Topic: 26mm CR Specials on a CB400F

[MRieck]

 Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

[davesprinkle]

Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

1700 using the mechanical tach.  I suspect it's likely inaccurate.

[MRieck]

Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

1700 using the mechanical tach.  I suspect it's likely inaccurate.

You'd be correct in that assumption Dave.

[paulages]

Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

1700 using the mechanical tach.  I suspect it's likely inaccurate.

dave- didn't you tell me you had rigged up tach wires for the dyno? couldn't get an accurate reading that way? i admit, it's a pretty silly way to check the accuracy of your tach, but if you're already on there...

[davesprinkle]

Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

1700 using the mechanical tach.  I suspect it's likely inaccurate.

dave- didn't you tell me you had rigged up tach wires for the dyno? couldn't get an accurate reading that way? i admit, it's a pretty silly way to check the accuracy of your tach, but if you're already on there...

Yeah, that's right, Paul.  I didn't do an exhaustive analysis of the error, but one spot-check showed a true speed of 1100 for an indicated speed of about 1300.

[paulages]

Are saying 1,700 RPM for idle using the mechanical tach or a dwell meter etc?.

1700 using the mechanical tach.  I suspect it's likely inaccurate.

dave- didn't you tell me you had rigged up tach wires for the dyno? couldn't get an accurate reading that way? i admit, it's a pretty silly way to check the accuracy of your tach, but if you're already on there...

Yeah, that's right, Paul.  I didn't do an exhaustive analysis of the error, but one spot-check showed a true speed of 1100 for an indicated speed of about 1300.

i like my idle over 1000 anyway- it always has better off-idle response. if you're indicating 17K, then you're probably actually at 15. some may think that's high, but i don't mind it there.

[turboguzzi]

Hi dave

had to work pretty hard on my 27mm VM carb cables attachments for my CB500 too, swoo can appreciate the work...

nice stuff indeed! just a few comments that you might find useful

1. Your replica triple clamps seem to have A LOT of trail built in! if you sharpened the steering angle with longer shocks, you might want to fit a set with less offset.
2. the 35mm pantah forks are a common racing mod in my class, people often run them with twin "small" brembo calipers for a more period look.
3. dont know if you already run your bike with the velocity stacks shown. Built a similar set but just couldnt sort out the jetting. they gave a huge boost al medium revs but killed the top end. they might work better with your stock cam.

my 0.02
TG

[davesprinkle]

Hi dave

had to work pretty hard on my 27mm VM carb cables attachments for my CB500 too, swoo can appreciate the work...

nice stuff indeed! just a few comments that you might find useful

1. Your replica triple clamps seem to have A LOT of trail built in! if you sharpened the steering angle with longer shocks, you might want to fit a set with less offset.
2. the 35mm pantah forks are a common racing mod in my class, people often run them with twin "small" brembo calipers for a more period look.
3. dont know if you already run your bike with the velocity stacks shown. Built a similar set but just couldnt sort out the jetting. they gave a huge boost al medium revs but killed the top end. they might work better with your stock cam.

my 0.02
TG

Thanks for the comments, TG.  Yeah, the cable attachment mod wasn't easy.  And good eye noting the big offset on the Ceriani triple.  Yes, the new yokes have a lot less trail than the stocker -- 13mm less.  The bike is most definitely twitchier than it used to be.  It hasn't shaken its head yet, though, even with the damper turned fully out.  And the longer shocks just balance the longer forks; rather than steepening the head-angle, the shocks brought it back to near stock.
I wasn't really impressed with the Pantah forks.  Lots of stiction.  I had to rework the internals -- it's still not perfect, but good enough to ride.
Thanks for the comment on the brakes.  I went with the large rotor because I wanted to evoke the effing huge 330mm drums from back in the day (without actually using drums).  Too late to go back to dual discs -- I've trimmed off the lugs on the right fork leg.

I haven't yet ridden the bike with the aluminum stacks, but I have ridden with the plastic stacks.  The aluminum stacks are identical replicas of the plastic versions, though, so I don't anticipate that the bike will run any differently.  The bike ran great with the plastic stacks, though.  I found jetting for the filters to be more difficult to sort out.

[turboguzzi]

Well, my approach is that the bike should be stable enough without the damper screwed on as that definetely makes steering heavier. Just keep an eye on that

I managed to find some similar sized 35 clamps off some modern italian sports 125 (Cagiva C9) and it gave back a lot more "feel" from the front. Those ceriani clamps where made for really old bikes that had close to 30 degs of rake, with our CB's having around 24-25, you could do well to fit some with less trail.

Nice work nevertheless!

Cheers
TG

[Kevin]

Dave,
Thanks for the excellent documentation, you're a genius!!! I am sure this will benefit me when I start to dial in the motor on my cafe' bike.

 I bought a set of  K&N air filters, I think they are the same as what you have, they are stamped F020A4. The K&N part # is RC-1820 and Sudco part # 005.140. It looks like I am going to have to do some serious manipulating to get #1 and #4 to fit.

Thanks Again,
Kevin

[davesprinkle]

Dave,
Thanks for the excellent documentation, you're a genius!!! I am sure this will benefit me when I start to dial in the motor on my cafe' bike.

 I bought a set of  K&N air filters, I think they are the same as what you have, they are stamped F020A4. The K&N part # is RC-1820 and Sudco part # 005.140. It looks like I am going to have to do some serious manipulating to get #1 and #4 to fit.

Thanks Again,
Kevin

Thanks for the kind words, Kevin.  They're particularly meaningful in the context of the incredible bikes you've built.  By they way, the sidecovers on my bike are the ones you make.  I may not have mentioned this in the past, but those sidecovers are without question the highest quality aftermarket parts I've ever purchased.  Better quality even than the stock sidecovers.  Good work.

[davesprinkle]

This past weekend, I spent some time tuning my friend's CB400F, running 26mm CR Specials. 

Engine specs:
449cc
OE header
OE muffler
OE cam
Dyna S ignition and coils
K&N pod filters

Atmospheric conditions:
~75 degrees F
~1200ft above sea level

When I arrived, the bike required a full turn in on the idle stop adjuster to idle, and wouldn't accept throttle without dying.  My friend told me that the bike had poor power and wouldn't run faster than ~60mph.

I'm embarrassed to admit that we did the needle-swap tango a couple of times with no improvement before it finally occurred to me to check the headers.  2 & 3 hot, 1 & 4 cold.  Oops, should have done that first.  But there you are, clear pointer to an ignition problem.  Swapped in the OE points and coils and the bike fired up, idled at 6K.  Turned the idle stop adjuster back down to ~2500rpm.  All 4 headers were hot.  Off-idle throttle response excellent.  A test-ride confirmed no flat spots.  Jetting was perfect.  Just to confirm, here are the specs again:

Slides: 3.5
Needles: Y8
Clip position: #4 from top
Main jet: 98
Main air jet: 150
Pilot jet: 65
Airscrews: 1/2 turn out

I realize this may seem like a pointless resurrection of a petrified thread, but I recall that recently another forum member was struggling with CR jetting on a 400.  In that thread, he suggested that this jetting setup wasn't successful for him, and he also mentioned that the bike wouldn't pull beyond ~90mph.  The symptoms are similar enough to suggest that he also might have a pair of dead holes.

Too bad I had to learn this lesson again -- check the spark first.

[Sam Green Racing]

Superb thread Dave, well documented and what a stunning motorcycle, thanks for bringing it here.

Sam.

[Kevin]

Dave,
You are a genius!!
Thanks so much for taking the time to document your findings.
This information is going to save me a bunch of time and frustration when I dial in my cafe bike.
If the bike were at sea level, what what you do differently?
Kevin

[Sam Green Racing]

Kevin, have you got a bigger pic of Purple Haze?

Sam.

[Kevin]

Yup,
http://mysite.verizon.net/kvnshwn/

[davesprinkle]

If the bike were at sea level, what what you do differently?
Kevin

I would suggest a slightly larger main jet.  My bike is at sea level and runs a 100 main.  (Refer back to the jetting specs for open trumpets if you'd like the full jetting list.)  

At sea level, air will be roughly 6% denser than at 1200'.  A 100 main jet has 4% more area than a 98.  A 102 main has 7.5% more area.  Either would probably be a good choice.

[rudi]

Good Morning USA,this is a CB 400 Four Guy from Germany.
I am the Owner of a Cb 400 f /1976 , an EGLI Honda CB 500 four with 590 ccm³ Engine, Egli Kawasaki Z 1000R and a Kawasaki GPZ 305.
I am since 1 Year only listen to this Forum and know I found what I am searching for : Somebody who ownes the same Type of Piston than me!!!!!!!!
My question to you : From where did you got the 53,5 mm Pistons and on which Bike they are Original used ?
I got my Set of 4 Pistons in 53,75 mm from Australia (via EBAY) and Nobody here in Europe can Identify these Pistons. I am searching for a Set of four Piston Rings for these Pistons.
My Honda CB 400F is equiped with Yoshi ST 1 Camshaft,Frame Mod. with Chrome Rear Swing box Arm, Borrani Alloy rims . Future Modifications : Yoshi 450 ccm³ Pistons with low Friction Coating (ready to be installed) Dry Clutch conversion , Modifyied 6th Gear Assy (Prototype is ready ), Full Race Cylinder Head incl. 1.5 mm Oversize Intake Valves opend Valve seats an ported to run with Mikuni CR 29 SS Carbs or 31mm CV Flat Side Carbs from Kawasaki ZXR 400.

Thank you for a reply !!
In the Case that you did not get an Anwser just in Time : I am on Holiday for the next 10 Days.

[Sam Green Racing]

Welcome Rudi, nice to have you on board. This is not just the USA, we have members world wide who share a passion for the SOHC4s and the tuning of them and are getting together on this new section of the forum.

Oh, I didn't mention, they like pitures

Sam.

[davesprinkle]

Good Morning USA,this is a CB 400 Four Guy from Germany.
I am the Owner of a Cb 400 f /1976 , an EGLI Honda CB 500 four with 590 ccm³ Engine, Egli Kawasaki Z 1000R and a Kawasaki GPZ 305.
I am since 1 Year only listen to this Forum and know I found what I am searching for : Somebody who ownes the same Type of Piston than me!!!!!!!!
My question to you : From where did you got the 53,5 mm Pistons and on which Bike they are Original used ?
I got my Set of 4 Pistons in 53,75 mm from Australia (via EBAY) and Nobody here in Europe can Identify these Pistons. I am searching for a Set of four Piston Rings for these Pistons.
My Honda CB 400F is equiped with Yoshi ST 1 Camshaft,Frame Mod. with Chrome Rear Swing box Arm, Borrani Alloy rims . Future Modifications : Yoshi 450 ccm³ Pistons with low Friction Coating (ready to be installed) Dry Clutch conversion , Modifyied 6th Gear Assy (Prototype is ready ), Full Race Cylinder Head incl. 1.5 mm Oversize Intake Valves opend Valve seats an ported to run with Mikuni CR 29 SS Carbs or 31mm CV Flat Side Carbs from Kawasaki ZXR 400.

Thank you for a reply !!
In the Case that you did not get an Anwser just in Time : I am on Holiday for the next 10 Days.

Hi Rudi,
I purchased my big-bore kit from the same person you did -- an Australian seller on Ebay.  The piston is a close copy of the OE Honda casting, but has some very subtle differences.  Also, although the part number printed on the box adheres to the Honda pattern, I inquired with Honda and was told that it is not a true Honda number.  Based on this, I suspect that these piston kits were aftermarket copies of the OE piston.  I'm sorry, I don't know the manufacturer.

Regarding the rings -- during my engine build, I broke one of the oil rings and needed a replacement.  I was unable to find any manufacturer who made a replacement.  However, at the time (4 years ago) the original seller in Australia still had replacement rings.  I don't know if he still has them.

[turboguzzi]

Welcome Rudi, nice to have you on board. This is not just the USA, we have members world wide who share a passion for the SOHC4s and the tuning of them and are getting together on this new section of the forum.

Oh, I didn't mention, they like pitures

Sam.

and we certainly want to see pictures of the egli 500!

dont login again without them

[paulages]

Good Morning USA,this is a CB 400 Four Guy from Germany.
I am the Owner of a Cb 400 f /1976 , an EGLI Honda CB 500 four with 590 ccm³ Engine, Egli Kawasaki Z 1000R and a Kawasaki GPZ 305.
I am since 1 Year only listen to this Forum and know I found what I am searching for : Somebody who ownes the same Type of Piston than me!!!!!!!!
My question to you : From where did you got the 53,5 mm Pistons and on which Bike they are Original used ?
I got my Set of 4 Pistons in 53,75 mm from Australia (via EBAY) and Nobody here in Europe can Identify these Pistons. I am searching for a Set of four Piston Rings for these Pistons.
My Honda CB 400F is equiped with Yoshi ST 1 Camshaft,Frame Mod. with Chrome Rear Swing box Arm, Borrani Alloy rims . Future Modifications : Yoshi 450 ccm³ Pistons with low Friction Coating (ready to be installed) Dry Clutch conversion , Modifyied 6th Gear Assy (Prototype is ready ), Full Race Cylinder Head incl. 1.5 mm Oversize Intake Valves opend Valve seats an ported to run with Mikuni CR 29 SS Carbs or 31mm CV Flat Side Carbs from Kawasaki ZXR 400.

Thank you for a reply !!
In the Case that you did not get an Anwser just in Time : I am on Holiday for the next 10 Days.

the tech dept at hastings has been very friendly with me regarding finding difficult rings. you can bet they make them, they just won't have them listed for your application. if you can provide groove and bore dimensions, i bet they can help. if you need someone stateside to talk with them over the phone, PM me with specs and i'll do what i can to help.

[rudi]

I use the second Compr. Rings from a Set of CB 72 Piston Rings and Oil control Rings from Wiseco Order No.: W2126XE.
I send more Details and Tricks about my CB 400 f when I am back from Holiday in 11 Days.You will be surprised........................
Have a look into our WEB Page CB400F.de a little bit is shown there....

[rudi]

 This is My Egli honda CB 500/590. More Details about the Bike and Engine after my holidays....

[rudi]

This is my Race Cylinder Head
Modifications:
+ 1,5mm bigger Intake Valves
STD Exh. Valves
Valve seats opened , Intake + 1,5mm , Exhaust + 1mm and Fully ported !!
Mikuni VM 29SS Carbs heavily modified to match with the Cb 400 f Head
Alloy Valve Spring Caps , STD Vave Springs
HRC TT Formula 2 Race Camshaft (very rare!!)
Alloy Allen screws