Topic: CB350Four Tuning

[andyman]

Hey guys!
I have built a 350Four Racer just for fun. Head ported, open stock carbs without choke, open 4into4 and a WebCam Stage1. 32hp at the rearwheel at 10 000revs.

There is now a 400 class in austria so i want a little bit more power.

Is there anyone who has installed the 50mm bigbore kit to bring the 350 to 393ccm?

And is it possible to install the 500Four carbs on the 350 engine?

I know i could put a 400F cylinder and head on it but i have many 350 parts in very good condition and the crankcase does not need to be spindled.....


So i hope you can help me!

Regards from Austria!

Andy

[carnivorous chicken]

Don't know about the kit, would guess you might be able to make the carbs work with some kind of modificaiton, but... mostly interested in seeing a photo!

[turboguzzi]

it all really depends how competitive is the class... and you...
in a 400 class, the CB400F will have too many advantages compared to a 350, so i would start a project with a 400, not a 350.
But if you want to still build a 350/393, just do like these guys

http://www.teamhansenhonda.com/hailproj.htm

[andyman]

Which advantages do you mean? I doesen't miss the sixth gear....

[turboguzzi]

I meant that 350 is 5 speed and 400 is 6 speed,
but it's not only that, crankshaft, rods, frame and other stuff too, the 400 was a serious upgrade from the 350, it's simply a better and faster bike. No wonder that the 350f didnt achieve much in racing, the 400 had huge racing success.

[innovativems]

I’ve heard quite a few issues with the cruisin image rings on the 393 big bore. 

Have you considered boring your carbs?  I have mine done by rick in Canada and they did great on my built 400


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[andyman]

@turboguzzi: Crank and rods have the same parts number on www.cmsnl.com, i think they are identical. What differences are there in the engine? 6speed gearbox ok, bigger pistons ok but i don't think that is such a better engine than the 350?

[turboguzzi]

im not a 350/400 guy, just knowledge from a race tuner friend who told me not even to consider the 350... as well as reading about what the 350 achieved in racing compared to the 400.
the 400 crank/rods might fit the 350 but it is an upgraded component ASFAIK, but dotn take my word for it. BTW frame is certainly improved
the main racing expert on 350/400 here is member  "ttr400" , try contacting him and ask http://www.ttr400.com/index.html
there is an email link in the bottom of page.

[innovativems]

Kevin at ttr400 is the man.  Bottom end is the same between the two, Trans is obviously different.  I have both bikes and have rebuilt both. 

The head is different and if memory serves me right the intake valves are larger.  Also bolt pattern and stud length is different. 


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[andyman]

Intake +0,5mm, exhaust +1mm than the 350.

But i have installed a WebCam Stage1 Camshaft, the competitors have stock camshafts in the 400 engines.

In my 350 engine many parts are new, Rockers, camchain, primarychain and so on so it would be a great pity to stop using it....

[Rick4004]

I've heard of CB500/550 carbs being installed on 400's, but I don't know how they did it. The 500/550 carbs have much wider spacings than the 350/400 carbs.

Check out my website for more information on carb boring. The 350 carbs are the same as 400 carbs. www.denoonsp.com

[andyman]

Thanks, i will think about it!

[andyman]

So guys after a time of thinking i will build a second 350 engine.

Similar to the first engine but bored carbs to 24mm, more compression ratio and the WebCam Stage1 camshaft which i am also using in the first engine.

I want to machine the pistons for enough piston/valve clearance, and brandnew valve springs.....at cms i saw that there are new stock springs, for the Stage1 the Kibblewhite springs are not necessary.

What do you think abaout this project? Any tips?

Greets Andy

[MRieck]

So guys after a time of thinking i will build a second 350 engine.

Similar to the first engine but bored carbs to 24mm, more compression ratio and the WebCam Stage1 camshaft which i am also using in the first engine.

I want to machine the pistons for enough piston/valve clearance, and brandnew valve springs.....at cms i saw that there are new stock springs, for the Stage1 the Kibblewhite springs are not necessary.

What do you think abaout this project? Any tips?

Greets Andy

I say use the Kibblewhite springs.....don't use stock springs (that have about 30lbs on the seat).

[andyman]

For whatever reasons?

The WebCam Stage1 has almost the same valve acceleration as the stock cam.

The springs mean power loss so please clear me up

[MRieck]

For whatever reasons?

The WebCam Stage1 has almost the same valve acceleration as the stock cam.

The springs mean power loss so please clear me up

Valve control is critical to making power especially at higher RPM....that's it. You would have to run very high pressure springs to lose power and even at that the loss is negligible compared to the power and valve control gained. Look at beehive springs and check out the seat pressures and overall benefits.
 If you want to run stock springs it makes no difference to me.....you asked a question. If nothing else I'd throw a shim in there ( and check for coil bind as those springs are wound tight.)

[andyman]

Ok thanks for answering now i understand what you mean!

So the problem you mean is the spring preload from the stock springs when the Valves are closed?

How many stronger are the Kibblewhite springs? Are there any Problems with the rockers?

[MRieck]

Ok thanks for answering now i understand what you mean!

So the problem you mean is the spring preload from the stock springs when the Valves are closed?

How many stronger are the Kibblewhite springs? Are there any Problems with the rockers?

Andy.....here are the numbers for the Kibblewhite springs. Installed height 1.270" Seat Pressure 40 lbs.  Max open pressure 131 lbs at .400 lift. If you want the springs but cannot find them I can ship them to you as I have a dealer account with Kibblewhite.
Mike

[jamesv220820]

Here is what Kevin suggested to me a while ago

What can you do to the CB350F Motor?

There are many options; it just depends on how much you want to spend.

Here are a few for you to think about.

Option 1.

Fit new TTR sleeves and bore for STD CB400F 51mm pistons and rings etc.
This also requires the upper crankcase to be opened up larger.
Good port and flow on cyl head and valves (std valves). Fast road camshaft (Webcam or megacycle)
Stock carbs with stock air box. Or pod filters is OK.
A copper head gasket will be required. New pistons, rings and pins are available from David silver spares.

Option 2.

Fit a complete CB400F top end. Upper crankcase will need to be opened up larger.
Bore and fit the Yoshimura 466cc kit (54.5mm) or fit 0.25 OEM CB400F pistons. Rings etc. The 2 front middle cyl studs will need to be changed for custom items. (I can supply these if required)
Good port and flow on cyl head and valves (std valves). Fast road camshaft (Webcam or megacycle). I would also include a set of performance valve springs.
Stock carbs with stock air box. Or pod filters is OK.
You could also have your STD carbs bored larger with the above motor. Rick Denoon in Canada can do this.

Option 3.

As per option 2 but with a full race camshaft and oversize stainless steel valves and bronze guides. But with Keihin 26mm CR Carbs.

OK these are just 3 options for a nice street motor. For a full race motor with no limits more can be done!

For good cyl head work in the USA, I would recommend Mike Riek (on the SOHC forum)

With any of the above options I would also balance the crankshaft, rods and pistons.  I would also fit a new heavy duty cam chain and replace all the cam chain adjuster related parts.

[andyman]

My Project:
original 347ccm
WebCam Stage1
Kibblewhite springs
Head porting
open carbs and bored to 24mm
open 4into4
Ignitech ignition
compression ratio 10:1-10,5:1

I think that will be good...

[jamesv220820]

My Project:
original 347ccm
WebCam Stage1
Kibblewhite springs
Head porting
open carbs and bored to 24mm
open 4into4
Ignitech ignition
compression ratio 10:1-10,5:1

I think that will be good...

Every performance guru i have talked with says go 4-1 with exhaust . Not to familair with the ignitech but if you are doing electric toss some dyna coils on it, plugs wires and caps

[andyman]

i will take 4into4 because i like the sound.

[jamesv220820]

i will take 4into4 because i like the sound.

which 4-4 did you have in mind?

[andyman]

I have the 4into4 already on my 350 racer, i only build a second stronger engine for it.

http://www.moto25.de/media/gallery/goisern.2016/002.jpg

http://www.moto25.de/media/gallery/kampenwand_m.2016/025.jpg

[jamesv220820]

i will take 4into4 because i like the sound.

which 4-4 did you have in mind?

That is a fun exhaust system. Custom made?