pistonguy, lol.. yes that does suck but you are wrong about his head. He has upgraded bored head and he even bored out the intake manifold, upgraded valves and springs. Basically we were about even until I developed the intake leak, but his scooter for some reason was always a bit faster from mine in stock form. He is also running an A12 cam and I am running an A9.
I am just trying to see where I can gain some extra power and since I value your opinion I ask. When you said my head was no good, what kind of symptoms were you expecting me to get? Were you thinking it would seize on me or would it deliver very little power? I have about 1k miles on this head now. thank you
K, cool, I'll try to help ya smoke your buddy.
I may poke fun or make extreme example just bear with me.
I have had suspicions on the various cylinder head volumes (cc's) for some time.
If some are not sure wh we have a 61mm head for the 61mm bb cylinder is for a few reasons.
First going up in Bore Size (volume) alone will increase your compression ratio, hmm ok.
So by increasing the Diameter of the Combustion chamber by this same amount will Maintain my Stock OE Compression Ratio, (we'll work with (9:2-1).
The Mfgr's try to idiot proof this stuff, what good is a 14:2-1 head that requires Methanal to run? can't sell many of those.
Second and few know this is that if we used the stock diameter cylinder head on the BB cylinder, now the
Flat Part of the Cylinder Head is now in the Bore, not good for flame travel, detonation on theses outer edges and in some cases the piston can hit this part of the head hanging inside the cylinder bore.
I Highly suspect most of this junk the MFR chucked them up and increased the Combustion Diameter to the Bore Size and has NO Idea were our Compression Ratio is now, I'd Bet LOW.
So If I started with 9:2-1 and now installed the Fake High Perf. Head and now I'm at 8:5-1, OHhh snit.
They don't advertise the Cylinder head volume cuz they don't know, and if they did could sell Allot More by Marketing a 61mm 10:5-1 Head,, duhhh.
I;m going to do both Port Volume and Combustion Chamber Volumes (in cc's) on both my Stock oe and my 61mm head, I want to see for sure exactly what our stock oe compression ratio and port volumes and my 61mm set-up. are
Then I have some base numbers to go on.
I stand corrected on your buddy's head, I see on the other you state he has a Taida 61mm head.
Is he using Stock Gearing?
Well form why I've seen of there product its pretty darn good and best Chance of having at least matching compression ratio of his stocker.
Then that may make sense your head made you lose power (lowered compression ratio) and his made power (good quality head/maintained compression ratio).
we can spend a life time on cylinder heads and valve train. fun tho.
ya know I have issues with what was done to the head, I really think went backwards.
We always need to be thinking on keeping velocities up, I've made comments of "Flushing a toilet into a Straw" so not knowing the cc's of the ports and hogging them out is going to make you go slower.
Matchin the Intake and Exhaust Manifolds is beneficial but not as much as one may think and this is Not porting.
There is only a Little work to be done in the Bowls and the rest just looks pretty and thats All.
Ive addressed most of the Valve job etc questions on the other site and will post a link.
Lapping Valves, Wow, I've seen that stuff in museums, Barbaric way to Destroy a valve Job.
Sorry arse snit a manuals is written today with no updates from 80 years ago. then this is passed down as
Monkey see Monkey do as the thing to do. Wrong.
Sum this up I Believe that if you Bolted on a Taida 61mm Head, (check/match you manifolds), Leave the rest Alone and will get you back on the right track.
