OzVMX Forum
Marque Remarks => Yamaha => Topic started by: Marc.com on January 19, 2009, 06:36:40 pm
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Anyone used twin plugs with dual output coil. What happened ???
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where does the second plug go?
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they come in from either side, looks like Harley might save the day by using twin fire performance coil
(http://i245.photobucket.com/albums/gg71/marcFX_photo/iwataco-img600x450-1213856187yi80lm.jpg)
(http://i245.photobucket.com/albums/gg71/marcFX_photo/iwataco-img600x450-1213856197d9s-1.jpg)
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is that std? im sure ive never seen it before. is it only on TT's? whats that head off? i looked a 500 before and it only has one plug hole
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Daytona high port head for SR500, supposed to be 7 hp in there some place
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ohh. is that a aftermarket head then? or is a daytona head std on a SR 500?? ive never heard of them before.
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std sr heads have 1 plug i have 1 on my methenol tt500.its fast enough with out all that extra problem of 2 of everything for spark.czs are like that though std 2 spark plugs firing at the same time.i have 2 of those.that is going to be interesting.
cheers
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so DAYTONA is a aftermarket head? where is it made? i never knew of aftermarket heads for 4 strokes
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RD/RZ run a waisted spark ignition would work a treat on that......................thing
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so DAYTONA is a aftermarket head? where is it made? i never knew of aftermarket heads for 4 strokes
DAYTONA are Japanese performance company for SR500 motors, there are a couple of others that also make big fin heads, but Daytona is the only one that is cast as opposed to weld up. retail is an eye watering 200,000 JPY, lucky my local store was having spring clean. I am using Megacycle MX cam and 90mm piston at 10:1.
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RD/RZ run a waisted spark ignition would work a treat on that......................thing
do they fire the plugs at the same time, wasted spark, guess they do. Harley coils give you a range of resistances that i can match with the SR CDI
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can you still buy these heads now days?
ive seen in some old french magazines some kits that they use to sell over there for the 500's. there was a maker over there who used to sell some big bore kits and the barrels seemed to look like the fins were out wider and maybe were a aftermarket barrel.
they also made heaps of big bore kits porcupine heads for YZ, TY and MX yams. the company was called 'Ch Rayer' or soemthing similar. you just search french ebay for 'kit Rayer' i dont think this brand was ever sold or marketed in Australia
the french were really into XT500's so they had a lot of hot up gear for them over there.
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you can still buy a few SR bits in Japan, mainly to make them look like BSAs. There are some pretty interesting kits for building MANX SR and 7R SRs..... SR400 is still in production in Japan and still popular.
I know there is a 570 crank and dry clutch but you would need a very big wallet.
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the french were really into XT500's so they had a lot of hot up gear for them over there.
spot on, found a frenchie with twin output coil that works with SR500 CDI.....probably no performance gain but twin plug leads on the HL will be the VMX equivalent of spinners on your 23" chromies.
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i heard that some- body on the gold coast makes up a twin plug set up for a particular model bmw tourer 600cc i think, that is known for rough idle and ragged small throttle running. apparently he uses a holden v6 coil [which has two leads,one for a waste spark on another cylinder.] this of course will fire 2 plugs simultaniously.sounds interesting.
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ran a twin plug setup on my matchy road race motor,it's all to do with flame propagation,with old school high domed style pistons the combustion flame has to travel from the side where the plug is to the other side,this does take significant time,(traditionally overcome by big advanced ignition timing),where theres opposing twin firing plugs ,there is a more complete/instant flame burn,(shorter flame path),but the greater gain i could appreciate is in the ignition timing which can be significantly retarded,thereby giving the bigend a easier life expectancy,in my own motor it was from 38 to 28deg,addmitedly my comp ratio wasn't extreme,only 10.75 to 1,but the motor was a more forgiving beast for it,unusual to be twin plugging a SR type head,as their pistons generally are a flatish dome on top??,maybe just the bling factor?? ;D,,or indeed saving the bigend from high comp effects?, :P
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Daytona head is completely different shape to stock SR, the inlet port is positioned much higher. I guess it is set up for twin plugs as 'another thing you can do' to enhance performance. Head was designed for race Sr500. Rest of the set up is CR carb and high lift cam, I am using Megacycles as they are not regrind.