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Author Topic: Port timing  (Read 7946 times)

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Offline kwakman

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Port timing
« on: January 05, 2009, 10:26:41 AM »
Been flicking thru the manual and the port timing section has info that appears wrong to me. I'll post the whole lot in a while, but first a question.
 For the 89 onwards 500, it gives two specs for the exhaust port, one for high engine speed (powervalve open), and one low speed(powervalve closed.
 The 89 onwards model has the centre flap type port, which moves into a raised position at high rpm.This has the same effect as raising the exhaust port, which if I'm correct, gives a longer total exhaust duration to allow extra 'blow down' time for the cylinder which is needed at high rpm as there is less time to fill and empty the cylinder.
 However, the manual,(Clymer covering 500 models 83 - 93) gives the high speed exaust open as 83.5 deg BBDC, and the low speed timing as 93.5 deg BBDC. Isnt this the wrong way round?
     Anybody....
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And the unbelievers did quake in their boots....

Offline kwakman

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Re: Port timing
« Reply #1 on: January 05, 2009, 10:46:23 AM »
Sorry its crude, too busy fiddling with fives to learn computer stuff....   

Year      transfer   transfer        exhaust    exhaust        total   total
              open       close            open       close           inlet     ex
              BBDC       ABDC            BBDC       ABDC          DEG    DEG

85            62           62                92          92             124    184

86           59.5        59.5               96          96             119    192

87           59.5        59.5               86.5       86.5           119    173

88           60           60                 90          90             120    180

89on        60           60           H.S.83.5       83.5           120    167 High rpm
                                           L.S.93.5       93.5                    187 Low rpm

           This Is How It Is In The Manual, But are HS and LS specs the wrong
                                  way round????????
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

Offline kwakman

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Re: Port timing
« Reply #2 on: January 05, 2009, 11:16:08 AM »
Also for your delectation, compression ratios by year...  KX500

84       7.0 to 1    (US 6.7 to 1)

85       7.9 to 1

86       8.4 to 1

87       7.4 to 1

88       7.1 to 1

89       7.7 to 1   Low speed 
          6.8 to 1   High speed

90on    8.3 to 1   Low speed
          7.4 to 1   High speed
 
If Stewart, BDI, Doordie or anyone can summarise the effect of the timing and compression for each model year as to how each should perform I'm all ears.....
               My money's on the 86 but I am ever so slightly biased :roll: 
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

Offline doordie

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Re: Port timing
« Reply #3 on: January 08, 2009, 11:42:08 AM »
Quote from: kwakman on January 05, 2009, 10:46:23 AM
Sorry its crude, too busy fiddling with fives to learn computer stuff....   

Year      transfer   transfer        exhaust    exhaust        total   total
              open       close            open       close           inlet     ex
              BBDC       ABDC            BBDC       ABDC          DEG    DEG

85            62           62                92          92             124    184

86           59.5        59.5               96          96             119    192

87           59.5        59.5               86.5       86.5           119    173

88           60           60                 90          90             120    180

89on        60           60           H.S.83.5       83.5           120    167 High rpm
                                           L.S.93.5       93.5                    187 Low rpm

           This Is How It Is In The Manual, But are HS and LS specs the wrong
                                  way round????????
Yes,HS and LS are wrong,Duration HS=187* and LS=167* (more duration,more rpm) :wink:
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Offline doordie

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Re: Port timing
« Reply #4 on: January 08, 2009, 11:56:59 AM »
Quote from: kwakman on January 05, 2009, 11:16:08 AM
Also for your delectation, compression ratios by year...  KX500

84       7.0 to 1    (US 6.7 to 1)

85       7.9 to 1

86       8.4 to 1

87       7.4 to 1

88       7.1 to 1

89       7.7 to 1   Low speed 
          6.8 to 1   High speed

90on    8.3 to 1   Low speed
          7.4 to 1   High speed
 
If Stewart, BDI, Doordie or anyone can summarise the effect of the timing and compression for each model year as to how each should perform I'm all ears.....
               My money's on the 86 but I am ever so slightly biased :roll: 
-86 a wild beast with a low to midburst in power,need higher oktanrate to not pinging.Hard to ride! :evil:
-90 a slightly "tamed" beast in low to midrangepower.Easy to ride! 8-)
as always just my 2 cents :-D
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Offline kwakman

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Re: Port timing
« Reply #5 on: January 10, 2009, 01:58:59 AM »
doordie,
          thanks for that. Its nice to know I cant be fooled by a manual. This time.
As your aware, I'm on a quest for a top end powerband, so I'm running later 2 ring piston,(less dome, cant find a forged 86 spec) to reduce compression, gonna get top end port job, and probably an fmf desert pipe.I've retarded the ignition timing, and I'm gonna preload the p/valve spring with a washer so it opens later. anything else anyone can think of?
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

Offline kwakman

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Re: Port timing
« Reply #6 on: January 22, 2009, 04:35:10 AM »
Seems 2 me the 86 has ex timing for high rpm, yet transfer timing better suited to low rpm. Or am I just talking 2 myself again........126 degrees of transfer would match the ex timing better, wouldnt it..... hello.......
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

stewart

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Re: Port timing
« Reply #7 on: January 22, 2009, 12:50:13 PM »
i am listening,,i take it you have an 86
« Last Edit: January 22, 2009, 12:51:53 PM by stewart »
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Offline kaw rider

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Re: Port timing
« Reply #8 on: January 22, 2009, 01:19:16 PM »
kwakman
you are right about 126.  But with 126 low to mid will be in the toilet. It depends on your motor set up
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Offline kwakman

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Re: Port timing
« Reply #9 on: January 23, 2009, 03:25:30 AM »
Is it really that obvious?  :evil: yes I do. On one of the threads, it says your running 130 deg transfer and 200 deg exhaust stewart; did this bugger your bottom end?
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

Offline kwakman

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Re: Port timing
« Reply #10 on: February 16, 2009, 02:39:29 AM »
is anyone staggering there port timing? i.e. opening rear boost ports 1deg before transfers so as to purge the exhaust gas from cyl as this helps get more fresh charge  in as the exhaust gas at top of cylinder is the hardest to get moving...
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

stewart

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Re: Port timing
« Reply #11 on: February 16, 2009, 05:16:59 AM »
i thought the bigg port timing numbers lost bottem end power lots of comprsion and timing helped it some but not as much as getting the power from modest compersoin and less port timing with some retard igntion for over rev ,,i think the stagger timing has been deserted not enough differance
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Offline stroke.n.smoke

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Re: Port timing
« Reply #12 on: February 18, 2009, 02:10:59 PM »
When I measured up my stock '01 cylinder and made a port map of it I got these numbers (all numbers with the pv open) add 5 degrees to port opening with pv closed and take 10 degrees off the duration with it closed...

ex port opens 90 degrees ATDC
ex port duration 180 degrees.

Transfer ports open 117 degrees ATDC and has 126 degrees duration.  I can't remember what base gasket was in there, but wasn't anything out of the ordinary.  When I measured the squish it was at least .070" but not much of a squish band at all.  Plus or minus a couple degrees since I'm not an expert at this.  Also, all the transfer port heights are the same including the rear boost port. 

Just for comparison my RZ 350 twin uses this for port timing

ex opens 83 degrees ATDC
ex duration 194 degrees (I have seen them at 202 degrees duration) But with 114opens/132duration transfers.
I also try to use a squish band of 55% of the bore.  On the 350 it would equal 17.5mm wide which is increased from 10mm wide for the stock head.  Also the squish band is recut at 1degree more than the top of the piston, approx 14 degrees. (dome top) Which leaves me a little confused with the KX 500's flat top piston, what do you do to the squish band?
 
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Offline kwakman

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Re: Port timing
« Reply #13 on: February 24, 2009, 02:15:37 AM »
All im saying is that the transfers are open the shortest duration for all years and ex ports are open the longest. the 86 has higher compression than all other years so my plan is to raise the transfers to give more port time and to closer match the ex port timing and maybe lose a little compression to increase my top end, along with a platinum pipe. the 86 has bags of low and middle and i want to trade it for top end as it runs flat up top even with retarded ignition timing.what duration should i be aiming for on the transfers to move the power up the rpm band? Im thinking 124 to 126 but i will listen to your thoughts before doing it.................... :-P
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....

Offline kwakman

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Re: Port timing
« Reply #14 on: March 03, 2009, 12:32:04 AM »
I'm still here....... :-P
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And lo, I did loft the front wheel and carried it forth to the unbelievers, and cast it down before them and said unto them ''look now upon the might of my throttle control ye pitiful cretinous ones''
And the unbelievers did quake in their boots....
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