Blata B1 port timing vs B1 Rep port timing - Pocket Bike Forum - Mini Bikes
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post #1 of 26 (permalink) Old 03-24-2006 Thread Starter
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Blata B1 port timing vs B1 Rep port timing

I have now measured the port timing on a B1 rep to compare with an original Blata engine,the first pics are the equipment/setup I used, the dti gauge is just to ensure the piston is at tdc to zero the degree wheel,the third pic are the results.
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File Type: jpg timing set up.JPG (768.0 KB, 106 views)
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File Type: doc Original Blata B1 pocket.doc (34.0 KB, 146 views)
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post #2 of 26 (permalink) Old 03-24-2006
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Re: Blata B1 port timing vs B1 Rep port timing

Interesting that the Chinese version evacuates the cylinder sooner and stays open for a 12 degree longer moment and as interesting the Chinese version opens the boost port 5 degrees sooner and holds it open for 10 degrees more than the original too...think they planned to let it breath a little deeper or did somebody mess up the casting dimensions

Last edited by steveg; 03-24-2006 at 08:24 PM.
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post #3 of 26 (permalink) Old 03-24-2006
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Re: Blata B1 port timing vs B1 Rep port timing

Have you split the crankcases on those engines ? Hows the rest of the castings comparing ?
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post #4 of 26 (permalink) Old 03-24-2006
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Re: Blata B1 port timing vs B1 Rep port timing

thanks for that info... good comparison.. i too would like to see internal pics of the blata case & cylinder if you have them..
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post #5 of 26 (permalink) Old 03-25-2006
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Re: Blata B1 port timing vs B1 Rep port timing

i have two b1r engines and the port timming is different also what base gasket has the b1r compared to the blata ?
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post #6 of 26 (permalink) Old 03-25-2006
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Re: Blata B1 port timing vs B1 Rep port timing

While you're at it, could you have a look at the flywheels of both and tell me how much difference there is in timing advance between the two? Also if you have access to some timing equipment, could you investigate the dynamic timing advance when the engines are running? Reason being, there is some controversy over the validity of using advancing keys on b1reps. My engine runs better with one but I'd like to get to the bottom of this question.

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post #7 of 26 (permalink) Old 03-25-2006
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Re: Blata B1 port timing vs B1 Rep port timing

curious about the difference in port area size also...
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post #8 of 26 (permalink) Old 03-27-2006
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Re: Blata B1 port timing vs B1 Rep port timing

Quote:
Originally Posted by steveg
think they planned to let it breath a little deeper or did somebody mess up the casting dimensions
i suppose they didn't "plan" anything. they just messed up the exhaust port's position (around 1.5mm towards the cylinder top), therewith messing up the whole cylinder design.

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post #9 of 26 (permalink) Old 03-27-2006
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Re: Blata B1 port timing vs B1 Rep port timing

i cracked a few cases open and took a few pics 2/3 months back

there are 2 different shapes!!

guess which ones match the barrel best





the one with the angled port join came with my engine that has a "2 cast" barrell fitted
the other one is what came with the bike.......
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Re: Blata B1 port timing vs B1 Rep port timing

the pic's werent' there.
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Re: Blata B1 port timing vs B1 Rep port timing

no pics....
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Re: Blata B1 port timing vs B1 Rep port timing

i can see them just fine...

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Re: Blata B1 port timing vs B1 Rep port timing

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Re: Blata B1 port timing vs B1 Rep port timing

you must have google vision


Quote:
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i can see them just fine...
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Re: Blata B1 port timing vs B1 Rep port timing

i see them now.. had to wait for the link to redirect, copy & paste wasnt working... those are both of a c1 though??
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Re: Blata B1 port timing vs B1 Rep port timing

yes they are both c1 engines

although i tok one pic upside down by mistake

if you look at the pics badazz posted of the c1 engine a while back from inside, the parts that do not match need ground back

on the engine pic i posted 1st you can see the transfer join is cast into the correct shape so this work is not needed
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Re: Blata B1 port timing vs B1 Rep port timing

and this forum is so ****en *** with outside links IMO
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Re: Blata B1 port timing vs B1 Rep port timing

Quote:
Originally Posted by rasputin
i suppose they didn't "plan" anything. they just messed up the exhaust port's position (around 1.5mm towards the cylinder top), therewith messing up the whole cylinder design.

r
I don't think they messed it up too bad as I've never heard one popping or expelling unburnt fuel...one of the tricks of 2 stroke tuning is raising the exhaust port so as to evacuate the cylinder sooner and I've read somewhere that tuners were applying that trick to the real deal B1's.
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Re: Blata B1 port timing vs B1 Rep port timing

Quote:
Originally Posted by steveg
I don't think they messed it up too bad as I've never heard one popping or expelling unburnt fuel...one of the tricks of 2 stroke tuning is raising the exhaust port so as to evacuate the cylinder sooner and I've read somewhere that tuners were applying that trick to the real deal B1's.
for a powerful and well-performing engine you need ports that have the correct port timing and the correct ports cross-sections. the scientifical approach to this is called "time-area calculations".

example: while a straw is great for sipping a cocktail, it's just too small for drinking a pitcher of beer within one minute. you might use two straws, or even more, but you'll soon discover that the cross-section becomes too big to suck the beer into your mouth. so you have to agree upon a compromise, i.e. "five straws for best drinking performance".

the same thing is valid for engine ports. at low rpm they're too "big" to flow properly, at high rpm they're too "small", throttling the engine. the range between these two rpm is called "power band". regarding the cylinder, the transfer ports have one such power band, and the exhaust port(s) has/have one such power band. the secret for a optimum performance is to combine these two power bands in certain ways.

the blata cylinder is properly engineered, the two power bands are ideally "in tune", resulting in a wide power band.
the chinese cylinders feature the same port dimensions, but different timings. the two power bands are not "in tune". this means that at low rpm the transfer ports are "okay", but the exhaust ports are too "big", and at high rpm the exhaust ports are "okay", but the transfers are too "small". and there's no way one can eliminate that.

the c1 engine is still able to "produce" a lot of power, but it will never perform as well as a blata cylinder.

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Re: Blata B1 port timing vs B1 Rep port timing

"the blata cylinder is properly engineered, the two power bands are ideally "in tune", resulting in a wide power band."
within the confines of mass production tolerances, of course.

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