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 Post subject: FL250 PORT TIMING
PostPosted: Mon Aug 31, 2015 10:49 pm 
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Joined: Wed Aug 26, 2015 6:40 am
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Where should I be on port timing with a modified fl-250? I have an aftermarket pipe, 36mm mikuni carb, .080 overbore, port work to cylinder, ports have been raised by cutting the jug. Piston now sits out of the bore by .080 with one case gasket. I know there is not a perfect answer for this but just a guideline would help lots!! Thanks, Joe


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Mon Aug 31, 2015 11:05 pm 
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Location: Hope, B.C Canada
Adnoh is your guy for that. He is the resident math propeller head here. Send him a PM (private message). Click on members tab above, find his name, click on the PM tab.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Mon Aug 31, 2015 11:05 pm 
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Location: Hope, B.C Canada
By the way welcome new guy


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Tue Sep 01, 2015 9:11 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22512
Location: Chicago
Any pictures of the cylinder this a CR cylinder?

If someone cut the bottom of the cylinder I bet they also raised the exhaust port.

Seen this yet? viewtopic.php?f=1&t=3721&view=previous
And http://www.pilotodyssey.com/billtips.htm


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Tue Sep 01, 2015 9:39 am 
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No it is not a cr cylinder. I can post some pics of it next week. Thanks for the welcomes. Joe


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Tue Sep 01, 2015 9:52 am 
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Location: Chicago
Seen this yet? viewtopic.php?f=1&t=3721&view=previous
And http://www.pilotodyssey.com/billtips.htm


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 1:12 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Lets discuss the cutting of the jug and it's bore. We need more detailed information as did they mill the base of the jug or did they adjust the ports roof, base, angle and area. As a rule when you over bore a cylinder it lowers the ports roof based off of angle (retards). If you mill or cut the jugs base it also does the same (some what) as well as change piston position due to crank angle and port time open in degrees(dwell). The piston it's self could account for the above deck as well ad with this it changes the ports timing not only on exhaust but intake. The we look if the jug is boost ported of just a bottom feeder.

So maybe we should start with what you have and go from there. year of FL 250 with what jug (cylinder). Piston? rod?
Then all can help you better from there. Look forward to your post and having some fun.

Adnoh

canadian oddy gives me way to much credit however thank you. Can I be an impeller head since we have been talking jet skis aka water craft. The two have different displacement theory.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 1:49 pm 
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Posts: 22
Not sure of the year of the odyssey. I know it has a stock crank and rod because I bought a used one on ebay. It is definitely a fl-250 head. Weisco .080 over piston no boost ports. Just standard transfer ports in jug. Thanks for your help!!


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 5:23 pm 
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Posts: 3620
Location: Wichita ks
Ok that is helpful. There is a # on top of the piston. please provide this number. This will make sure the piston is the right one than we can start to look at the cylinder for answer's.

Few more questions that may help.
was the Engine yours to start with
was the new crank assembly installed by you or some one you knew
do you have the old crank assembly
was the cylinder on the Engine to stat with
was there a cylinder spacer on the Engine that may have been removed.
does the head have a recessed pocket to accommodate the above deck of the piston.

What I'm trying to do is see if it was this way before or after the new crank assembly and cylinder or if you bought all the parts than assembled an Engine form those parts.


Yes pictures help a lot.

I bet between every one on the board we can figure it out.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 8:09 pm 
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Posts: 3620
Location: Wichita ks
I went and pulled some pics from a 1981 manual that list the port time. We can use this to determine the alteration based off of stroke and rod length. Then we can look up the piston on wiesco cat and do some number crunching using you measurement's.

Man, HONDA sure was a lackey in the 350 and 400 manual compared to the info in a 250

The static is about 128 psi


Attachments:
fl250 port timing #1.jpg
fl250 port timing #1.jpg [ 43.5 KiB | Viewed 2114 times ]
fl250 port timing #2.jpg
fl250 port timing #2.jpg [ 43.48 KiB | Viewed 2114 times ]
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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 8:21 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
I was doing some resurch for you and seen that a replacemtn rod kit for the 250 also comes with a spcer plate and this may be why yours is above deck.

"

Product Description

THE ORIGINAL CONNECTING ROD FOR THE FL250 HAS BEEN OUT OF PRODUCTION FOR YEARS.WITH THIS KIT–YOU CAN TOTALLY REBUILD YOUR CRANK. THE SPACER PLATE LIFTS THE CYLINDER UP SLIGHTLY, AND THE ROD SUPPLIED IS SLIGHTLY LONGER–BUT THE SAME AS THE ORIGINAL ROD ON BOTH ENDS. IT WILL WORK PERFECTLY ON YOUR ODYSSEY.PEOPLE HAVE BEEN DOING THIS FOR YEARS.

YOU GET

THE CUSTOM MADE SPACER PLATE,THE COMPLETE ROD KIT WITH ALL BEARINGS AND THRUST WASHERS,WRIST PIN BEARING, GASKETS, AND LONGER BLOCK DOWELS–EVERYTHING IN THE PHOTO,


Attachments:
fl 250 rod kit.jpg
fl 250 rod kit.jpg [ 12.37 KiB | Viewed 2114 times ]
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 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Sep 02, 2015 8:22 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
need anything else ask away.

If you want send me you port open numbers in mm from deck and I will run to be sure your good

Adnoh

If your rod has a number on it please post.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Sep 03, 2015 11:42 am 
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Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
The Engine came with the odyssey. It was together but had a bent crank and stuck piston. I bored and honed cylinder out to 72mm, .080 over and bought a used crank and rod on ebay. Checked it for straightness, put new crank bearings and seals in bottom end and then realized as I was putting the jug on that the piston was hitting the head. I have a cometic head gasket that is .050 thick but it stills has .005 to .007 interference. I can probably get it to clear if I stack case gaskets but I want to know where I should be for port timing before I start moving jug. I can always machine the chamber if I need to or even cut the piston to get where I need to be. There was no cylinder spacer on the Engine when I took it apart but I do remember that there was more than one case gasket. I will get you pictures and part number of piston next week. Thanks, Joe


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Sep 03, 2015 7:53 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
FIRELS1 wrote:
The Engine came with the odyssey. It was together but had a bent crank and stuck piston. I bored and honed cylinder out to 72mm, .080 over and bought a used crank and rod on ebay. Checked it for straightness, put new crank bearings and seals in bottom end and then realized as I was putting the jug on that the piston was hitting the head. I have a cometic head gasket that is .050 thick but it stills has .005 to .007 interference. I can probably get it to clear if I stack case gaskets but I want to know where I should be for port timing before I start moving jug. I can always machine the chamber if I need to or even cut the piston to get where I need to be. There was no cylinder spacer on the Engine when I took it apart but I do remember that there was more than one case gasket. I will get you pictures and part number of piston next week. Thanks, Joe


Sounds to me like Adnoh is asking for rod length or number, piston number and measurement from deck to the top of the ports. He mentions a cylinder spacer. Sounds to me like this spacer would save you a lot of grief as you don't have to modify anything, just make the correct size spacer.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Sat Sep 05, 2015 10:34 am 
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Posts: 3620
Location: Wichita ks
do you know what caused the rod to bend in the old Engine and the piston to seize. look forward to provided information so we can look at the whole assembly. if indeed you have a long rod adjusting the cylinder up to clear the head is beneficial however it does change the dwell time of the ports due to the rod ratio.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Tue Sep 08, 2015 9:50 am 
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Posts: 3620
Location: Wichita ks
Good morning.

I have mentioned a few items to look and consider for this application. Now we will look at another, since we do not have any numbers yet to compare we can look at the piston it's self. When we notice a positive deck height and assume maybe something is different we start comparing parts. So what should one look for at the piston when it comes to deck height? This would be Compression Height or the distance from pin center to top of the pistons deck or edge above the top land. When using a long rod or stroker with a fixed cylinder block or this case maybe a stock cylinder. We need to consider the rods length and Compression Height of the piston compared to the swept length of the cylinder and the cranks stroke. Please consider I'm just talking about the positive deck for now. In short where is the hole in the piston related to the top edge of the piston? Before we start adding spacer plates etc., we would also or should think about the rods length and its effect on the cylinder configuration. Hopefully to make it simply remember this is nothing other than lever arm. The piston speed and dwell for piston speed are based off of the stroke and the rods length or rod ratio. The time the piston spends within a given amount of crank angle is the dwell. A short rod will cover this distance quicker than a longer on traveling around the same axis (crank stroke). You may ask why I bring this up. Well look at the pictures I posted on the engines numbers. Anything stick out, two things stuck out to me, #1 the static psi (128) and #2 being the CR or compression ratio(6.6). Honda gave us a good idea behind their choices. We just had to change it didn't we. Going with one theory of a longer rod we changed the Dwell at TDC (Top Dead Center) and BDC (leave out the rest for now), so what does this do to the already low static and high CR. First back to the Chart picture notice the timing at 5 degrees BTDC. Also look at the port duration and when it opens on the exhaust. Let’s recap that for a minute the exhaust opens at 87 degrees before bottom dead center or 93 degrees after top dead center I like to look at the ATDC my brain just works that way. Plus it is easy to put into numbers, 360-93-93=174. The plot shows 174 degrees of exhaust duration. Another item to consider here is wrist pin offset and we can gather from the timing numbers for exhaust open and close it is ZERO. So remove pin offset from your brain for this application.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Mon Sep 28, 2015 8:59 pm 
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Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
Here are a few pics.


Attachments:
Building 5-1-2015 004.JPG
Building 5-1-2015 004.JPG [ 63.77 KiB | Viewed 2064 times ]
Building 5-1-2015 005.JPG
Building 5-1-2015 005.JPG [ 31.13 KiB | Viewed 2064 times ]
Building 5-1-2015 006.JPG
Building 5-1-2015 006.JPG [ 40.11 KiB | Viewed 2064 times ]
Building 5-1-2015 007.JPG
Building 5-1-2015 007.JPG [ 36.36 KiB | Viewed 2064 times ]
Building 5-1-2015 008.JPG
Building 5-1-2015 008.JPG [ 33.14 KiB | Viewed 2064 times ]
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 Post subject: Re: FL250 PORT TIMING
PostPosted: Mon Sep 28, 2015 9:17 pm 
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Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
Rod is definitely stock length at 121mm. Piston # is 338M07200. The first time I built this Engine I used the same piston @ .0035 clearance. I fired it up and it ran for about 5 min. with no load and then stuck. When it stuck it bent the crank. So I tore it down put all new bearings, seals and found a good used crank and rod off ebay. I checked it for straightness and clocking. Honed out the cylinder another .001 with new piston and when I went to put the head on I noticed that the piston was .080 above the deck. However, at BDC the top of the piston lines up perfectly with the bottom of exhaust port. I am guessing that the piston was too tight last build and that's why it stuck. Also, I was not sure where the timing was when I fired it up because it had an adjustable mount for the points. So, this time I have a CDI (Capacitor Discharge Ignition) and I also have an external TDC (Top Dead Center) mark on the clutch so I can time it with a light while running. I am not sure how much advance is in the CDI (Capacitor Discharge Ignition) or if it has any. I guess I will find out when I get there. Sorry for the delay I had to build an Engine stand so I could take these pictures. LOL JOE


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Oct 22, 2015 7:03 pm 
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Posts: 3620
Location: Wichita ks
Ok it's been a while since I reviewed this and thank you for the information. I still do not have a clear picture of why the piston is above deck other than your first post " cut the jug" . So let get to it

First I need Yes and NO answer's

#1 did you or have some one deck the cylinder (remove material for the top side of the cylinder) or have the base cut (remove material for the base of the cylinder)?
#2 Was the piston above deck before you re-honed or did and mods to the cylinder?
#3 was the head recut to accommodate the above deck condition either pre or post re-hone for new piston. If Yes, how much?
#4 just to be sure the rod is the stock length?
#5 the compression height of the two pistons are the same?? New and the one that stuck.

OK time to throw some numbers your way to do some measuring. Since we have a dilemma of sorts lets start with something simple for me to start with.

Deck is positive .080 ( piston above deck)
Book exhaust open is 93 ATDC
Rod is 121 mm
stroke is 64.4 mm
Exhaust open is mm from deck would be 38.1562 mm or 1.5022 in
SO lets see just what yours is. Lower your piston to where you can just fit a .005 mm feeler gauge into the port make a line on the cylinder with a fine tip marker than measure from deck down to the line. Lets see how close we are and go from there. It will not be exact due to over bore, as you over bore your port roof get lower if not measured and reshaped to maintain distance.

Once I have that we will convert it to degrees and than do some more math to find you angle area mean line in degrees and start some kind of plot. This will also start a plot for port timing and seeing a change in degrees from stock. Another item to remember and write down is you base gasket crushed thickness.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 23, 2015 3:50 pm 
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1. Not sure about if the cylinder was cut. I just assume it was because piston is out of hole. .055
2. Piston was only slightly out of hole before I bored cylinder. Maybe .027
3. I didn't cut the head
4. yes
5. yes
When I was tearing down Engine last time I remember being a stack of base gaskets. I have done some port timing measurements:
Single gasket under jug. Piston out of hole .055
EO-90.5 ATDC
TO-120 ATDC
TC-59 ABDC
EC-88 ABDC
IO-82 BTDC
I FULLY OPEN-35 BTDC
IC-35.5 ATDC
I FULLY CLOSED-81.5 ATDC
It would take a .027 shim under the jug w/single gasket to get the port timing back to factory specs. Piston would still be out of deck .028. If I made it 0 deck it takes a .055 shim under jug w/single gasket and port timing is as follows:
EO-88 ATDC
TO-116.5 ATDC
TC- 61.5 ABDC
EC- 90.5 ABDC
IO- 80 BTDC
IOF-32.5 BTDC
IC- 31.5 ATDC
IFC-79 ATDC


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 23, 2015 6:42 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
I'm I being punked? Hell I'm lost


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 23, 2015 7:18 pm 
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Posts: 7698
Location: Hope, B.C Canada
I think he kind of gave it away when he said: "When I was tearing down Engine last time I remember being a stack of base gaskets".
That tells me someone did something to that Engine and when he put it together this time without those extra gaskets nothing fit anymore. Sounds to me like they used extra gaskets as spacers.
Also check out this comment earlier in the post. He said: "The Engine came with the odyssey. It was together but had a bent crank and stuck piston. I bored and honed cylinder out to 72mm, .080 over and bought a used crank and rod on ebay".
The key words here are "bought a used crank and rod".
No idea what he has now. Looks like he is going to have to spacer it to work.
Just my nickels worth.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Sat Oct 24, 2015 12:47 pm 
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Location: Wichita ks
OK maybe not being punked. I took last night and purged my brain and took new direction.

What I did was enter his numbers in to a speed sheet and logged them on a degree wheel. I did Stock and both of his posted numbers. Please review and let me know if this is correct and OK. I included a pdf for printing and review as well to take notes and advise.
I know he need to make a change in several areas, I feel he knows this as well. Now we can come up with what will soot the FL the best. Looking at the degree wheel set ups it's easy to see the retard in port timing.

Before commenting on what I feel is a good combo or good direction to take. I will let him review the newly posted information and then go from there. Once were on the same page we can work tighter and resolve other than just throwing parts at it.


Attachments:
Resize of FIRE port degrees.jpg
Resize of FIRE port degrees.jpg [ 36.72 KiB | Viewed 1990 times ]
Resize of FL250 stock port degrees.jpg
Resize of FL250 stock port degrees.jpg [ 40.7 KiB | Viewed 1990 times ]
FIRE port degrees.pdf [275.65 KiB]
Downloaded 136 times
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 Post subject: Re: FL250 PORT TIMING
PostPosted: Sat Oct 24, 2015 6:49 pm 
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Ok studied the plot a little to get a better idea of things so we can move forward. I did some basic math for all three plots.
Good news all the basic math adds up. For those who are following and would like to do some math of there own to see how this all works lets start with this.

Take plot #1 : single gasket under jug. piston out of the hole .55
Lets take the Exhaust numbers and turn them into duration EO @90.5 ATDC and EC @ 88 ABDC
so take 180 degrees bottom dead center (BDC) and subtract 90.5=89.5, then add 88 ABDC to 89.5=177.5of exhaust duration. Now lets look at the transfer or scavenge. 180-120ATDC (transfer open)= 60+the transfer close of 59 ABDC=119 degrees of duration.
Here is where it get fun. We need to figure blow down or the degrees for when the exhaust port opens to when the transfer opens. So we take EO @90.5 ATDC and TO @120ATDC. we subtract 90.5 from the 120: 120-90.5=29.5 degrees.

Here is where it get really fun: take the blow down multiply it by 2 and then add the transfer duration and see what you get. 29.5 x 2 =59 then add in transfer duration 59 + 119=178 see how close this to exhaust duration or the base line number for the exhaust duration. Now do all three and post your results.

If you do your math right you will see what base line change will need to made or other alteration required for #1 and #2.

Next we will look at the basic transfer duration in relation to your findings.


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 Post subject: Re: FL250 PORT TIMING
PostPosted: Sun Oct 25, 2015 3:25 pm 
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Location: Wichita ks
Well I may have jumped ahead a touch to the transfers. I'll back up a little and do some more fun math since we have all the durations and the basic run down on each plot. Let look at the exhaust port since the new math supports a deferential from stock. Both 1 and 2 are close to 3 however there not, one higher one lower see how there relevant to how you move the cylinder from base line (stock). Since we use blown down to find that value lets look at another relevant factor to moving the cylinder up or down. We will start with part of the equation for angle area. We need to find the ports mean area as this is relevant to Engine power at a given rpm. So we start with the exhaust port. So far the plot has proven to be some what predictable until now. In order to find this number again not hard just take the EO to BDC and divide by 2. So for plot #1 we take EO @ 90.5 and BDC of 180 and get: 180-90.5=89.5/2=44.75 degrees. The area of the port in square mm is what were using for that part of the equation. Now do this for each and go UMMMMMM. If you have been logging you plot info you will see a change in trend. Remember you valve (reed valve/boost port) guys this is a piston port Engine and we need think about blow back as it's greater than in a valve Engine. If you do a cylinder port plot you can no take that plot and draw a vertical line across that port and count up your mm2 for each plot. Next we find TIME or port open time for a given rpm or rpm range.


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