Break In What period for a 70cc break in? - I have contradictory info

Discussion in '2-Stroke Engines' started by Rusty Biker, Apr 14, 2013.

  1. Rusty Biker

    Rusty Biker New Member

    I recently purchased a 70cc for my mountainbike - it was all installed for me.

    I was given a manual of sorts explaining the ins and out and maintenance etc.

    There is a contradiction in the information regarding the break in period.

    On one page is says:

    Do not exceed 20km/h during break-in period. Speed may be increased to 35km/h after the first 500km (break in period).

    But on the next page it says:

    To correctly break the engine in, do not exceed 15 mph (25km/h) or 30 min. continual running for the first 50 miles (80km) during engine break in. Engine will develop more power after break in.

    There are two contradictions here - the maximum speed I should ride and how long before I can increase the speed.

    I'd have to guess how fast I was riding in any case. I don't have a speedometer. :rolleyes7:

  2. Fabian

    Fabian Well-Known Member

    It's dead easy:

    Make sure the carburettor is jetted correctly and use a 20:1 oil/fuel ratio for the first gallon or 5 litres of fuel, then change to 25:1
    It is preferable to use a 2-stroke oil that is designed for air cooled engines but at 25:1 it's not of any real importance as you can get away with any kind of 2-stroke oil at that ratio.

    Just ride your bike as you normally would and don't worry about any break-in procedure.

    All of the engines i've ever had in my possession 2-stroke or 4-stroke (car, motorbike, rc engines, motor bicycle engines) have never used a gentle break-in procedure and have always given good performance.
    Last edited: Apr 14, 2013
  3. Fabian

    Fabian Well-Known Member

    The most important thing with these engines is not to over-rev them; ideally keeping rpm's below 5,000 as well as using a Jaguar CDI to prevent detonation and consequently, preventing the connecting rod big end bearing form being hammered out.
  4. Rusty Biker

    Rusty Biker New Member

    Odd, the cobbled-together manual also states that I should be using 16:1 for the break in period and then go to 20:1.

    Why do some on this forum say that 32:1 is ok after break in?

    Contradictions all round then! :tt1:
  5. crassius

    crassius Well-Known Member

    perhaps gas & oil vary in different places

    here in the US, some friends and I like 16:1 for first two tanks followed by 32:1 thereafter

    seems to work for us
  6. Skyliner70cc

    Skyliner70cc Active Member

    Yeah! Another oil thread. 32:1 all the way since day one. Lots of newbies have problems starting their engines on 16-20:1 oil mixtures. Try 32:1 and if you really think you need more oil, add it to your tank after you at least got it running..

    As for break in, ride it normally. Vary engine speed and rpm for first couple tanks and DO NOT OVERHEAT the engine. That is all you have to do. I personally do not limit engine RPM but do vary engine load. I'll go WOT max RPM on a straightaway and then back off going up hill and then let it rev going down hill but not with a closed throttle.

    Have fun and keep your first couple of trips nearby so you don't have to pedal far if something breaks or requires adjustment.
  7. Rusty Biker

    Rusty Biker New Member

    Talk about annoying! I only just got the 70cc engine because the 50cc I had bombed out. Went on what was to be my first proper trip today and got a sudden flat tyre just a few blocks away! All the time I road the 50cc over the last 3 or 4 years I never had a flat tyre. So I took it round to where I had it installed but the guy there suddenly has no time for me and let me know in no uncertain terms. I've had problems with the previous engine and I think he's suddenly lost all patience with me. But this isn't an engine problem, it's as simple as a back tyre puncture and I really don't know how to do something as basic as this on an engined bike. It's complicated by all the chain settings etc being there and I'm afraid I'll mess something up I'm pretty sure you're not suppose to turn an engined bike upside down. I might try an ordinary bike shop but I'm not sure they like handling engined bicycles, even to just fix a puncture.
  8. Fabian

    Fabian Well-Known Member

    I've never multi-quoted a post so many times whilst on this forum.
    Honestly i can only give one suggestion - give it up - sell the bike - move on to a different form of transport.

    To make this hobby/transport useable requires a high level of mechanical skill and a good understanding of electrics as well as having a comprehensive understanding of how the fuel system and lubrication system works (regardless of the fact that it has a simple carburettor) - if you don't have any of those skills it's a complete waste of time, as many others have found out over time, not to mention the never ending repeat questions posted on the forum of why their bike doesn't work or won't run.

    It's taken me 2 years of pain and heartache to create a motorized bicycle that not only useable and functional, but most importantly, "reliable".

    This game isn't for the faint of heart or for those who lack the patience of a nun on beta blockers.
    Ironically, for something that uses such a simple design and a bargain basement price which makes it a disposable item, it has required all of my knowledge and skill; pushing me to the edge of my sanity trying to work through what seemed like impossible and mysterious problems. Nothing i've ever owned has caused me so much heartache; so much pain; so much despair and at times almost crushed my will to live (trying to solve technical problems), yet paradoxically nothing i have owned has given me so much joy.

    If you don't have a good skillset to deal with these engines, you are doomed.