Break In am i running my new engine too hard?

Discussion in '2-Stroke Engines' started by back2theborstal, Jan 29, 2011.

  1. hello all. i have an sd stinger engine kit 66 (80)cc. i got it about a month ago now, but i have only road the bike for about 15-18 miles. my question is am i running it too hard since it is still in the very early break in. i am very often going wide open throttle with it, yet i do not leave it wide open for more than 10-15 seconds. and usually not that long. i varry my speeds alot and throttle positions alot. and dont run the engine for more than about 30 minutes at a time. but i feel like i might be running it too hard. i have read where you should not go wide open throttle for quite awhile. and you should gradually work up to it over 100 miles or so. i am using 87 octane gas, and a 16:1 mixture using lucas semi synthetic oil. i am trying out different spark plugs. the stock LD, NGK b5hs, NGK b7hs. and i also have a NGK B4L but havent tried it yet. but they told me it was a direct replacement for the stock plug at napa. but its funny because i dont see any talk about using that plug on this or any other site. i have also moved the needle clip back and forth between the 3rd and 2nd notches quite a few times. it came with it on the 3rd. but its funny because it seems like its running too rich. and will have some oil on the plug. yet the plug starts turning gray like its running lean and burning too hot. so its a little confusing. seems no matter what i do it wont get in the right running condition.

    another really dumb thing is it is very hard to start no matter what. and then i was reading on here where someone said they heard of a guy who had to heat their cold engine up with a hair dryer before it would start. i decided to try that and guess what. IT WORKED! my engine will not start unless i heat up the engine and carburetor, and open up the choke and throttle and heat up the inside, and take the spark plug out and heat up the inside of the cylinder. then it will sputer and barely want to start and i have to keep twisting the throttle until it will finally hold an idle. now im not sure if it has anything to do with the cold 20 degree tempuratures or not. but its a real pain.

    another thing i wanted to bring up and ask about is this. after i run the engine for about 20-25 minutes it will be running fine. but then it will start to get a roughness in it. and have alot of vibration. and i can tell i should give it a rest. like its either getting too hot, or running too lean, or not getting the right lubrication. now is this how these engines are all the time? or is this how they act during break in, and why it is said not to run them more than 30 minutes during the break in? does this sound normal?

    i just wonder if i am doing anything really wrong and if anyone thinks i am messing with it too much and running it too hard too soon? how does everyone else go about break ins?

  2. professor

    professor Active Member

    There was a good discussion here on break in. I am of the opinion with the floggers. See if you can find that thread (I think it was on this site).
    There is no way in the cold that your engine is getting too hot unless the cylinder to piston fit is too tight.
    As for starting in the cold, aren't all snowmobiles 2 strokes?
    My little Toro two stroke starts pretty good in winter, it has a primer button. Does your carb have a little button to push to prime the carb with fuel ? (they let a little gas into the carb throat).
  3. motorpsycho

    motorpsycho Active Member

    The reason they say to only run it for 30 mon. at a time during break in is to allow the cylinder and rings to expand and contract several times. This helps seat the rings to the cylinder for a better seal.

    moving the clip on the needle will only help with the mixture from idle to about 1/2 throttle. Anything over 1/2 throttle and the needle is not ebvn in play at that point. so, sometimes it will run rich when you are running it less than 1/2 throttle because of where the clip is set on the needle. the needle regulates how much fuel is coming through the main jet. And then when you go wide open the needle is out of play and now only the main jet is determining the air-fuel ratio which may make it run lean (if the jet is too small). tuning these carbs for the perfect air-fuel mixture from idle to wide open throttle can be tricky and it usually requires changing the main jet.
    BUT, in cold weather, and engine will want to run richer because cold air is a lot more dense than warm air.

    if you have to twist the throttle to keep it running when it's cols it's because the engine is still tight, and the air is so cold.
    is the lucas oil that you're using actually 2 stroke oil?
    a 16:1 gas-oil ratio has a ton of oil in it. think about how cold that oil is that's mixed in with the gas when it's 20 degrees outside. I think part of the problem is that the engine is having a hard time with that much oil in the cold weather until the cylinder gets warmed up. I also think that the hair dryer trick is helping because your gas-oil ratio is so high. after break in, and you go with (for example) a 32:1 ratio, you should have no problem starting the engine in very cold weather. use the choke, prime the carb and it should start right up.
    I did my break in at 20:1 for 2 tanks, and then i went to 32:1 and both of my engines are fine. I have even ran one of them at 40:1 a few times with no problems.
  4. DuctTapedGoat

    DuctTapedGoat Active Member

    Simple enough - don't worry about it, these motors are tougher than people give them credit for. If it's a fouled engine, it's gonna die no matter what. All you /really/ need to worry about is making sure everything stays tight (but don't touch the head unless you have a torque wrench, 90% of the time they're fine).

    My favorite sparkplug was recommended in the guide that came with it (NGK BR7HS), I've avoided anything else like iridium tips so I don't chip my piston.

    As far as running rich or lean on your throttle pin, for now you should just worry about getting past the breakin point, you're going to need to retune after it does (and you'll know it when you do, you'll feel it and hear it).

    This is what I do with my motor, some oppose, most don't care. I leave the gas on all the time and leave the choke wide open. 24/7 all day long. It helped significantly in breaking it in, and after that I can pedal start this up in less than 10 yards in 20 degree temps.

    Make sure your major gaskets (exhaust and air intake) are good and everything is well seated. I will say this now - go get some steel bolts to replace everything you reasonably can on the bike! Mainly your air intake mani stud bolts, your motor mount stud bolts, and your exhaust mount stud bolts. Do consider this - too much lubrication isn't good either. It would be good to mix a lean breakin batch, and put 10 ounces in your tank, see how it runs after 20 minutes. Keep adding to this tester batch ever so slightly - you'll eventually find what ratio is causing this. Don't worry about it much though, just get it broken in and then you're good to go with a different oil mix! I never ran less than 20:1 in my breakin, I hate gunked up jugs.
  5. the lucas oil i am using is 2 stroke oil. i do know a fare ammount about mechanics. i have a couple old chryslers i work on. im just saying im not a total newbie to working on engines and mechanical things. although 2 strokes and these bicycle engines are new to me. i feel i have bad luck with vehicles. just like with my old chryslers. it seems like everytime i get in and start them up they run completely different. and now its the same with this sd stinger kit. i feel like my vehicles are haunted haha. i guess ill just have to keep messing and experimenting with the thing. after all the kit only cost me $180 , so its not like ill be out a whole lot if i sieze the motor or something. thats part of the reaon why i bought the thing. i get so worked up when working on my old cars. because they are rare and i paid alot of money for them. so i figured it would do me good to have a $180 engine to work on. because i wouldnt get so ****ed when something went wrong with it haha. i will have to say the worst part of these kits are the crappy bolts and nuts. i have had almost all of them strip or break on me. even though the sd stinger folks say "their bolts dont break". but everytime i tightend anything down i have stripped a bolt. and its a real pain. i think i just stripped one on the rear motor mount. i always check to make sure things are tight before i ride. the thing that keep giving me the most trouble is the chain tensioner pully. it doesnt have a bearing in it and also the washers i use to secure it keep bending when i tighten the nut. i bought the strongest washer i could from a local hardware store, and it still bent. so all that is giving me the most grief. then next would be how hard it is to start the engine when cold. my carb does have the "tickle" botton. but it seems if i do push it once or twice it floods the engine and then it really doesnt want to start.

    so what spark plugs does everyone use? duct tape goat, you say you use a NGK br7hs what is the difference between that and a b7hs? what does everyone else like to use? what would be a good champion or autolite plug?

    also i notice my drive chain has spots where it will be tight, and then you roll the bike and another section of the chain will be loose. is this common? also how tight do you really want your drive chain? the kit came with a 415 chain.

    one other thing i noticed is when i mix my oil and gas. i can see little oil spots in the gas that havent completely mixed in. is this normal?
  6. motorpsycho

    motorpsycho Active Member

    you'll be taking your chances by going with a champion spark plug. I wouldn't put a champion spark plug on a tricycle!
    NGK b6hs a good plug choice, NGK br7hs is a little hotter than the B6hs i think.

    yes, the problem with the chain that you describe is very common. This is because the center hole in the rear sprocket is not perfectly centered or you have mounted it to the rim off center, sometimes the hub where the sprocket goes is a little smaller than the hole in the sprocket. So getting it the sprocket perfectly centered is a challenge. you want about 1/8" of play in your drive chain. you don't want it super tight, or super loose. you need s little bit of up & down movement in the chain.
    The chain tensioners that come with these kits are literally garbage. they are useless, and your best bet is to either get both chains adjusted so that you don't need a tensioner, make your own spring loaded tensioner, or buy a spring loaded tensioner.

    starting your engine when cold should be just like any other engine with a carb. on it. (you should know that since you work on old cars).
    close the choke, push the primer button one time and start it, it should start right up within 1-2 tries (both of mine do anyway). let it idle for a minute or 2 with the choke on, and then turn the choke off when the engine starts running a little rough. you will have to give it gas a little here and there, but it should stay running.
    if you push the primer button more than once, all you're doing is puttig more fuel in the cylinder than what's needed, and this can cause hard starting.
  7. DuctTapedGoat

    DuctTapedGoat Active Member

    Just don't prime it when you start it, it's not necessary by any means.

    Not sure, I'd have to investigate that one!

    Your rear sprocket on the motor side is not centered on the hub.

    Your oil is too cold, bring it to room temp and then mix.
  8. Skyliner70cc

    Skyliner70cc Active Member

    There's nothing wrong with a champion plug. the only plug I don't use are the Chinese ones. I had to pedal over 10 miles one day when a Chinese plug failed internally. Never had a champion plug fail me but we all know that plugs only fail when you don't carry a spare ;-)
  9. motorpsycho

    motorpsycho Active Member

    I beg to differ with you on that because i bought a set of champion plugs for one of my cars way back when i was 16 years old.
    the thing only ran on about 6 cylinders.
    I went and bought a set of A/C plugs, and then it ran on all 8 like it was supposed to.
    I have heard many stories of champion spark plugs being no good right out of the box, and to this day I will never buy another one.
    This is just my opinion, but I will bet that a lot of others here will agree with me.
    the best plug to run in a h.t. engine is an NGK.
    I will run nothing but NGK plugs in anything i own that is 2 stroke (m.b., dirt bike, weedeater) I use A/C plugs in my lawn tractor and I put nothing But A/C plugs in my g.m. cars, and my old triumph motorcycle I use Bosch plugs in my chrysler cars.
    I hear that those new e-3 plugs are supposed to be really good, but i haven't tried them yet.
    Last edited: Feb 1, 2011
  10. goodtime65

    goodtime65 Member

    have heard many stories of champion spark plugs being no good right out of the box, and to this day I will never buy another one.
    This is just my opinion, but I will bet that a lot of others here will agree with me.
    I agree with this. I worked at a boat shop one summer and you would not believe the problems I ran into because new plugs would not fire I only use NGK since than
  11. wzuccarello

    wzuccarello New Member

    The cold air causes the fuel/ air mix to be LEANER. The air is denser, and that means more oxygen per each intake stroke.Not more fuel.

    The ultralight aircraft engines are run near critical temps,and monitored with guages. I raise the needleclips on my Rotax 503 in the
    winter, to keep from getting to close to max egt .

    I've ran all my ultralights at 50/1 oil mix, Walmart oil. Some guys get 1200 hours on them with this mix.
    Since I always have 50/1 mix around, that's whay my chinagirls get, and they seem to like it. Bout 1000 miles on a strait head and 250 miles on a slanthead.
    My weedeaters and chainsaws like it too.

    No reason to run rich oil mix nowdays, we have modern 2-stroke oils.
    The old school numbers, 16/1 24/1 ect were for using strait mineral oil.

    Too much oil causes more frequent maintenance. Early carbon buildup in the ring lands causes ring sticking,sometimes bad enough to overheat the piston and sieze.One of the jobs of the rings is to transfer heat from the piston to the cyl wall.
    Xtra oil also causes the exhaust system to clog with carbon too.
    Last edited: Feb 8, 2011
  12. gator joe

    gator joe Member

    Everything u r saying sounds about right. If I were u I would run 8oz per gallon the first two tanks 6oz next two and 4oz the rest of the time.yes they run ruff wile doing the break in. Should not run longer than 20 minutes first two tanks. Is it cold were u live. .that's the only thing I could think of why you would have to use the hair dryer to heat it up thats weird I've never experienced that
  13. Fabian

    Fabian Well-Known Member

    :iagree: Every engine i have ever owned has been run at full power from the very start, with no bad effect.
    My engines have always made more power on the dyno than those people who were very gentle with running in their engine.
  14. Fabian

    Fabian Well-Known Member

    Completely incorrect advise when it comes to these Chinese 2-stroke engines.
    2-stroke oil not only lubricates, because an engine with poor metallurgy and high levels of cylinder bore distortion, has a much greater requirement for hydrodynamic piston ring to bore sealing in dynamic operation, especially when the engine experiences low airflow over the cooling surfaces.

    In my situation where the engine experiences almost 100% duty cycle with low airflow, 25:1 has proven to be the minimum oil/fuel ratio for dependable power output and good engine life.
    For this reason, the oil quantity is important, not for lubricity purposes, but to combat blow-by caused by excessive bore distortion due to rubbish metallurgy.

    Because 25:1 exceeds lubrication requirements the specification of the oil is largely irrelevant, other than it be rated for 2-stroke """air cooled""" engine operation.

    In short, for these Chinese engines, get the cheapest """air cooled""" specification 2-stroke oil that you can get your hands on. The engine will live a long and happy life, so long as it is not over revved.
  15. butre

    butre Well-Known Member

    all this talk of bore distortion and ****ty engines reminded me, a guy in Miami by the name of Bert Rod is cooking up a billet jug with a cast iron sleeve that should solve that bore distortion problem and improve cooling. knowing the way he works it'll probably be around $400 USD but it'll outlive a few hundred chinese top ends.
    Fabian likes this.
  16. Fabian

    Fabian Well-Known Member

    +1 Put me down for a jug and piston
  17. crassius

    crassius Well-Known Member

    I order kits from whomever is cheap & acceptable. Some kit suppliers have engines that consistently run in faster and run faster after run in, no matter what break in method is applied.

    Just no way to tell what is going on inside the motor.
  18. Fabian

    Fabian Well-Known Member


    Even from the same shipping container, some engines run better than others, despite appearing to be identical, both inside and outside.
  19. gator joe

    gator joe Member

    U can always tell what is going on inside ur motor. U just need to use common sense to determine what is going on. It will tell you just listen and look .i.e. cylinder. Spark plug. Carb..n so forth.sounds have always told me everything.
  20. crassius

    crassius Well-Known Member

    Which sound tells you when two of the ports have been machined out 2mm lower than they were supposed to be, or the bore measures a couple thou larger than the others do?