Topic: 750K2 Hot Rod Revival - Early Christmas

[CBJoe]

After a few years without a SOHC4 Running in the garage I’m back in the game.  Starting this thread to track bringing a Hot Rod CB750 K2 out of a many year hibernation.  I purchased this bike from member Sparty (Art) recently and just got it home and into the garage.

It was originally built around 2007/2008 and was run off an on.  Has about 1300 miles on it since the Engine Install. 

Too much to list, but below is a summary of whats in the bike.  Complete Engine built by the master MRieck himself  .  Dyno’d at around 90 – 93HP….will get it on a dyno again once it’s all up and going.

Top End Parts and Labor:
Megacycle 125-75 Cam
Megacycle Adj. Camshaft Sprocket
Kibblewhite Ti Valve spring retainers
Kibblewhite H-D racing valve spring springs and shims
Kibblewhite bronze valve guides
EV8 Polished SS oversized intake valves 33.5mm
EV8 Polished SS exhaust valves 28mm
Tsubaki H-D cam chain
M3 Racing can chain tensioner
APE H-D Top End Studs
JMR Stage 3 Head porting, polish, and mill
Serdi valve job
Balanced Alt. rotor and clutch basket

Bottom End Parts and Labor:
Wiesco 836cc Piston Kit
Falicon Knife Edge connecting rods with ARP premium bolts
New OEM Honda cam bearings
New OEM Rod bearings
Swain Tech piston coatings (TBC & PC-9)
APE H-D Bottom end bolt kit
JMR Cylinder decking (total squish .053)
New OEM Honda primary chain tensioner
JMR Bore and Hone cylinders (top cut .014 and recut o’ring c’bores)
APE lightened and balanced crankshaft (balanced for sustained operation to 14,000RPM)
Barnett H-D clutch springs
New OEM Honda clutch fibers and disks
FAST by GAST undercut transmission

Fuel and Ignition Parts:
Keihin CR carbs 29mm
Dyna 2000 electronic ignition w/ 3 ohm coils w/ Dyna suppression wires
Kerker 4:1 Megaphone header with comp. Baffle

Suspension and Drive Train:
YSS Z- 302 Twin w/ chrome springs
530 O-Ring chain
JT Front sprocket 17T
Progressive Suspension fork springs

Frame was powdercoated when the engine was built (2008’ish) and all of the engine covers were professionally polished.

Electrics are mostly stock minus the ignition system.  I installed a Shorai LiFePO4 Battery and have a Ricks Lithium Ion Safe R/R Combo on order now.

Current plans are:

- Oil Change
- Go through the CR29s and give them a good cleaning.
- Replace the Throttle Cables...and maybe the throttle sleeve as well
- Clean and rebuild clogged petcock or replace with a Pingel Power-Flow
- Replace Tires/Tubes - Thinking of BT45's 100/90 up front and 120/90 in rear.
- Check Valve Clearances
- Check into upgrade to dual disks up front (discussing with member Godffrey)
- Likely will replace the handlebars...but i’ll give the clubmans a chance.  I have my eyes on renthal ultra low street bars.

Anyway...thats all a start    Already have the tank and covers off and carbs removed for sorting.  Just need some warmer temperatures to make garage work nicer.

Cheers, Joe

[seanbarney41]

really cool bike...you won't like the clubmans without rearsets, I think the Renthals are a fine choice.  I'd definitely be wanting more whoa with all that go.  I'd also be changin' up that tail light/license plate set up, if there is any chance at all of it scraping in a turn, you will lowside...at the very least you avoid scraped shins and torn pant legs movin it around the garage.

epic bike though.  I think I remember reading this one's build thread before I signed up here

[CBJoe]

really cool bike...you won't like the clubmans without rearsets, I think the Renthals are a fine choice.  I'd definitely be wanting more whoa with all that go.  I'd also be changin' up that tail light/license plate set up, if there is any chance at all of it scraping in a turn, you will lowside...at the very least you avoid scraped shins and torn pant legs movin it around the garage.

epic bike though.  I think I remember reading this one's build thread before I signed up here

Thanks for the call out...didn't think about it but I'll be sure to double check the license plate bracket lean clearance. I don't think its an issue, but better safe than sorry.

 

 

[SOHC4 Cafe Racer Fan]

The Sparty bike lives!

[eatpez]

Wow. A real beauty to look at and probably a beast to ride!

[CBJoe]

Cleaning the CR29s and noticed this open port where it appears a screw should go. 

Anybody know what this port specifically is and if it’s supposed to be open?

Edit....it seems to be where an air screw would be...but the threading is much smaller than the air screw ports on Carbs 3 and 4.  Carb 1 doesn't have a threaded port for a screw.

Can anyone clarify?




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[seanbarney41]

looks like the sync port, where you attach vacuum lines for your gauges?

[CBJoe]

looks like the sync port, where you attach vacuum lines for your gauges?

I found a few pictures online as reference and I don't think its a port for anything.   Looks to be a screw mount for a bracket that clips on the fuel rail according to the attached pic.

So...thats good...but I'm curious why only 2 of the 4 carbs have air screws.  Maybe someone with CR experience can chime in.

Joe

[scottly]

looks like the sync port, where you attach vacuum lines for your gauges?

1+

[PeWe]

About rear tire.
I had  several120/90-18 on stock rim. They became flat rather quick with horrible handling when leaning the bike a little. I have now stock 4.0-18 tires as I have read should not become flat as fast as the 120.
Also BMW forums have threads about tires where stock sizes often is written to give best handling.

My bike got 120-130 tires in the 80's. Now back to stock for first time after I bought it 1979

I'll see how long the tire will live this time and if it will get same rotten handling after around 3500-4000km, replacement at max 5000km.
Around 90 rwhp will not prolong the life of it
Front has 100/90-19, 3.25-19 next time

Friends with newer bikes have wider front tires than my rear! 

[MRieck]

 Not a synch port. The carb bodies are not made left or right...they are universal. Depending on whether the carbs are for 1/2 or 3/4 that hole is tapped for the idle mixture screw. If you look at #4 carb you can see it. There is no screw in there.

[CBJoe]

Not a synch port. The carb bodies are not made left or right...they are universal. Depending on whether the carbs are for 1/2 or 3/4 that hole is tapped for the idle mixture screw. If you look at #4 carb you can see it.

Geez...I feel like a proper fool.  I just went back out to the workbench and you are correct.  My eyes were playing tricks on me last night.

[CBJoe]

Carbs are all disassembled for cleaning....not too bad.  Some varnish buildup

[MRieck]

Not a synch port. The carb bodies are not made left or right...they are universal. Depending on whether the carbs are for 1/2 or 3/4 that hole is tapped for the idle mixture screw. If you look at #4 carb you can see it.

Geez...I feel like a proper fool.  I just went back out to the workbench and you are correct.  My eyes were playing tricks on me last night.

Don't beat yourself up over it. Those carbs look to be in excellent condition.

[Jerry Rxman Griffin aka MuthaF'er]

Kinda small but they'll do 

Just hoping to have mine rideable for October. Looking at July for wrenching. In the islands now, then do some Vette touring, 10 days work, some bike touring and THEN wrenching. August is Bonneville, Sept is CO mountains and Telluride Blues and Brews. Oct is KY. November is GA and Manufacturers Cup. December is back to my new VI condo. I'm fully booked.

[CBJoe]

Kinda small but they'll do 

Just hoping to have mine rideable for October. Looking at July for wrenching. In the islands now, then do some Vette touring, 10 days work, some bike touring and THEN wrenching. August is Bonneville, Sept is CO mountains and Telluride Blues and Brews. Oct is KY. November is GA and Manufacturers Cup. December is back to my new VI condo. I'm fully booked.

Phew Jerry!  Thats a lot of activity

[andy750]

"Thinking of BT45's 100/90 up front and 120/90 in rear."

Completely agree with PeWe - been there done that. Exactly as PeWe described about squaring off and horrible handling. Stick with stock size difference is night/day.

[CBJoe]

"Thinking of BT45's 100/90 up front and 120/90 in rear."

Completely agree with PeWe - been there done that. Exactly as PeWe described about squaring off and horrible handling. Stick with stock size difference is night/day.

Hmm....I pulled the trigger a few days ago on Pirelli Sport Demons in the mentioned tire sizes after I got a really good deal. 

This bike will not get a ton of miles on it.  I may just go through these tires and come back to stock next time around.

I realize I'm opening an oil can here, but in the stock sizes what are the preferred high performance tire?

- Metzeler Sportec Klassic
- Avon AM26
- Michelin Pilot Active
?

[andy750]

Oh Pirellis! I am interested to know how these perform.....heard good things

[seanbarney41]

Love the Sport Demons!  Unfortunate they don't come in proper cb750 sizes.  I think Avons AM26 are the best all around.  Have used lots of Lasertecs over the years too...they last a little longer.

[PeWe]

I have 2 rear wheels with new Heidenau K36 4.0-18. It look good for a CB750 with vintage look. I have read good about it.
No road test yet. The Dunlop Streetsmart has to be worn out first.

Front Heidenau K44, also the old look and not tested yet. The wheel that has it need an assembled bike. My K2 need to be put together.

[MRieck]

 The bike could really use a dual disc set up Joe....it makes enough power to mandate it.  I saw you mentioned it in a post.....I'd go for it brother.

[SOHC4 Cafe Racer Fan]

Of those choices, the Avons have great grip.

I've done a 130-135 BT45 rear with no detriment to handling.

[CBJoe]

The bike could really use a dual disc set up Joe....it makes enough power to mandate it.  I saw you mentioned it in a post.....I'd go for it brother.

Totally agree.  Currently discussing it with Godffrey.  Luckily Art had already installed a Nissin Radial master cylinder.  So should be good there   

[CBJoe]

Hey Mike...or other CR Carb Guru's.  Looks like carb#4 is indeed missing a "plug".  The CR Carb Diagram shows this as an "Air Leak Jet" I pulled the one from another carb and it appears to just be a solid plug. #85 in this diagram....http://www.sudco.com/images/CR.gif

I was thinking that maybe it fell out while cleaning, but I went to my original disassembly pictures and can see it's missing right from the get go.

Looks like it goes straight down to the throat of the carb. Not sure what effect this would have had on the running (if any)

Thoughts?

Joe