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Discussion in 'Motorized Bicycle General Discussion' started by SchwinnStingray, Jun 4, 2014.
Are there any service books or maintenance manuals for the HT china girl or similar?
You're logged into the best source of HT, China Girl information available. Use the search feature and you'll have all the information you could possibly want.
Any book would end up being someone's opinions and here you get a good cross section of input. Read, compare then make your own decisions on what is good information and what isn't.
you're reading it
I appreciate what your saying about searching, I'm not after what people have done or opinions on what to do, I am after simple facts like ring gap and tolerances, min and max compression readings, port to crank timing, min and max ignition readings, torque settings etc.
I can assume that no manufacture have ever published any figures?
Tolerances, ect vary so much!
Sorry for the confusion, I mean, if a cylinder is manufactured at 44mm, what is the tolerance measured for wear, 44.4mm???
If a ring is manufactured for a 44mm bore then what is the end gap set to?
At what duration of crank degrees should the port timing be etc etc etc...
Port timing varies considerably from one motor to another.
The Plating on the barrel is very thin, if a barrel was to wear through the plating it is stuffed.
normally scoring of the barrel would be reason to replace it,
Ring gap is something I check on motors I build, but have not needed to adjust as it has always seemed sufficient.
There is a formula for determining the ring gap somewhere, maybe in Gordon Jennings' 2 stroke tuner's guide... usually the ring gaps on these are plenty wide enough that they don't need to be adjusted.
Port timing and ignition timing on these things is all over the place as well and you can have 2 engines side by side that are totally different but you can look up port timings in here and in other places to get an idea what works and what doesn't... or just ask, I'll answer if I see the question instead of sending you on a search and so will most of us.
My port durations are a little longer than I originally wanted because I used my old jug on my new bottom end but it still makes good low end power and the high rpm power is really strong, but if I remember right, mine are 126 for the intake duration, 132 for the transfers, and 168 for the exhaust. I'd normally run closer to 120, 125, 150 for my ports but since I had to raise my jug by putting a 1mm spacer under it to keep the piston from coming out the top, but the port durations came out about 12 degrees higher than I'd normally run on a piston port setup... It ran good when testing so I kept it the way it is and it's most likely the high compression and 44 tooth sprocket that lets me get away with those timing numbers, I wouldn't recommend these timings to a new builder but they are working...
Because of manufacturing tolerances, or lack thereof, with the Chinese 2 stroke, anyone writing a comprehensive specification guide would only be speaking from his/her experience or, again, giving opinions.
If they were Harley or Honda engines, the factory would have exact figures to go from. Unfortunately because of the many and varied Chinese factories producing these engines all figures would only be 'ball park' at best.
As for as torque values there are standard charts published that cover steel fasteners into cast aluminum threads. Typically speaking you only have about three sizes to deal with on an HT. 5, 6 and 8mm which equates to 18/25 inch pounds, 40/60 inch pounds and 120/140 inch pounds. Those are safe numbers, not carved in stone, again because of the quality control issues of the metals we have to deal with.
I feel you are over-thinking the engine. They're crude and low quality, but lots of fun. Maybe you should consider compiling the info you want based on your findings with your engine. I think you'll see the inconsistencies I'm referring to when compared with other engines.
Maybe we could backward engineer it then,
For example, my heritage is with V8 engines, to set a ring gap, we use a base formula of .0050 per inch of bore (you would use .0045 for a tight ring and .055 for a loose high revving thing) as a rough guide so for a 4.0350 inch bore you would have;
.005 x 4.035 = .020 or 20thou ring gap.
Piston to bore clearance is calculated similarly and so on and so on...
Is any of this making sense or shall I just start asking questions one by one as need be.
Was going to say, the ring gap on my motors are around 20 thou.
That's always been good, but thrown away a few rings that were not round.
yes, that is with rotating rings - these are both, fixed and traveling across ports, so consulting a modern 2-stroke book might be required
My knowledge of 2 strokes is very limited, I will do some more research.
can anyone expand on this;
Here's an old thread started by a member from Moscow. It looks like that link you posted got a lot of information from it. Even the photos have Dagger's name on them. Most were his originally.
Wow, those Russian engines look a LOT like the China Girl... I bet that's the design China copied to make these engines... Too bad they didn't use the case induction and reed valve configuration tho...