Author Topic: CB500/4 racer resurrection  (Read 7230 times)

0 Members and 1 Guest are viewing this topic.

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #100 on: February 05, 2019, 09:38:23 am »

Remember that i still have to start working on the exhaust port, so little time for extreme modifications.

yes yes I know but one can dream especially if I am not the one that needs to do actual modification :)
well mirko, if you have time you can have a look here, there are tutorials too..... maybe once you master it i can send you my 3D's :)

https://sim-flow.com/download-simflow/

Offline MessnerMoto

  • Hot Shot
  • ***
  • Posts: 644
Re: CB500/4 racer resurrection
« Reply #101 on: February 07, 2019, 12:51:48 am »
nice yoss... actually I will need it soon for myself

I need to get used to that app

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #102 on: February 20, 2019, 01:01:58 pm »
This whole experiment turned out to be super educational and somewhat constructive, ending up with about 5-6% flow increase, even if it has fallen short of my target of 10%.... I produced in these weeks some four plaster "flow boxes", three 3D printed port cores with different shapes and overall tried some 10 different configurations/variations.

First big lesson is that at least IMHO, it is almost impossible to judge the value of a port just by looking at it, pocking fingers in or what have you.... sometimes enlarging an area by 1-1.5 mm would worsen the flow by 10 CMF!
The other interesting lesson was that just "raising the floor" can easily make things worse. It's super critical WHERE do you raise it and by how much. Again, cant think of any other way to find out rather than make many variations and see what works on the flow bench.
I ended up with two final candidates, one is just a smal development of the current port (pink casting) by enlarging the throat to 90% of the 27mm valve + further enlargement of the two passages around the valve area, creating two "side bowls" before the seat and taking care that they are fully symmetrical (they werent before). this port peaked out at 92CMF compared to 87 before the work.
The other port shape that worked well is quite radical. It didnt manage to improve flow in the high lift range, but did meaningfully improve flow in the 3-5mm lift range. This is the only port shape that worked with raised floor but the main issue is that it required also lowering the roof of the port and that would be quite a difficult thing to do. It's goes very wide and shallow around the valve and has noticeable less volume, so could give in my opinion better throttle response and better use of inertia charging during overlap. Maybe one day and with access to a 5 axis mill i will give it a try...
Now it's back to cleaning all the plaster dust in the workshop and start applying the changes to the actual head.

« Last Edit: February 20, 2019, 01:07:11 pm by turboguzzi »

Offline Tintop

  • Old Timer
  • ******
  • Posts: 3,761
Re: CB500/4 racer resurrection
« Reply #103 on: February 20, 2019, 02:00:52 pm »
Good information TG, thanks for letting us look over your shoulder.  Wondering if the roof had to be lowered after the floor was raised to move the middle of the air stream back into the flow sweet spot?
1977 CB550/4 Cafe - Speed Warrior / BOTM 03/11
1980 CB750F (project)
Whittaker GBF Vintage Racing Sidecar (XS750 power) - ITG / 151's / CMR Racing Products (SOLD)
1976 CB400 SS - stock / BOTM 04/11 (SOLD)
1973 CB750 K - basket case (SOLD)
77 CB550 Cafe build
550/750 Filter Thread
Sidecar Rebuild Thread

Offline MRieck

  • Really Old Timer ...
  • *******
  • Posts: 9,705
  • Big ideas....
Re: CB500/4 racer resurrection
« Reply #104 on: February 20, 2019, 02:56:38 pm »
 Any experimenting with port length?
Owner of the "Million Dollar CB"

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #105 on: February 21, 2019, 06:16:44 am »
Good information TG, thanks for letting us look over your shoulder.  Wondering if the roof had to be lowered after the floor was raised to move the middle of the air stream back into the flow sweet spot?
hei TT, very hard to put into words.... blue surface is my current port (mostly modified around the valve stem area), green surface is the "high velocity" port.
in second pic you can "peek inside" and see how much smaller it is while still flowing about the same.

mike, the ports you see in the casts and 3D are pretty much minimum length i can do them, cant really get the carbs closer to the head than this. Didnt try longer ones. That could be a variable to test by different stack lengths.

Offline Tintop

  • Old Timer
  • ******
  • Posts: 3,761
Re: CB500/4 racer resurrection
« Reply #106 on: February 21, 2019, 06:04:41 pm »
Thanks for the screen shots TG.
1977 CB550/4 Cafe - Speed Warrior / BOTM 03/11
1980 CB750F (project)
Whittaker GBF Vintage Racing Sidecar (XS750 power) - ITG / 151's / CMR Racing Products (SOLD)
1976 CB400 SS - stock / BOTM 04/11 (SOLD)
1973 CB750 K - basket case (SOLD)
77 CB550 Cafe build
550/750 Filter Thread
Sidecar Rebuild Thread

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #107 on: March 18, 2019, 02:02:22 pm »
porting project pretty much done, lets start with exhaust side? i widened quite heavily the area around the guide and carved quite a lot into the hump behind it as stock it really chokes the port.
finished to very glossy 320 grit finish so carbon build up will be low and hopefully heat reflection higher.
Last step is preparation of these bungs in order to D-port the exit as theres nearly no flow in that area. the bung is going to be fixed to the floor with an M6 allen from bellow.

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #108 on: March 18, 2019, 02:09:37 pm »
inlet is done too, seat was opened to 90% valve diameter (27mm X .9 = 24.3 ). Was kind of worried itll be a difficult job, went quite smooth with the good control the die grinder gives.
similar approach to the port itself of working quite a bit around the guide, only here the side walls open up and then kind of venturi into the seat area. Still left to finalize the exact height of the bung to fill up the floor a bit.

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #109 on: April 08, 2019, 02:58:58 pm »
Almost reached my target of +10% degree increase in flow, so time to stop playing around and put the thing back together. The ports you see in the pictures above ended up giving with 9mm lift 94 CFM @ 28"H20, something like 7 CFM over the 87 i started with, so that's a cool 8% increase. Mind you, over the stock port (green line) it's a good 30% increase or more... :)

Tried every possible configuration of creating inserts to give the inlet port more of a "D" shape but nothing worked, all what i tried lowered the flow, so giving up on this feature.

The insets for the exhaust work well, so they are going in, even if i dont have reliable CFM numbers to aim at as my flow bench is not really built to blow air, i'm measuring the exhaust by vaccum on the exit rather than pressure from bellow the valve.
« Last Edit: April 08, 2019, 03:04:15 pm by turboguzzi »

Offline MessnerMoto

  • Hot Shot
  • ***
  • Posts: 644
Re: CB500/4 racer resurrection
« Reply #110 on: April 08, 2019, 03:22:37 pm »
I really like and support scientific approach. Data don't lie ;)

Offline bwaller

  • Really Old Timer ...
  • *******
  • Posts: 7,192
Re: CB500/4 racer resurrection
« Reply #111 on: April 08, 2019, 03:52:34 pm »
Great work TG. How's the leg?

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #112 on: April 08, 2019, 04:18:40 pm »
plate has been removed 11 days ago, so far so good. but operation was a bit more invasive than i thought... he had to make a 7" cut form top to bottom to lift the plate up from the bone as it was starting to stick already... was hoping Doc would be able to slide it off from a small cut...
so have now a long cut with some 20 stitches holding it together.
ugly but improving fast.
changing bandages tomorrow, will post a shot :)

Offline scottly

  • Really Old Timer ...
  • *******
  • Posts: 12,715
  • Humboldt, AZ
Re: CB500/4 racer resurrection
« Reply #113 on: April 08, 2019, 09:33:53 pm »

The insets for the exhaust work well, so they are going in, even if i dont have reliable CFM numbers to aim at as my flow bench is not really built to blow air, i'm measuring the exhaust by vaccum on the exit rather than pressure from bellow the valve.
Six of one, half a dozen of the other. ;) The pressure below the valve is higher than the exit by 28" H2O.
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #114 on: April 09, 2019, 12:43:56 am »
yes, i know, pressure delta is pressure delta, but still seems like many flow benches have a "blow" mode for EXH work.

Offline scottly

  • Really Old Timer ...
  • *******
  • Posts: 12,715
  • Humboldt, AZ
Re: CB500/4 racer resurrection
« Reply #115 on: April 09, 2019, 09:48:06 pm »
It's easier to reverse the flow, if the bench allows, than to reverse the head?? ;) Perhaps your readings were affected by a poor seal from the exhaust port to the suction side of the bench?
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline crazypj

  • I'm brill, me
  • Old Timer
  • ******
  • Posts: 4,464
  • first 100,000 miles. 1977 CB550F
Re: CB500/4 racer resurrection
« Reply #116 on: April 17, 2019, 04:15:15 pm »
inlet is done too, seat was opened to 90% valve diameter (27mm X .9 = 24.3 ). Was kind of worried itll be a difficult job, went quite smooth with the good control the die grinder gives.
similar approach to the port itself of working quite a bit around the guide, only here the side walls open up and then kind of venturi into the seat area. Still left to finalize the exact height of the bung to fill up the floor a bit.

That's a ton of great information. I guess I got real lucky when I did my 550 back in 1979, looked a lot like your port shape, wider around valve guide. Very interesting about exhaust port filler, are there details of dimensions in posts somewhere?
I fake being smart pretty good
'you can take my word for it or argue until you find out I'm right'

Offline turboguzzi

  • Old Timer
  • ******
  • Posts: 3,728
Re: CB500/4 racer resurrection
« Reply #117 on: April 18, 2019, 05:50:37 am »
i'm fine tunning plug size at the moment,

just like with inlet porting, the exh plug us very sensitive to dimensions,

biggest challenge is to make the clay stick to the polished port when the vacuum is sucking on it!!!




 

;