Topic: Result from Dyno run: Too rich at 4500-6500 rpm 4-2-1 exhaust better than 4-1?

[kmb69]

PeWe, I think you're correct.
What length muffler and which tip is that?

[Garage_guy_chris]

My photos are of the long muffler 16" w/ classic tip. I went with the long style to maybe quiet it down a bit over the 12".  Yes you will have to remove at least one side of the exhaust to get at the oil filter. It comes with flanges and springs so all you do is take the springs off the flange to pipe and pipe to collector and yank off hopefully just one side of the headers to access the filter

[PeWe]

Anyway, the Hindle system is one way to get a very slim system with no clearance issues. Use best oil and less oil change.
I have no problem to drive 6000-8000km before filter and oil change. Or every winter stop before the sleep.

[754]

My whole Hooker 4-1 would come off in 3 minuts or less.. Spigot mount..

[Kemp]

Don't mean to hijack your thread but just answer a couple of questions posed about the Hindle 4-2-1. We developed a 4-2-1 to get maximum torque and horsepower, a design that Hindle has been using on all his modern era pipes. This has been really successful in dyno runs over conventional 4-1 pipes from the era. Hindle has tried the crossover many years ago and couldn't get any improvement from combining 1&3, 2&4 over 1&2 and 3&4 so we stick with 1&2 etc as we also prefer the sound in this combo with the 4cyl models. We use a 1.5 inch headers and thin wall stainless steel much like some world superbike racers for light weight, durability and cost benefit over titanium. The system is all spring mounted for easy access as we pattern our vintage exhaust models after Lang's Championship winning superbike. It's truly a blast working with Hindle to design and manufacture these vintage systems.

[PeWe]

Good information is always welcome. I was looking for information about header design and hp.
About dyno tests... with a std CB750 or modified?
I guess it is different with larger carbs, hotter cam, more cc. More flow in that need to come out efficiently.

[Kemp]

We did run a dyno test on a CB750 with an 836 kit, mildest web cam, stock carbs running 125 mains, stock head, pods. Unfortunately the engine dropped a valve (piston to valve clearance too tight) on the first run at about 7800 rpm at which point it made 83hp. Not pleasant! We hope to get another shot at this machine as it seems 836 is a favorite bore increase that many builders are using on their CB750s

[MRieck]

We did run a dyno test on a CB750 with an 836 kit, mildest web cam, stock carbs running 125 mains, stock head, pods. Unfortunately the engine dropped a valve (piston to valve clearance too tight) on the first run at about 7800 rpm at which point it made 83hp. Not pleasant! We hope to get another shot at this machine as it seems 836 is a favorite bore increase that many builders are using on their CB750s

  What pistons were you using? No disrespect intended but 83HP @ 7800RPM with no headwork and a very mild cam seem really high. Like I said....no disrespect intended.

[Retro Rocket]

We did run a dyno test on a CB750 with an 836 kit, mildest web cam, stock carbs running 125 mains, stock head, pods. Unfortunately the engine dropped a valve (piston to valve clearance too tight) on the first run at about 7800 rpm at which point it made 83hp. Not pleasant! We hope to get another shot at this machine as it seems 836 is a favorite bore increase that many builders are using on their CB750s

  What pistons were you using? No disrespect intended but 83HP @ 7800RPM with no headwork and a very mild cam seem really high. Like I said....no disrespect intended.

Yes, I'm finding this pretty hard to swallow, I know how much work it takes to get 80HP out of one of these engines, without head work its virtually impossible.... Besides, unless the bike had a massive bore, you'd NEVER get 83hp at 7800 RPM..... I think you've mixed up your numbers Kemp, 63HP possibly....?

[scottly]

Kemp, what "stock" head were you using? (Mike, how much better does the F3 head flow, compared to a stock K head?) Also, do you have back-to-back dyno tests of your exhausts, which look VERY nice, compared to a typical 4-1, like a Kerker? Rather than continuing the hijack of PeWe's thread, feel free to share your findings here:
http://forums.sohc4.net/index.php/topic,149662.0.html

[PeWe]

It's fun that this thread is still alive!
Exhaust vs power. Streetable power even better.

My bike reached 80hp at 8000 rpm with the megacycle 125-20 cam (peak 83hp), at 8500 with the milder Action Fours SS-1 cam.
See charts here: http://forums.sohc4.net/index.php/topic,147350.msg1681942.html#msg1681942
836, ported head (IN 34mm oversize), TMR32 carbs

Now HM300 replicas with baffles.... I'll remove the baffles when the bike is too silent and less responsive. Carbs jetted for screaming 4-1

[754]

Pewe, how long does a cam change take you?
 I am thinking taking the frame section out is like 3 minutes or so..
 Do you remove the coils or just unbolt and pull them up to make room. ?

[PeWe]

Coils still in place. Dyna coils. It take a few hours with timing the cam.

Remove tank, head cover, rocker arms, cam sprocket with chains slide off, remove remaining cam bolts. Cam off  thru chain ,sprocket follow. Lighten the chain tensioner. I forgot it last time, it worked any way.
This take not long time. I guess 30 minutes so far.
Now another cam in IF not finding any bad threads. Finding the correct position to put sprocket on so the  chain will be mounted without problem.
I have an adjustable sprocket with oval holes I think are too wide. If bolts slide sprocket will be atleast 2 cogs wrong.

Timing the cam will take some time. Eeasier with training. Last timing was quick, maybe 1 hour.

Below mixed photos from 2 different cam sessions. Last with coils still in. Other photos when I lifted head and replaced the cylinder studs.

[Don R]

The 4-2-1 looks a lot like an F2 header. Except pretty.

[PeWe]

Update:
I have replaced the old 4-1 with Yamiya no numbers 4-4, HM300 replicas. Early model with long diffusers.
After some rides I prefer to drive without diffusers that restrict the power too much.

Carbs TMR32 jetting: Latest setting work well and correct smell at idle. Not too rich.
Pilot 30  (std 27.5)
Fuel screws 1 turn out. (before 1 1/2+1/8 turn with 27.5 pilot and 4-1)
Needles 4:6 as before
Main 132.5 (135 with 4-1)
Still KN pods as always

4-1 gave more and more abrupt power. Bike is heavier with 4-4 and center stand.
4-4 OEM style is back to the roots of the old beautiful CB750.

A daytrip of 300kms driving very slow all the time cleared the pilot circuits that earlier were a little bit clogged. I had to close the fuel screws a little bit when it started to run rich at idle. Earlier too much tests with mostly WOT. Slow driving cleared the important pilot ciruits making the bike streetable

[PeWe]

Update for those that has or will try the carbs Mikuni TMR32-D7 with filter adaptors and KN oval pods
Jetting verified on dyno with 2 types of 4-4 exhausts without any diffusers when measure A/F ratio. No numbers (HM300) and the more open Lotus Root (earlier Sandcast model)

Pilot 30
Fuel screws about 1 1/4 turn out.  I guess the range is between 1- 1 1/2
Needles 2:6  too rich earlier and can explain the graphs here and sooty plugs
Main 135
KN oval pods

Engine updated too since this post was started
Now JMR billet block 1005cc 10.5:1 JE pistons 71.25mm (machined 12.5:1 to match the 24.4cc chambers for old RC 65mm), head slightly more ported when Kibblewhite 5mm valves went in (34/28)
Cam DP315.

- 4-4 restrict the rpm and upper power to around 8000 rpm
- Lotus root give less power than No numbers But broader torque curve with better response at WOT when passing cars on a country road.  Also better with modified diffusers than No numbers that will be too restricted with any kind of diffusers. Note! Torque is the same on all measurements. Lotus Root w diffusers got 85,34 Nm, all other 87,2-88,7 Nm

I guess that a 4-2-1 will help to extend the power curves and open up for playing around with my other cams. 4-4 might be enough on 1 bike, my ongoing K2 with 736cc and no power mods.

- Hindle 4-2-1  http://www.ripplerockracers.com/product/cb750-hindle-vintage-racing-exhaust-system-fits-1969-78/
This is the way since bike will be able to use rear std footpegs, right?
Update: A system is waiting in my garage to be mounted, I ordered both mufflers, long and short just for sure. (Order one later on will be too costly with shipping customs etc)
Kemp at Ripple Rock Racers is really helpful and nice doing business with!

Below more race style were a passenger is not welcome except in the winning room afterwards sharing the champagne....
- http://www.schuele-maschinenbau.de/pages/klassik.htm
-  motogpwerks

Other canididates of max power within reasonable sound levels?

[Jerry Rxman Griffin aka MuthaF'er]

You are getting there. Time and money!

Any plans to go to 34's once you get the pipes configured?

Do those first 2 charts make sense with the numbers and the way the lines run??

[PeWe]

The project changed since I wanted bigger bore.
The carbs runs fine, no need of bigger. The limitation is the exhaust. EDIT: Reading this forum and input from you guys can make me to change my mind! I must try to resist!! $$$$
Charts are backwards.
1. is the result. Green lines with diffusers in. Bike runs rather good and comfortable sound level.
2. The first dyno with Lotus root system and 2 dyno runs with cyl 1+2, 3+4  A/F ratio
3. First dyno with 1005cc and No numbers system, the thin blue lines on A/F ratio are cruising speed. It ran way too rich.

I lowered the needles 1 step and still sputtering around 2800-almost 4000 rpm. Needles lowered 1 step further and it ran OK which is measured on chart 2. But cyl 1,2 were too lean.

Chart 1. Changed floats to richer 1,2  which are measured A/F ratio to be as the 3,4 on chart 2.
(My fault since I checked all float levels before with clear tube and found 1-2 higher than 3-4. I should not have lowered the float levels. I understood too late that my earlier adjustment was the root cause of lean 1-2 at WOT. I'm happy that nothing really bad $$$ happened!)
Cruising experience worked fine both with open pipes and with diffusers.
If I change exhaust to a 4-1, I'll have better start. I like the stock look and have much torque when twisting.

I'm sure I'll have problems to not play around more with my other cams and my old 4-1 to start with.

[PeWe]

Update for those that search for Mikuni TMR32 jetting. They have KN Pod filters that fits the Mikuni filter adaptors on carbs.
Carbs works really fine now. From low lift cruising in town to more initiated riding.

- Pilots 27.5
- Fuel screws 3/4
- Needles 9D3-52           
  (9E11-52  too rich, not
  possible to get right)
- Needle height 4:6 from top
- Mains 135 (increased to 142.5 with exhaust Hindle 4-2-1 instead of the 4-4)

Plugs DENSO X24ES-U
Exhaust 4-4 Lotus Root with drilled diffusers to open them up. Reaplaced by more open Hindle 4-2-1 w long baffle from ripple Rock Racers
Cam RC295 later 125-75
1005 cc JMR Billet block
Ported K head
Fuel: Shell V-Power
Oil: Red Line 20W-50. Will test 20W-60 which seems to be needed warm summer days when ambient temp is over +30C
Extra ventilation from clutch cover helps to avoid any oil leak. Before minor oil mist around oil filter, front case.

Ignition: TEC point plate + springs cut 1/2 wound each + Hondaman module + Dynatek 5 ohm coils
 Dyna-S went on later