Topic: My first complete build 72 CB750 - completed for now...

[seanbarney41]

Engine sounds great!  Congrats on excellent work.  Not many get that much right the first time.

[Tews19]

Your bike looks great! Awesome color combo!

[slikwilli420]

I would get moving on upgrading the caliper to something period, like Grimeca or AP Racing. They are phenomenal brakes and can be adapted to your current forks.

I was think about an upgrade, but wanted to ride it a while as is. I initially wanted to keep it retro.  But I have a feeling that I would upgrade the whole front end after a while. who knows... It might end up like Café Racer Fan's 9 lives bike. no offense.

btw. I'm looking at the Grimeca, who's the vendor. can't seem to get much listings of google.

No offense taken.  I think that the AP calipers might be better than the Gold Wing calipers I used on the Nine Lives bike, but on that bike I transplanted an entire Gold Wing front end.  The AP Racing calipers might give you some clearance issues to the spokes and that's why I didn't use them on my 750 (why I ended up doing the Goldwing front swap).  Another, less period correct solution is transplanting an older R6 front.  Several members have done this including (most recently) Dave Barbier; FunJimmy and Oette also did this swap.  It's a conventional (NOT upside-down) fork so it does not stick out to the eye (and his not nearly as heavy as the Goldwing front), but the brakes and forks are a huge step forward.

I looked at Andover's website, doesn't seem like they carry anything except OEM Norton calipers. It has been six years since. However have you known of anyone who's swapped stock calipers for AP's and resolution for the clearance issues?

Gotta search part numbers. Their site is horrible.

https://andover-norton.co.uk/en/shop-details/18254

This is a pretty decent price and is about $219 as of today. Shipping will be a bit nuts, but I get things in about 3 days from the UK here in Michigan.

Regarding clearance, that can be a challenge. You may need to space the rotor out a bit to get more clearance since you don't want to go to the trouble of wider triple trees. To make a Grimeca fit and center the wheel in the forks I added 0.83" to the width of stock 750 triples. It can be done and is very worth doing, but will take some work. I have an iron rotor and single Grimeca on my race bike, and while 2 calipers would be even better, one is plenty. If it works for racing, it will be fine for the street.

[algophobe]

Your bike looks great! Awesome color combo!

Engine sounds great!  Congrats on excellent work.  Not many get that much right the first time.

thanks for the complements. I'm definitely hooked!

[algophobe]

I would get moving on upgrading the caliper to something period, like Grimeca or AP Racing. They are phenomenal brakes and can be adapted to your current forks.

I was think about an upgrade, but wanted to ride it a while as is. I initially wanted to keep it retro.  But I have a feeling that I would upgrade the whole front end after a while. who knows... It might end up like Café Racer Fan's 9 lives bike. no offense.

btw. I'm looking at the Grimeca, who's the vendor. can't seem to get much listings of google.

No offense taken.  I think that the AP calipers might be better than the Gold Wing calipers I used on the Nine Lives bike, but on that bike I transplanted an entire Gold Wing front end.  The AP Racing calipers might give you some clearance issues to the spokes and that's why I didn't use them on my 750 (why I ended up doing the Goldwing front swap).  Another, less period correct solution is transplanting an older R6 front.  Several members have done this including (most recently) Dave Barbier; FunJimmy and Oette also did this swap.  It's a conventional (NOT upside-down) fork so it does not stick out to the eye (and his not nearly as heavy as the Goldwing front), but the brakes and forks are a huge step forward.

I looked at Andover's website, doesn't seem like they carry anything except OEM Norton calipers. It has been six years since. However have you known of anyone who's swapped stock calipers for AP's and resolution for the clearance issues?

Gotta search part numbers. Their site is horrible.

https://andover-norton.co.uk/en/shop-details/18254

This is a pretty decent price and is about $219 as of today. Shipping will be a bit nuts, but I get things in about 3 days from the UK here in Michigan.

Regarding clearance, that can be a challenge. You may need to space the rotor out a bit to get more clearance since you don't want to go to the trouble of wider triple trees. To make a Grimeca fit and center the wheel in the forks I added 0.83" to the width of stock 750 triples. It can be done and is very worth doing, but will take some work. I have an iron rotor and single Grimeca on my race bike, and while 2 calipers would be even better, one is plenty. If it works for racing, it will be fine for the street.

I have to read thru your build thread on that race bike and do much research before I jump down that rabbit hole.

[algophobe]

well the celebration didn't last long before the gremlins creep in. I put in about 16 miles over 2 days up in the mountains near my house. she ran fine, but you can hear her struggle in higher altitudes likely from the engine and carbs finding richer conditions. however I tried to take her out this morning after about 5 minutes of warming her up. got her about 3 blocks up and the engine dies. I managed to get her home having to rev the engine higher to provide enough umph! to get her back.

it sounds like 2 cyclinders aren't firing.. i hooked up the timing gun to check if i'm having the same issues as before with cylinder 2 and 3 not firing and yes this was the case... 2/3 does fire but very erratic.

if you recall, i had issues prior with the 2/3 plugs fouling out. a member recommended running hotter plugs D7EAs and it fixed the problem immediately.

I took out the plugs to inspect them. all 4 are black as expected, but 2/3 is only slightly wetter. I dropped a cheap harbor freight camera down the hole for a quick look and things seem to be fine. can't inspect the valves however unless I borrow my buddies' medical camera. I cleaned all the spark plug contacts and reinstall them, except I use a brand new plug as control for my experiment on cylinder 2 and fired her up. now no signals are read from 2 and 3 at all.

any suggestions?

should i just chuck this PAMCO out the door?

[algophobe]

Swap the leads from the Pamco to the other coil to see if the problem follows the coil. You’ll need to swap the plug wires too.

will certainly try that. hopefully its something simple like a loose contact.

[754]

Over on vintage Flattrack .org.. I think that's the name.
 Kosman offered new AP type calipers , not marked AP. . For about 135.00 US without pads..

[algophobe]

Over on vintage Flattrack .org.. I think that's the name.
 Kosman offered new AP type calipers , not marked AP. . For about 135.00 US without pads..

have you heard how they perform? I'm assuming you would use AP brake pads, also if its a knock off of AP, probably has the same clearance issues. but I guess at that price I can try it out.

[SOHC4 Cafe Racer Fan]

Here are the specs on the AP calipers. I imagine one could make casting molds from an existing caliper.

[slikwilli420]

Here are the specs on the AP calipers. I imagine one could make casting molds from an existing caliper.

Likely what happened with the Kosman copies. Surprised they did a perfect copy, would have thought there would be legal issues with that. It would be hard to cast something that low volume and make money on it unless done overseas... far overseas. AP cost that for a reason, they are high quality. I would hope the Kosman ones will take all the spares from AP, but no way to be sure unless you buy one.

I agree with the OP, clearance issues will come into play just the same, and will with pretty much any 2-piston opposed caliper out there.

[754]

Best plan, open one up, measure the meat, figure the angle and mill some off.

A good plan though is wider trees, makes it easier.
 I did sneak a 6 piston onto a Ceriani GP.
 The wheel with the most clearance, Yamaha mags, we used a 18 inch front  likely has even  more clearance. 
 I checked a bunch of wheels.

[algophobe]

All something to think about. I did write to Kosman and he wasn't aware of any clearance issues, however he uses them mainly for Nortons and Triumphs. but if they are reproductions, same issues should apply as you guys indicate. For now I'll have to work on getting her reliably to GO, then worry about improving her STOPPAGE at a later time.

I did some work in tracing this ignition problem on cylinder 2/3. I first swapped the spark plug wires 1/4 for 2/3 and again nothing fires for 2/3. then i swapped the coils, and same issues. both coils get warm, but no sparks sent for 2/3 cylinders. I inspected the lines and they seem to be in good condition. of course i tested it by pressing the attached spark plug to the engine and pressing the started (looking for sparks). I would have to conclude that the timing signals aren't being sent from the contacts to the coil. Grossly, the PAMCO seems intact.

Correct me if i'm wrong but the PAMCO green wire is coming from the pick ups, which I changed in the second picture to blue for cylinder 1/4, and orange for 2/3. the red wire I changed to grey (black/white wire equivalent for the kill switch).


i'm now curious if this was the issue during the build as well, until it finally failed after 16 miles of riding. don't know if any of the experts here have encountered this. the question is now whether I should just get another PAMCO or switch to dynatek?

[scottly]

Spoke clearance isn't an issue with the Honda twin piston calipers, and the 32mm version has more clamping force than the AP.

[scottly]

Correct me if i'm wrong but the PAMCO green wire is coming from the pick ups, which I changed in the second picture to blue for cylinder 1/4, and orange for 2/3. the red wire I changed to grey (black/white wire equivalent for the kill switch).

Sorry, but I'm confused??!! To prove out the coils vs ignition, you only need to swap the two coil wires, which would be the blue and yellow wires with stock coils.

[algophobe]

Correct me if i'm wrong but the PAMCO green wire is coming from the pick ups, which I changed in the second picture to blue for cylinder 1/4, and orange for 2/3. the red wire I changed to grey (black/white wire equivalent for the kill switch).

Sorry, but I'm confused??!! To prove out the coils vs ignition, you only need to swap the two coil wires, which would be the blue and yellow wires with stock coils.

an experienced builder would do that of course. but you're dealing with a novice. actually i swapped the spark plug wires to see if there's anything wrong with the wires and work backwards. to swap the blue/yellow leads i have to remove the mounting bolts as they're in the way. since i built the wire harness from scratch i wanted to see if i some how fried it.

[algophobe]

Spoke clearance isn't an issue with the Honda twin piston calipers, and the 32mm version has more clamping force than the AP.

that set up is a twin piston on single disc? is there major difference with spoked wheels?

[scottly]

Yes, I'm using a 32mm twin piston caliper with a single 320mm Ducati disc, but this is not a bolt-on.
There are off-the-shelf parts that allow swapping the twin piston calipers. The only extra modification is to have the 550 275mm rotor(s) thinned from 7mm to 5mm.
You will need 750 F2/F3 forks; they will slide into your 550 triples.
You will need the twin piston caliper brackets that fit the F2/F3 fork lugs.
The caliper(s) will need to be shimmed to align with the disc(s) on the spoke wheel.
A single 275mm disc, with a 30mm twin piston caliper and the stock master is better than a  stock 550 38mm caliper, and even better with a 32mm twin piston caliper. Two 30mm calipers with dual discs would be better yet, but would be on the verge of needing a larger master. Two 32mm twin piston calipers with dual 275mm discs would be the ultimate stopping power with mostly bolt-on parts, but would require a larger MC. 

[SOHC4 Cafe Racer Fan]

I thought you could use the twin piston calipers with F2 forks.

[algophobe]

Christmas in 102 degrees So Cal. Hopefully will get a chance to spend time with the ol' girl putting this in this weekend.

i'm looking over the wiring. in comparison to PAMCO, which has a separate grounding wire on the ignition unit, the DynaS doesn't. i'm assuming it grounds via the bolt and plates?

I'm looking at this tutorial video below. the guy mentions something about nylon bushings to prevent grounding out of the coil at 13:45 minutes into the video. which i don't get. isn't that the point? the coils grounds thru the frame from the mounting bars?

[scottly]

The coils are not grounded to the frame; the yellow and blue primary wires are switched to ground by the points, or Pamco, or Dyna during the coil "charging"(dwell) time, and the ground is disconnected at the firing time for each coil, allowing the stored energy in the coil to discharge through the spark-plug gap.

[scottly]

I thought you could use the twin piston calipers with F2 forks.

With the F2/3 forks and the F2/3 Comstar wheel and 275mm, 5mm thick, 5 bolt rotors, the twin piston calipers and correct brackets are plug-and-play. With a spoke wheel and 6 bolt rotors, some "adjustments" are required.

[algophobe]

The coils are not grounded to the frame; the yellow and blue primary wires are switched to ground by the points, or Pamco, or Dyna during the coil "charging"(dwell) time, and the ground is disconnected at the firing time for each coil, allowing the stored energy in the coil to discharge through the spark-plug gap.

I see.. that's why if it's not discharging to the spark plugs, it heat up hotter than the coil that is working normally.
..then the Dyna IS grounded by the plate and screws to the engine case compared to Pamco.

[algophobe]

got the Dyna ignition on. everything seems to be "made better" for that extra 40 bucks. I like that you can attach the rotor magnet on, torque it down, then slip the plate over. a single wire (instead of 2 wires in PAMCO) routes under the engine and oil lines. the connection from timing plate simplified from 6 wires to only 3.

I change the spark plug wires back to the original PAMCO's that I bought. Yellow ones that was the inspiration for the color scheme initially. The system was strobe light timed to +10. the 2/3 coil fires more steadily than the PAMCO ever did.

i did noticed however the air screw had to be richened by 1/4 turn to run better. is that expected?

[algophobe]

finally got around to wrapping the pipes and coating them with high temp silicone seal. not sure how much performance improvements this would provide but, it was mainly done to hide the yellowish discoloration on the pipes from the heat.

now debating on whether or not to hang the end of the pipe. spoke to the cycle X guys, they say it could go either way. I was thinking of using the T bolt clamp and run a strap to cross bar of the frame and using another C clamp.

i've taken her for about 30 miles total with the new ignition system on and she runs like a champ. will be testing her up to Angeles Crest Highway hopefully soon.