Author Topic: '76 CB750K Project #3 - Long and Low - Final thoughts and pics (Read 25569 times)

brandEn · « **Reply #75 on:** September 15, 2014, 05:59:01 PM »

I like your Pamco mod. I love my two Pamco ignitions and had the only bad things to say about them are the two short cable and 6 tiny wires to splice together. Got any details on exactly what you did? Pete is a member here and he may be able to offer this as an option.

SOHC4 Cafe Racer Fan · « **Reply #76 on:** September 15, 2014, 06:46:37 PM »

That was so cool. I wish there was video of your bike trolley!! Awesome solution.

Stoli · « **Reply #77 on:** September 15, 2014, 07:55:10 PM »

Quote from: BPellerine on September 15, 2014, 04:54:39 PM

is it ready to fire up?bill

Almost. I have a few more things to address before I turn it over. Hopefully I will have time tomorrow. To be honest, I am a bit nervous about this one since it is made up of pieces of different engines and the carbs were in such bad shape when I started. Combine that with the velocity stacks and the drag pipes and I am basically shooting in the dark with the jetting. I'd like to have a baseline but obviously don't with this bike. Normally that wouldn't bother me too much (I like a challenge) but I really want to ride this bike down to a small vintage motorcycle show down in Salisbury Mass next weekend. Unfortunately everything would have to go perfect for me to be able to do that. Possible but unlikely. Although miracles do happen - I was shocked this morning when I finished the wiring and everything actually worked the first time I tested it. I expected to spend the next two days chasing down a fuse-blowing short or mis-wire but it all worked. The wiring harness is all custom and I changed a few things - the hi/low beam switch is actually a headlight on/off switch and the high beam is a momentary on/off with the horn button. That is all controlled through a Bosch relay. Bike is kick start only because of the small battery but it has an option to use the electric starter by hooking up an external battery for workshop tuneups, etc. Pamco is a bit non-standard and had to use some diodes for the directional light on the new gauges. etc, etc ... Big relief when it all worked as planned.

Stoli · « **Reply #78 on:** September 15, 2014, 08:38:15 PM »

Quote from: brandEn on September 15, 2014, 05:59:01 PM

I like your Pamco mod. I love my two Pamco ignitions and had the only bad things to say about them are the two short cable and 6 tiny wires to splice together. Got any details on exactly what you did? Pete is a member here and he may be able to offer this as an option.

Thanks for the positive feedback guys. It is always nice to know someone is interested in the project.

BrandEn - I picked Pete's brains about why the PAMCO is wired like it is and it all boiled down to a cost savings for him/them. He also mentioned that using the plate as a ground was problematic when adjusting the timing (I sort of agree with that because I have encountered some sparks flying around when adjusting the stock points plate which uses the plate as ground). I can't really blame them. All things considered, the cost of the PAMCO is pretty low.

As you know, the PAMCO runs 3 wires out for each trigger (+12v red, ground black, and coil green). What I did was eliminate the ground wires by grounding them to the plate via one of the 3 mount screws. The plan is to temporarily switch that connection to the cover mount screw when adjusting the timing to avoid the fireworks since the plate mount will need to be loosened at that time. I also combined the red wires since there is no need to run separate power wires for each trigger. The way I accomplished that:

- Unsolder the red and black wire from the 2-3 trigger
- Route the three 1-4 trigger wires over to the the 2-3 trigger
- Splice the 1-4 green wire to the 2-3 black wire
- Solder a short length of black wire (excess from the 1-4) to the black connection on 2-3 trigger
- Tie the 1-4 black wire with the above to an eyelet connector and ground to the plate mounting screw.
- Solder a short length of red wire (excess from 1-4) to the red connector on 2-3 trigger
- Splice the other end of that red wire with the 1-4 red and the 2-3 red wires.

The resulting 3-wire bundle from the 2-3 trigger: red is a +12v common for both triggers, green is the coil wire for 2-3 and back is the coil wire for 1-4.

I realize that explaining this without detailed pics might be confusing so feel free to ask questions if you need clarification. The important thing is that theoretically this mod should not affect the way that the ignition works. As a matter of fact, Pete mentioned that previous versions of the Pamco were wired in a similar fashion with the only difference being a 4 wire bundle instead of 3 because they preferred to run the ground out instead of using the plate.

-

brandEn · « **Reply #79 on:** September 15, 2014, 08:46:03 PM »

Thanks for that detailed response. It makes sense to me for the most part. Good to hear you had some support from Pete. I have dealt with him a few times and have always had a good response. Pamco ignition is the way to go IMO.

atm cycles · « **Reply #80 on:** September 16, 2014, 06:37:33 AM »

Very nice build!!! Very talented !!!tim

Sent from my iPhone using Tapatalk

BPellerine · « **Reply #81 on:** September 16, 2014, 04:35:11 PM »

nice to see one of these builds get to completion,most seem to sputter out after they rake the frame.hope it runs well.bill

Stoli · « **Reply #82 on:** September 16, 2014, 05:55:25 PM »

Bill,

So far so good. I spent a few hours trying to figure out why oil wasn't getting to the top end. I must have turned it over for 3 minutes and was getting no oil pressure on the gauge and the top end was dry. I wound up dropping the pan and removing the oil pump, disconnected the feed line, then put it all back together and it started working. Cavitating pump? Who knows. The oil lines I am running are a little smaller than stock so that might have had something to do with it.

Anyway, after I was sure I was getting good oil to the cam, I turned on the gas and spark and she fired right up. Did a preliminary carb sync and timing check to smooth it out a bit. Took it for a quick spin around the block. Runs nice. A bit loud, as expected, but not too bad. Pops a bit on decel so I think I'm running a bit lean on the bottom end. Not surprising since I still have the stock pilots in there. The velocity stacks with the mildly baffled drag pipes would probably be happier with a slightly larger pilot. I did put 120 mains in but haven't had a chance to open up the throttle that much. A leaky petcock cut the day short. Should have that fixed by morning.

Stoli · « **Reply #83 on:** September 17, 2014, 04:42:22 PM »

Drilled out the pilot jets to about a 44-45 (.017") this morning. My first build had PD carbs so I am getting aquainted with the earier style that this bike has ('76K). These are much easier to work on - pretty easy to replace the jets with the carbs still on the bike. Can't really do that with the PDs. I like the air screws as well. Adjusting the "pilot screws" on the PDs is a huge pain compared to the air screws on these carbs.

Anyways, put 50 miles on her today. Not running perfect and it will take me a while to get her dialed in with the modified aspiration but all things considered it is running better than expected. She likes going really faast in a straight line. Steering is a little heavy at slow speeds - not as nimble as a stock geometry but to be expected with a 6.5" trail. The form vs. function tradeoff. Still, it manuevers much better than expected as well.

brandEn · « **Reply #84 on:** September 17, 2014, 04:52:07 PM »

What paint did you use on the engine? I like the color.

BPellerine · « **Reply #85 on:** September 17, 2014, 05:20:31 PM »

good to hear that it ran for you and got oil pressure ,did you prime the pump before install?I like these custom builds and am trying to make a hotrod myself for the street but mvi here does not allow frame mods such as raking without it being approved by an engineer.so I am going with a longer swingarm to try and lower it a bit.bill

SOHC4 Cafe Racer Fan · « **Reply #86 on:** September 17, 2014, 05:21:07 PM »

Stoli,

This bike is looking sick (in a good way - the way the kids say it). I'm not a fan of RIDING motorcycles with Firestones (no edge grip) or super-stiff rear shocks but this bike looks cool. This is a definite BOTM candidate for next month.

Don

Stoli · « **Reply #87 on:** September 17, 2014, 07:06:34 PM »

Quote from: CB750 Cafe Racer Fan on September 17, 2014, 05:21:07 PM

Stoli,

This bike is looking sick (in a good way - the way the kids say it). I'm not a fan of RIDING motorcycles with Firestones (no edge grip) or super-stiff rear shocks but this bike looks cool. This is a definite BOTM candidate for next month.

Don

Wow, thanks Don. Sick was exactly what I was going for.

I haven't found a single positive comment about the performance of the Firestones, yet you see so many professional custom builds that use them. Mainly for that old school look no doubt.

Cheers

Stoli · « **Reply #88 on:** September 17, 2014, 07:15:24 PM »

Quote from: BPellerine on September 17, 2014, 05:20:31 PM

good to hear that it ran for you and got oil pressure ,did you prime the pump before install?I like these custom builds and am trying to make a hotrod myself for the street but mvi here does not allow frame mods such as raking without it being approved by an engineer.so I am going with a longer swingarm to try and lower it a bit.bill

I did prime the pump but I guess I didn't do a very good job of it. Earlier today I was talking with a guy who has rebuilt a few of these engines and he mentioned that if you take the cap off (where the oil gauge is) while you are first turning it over, it helps to get the oil moving. Just be careful because once the oil reaches up to that point it will tend to shoot out of there pretty good. Maybe that is common knowledge but I missed that tip.

Sounds like you need to get certified as an engineer. That way you can do whatever you want.

seanbarney41 · « **Reply #89 on:** September 17, 2014, 07:17:50 PM »

Quote from: Stoli on September 17, 2014, 07:06:34 PM

Quote from: CB750 Cafe Racer Fan on September 17, 2014, 05:21:07 PM
Stoli,

This bike is looking sick (in a good way - the way the kids say it). I'm not a fan of RIDING motorcycles with Firestones (no edge grip) or super-stiff rear shocks but this bike looks cool. This is a definite BOTM candidate for next month.

Don

Wow, thanks Don. Sick was exactly what I was going for.

I haven't found a single positive comment about the performance of the Firestones, yet you see so many professional custom builds that use them. Mainly for that old school look no doubt.

Cheers

just wear 'em out fast and get some Avons...Speedmaster front, Safety Mileage rear...nice freaking bike

Stoli · « **Reply #90 on:** September 17, 2014, 07:37:26 PM »

Quote from: brandEn on September 17, 2014, 04:52:07 PM

What paint did you use on the engine? I like the color.

Sort of an experiment. It is a 2 part epoxy primer sold by Kustom Shop. The trick was in the application. If you lay on your last coat a medium thickness, the finish will be like you see on the seat and fender. On the engine, I let the 3rd coat dry for about 20 mins and then shot the final coat holding the gun back a bit and only a fine mist. That gave the finish a slight texture. Looks very cool. The texture is prone to scuffing and shows an oil drop but it cleans up nice. Resistant to fuel spills.

Valve cover is powder coated "blackjack" the same as the frame and wheels. The original cover had peeling chrome on it and I wasn't too keen on prepping the surface for the epoxy so I handed it off to the powder coater. I was worried it might look out of place but it actually ties things together nicely.

Now I need to decide what to do with the seat and tank. The old F2 decal on the tank has grown on me so I might reproduce that scheme with a matte clear instead of gloss. Will most likely go though a few cases of IPA and a bottle of tequila or two (not in the same sitting

) trying to make that decision. I am tempted to keep the tank as is but the seat doesn't match it very well. If I paint the seat to match, then the tank won't look right with all it's chips and dings.

brandEn · « **Reply #91 on:** September 17, 2014, 08:18:26 PM »

Well it turned out awesome. I was hoping you were gonna say it was a rattle can so I could go get some and do it myself! lol

Stoli · « **Reply #92 on:** September 30, 2014, 10:28:01 AM »

Some final thoughts and then a barrage of pics (because everybody likes pics)....

My goal for this project was to make a clean but rideable, unique bike out of the rusty neglected motorcycle that my son pulled out of the woods in the POs back yard (pic is in the first post in this thread). A functional, fun to ride bike, but letting form take a front seat to function when necessary. $2500 max budget (went over by a few hundred but when has a CB750 rebuild come in under budget?).

Ride - Maneuvers better than I thought but not quite as nimble as a stock frame. The trail is right around 6.5" so she is a bit heavy in the turns. No suprise there. I don't think the choice of tires help it much in that regard either. Sore ass after about an hour (maybe should have gone with 3 layers of yoga mat in the seat instead of 2

). A little loud for my taste but man does it sound nice.

Performance - The engine is running great. Nice low idle, no noticeable hesitation in any throttle regime. Some roughness in high crosswinds and turbulent air - as to be expected with no airbox. Clutch was a bit grabby at first but that seems to be smoothing out over time. Has a slight vibration right around 2500 rpm. Smooths out above 3000 and below 2000. Probably the engine since all wheel and steering bearings were replaced. Took her up to the ton after I was confident the wheels weren't going to fly off. She had more left but I backed off because I'm a pussy.

Future - Will probably paint the tank and seat/fender next year. Right now I'm leaning toward the same black paint scheme (repro of same decal) finished with a matte clear to keep that slightly ratty look. No badges - will fill in badge strap areas.

Parts -

Frame: 76K modified to 10 degrees additional rake and CB650 swingarm
Engine: Mostly 74K with parts from a 76K
Carbs : 76K with 120 main jets, 44 slow, needles raised 1 notch, air screws out 1.25 turns
Steel Dragon velocity stacks
Exhaust: 78K headers with mufflers chopped off, extended with stainless steel pipes, 4" baffles
CycleX flanges
Oil Tank: Custom
Gas Tank: 77F modified to sit slightly higher and aft to accommodate frame rake mod
and carb clearance
Seat/Fender: Custom (fiberglass)
Wheels: Stock 76K hubs, Buchannan's custom spokes, aftermarket Harley rims
Shocks: 78K stock (they suck but they were free - left over from another build)
Headlight: Aftermarket Harley
Gauges: DCC minis with DCC bezels
Hand Controls: 76K stock with modified MC to fit on drag bars
Electrics: AntiGravity battery, Rick's Reg/Rect, Pamco ignition,
Kickstart only with capability to electric start from external battery