))) I dont get it, Hey I dont know everything but from my own 2 personal bikes and the 5 others i built and from reading Gordon Jennings over and over 20 times and Mike (jaguar) Dragonfly75 stuff and all the Forum threads and post daily and nightly every day for almost a year now I have a pretty good grasp on these engines (6 different versions i think so far out there) and Bikes,, Its a lot to learn and a lot of variations but i know what I am doing and still learn something everyday..
    Anyway back to what I was getting at, when I went to see the joe shmo he tried selling me the farm,, it was funny he showed me a box with 10 RSE 6cc round compression heads and told me that he makes machines these and tried selling me one for $85 bucks...lol... I was going to call his Bluff but didnt want to make enemies right of the Bat..I guess he thought I was super new at this,, but he dont know that I have seen and compared all the different vendors out there and EBAY.. There is not a sale page I havent read and studied,..

    But he also tried selling me a set of Wiseco chromally rings for $10 bucks... they were thinner and tighter.. He said you can also just run one top ring cause they had a tighter better seal to get faster higher rpms,, So LSR what is the deal with these rings,, I mean they really did look nicer.. and can you get a set of piston and rings and wrist pin 10mm and wrist pin bearing and circlips from Wiseco or some other manufacturer and would they be better then the china special ????? I used to us Wiseco parts on my Dirt Bike and ATVs growing up !!!!

    WHAT YOU THINK ??? and whats a better wrist pin bearing and should i change mine before it falls apart,, I heard stock ones due that,,, here is two pictures,, stock is the first one and its got sighns of ware which i dont like at only 200 miles,,, the second photo is JNM motors they sell and there is a third one out there that i have seen and its pins are shorter and more cage material

    Thank you for your help LSR and everyone else STEVE

    it wont let me upload photos again,,, so look above at the previous post i did,,,sorry
     
  18. salorr33cc

    salorr33cc Member

    Joined:
    Apr 30, 2016
    Messages:
    49
    Likes Received:
    0
    wrist pins,,,stock is first one
     

    Attached Files:

  19. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    I am not aware of wiesco parts that work. I have seen a builder that went by foureasy run a single piston ring in the top groove and he also built a China girl with a Puch moped racing top end and backed it all up with video on the dyno and the street. It flat screamed. That said getting into the trial and error of mis matching parts from other motors may yield gain but be ready to spend over and over finding combinations that work. I don't think a plated or moly ring will seal well in our cylinders unless you sleeve it with an iron sleeve. One side of the other of the ring/cylinder interface needs to wear or give in to the other however you want to look at it.
     
  20. LandSpeedRecord

    Joined:
    Dec 11, 2014
    Messages:
    604
    Likes Received:
    0
    Sorry I keep losing my reply so I'm going to do a few smaller ones. It sounds like you are well studied in pre mix and have been at it for a while. If I ever doubt my mix I pour it in the family Jeep lol and just buy a 3.2 ounce bottle of good 2 cycle oil and mix up a fresh gallon. In the race motor I may have different magic brew but when diagnosing I just want a simple powerful mix so 87 octane at 40 to one give or take a few decimals I know I should be able to safely hammer on a two stroke.
     

Share This Page