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would honda CB headwork work for the FJ ?

Started by nlovie, September 25, 2021, 02:14:55 PM

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nlovie

stripping my 1st FJ I see a lot of the old Honda CB - F in the cylinderhead. OK the master for tuning honda CB's is a Guy called Brent Hyde - amongst other things, he does major rework to straighten out the inlet ports - now over 180hp at back wheel, whilst limited in CC compared to FJ options - - could this be transferred to the FJ head ?

fj1289

Paging Mike Rieck .... (he is JMR on this list and is also very intimate with the FJ head)



http://forums.sohc4.net/index.php?topic=84388.0

Pat Conlon

Quote from: fj1289 on September 25, 2021, 02:37:58 PM
Paging Mike Rieck .... (he is JMR on this list and is also very intimate with the FJ head)



http://forums.sohc4.net/index.php?topic=84388.0

....and Mike is also our go to guy on the Honda CB's
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

T Legg

That's a huge amount of horsepower out of a CB .
Is it a 900 or the 1100 ? Post a picture of the whole bike.
T Legg

fj1289

Looked up the name - found a Facebook page.  Looks like he takes them out to 1220 cc's



Evidently the FJ head is very similar to the DOHC Honda head - as are all the dual cam, 4 valve heads of that era.  So, yes, that treatment should work if you are looking for max power and have enough cam and compression to support the higher, narrower powerband for racing - or very serious fun.  

If you are serious about building an FJ engine - 165HP (+/- depending on the dyno, altitude, etc) seems to be achievable while still maintaining a wide, flexible powerband that makes it easy to ride fast and still has good street manners.  That amount of power in a well sorted chassis (and well ridden) will hurt a LOT of feelings!


Oh - and one last closing thought - it only takes one small tuning error to turn that $$$$ head into a very expensive paperweight - DAMHIK!

nlovie

been following Brents progress ( he is quite open and public with it ) - it is indeed a case of progress / failure - learn - more progress etc.. - - main issues is the transfer of all this torque through the internal drive train. Anyway, as said - lots of hard earned development, some of which maybe of valued interest for the FJ engine
PS I think his next development is a larger nikasil / alloy liner :) he's now catching up with Yamaha

JMR

Since my name was mentioned I'll chime in. The FJ head can certainly use some work as can a lot of 4 valve side draft heads from the 70's and 80's. I recently ported a FJ head for fj1289 which will be used for LSR work. My own FJ makes just under 157 RWHP with 1314cc's and pulls about as strong as my Hayabusa.....it is a really fun bike to ride. My 75 CB750F makes just under 107 RWHP and uses a billet block I developed with several machinists. It has Nikasil cylinders and can take up to a 72mm piston (stock is 61mm). I sold those to people all over the world. If click on this link and scroll down to New Product #3 there are a couple of pics of the 750 porting.  http://www.cyclexchange.net/Honda%20Page.htm
Most of my work is focused on the SOHC CB750 and 550 but I have ported head from GS's, GSXR's, KZ's, Hayabusa's, modern 600's etc.
The FJ head is basically a copy of the Honda DOHC head. The big problem with these heads is the offset of the ports especially 1 & 4. If you really want to see port offset look at the #1 and #6 ports on a CBX head. Anyway....short of cutting off the intake spigots and welding up a straighter shot.... those ports can be opened up in the right areas to get more charge in. That and the use of oversize intake valves and boring the intake seats to .9 of the oversize valve will make a big difference. Also....as fj1289 stated....compression, deck height, cams etc are critical too.


fj1289

Wow ... sounds like the challenge of turning your high end extremely specialized mods into a business selling to more "average" customers that expect to R&R stock parts with speciality parts.

As bad as I'd like to see RPM start selling fuel injection systems, I commend Randy for waiting until he can make the large investments in time and equipment necessary to successfully launch an large involved mod like this - making sure to prioritize customer satisfaction over quick sales.  

Pat Conlon

Jeeeze Mike, I'm sorry to see you go through this shit. I also didn't know of your surgery.

I'm happy you made it through.

Pat
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

JMR

Quote from: Pat Conlon on September 30, 2021, 01:45:27 AM
Jeeeze Mike, I'm sorry to see you go through this shit. I also didn't know of your surgery.

I'm happy you made it through.

Pat
Pat....that whole debacle with Brent Hyde doesn't involve me BUT it does involve a good friend of mine. Personally I'd steer clear of the man. A fellow on the one of the CBX boards was distributing his cam chain tensioner kits but suddenly stopped as well. That link to the CB1100F forum isn't going back to the original link at this time. If anybody wants to read about several peoples experience I can send it to them. The language is salty and after reading it you can understand why.
No surgery for me Pat. I just retired the end of June and life is great....better than I imagined it would be!

fj1289

Quote from: JMR on October 04, 2021, 08:41:41 AM


No surgery for me Pat. I just retired the end of June and life is great....better than I imagined it would be!

Good to hear Mike!   :good:

nlovie

 

Pat
[/quote] Pat....that whole debacle with Brent Hyde doesn't involve me BUT it does involve a good friend of mine. Personally I'd steer clear of the man. A fellow on the one of the CBX boards was distributing his cam chain tensioner kits but suddenly stopped as well. That link to the CB1100F forum isn't going back to the original link at this time. If anybody wants to read about several peoples experience I can send it to them. The language is salty and after reading it you can understand why.
No surgery for me Pat. I just retired the end of June and life is great....better than I imagined it would be!
[/quote]

yes i'm also picking up some vib's - my own thoughts are "buyer beware" but this is for any highly tuned modifications: folks should always keep in mind - you want to take any engine beyond the manufacturer, you got to also apply the very expensive route of product replacement with limited life span  - way too much going on with fatigue / damping / shock loading etc.. that requires a huge amount of product testing ( beyond any typical aftermarket / tuning bit supplier ) -example personally i'm not a fan of modified crankshafts - forsure I know all the good reasons - its the unknown, the effect of reduced mass ref: damping and shock loading  - if you can't afford to replace them at given intervals then its black magic until it fails

nlovie

followed the link and read the story, - crap - my apologise for the start of this post, principle remains - i.e. ref: to work done on a cb transferring to an FJ, my choice of example to support this was a poor choice

JMR

Quote from: nlovie on October 09, 2021, 12:39:59 PM
followed the link and read the story, - crap - my apologise for the start of this post, principle remains - i.e. ref: to work done on a cb transferring to an FJ, my choice of example to support this was a poor choice
Nothing to apologize for.....the FJ head is pretty much a clone of the DOHC and Hyde has taken the DOHC head about as far as it can go (right to the point where the primary chain explodes on a regular basis.) I'd say Byron Hines did the same with the FJ engine. I am also not a fan of lightened cranks especially if there is not a charging rotor hanging off the end of it. I am a big fan of balancing the crank and associated parts.