Break In Running Rough

Discussion in '2-Stroke Engines' started by Benson, May 5, 2013.

  1. Benson

    Benson New Member

    80 cc 2 stroke (zoom bicycle ) with stock carb...Completed the break in period running at 16-1 ratio for two tank fulls and my engine ran perfectly. Used synthetic oil and non-ethanol gas at 40-1 ratio for my next tank . Engine runs for a while then sputters then dies then runs again. Will cruise at 20 -25 mph then will suddenly start losing power and die. It will also idle for a while then die. My first 2 tanks the engine never died at idle.... Any suggestions on what to look for ?

  2. crassius

    crassius Well-Known Member

    first thing I would do is go back to the fuel mix that worked - if that still works, then I'd look for why
    Benson likes this.
  3. wan37

    wan37 Member

    sounds like a faulty vented gas cap. I would loosen gas cap all the way and run it to see if it's better if so drill a small hole in the top of cap.
    Benson likes this.
  4. Benson

    Benson New Member

    Update......Today I drained the tank and went back to the 16-1 ratio. After about 20 minutes of running I got the bike to run ok by staying under 15mph,anything over that and the motor starts chugging and losing power.
  5. Fabian

    Fabian Well-Known Member

    Use the search function on the site to learn about carburettor jetting, and how to alter the air/fuel ratio to get optimal mixture.
  6. chupwns

    chupwns New Member

    Check your cyl head, that worked for me, the bolts may be loose
  7. Skyliner70cc

    Skyliner70cc Active Member

    Interesting responses. My tire's valve stem cap was loose and I had the same issue with engine running. I tightened it up and my engine ran perfectly.

    At 16:1 you air/fuel mixture is lean and when you reduce oil, your mixture richens up.

    You need to lean your carb when you run 32-40:1 Its that simple. Continuing at 16:1 is not the solution.
    Last edited: Jul 25, 2013
  8. HeadSmess

    HeadSmess Well-Known Member

    the valve cap? is that where ive been going wrong? i remove them for weight benefits!

    yep. little engine run bad big badda fuel! little engine like little fuel! is engine is be fat and lazy wallah wallah on big fuel!!

    (yeah, im going to PNG for a holiday :jester:)

    ha ha. lean it out a bit ;)
  9. Fabian

    Fabian Well-Known Member

    I only ask, when will a manufacturer release a compact fuel injection system (with O2 sensor) that can be retrofitted to these 2-stroke engines.

    That will solve all of the fueling issues once and for all.
  10. HeadSmess

    HeadSmess Well-Known Member

    of course it will!

    i stop and help people whos cars have broken down all the time!

    wait a minute, no i dont. an old HQ, yes. a new SS? ha ha. efi, ecu, plastic fantastic. ill help you push it off the road.

    fabian, you love to make things complex. nothing personal, so do i at times.

    efi is not simple at all. why do all mechanic shops now need this fancy gizmo called a scanner, and most apprentices these days wouldnt have a clue on how to do anymore than fit a turbo and remap the efi on a dyno? its oil changes and filter changes now. hard to find a mechanic that can tune by ear these days. try finding someone to dial in a stacked set of 42mm mikuni CV carbs on a 4 cylinder. it requires knowledge and feel. and some patience too!

    it is simple and reliable when its a stock setup, in good trim. its a nightmare when anything is modified or custom! its used predominately as an efficiency thing. though now its performance is up there! once again, EPA rules and all that :poop:. twostrokes are notorious for being ineeficient/dirty. so efi just wasnt ever really developed in that direction.

    (havent checked out dragsters for a while...what do they use? carbs or EFI? not sure...)

    lets see now... EFI...fuel pump. regulator. plumbing. injectors small enough to be precise. injectors need cleaning, and when you only have one... hmmm. two stroke engine, still needs oil.

    varying oil ratios affect viscosity therefore flow rate therefore throwing off all the calculations based on injector flow. dealing with microseconds of opening time, to deliver precise quantities of fuel! has to be accurate! it either needs to be injected or you have to be exact when mixing. each and every time.

    two stroke has a fuelling delay due to crank induction which (if an O2 sensor therefore feedback is used) leads to an unstable mixture as system overcompensates, then under compensates. injector would need to be direct cylinder injector. then hows the oil get in the crank? requires a "dry sump" like a harley. with an oil tank. that one forgets to top up occasionally. same deal when injecting the oil. level needs monitoring. still doesnt cure the fact that some oil will be sucked into the cylinder, which leads to the dirty factor again.

    still havent considered the electricity to run the processor or pump. that needs to be present before the engine can start, so you will need a battery. relevant wiring and switches. a generator as the fuel pump is going to chew the power up once running!

    standard o2 sensors get gummed up by twostrokes. putting one in the exhaust port will affect pressure wave formation in any exhaust fitted and get gummed up.

    a tuned pipe will really mess up any calculations used by the processor cus thats airflow it never considered that is next to impossible to measure or predict!!

    all of this to be available for next to nothing, or at least the price of a whole engine kit.

    (look up sarichs orbital. if you have never heard of ralph sarichs...shame on you! call yourself an aussie? i say this so you cant say "but isnt there a two stroke injector system in use?" yes, theres a few, invariably semi mechanical, not true EFI.)

    you can buy cheap kits for the thumpsters now.
    maybe worth experimenting? 399 US for the basic is pretty cheap!

    i wont be the first ;)

    used to be $2000+. honda and everyone elses love of efi has helped with small efi systems becoming feasible.

    but, lets move onto the software, the mapping!

    either you calculate every possible variation, and spend years tweaking each point on a dyno until the system is bulletproof and ready for the general public. air temp, rpm, TPS, O2, plus many others in complex systems! knock sensors! head temp! fuel temp! oh. crank angle sense is a must.

    i looked into this years ago, before it was so commonplace. yes, about a decade ago..

    i found this...

    contacted dr howlett himself, and that led into what software he used...

    basically, i downloaded the trial software, and with two simple variables, rpm and manifold pressure, i got this type of map

    fuzzy efi map.JPG

    it looks AMAZINGLY like a standard sort of efi map! and, with only a few variables, with only a few "steps", calibration/tuning is a breeze! any fool can tune it! with a smart phone, possibly, (OS dependant)on the fly!

    its not calculating a definite value and storing it in memory to be accessed when that situation arises like in real EFI, which takes time and computing power, then modifying those points via PC and dyno, its more a system of..."its near this point more than its near that point, so ill turn this on for about this long". very easy to theory! very hard to actually write code as puters dont like "sort of" as an input!

    so. software was easy to use. everything looked great to go. what processor to use? lil baby PIC14F82 or similar. easily programmed, cheap and useful. used in everything these days!

    the software even has a PIC compiler, for programming the thing. they do use a unique command system, with only 32 instructions. saves a lot of brainpower! have you ever played with boolean mathematics? tried tripling in binary? or even, converted simple hexadecimal to binary? and octal pops up occasionally. decimal? whats decimal? you need to know these things to program a pic chip! and then theres all that logic :poop: with parity and checksum bits and extra bits on a byte as its a 12 bit D/A converter that get carried to ..... its a big learning curve. i gave up on it after a bot or three. learnt the basics but.

    so, i got a quote for the software, didnt i? the freebie trial download wont actually compile code, of course.

    8000 Euro for a CDrom in the mail. and a black box :) not really worth it for my use...

    end story.

    Last edited: Jul 29, 2013
  11. HeadSmess

    HeadSmess Well-Known Member

  12. Fabian

    Fabian Well-Known Member

    This is a hot ticket item, if they would ever sell it to you:

    and this alternative option:

    and another example using larger engine capacity:

    Last edited by a moderator: Dec 15, 2015
  13. HeadSmess

    HeadSmess Well-Known Member

    and OS engines did produce this one commercially

    not sure what came of it.

    they do hold the prize for the smallest commercial EFI with a .91 version...


    rare as, seems to be one of those typical "japan only" releases.

    note. twostroke.

    i wouldnt mind getting one of the ectron kits for my postie one day. compliment the cams and the 140...
  14. Big Red

    Big Red Active Member

    Still sounds like it COULD be a badly vented cap. The OP didn't say if he tried running with the cap OFF.
    And yeah, getting a little off topic. We're on this thread to solve THIS problem. The guy probably isn't gonna try putting automatic fuel adjustment mechanisms or custom made carbs on his bike. I'm not saying it ain't interesting stuff, It just don't really help the OP much. So ya'all can tell me to F-off if ya want, It wont hurt my little feelers, It's just the opinion of this old geezer. Lets try to help the dude that started this thread.
    Big Red.
    Benson likes this.
  15. crassius

    crassius Well-Known Member

    had a couple engines recently had cold compression at 110lb - both ran weak past 1/2 throttle - clean out crap from one of the transfer ports & thinner head gasket took one to 125lb & ran acceptably, but not really nice - heads are large dome, so will try a smaller dome head sometime soon

    side note on injector - I'd be happy with a system from an old moped where one filled the gas tank, then pushed a plunger that squirted a measured amount of oil right into the tank - easy & clean
  16. HeadSmess

    HeadSmess Well-Known Member

    i like that :)

    tis true. i got carried away. i forgotten what was even wrong with the bike in the first place!

    fuel cap and or gunk/water in the carb... ;)

    OP! OP!!!!! where are you, OP? can you ask your question again ? :jester:
  17. Big Red

    Big Red Active Member

    Not"carried away" HeadSmess, Just Enthusiastic.
    But yeah, Could be a few different things. Cap vent, Clogged carb, Bad coil. Elec. short, ect, ect.
    Big Red.
  18. Benson

    Benson New Member

    My Bike is now running much better. Played with the oil /Fuel ratio and I can now run a consistent 20 MPH ( which is as fast as I want to go) It idles perfectly....Thanks to everyone's suggestions !