Tuesday, May 19, 2015

Carls Konged '78 CB750

Spent some time over at Carl's today to help get his bike back on the road. Needed lots of love after being his sole mode of transportation for a long time and then shoved in the corner for a few years like an old broom.

Just a few things off the checklist (stock k8 engine):

Set points:
Gap 0.012" to 0.016"
Static set 1-4 timing on F-mark with ohmeter
Static set 2-3 timing
Lock plate and roll.

Valve Lash:
E.O.I.C method
Intake 0.002"
Exhaust 0.003"

Set cam chain tensioner:
Push kicker to get tension on the front of the cam chain and slack on the rear. Loosen lock nut on tensioner and back out the set screw. Listen for movement in the tensioner and lock down the set screw and lock nut.

After setting the valve lash, I successfully snapped a Tappet cover off. Good word of advice: Just snug the Tappet covers down lightly. This one was fatigued or already broken because I didn't even get the gasket seated to the valve cover before it popped.

Meanwhile Carl replaced the fuel pump in his car. Lovely day.

Monday, May 18, 2015

Rock Flute Specifications:

For my own notes and for those interested, here are the specs on Rock Flute.  I'll update this as things change... because they always do. For instance, the green paint in the picture is actually a brighter green than the color code listed below.  I will update the picture as soon as the bike is repainted.

10.9 to 1 CR
1978 CB750 F bottom end
1976 K model cylinders, Decked
1976 K model Head, Stage II porting, decked by Mike Reick
                33.5 mm OS intake valves, stock exhaust valves
                Megacycle 125-75 cam, 0.005” Int/Exh tappet clearance, 105 int 104.5 exh lobe centers, no adv.
                                (More cam specs in chart below)
                Adjustable cam sprocket
                HD Valve springs and titanium keepers
                Late model cam towers with unbolted early model rocker shafts
Wiseco 836 forged piston kit
CycleX Super Rods
New primary chains installed
Reinforced valve cover with cam tower stabilizers

Transmission/Final Drive:
F model transmission, backcut with close ratio 4th and 5th gear
             Primary: 1.708:1
            1st:           2.500:1
            2nd:          1.708:1
3rd:           1.333:1
            4th:           1.133:1
5th:           0.969:1
Barnett Clutch plates and springs
Drilled clutch basket with oil grooves for added oiling
Final Drive: 17/48 2.82:1

Dyna 2000 ignition with Dyna minicoils
Total Timing Advance: 35*
Timing curve: 5
Rev limiter: 11,000 RPM
DR8EA Resistor type spark plugs @ 0.026” gap (resistor plugs used to eliminate noise in digital tach)

Ramflo Filters
Sudco VM29/CB750 Adapter boots with vacuum ports
Mikuni VM29 Smoothbore Carburetors
               Mains: 115
               Pilots: 15
               Air Jets: 1.1
Air Screws: 1.5 Turns
Needles: #5DL31-3 (verify) with clip @ #1
Needle Jets: 0-6 (verify)
Throttle Valves: 1.5
Float Height: 23 mm

4-2, 2” long baffle with 1.25” inner diameter

Cycle One Manufacturing rigid
2" forward
4" up
36* rake, Harley 1" neck
5" ride height
Paint: Sikkens Rally Black
Fuel Tank: 1969 Triumph Tiger Daytona 500
Rear Fender: 5" Ducktail ribbed fender, 7 Metal West
Paint: Gloss Black/MD State Police Green - BMB1B (ICI Autocolor paint code)
Seat: Satin black powder-coated Accufast seat pan with single leaf spring suspension
Suspension/Front End:
Vincent Style girder with Cannondale MTB air shocks
Front Wheel:  Satin black powder-coated SOHC CB750 rim laced to a CL450 dual leading shoe brake hub
Front Tire:  Shinko 705 110/80-19
Rear Wheel:  Satin black powder-coated DOHC CB750 rim laced to a late model CB750 drum hub
Rear Tire:  Shinko 705 130/90-19
Gauges/Info Center:
Vapor Computer System
     Speedometer, Tachometer, Trip/Odometer, Top Speed, Time, Head Temperature, Shift Lights/Redline Warning
Analog Oil Pressure Gauge
Headlight:  Cycle Standard 4.5 inch early style headlight with high beam indicator
Taillight:  Bullet style dual filament

Capacity: 5 Quarts
Mobil 1 20w-50 Full Synthetic

Capacity: 3.7 Gallons
Premium 91+ Octane

Curb Weight:
450 Lbs


Cam Specs
Valve Lift
Int. Open
Int. Close
Exh. Open
Exh. Close
Lobe Center
tappet Clearance
Sealed Duration
Megacycle 125-75
262 @.04
257 @.04


Saturday, May 9, 2015

Rewelding and cleaning up some of the parts on Rock Flute

So I found out my kickstand can't take the entire weight of the bike dropping down on it. 450 lbs bent the tab enough for me to have to reweld it. While I had the welder out, I also added a bit of metal to the headlight mount because it had a tendency to vibrate at high speed. Both problems fixed and covered with a half assed attempt to blend satin black paint.

Wrap up with some ginger beer

Wednesday, May 6, 2015

Carburetor Return Springs

Brought to you by you local hardware store.

Monday, April 27, 2015

Installing Vacuum Ports for Synchronizing

Here's a quick and reliable way to install vacuum ports on your bike if your carbs don't have them. My vm29s don't and I want to ensure good balance. Ensuring good balance between carbs has made a big difference in ride quality and performance on many of my other bikes and it's bothered me that I've never had a way to check these.

I bought 5 mm threaded vacuum ports to install in the rubber boot. Other places to add vacuum ports are on the carb body, behind the slide of course, or on the cylinder head by tapping into the intake port. There is no room on the vm29 carb and the head of a cb750 requires removal of cooling fins on the out cylinders to make a good spot. I don't want to do anymore work on the cylinder head so to the boots it goes.

This is easy enough. Just drill a hole in the boot the same size, or close, to the minor diameter of the threads on the vacuum port. Clean off the debris nd test fit the port. Add some gasket maker to the threads and screw them into the boot. Let them dry and cap them with the supplied acuum plug.  Done and done.

Now you can go back to the precious article and vacuum sync your carbs. Woohoo!!!!!

Vacuum port with gasket and sealant.

Installed.  Maybe a little tacky looking, but with the rubber caps and the carbs back on I dont think they'll be very noticeable.

Carburetor Bench Synchronizing: Mikuni VM29 Smoothbore

This goes for most mechanical carbs. The hardware is just different.  First take the top caps off, pry back the locking tab on the lock screw, loosen the lock screw and slide adjustment set screw.

Carbs off the bike.

The lock screw is toward the back and the set screw is the one toward the air filter (both are brass).  Ensure that your cap gaskets are in good shape.

Slide adjustment set screw and lock nut fully loosened.  Lock tabs are bent back and the lock screw is also loosened.

Next, unscrew the idle knob down to a low setting. A couple millimeters from the threaded steel mount is good.  Screw the slide height adjustment down on each carb until the slide is all the way down. I do this by watching the idle adjustment cam and the tops of the other slides to see when they begin to rise. Once they begin to rise, you know the slide you're adjusting is seated. Just turn the set screw back a bit to just before the others rise. Do this for the remaining three carbs.

This is the idle screw (knob) on VM29's unscrewed to a low setting.  Note the small gap between the throttle cam and the threaded steel mount.  You can close this gap completely for setting the bottom travel of the idle adjustment, I just prefer this way. 

Now your slides are pretty close to even but you want to ensure that you have the same slack in each linkage system. To do this, crank the idle knob in to lift the slides up. Snag a drill bit of any size. 1/8" is good. Tighten  the slide adjustment nut on the set screw and the lock screw on one carb, say the #4 carb. This will be your reference carb.

Drill bit under the carb slide.  

Place the back of the drill bit under the reference carb slide and turn the idle knob until the slide makes contact with it. You want to make sure that the slide isn't resting on it and become familiar with how it feels to slide the bit in and out. You will now set the height of the other slides to match the feel of the reference carb.

Move to one of the other three carbs, say carb #3. Place the drill bit underneath of the slide and lower the slide by adjusting the set screw down. Match the feel from the reference carb and then lock the set screw and lock screw. tightening the lock screw can make a slight change in the slide height so double check the feel on that carb after locking it all down. Repeat this for the final two carbs and you've successfully bench synchronized your rack-o-carbs.  If you dont want to, or cant vacuum synchronize the carbs, bend the locking tabs back over the lock screw and replace the top caps. You're done.

Locked and ready to roll.... to vacuum sync, if you're man enough.

The best method for synchronizing carbs is with vacuum gauges with the engine running. A meticulous bench sync can get you close, but a vacuum sync can get you dead on and compensate for any cylinder variation.

To vacuum sync, place the carbs back on your engine and warm the engine to its operating temperature. Next remove the top caps and pry back the lock tab.

Install your vacuum gauges or gauge and restart the engine. Set the idle a bit higher than normal and check the vacuum on each cylinder.

If they are different, you'll need to adjust them. I like to choose a reference carb that is in the middle of the readings. Set all of the other carbs to the same vacuum reading as the reference carb by adjusting the set screws. Once complete, lock it all down, replace the top caps, and drop the idle back down to normal. You're done... Again.

Check your vacuum every couple of months and adjust as needed. A well balanced set of carbs will provide optimum performance. Do yourself a favor and make it part of your regular maintenance program.

Complete: Rebuild and reinforcement of the Chianti box

Here's the last few steps for the chianti box.

Made some brass cap nut bolts, repaired some of the wood, glued the corner braces on, drilled and tapped the aluminum insert for the wood mounts, and finally taped and sprayed the interior with bedliner (best not to spray in the dark lest yee like runs in yer paint). It turned out incredibly sturdy and looks quite nice if I do say so myself.