Author Topic: Does anyone have a Yoshimura ported head?  (Read 2018 times)

0 Members and 1 Guest are viewing this topic.

Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Does anyone have a Yoshimura ported head?
« on: February 03, 2019, 04:19:17 am »
I’m looking to find someone with a head ported by the Yoshimura company in the 70-80s.  Cb750 head preferable, but others OK too.  I’m looking to see the style of porting they incorporated, specifically “valve guide out” porting or “valve guide in” porting.

George

Offline teebee67

  • Enthusiast
  • **
  • Posts: 160
Re: Does anyone have a Yoshimura ported head?
« Reply #1 on: February 03, 2019, 12:02:21 pm »
George,
I have a Yoshimura ported head which was done back on the day. It is fitted to my Yoshimura engine but a can try to get pics from outside the ports if that is any use to you?
Tony
I'm only old on the outside.

Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Re: Does anyone have a Yoshimura ported head?
« Reply #2 on: February 03, 2019, 12:54:09 pm »
George,
I have a Yoshimura ported head which was done back on the day. It is fitted to my Yoshimura engine but a can try to get pics from outside the ports if that is any use to you?
Tony

Yes, that would be fantastic😉.  A few good pictures up the intake ports with a smart phone with the flash on would be great.  Exhaust port a secondary interest.  That would tell me a lot.

George

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 4,072
Re: Does anyone have a Yoshimura ported head?
« Reply #3 on: February 04, 2019, 05:18:13 am »
george, pics are better than nothing but honestly, seek someone who can make silicon castings... see attached pdf.
im working quite a bit on the subject and exact shape and dimensions are super important for flow numbers, nearly impossible to judge from port pics

i use this

https://www.smooth-on.com/products/mold-max-30/



Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Re: Does anyone have a Yoshimura ported head?
« Reply #4 on: February 04, 2019, 07:00:09 am »
Yossef,

I totally agree, I am first trying to identify the porting styles in general and more specifically whether the particular cb750 head I have was plausibly ported by Yoshimura as was suggested possible by the seller(as 3rd owner of engine, 1st owner reportedly spent a pile with Yoshimura in the mid 70s, it had a hand bent Yoshimura stove pipe race exhaust and a set of Smoothbores 29s on it at the time that Ted (Ricky Racer) has kept.

Knowing whether Yoshimura stamped the parts they modified would be a great help too.  That was common back then(RC Engineering, etc)

George

Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Re: Does anyone have a Yoshimura ported head?
« Reply #5 on: February 04, 2019, 07:02:19 am »
For example, this is the intake port of a cb550 head that is also attributed to Yoshimura.  Notice both are “valve guide in” style.

George

Offline teebee67

  • Enthusiast
  • **
  • Posts: 160
Re: Does anyone have a Yoshimura ported head?
« Reply #6 on: February 04, 2019, 08:03:20 am »
Took some pics George but the quality is poor, I will try to get some better ones in the week if you
want me too. I haven't had the head off so don't know if there are any marks or stampings.
I'm only old on the outside.

Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Re: Does anyone have a Yoshimura ported head?
« Reply #7 on: February 04, 2019, 09:20:00 am »
Mine vs your head.  They sure look similar...😉

George


Offline teebee67

  • Enthusiast
  • **
  • Posts: 160
Re: Does anyone have a Yoshimura ported head?
« Reply #8 on: February 05, 2019, 02:21:02 am »
Yes they do George.
I'm only old on the outside.

Online PeWe

  • Really Old Timer ...
  • *******
  • Posts: 14,977
  • Bike almost back to the 70's 2015
Re: Does anyone have a Yoshimura ported head?
« Reply #9 on: February 05, 2019, 04:45:18 am »
I could not resist to adjust a little for a clearer view ;) 
« Last Edit: February 05, 2019, 06:11:24 am by PeWe »
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline Medyo Bastos

  • Master
  • *****
  • Posts: 1,520
  • Gusto mo titi ko?
    • project
Re: Does anyone have a Yoshimura ported head?
« Reply #10 on: February 05, 2019, 04:59:29 am »





Sent from my iPhone using Tapatalk

Offline gschuld

  • Master
  • *****
  • Posts: 2,346
Re: Does anyone have a Yoshimura ported head?
« Reply #11 on: February 05, 2019, 07:16:30 am »
Thanks Per.

Medyo, is that one yours?

Is it stamped Yoshimura anywhere?  It sure looks like a comparable porting style to other assumed Yoshimura porting examples.

George