How many rpm's when stock

Hello again guys.
Does anyone have an idea about how many rpm's a stock 66 cc 2 stroke kit should turn? I have a dept. store beach cruiser with just the parts that came in the kit on it. It starts right up hot or cold and runs as good as I would expect it too for the money. I have run well over 7 gals of fuel through it and just got a tiny tach so I would have a baseline to go by for tweaking. It seems to run about 4700 rpms wide open. I put a new autolite 216 plug in it and it seems to be a little lean. I can open the jet up a little if I need to just was trying to get an idea of what to shoot for. I am definately not going as fast as some are claiming. Also I am at sea level or just a few feet above it thankfully.

Thanks
Jack

The real trick to getting more power (& speed)from these engines is to 'free flow' the exaust & re-jet the carb.

As far as RPMs go, every engine runs a little different.

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Thanks VMB
I am getting ready to check the main jet now. The tach is going to be a help. I noticed that the rpms don't go up from about 3/4 throttle on even though the it doesn't bog or stutter, but it was hard to tell without the tach. I have a couple of #69 drills on hand. I remember a thread that discussed the jet size somewhere as between .7 and .8 mm. That should be real close. They are .0292. I'll let you know.

Jack

First, a drill does not drill an exact hole. Any machinist would say to be accurate with a hole you have to drill it undersize and ream it. That's even using a lathe and center-drilling it
That said, you are unlikely to get even those results with a hand drill or a press (you can't center it easily). You will likely have .300 if you're lucky.
I know it will upset many but this is NOT the way to rejet your carb. By drilling, you won't get the proper hole AND, more importantly, you will have no reference as to where you are in relation to standard jet sizes if you further tune. Jets are not "between .7 and .8 of anything". That is thinking with the "I'll drill it out" mentality and that allows huge variances.
It might help your problem or it could make it worse, then what size jet do you ask for? You also forever lose your baseline. 5mm jets are cheap($4) so buy several sizes over stock and work big to little. Then you can have a conversation using standardized tuning numbers like the big boys do.
In true 2-stroke tuning circles, drilling a good jet is a hack move and just not done. I understand the temptation for a quick and cheap fix but I would not admit it publicly if you do. You would have lot's of company here but you will not be taken too seriously by those who really know 2-stroke tuning.
Not trying to criticize, just preaching about a peeve of mine. I like to see people do it right - not hack.
Dave
KC

we're talking about jetting a china 2 stroke with an $8 carb. not a gp race bike. it's perfectly acceptable to solder the jet shut and drill it to the size you need, theres only 1 jet and if you look at a few of them there drilled pretty haphazardly to start with.

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My point exactly. And we wonder why they have to be modded.
Acme, $8 carb? Is that the way you are thinking here? We're sending 13 year olds out there on public roads at 35mph. Please!

As someone with something to sell you should be a leader for doing it the right way. How about selling and promoting a jet kit? $5 you start doing that.
Is the $800 Schwinn on your site run on a soldered jet? So now we aren't talking $8 anymore. This leads to the question, at what dollar amount does Acme labs start doing it "the right way"?
Not trying to be malicious but to make a point. An engine, Moto GP or Chinese HT, will be only as good as it's weakest link - and they have enough already. To promote anything else is poor craftsmanship.
JMO,
Dave
KC

get real man. if you feel it's unsafe for youngsters to ride around on $8 carbs ($100 for the whole kit) maybe you should contact your legislator. the point is, this is a fun cheap hobby, the stock carb is so cheap and basic that drilling your jet isn't making it unsafe.
coming off with an i'm an expert elitist attitude to a newer member isn't helping the hobby any.

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I am well aware that a drill will not make an exact or onsize hole. I suppose every apprentise learns that in the first or second week of training or if you have not been trained sooner or later you will just figure it out if you are paying attention or have ever bothered to mic a drill bit, but I have never seen one drill a hole ten times the size of the drill. I used a # 69 drill which is .0292 I have no idea how you would expect it drill a .300 hole. When I quoted what I saw a member contribute as to what he has seen with the jets that come in these kits he was talking in millimeters. That is the .7 to .8 which you were saying there is no such thing as. If you have a decimal equivelency chart and know how to read it you will see that .7 mm is .0276 and that .8 mm is .0315. As stated earlier the # 69 drill is .0292. If you do the math you can see where it falls in that range. It just so happens that my jet was .7mm or .0276. Yes I measured it first. So you can see I haven't lost anything. My baseline started when I got a tach. That was why I didn't try to do anything with it before I knew where I was. I was tuning and racing motorcycles in the late 60's and all through the 70's. Since I reject the premise of your comment that tries to separate me from the so called big boys I will not respond to that. The newbie next to my profile is because I just joined this board,and not for any other reason. My little 2.9 cubic inch Chiese 2 stroke wonder apparently doesn't know if the main jet was drilled, reamed or bored or if the hole in it is perfectly round and since my electron microscope is in the shop I don't know if it's perfectly round either, but what I can tell you is that the lean condition went away and that I picked up approximately 250 rpm's and that is what I was trying to accomplish. And if this a public forum I am admitting it publicy.I drilled it out. What works, works whether you take it seriously or not.




Jack

By "Big Boys" I was referring to big engines / big teams / big manufacturers. Not much about tuning HTs compared to the advances in 2-stroke tech of the 70s and 80s.
You have to realize no one knows what your understanding is when you ask a generic question like that. Just today, a guy thought he burnt a valve in his 2-stroke. He might not have known about drill bit variances and likely not even tuning principles. Some will read "I just drilled mine and got more power" and so they are on a search for a drill.

The .300 was obviously a typo. Point taken.

My reference to .7 to.8 was that it is a range - not a size. As you stated, it's very easy to drill a .03 with a .292 bit - even .315. So if you are okay with that range, fine. What exact size did you end up with and what would be the next step up?
Like I said. It may help your problem and I'm glad it did but I'll have to stand by the advice of using high quality jets for 2-stroke tuning rather than drill bits............ $100 engine or not.
250 RPM doesn't sound substantial unless 4700 is the stock max. Is it stock otherwise?
Dave
KC