davisag
Expert Class
Posts: 103
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posted August 27, 2003 12:07 PM
zx11 cylinder head flowing tips
hi doug
can you give any does and don'ts when it comes to flowing a zx11 head
based on extra work i had done on a cylinder head that lost me power i have some idea of some don'ts
so here goes before i start on another std head
would recutting the inlet seats to put the inlet valve seat a bit closer to the edge be better than 1mm
oversize valves in the middle of the seats
your opinion of epoxy on the inlet port floors to increase the velocity a bit
exhaust ports
leave them the size they are and just clean up a bit, or open up the roof of the port a bit
with J Bito 1137cc kit, 12.4-1 cr, yosh cams , 39mm flatslides ,stainless std size valves was making 175hp rear wheel
since compression raised to 13-1 , 1mm oversize inlet valves
ex port roof raised about 3mm and floor lowered about 2mm power has dropped and now struggles, to
make 170hp and down 3 ft lb of torque
arthur
   
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davisag
Expert Class
Posts: 103
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posted September 14, 2003 12:48 PM
well i guess Doug no longer looks in here or he has forgotten all about zx11s
anyone else heard of any does or don'ts
arthur
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted September 25, 2003 07:19 AM
 Edited By: dougmeyer on 25 Sep 2003 08:20
I was out of town and on a dial up so didn't do much online.
Basic rules for ZX-11's:
Stock size valves, 5 angle seats, no enlargement of the ports, just smooth all the surfaces and match the manifolds. Especially smooth the transition from the seat to the head in the port and streamline the divider wall edges. Clip the head .5mm.
As you know, you are pretty short on power for all that you've done. Major mistake going to the 1137, 1080's always make more power ultimately because the thicker cylinders stay round and the combustion chamber needn't be opened up to match the cylinder. The oversize valves have never shown an improvement. Keep going and you'll modify yourself into oblivion.
Doug
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davisag
Expert Class
Posts: 103
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posted September 25, 2003 01:53 PM
thanks doug
the 1137cc kit does come with high grade steel liners and deeper bands on the external side of the liners
, so i am sure there is less distortion than the 1109cc wiesco oil burning big bore i had previous
the 1137cc kit uses no more than a pint of oil in 2000 miles so must be keeping its shape ok
will let you know how things work out on this other head, and will pay particular attention to what you said
arthur
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davisag
Expert Class
Posts: 103
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posted November 19, 2003 01:51 PM
well
the mark 2 head has just been completed
back to std valve size, no enlargment of ports , and epoxy in inlet floors
compression down from 12.9-1 to 12.7-1 despite skimming a few more thou off this head
those big inlets sat a lot further out on the seats and so occupied more space in the combustion chamber
with dyna 2000 ign any suggestions as to what degrees i should set timing to
arthur
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted November 21, 2003 07:40 AM
42 deg., but be aware that the Dyna is hard to get precise with.The "score marks" on the plate are wide and close together. Take your time.
Doug
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davisag
Expert Class
Posts: 103
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posted November 23, 2003 02:56 AM
hi doug
thanks
i agree that the Dyna plate is hard to read , and i now use a degree wheel on the clutch side of the crank to get some accuracy
not wanting to question your undoubted zx11 expertise but when i see the figure of 42 degrees , for a high compression engine thats 2 more than the stock setting for a std engine
i have been running my dyna settings at 36 degrees since i got it on a recommendation, and the theory the higher compression , the less ignitioin advance needed
i suppose you will now tell me that dyno testing shows zx11s to make most power at 42 degrees , and maybe at 36 degrees another reason my bike is not making the power it should
arthur
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