43cc PistonPort Port map and port timing - Pocket Bike Forum - Mini Bikes
 
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post #1 of 20 (permalink) Old 01-14-2014 Thread Starter
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43cc PistonPort Port map and port timing

I realize this was a waste of time on this engine but, I hadn't done this in about 25-30 years and thought I could use the practice. With the head and cylinder as one piece and a small bore, it wasn't the easiest port map I have ever done. But why not. I figured someone may get some use out of this. The port map should be pretty accurate but, I'm sure, the port timing is off a few degrees. Regardless, it does show there is plenty of room for improvement.






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post #2 of 20 (permalink) Old 01-14-2014
Re: 43cc PistonPort Port map and port timing

What does the 40x34 stand for?? 40mm x .......??

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post #3 of 20 (permalink) Old 01-14-2014
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Re: 43cc PistonPort Port map and port timing

I thought the stroke for a piston ported engine is 32mm's and a reed inducted engine is 30mm's........
40x30 = 37.6cc
44x30 = 45.6cc
40x32 = 40.2cc
44x32 = 48.6cc
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post #4 of 20 (permalink) Old 01-14-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

34 is stroke. I saw the 32 number listed elsewhere also but, measure multiple times by two different methods shows 34mm. A quick check on an online displacement calc shows...... 40mm bore and 34mm stroke = 42.726 disp. (or 43cc rounded up)

http://performancetrends.com/Calcula...splacement.php

Last edited by ThumpLump; 01-14-2014 at 01:12 PM.
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post #5 of 20 (permalink) Old 01-14-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

I just rechecked, again. It is 34mm. 15mm bearing journal, halved, is 7.5mm. Add that to the distance from the journal to the center of the rod pin, which measures at 9.5mm and you get 17mm. Doubled and you get 34mm.
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post #6 of 20 (permalink) Old 01-14-2014
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Re: 43cc PistonPort Port map and port timing

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Originally Posted by ThumpLump View Post
34 is stroke. I saw the 32 number listed elsewhere also but, measure multiple times by two different methods shows 34mm. A quick check on an online displacement calc shows...... 40mm bore and 34mm stroke = 42.726 disp. (or 43cc rounded up)

http://performancetrends.com/Calcula...splacement.php
But wouldnt that make a 44mm bore a 52cc??...

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Last edited by CAM2; 01-14-2014 at 02:12 PM.
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post #7 of 20 (permalink) Old 01-14-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

Provided the stroke is the same, yes. I can tear down my 44mm bore piston port engine and check it's stroke as well. After all, this isn't rocket surgery.
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post #8 of 20 (permalink) Old 01-14-2014
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Re: 43cc PistonPort Port map and port timing

Yea 44mmx34mm=51.7cc's thats what the piston port motors are. Its the reeded cag motor thats has a 32mm stroke so the 44mmx32mm = 48? cc's



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post #9 of 20 (permalink) Old 01-14-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

Good. I really didn't want to tear down the 44mm bore piston port engine just to get the stroke. Of course, this will lead to the question, "Can a 34mm piston port crank fit the reed engine?"
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Re: 43cc PistonPort Port map and port timing

CAM2 put a P/P rod on a R/P FC crank, took some machining & welding. I am putting a Cag FC crank in a piston port case w/ the 2mm shorter stroke and cut down 43cc cyld and Cag R/P alloy head. The crank had to be turned down on one side to fit the small crank seal on the pull start side. That side would not fit the R/P cases I believe, its too long because of the generator/starter motor.

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Re: 43cc PistonPort Port map and port timing

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Originally Posted by ThumpLump View Post
Good. I really didn't want to tear down the 44mm bore piston port engine just to get the stroke. Of course, this will lead to the question, "Can a 34mm piston port crank fit the reed engine?"

Like EPR said it will take a way different seal to pull it off......I remember how hard it was to find a seal to fit the reeded full circle crank to fit in the piston ported engines without turning down the crank.......

Best bet is to get a FCC and pressing out the pin,,,welding up the hole and redrilling it 2-3mm's out to the edge more will work out better..........

I had a few nitemares when building these.............LOL


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Last edited by CAM2; 01-14-2014 at 08:51 PM.
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post #12 of 20 (permalink) Old 01-14-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

Don't confuse rod length with stroke. 34mm stroke piston port rod length is 62mm.
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Re: 43cc PistonPort Port map and port timing

Wow, you guys are right...Had me runnin for my digital calipers like a madman... I guess I overlooked that and my brain see's what it wants after hearing 30mm stroke, lol... So looks like the Chinese were importing engines over 49cc all along.

Just out of curiosity, would a single lip oil seal work in this application? This one looks like it will fit the p/p case w/ Cag FC crank.
http://www.ebay.com/itm/Metric-Oil-S...item233006c049

Last edited by flattie42; 01-14-2014 at 11:41 PM.
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post #14 of 20 (permalink) Old 01-15-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

What got me was the lack of duration on the port openings. Particularly the exhaust. I'll have to do some more looking and measuring of the barrel to see how much room there is to carve on. Ultimately, I will get a reed engine but for now, these old piston port engines are all I have. Might as well play with them.
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Re: 43cc PistonPort Port map and port timing

Thanks for the maps, I copied them, will look at them later. Have a timing wheel I copied, will mount it to plastic and make a pointer. First time for me using a wheel, so we will see what happens, lol.
The ports are like that cause it's a backpack blower engine, it runs at one speed, and lower compression so it runs along time. You have to mod almost everything from the front to the rear on the bike and engine too.

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post #16 of 20 (permalink) Old 01-15-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

With a one piece cylinder and head, the transfer ports will be tricky to get to, to measure with a degree wheel. Intake and exhaust, no problem. The only thing that comes to mind to do the transfers is to remove one half of the case and slide a thin piece of something up the transfer to see where it closes. From the top through the plug hole may be an option, but tough to see what you are doing inside.
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Re: 43cc PistonPort Port map and port timing

Since no one sells 2 pc. piston port cyld/head kits, someone started cutting the top of the cyld off, just under the 5th fin, and make a ring at the top to fit a 2 or 4 pc reed port B/B kit. With that setup, you mill down the top of the cyld. to get the squish you want and like you said, its easier to time with no head on the cyld. That is a modded clutch w/ 6 holes and hp spring. I had to take the top of the piston down to clear the compression cap.
Attached Images
File Type: jpg Piston Port cut Cyld and Piston.jpg (247.3 KB, 12 views)
File Type: jpg PP HP Photos1.jpg (289.8 KB, 10 views)

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Last edited by EPR; 01-15-2014 at 11:44 AM.
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Re: 43cc PistonPort Port map and port timing

You can do a reed conversion kit on your piston port motor just needs some extra porting done for it to work properly



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post #19 of 20 (permalink) Old 01-16-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

This looks like it may be some good software, for those that are really into porting and such. I haven't tried it but, it is tempting.....http://www.porting-programs.com/

I can no long find the TSR software online.
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post #20 of 20 (permalink) Old 01-19-2014 Thread Starter
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Re: 43cc PistonPort Port map and port timing

As an addendum, I measured the intake and exhaust duration with a degree wheel and found the duration measurements from the map to be pretty close. Intake goes to 114 degrees from 112, as measured from the port map and the exhaust goes to 132 degrees from 128, as measured from the port map. With that, I would say as a whole, the port map is within a couple percent of being spot on.
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