Author Topic: 1974 CB750, new bike, new owner, new user, and new questions :P (Read 10049 times)

piefairy · « **on:** April 30, 2018, 05:24:22 PM »

Hello all,

I just picked up a 1974 CB750 yesterday. I haven't ridden it much, it didn't have plates, but the motor seems strong. I have some questions on it if anyone is willing. The bike appears pretty stock except for the exhaust. Its has a 4-1 system on it with a straight pipe for a muffler, no baffles. I must replace it, way to loud for my taste. I know there are ALOT of aftermarket parts, anything that would have that would have more of a classic Triumph/Norton sound?

The neutral sensor light is always on, I have disconnected the switch itself and it still stays on and I cant find anywhere it may have been bypassed, but I dont know if its a normally open or normally closed circuit.

The clutch is VERY high. Its either on or its off. If I barely pull in the clutch it will disengage. I am pretty sure it just needs new plates, already ordered a set from Barnett. Anything else I should look for? I am replacing the the clutch plates, metal plates and springs. Might as well go for it all. The bike has 50k on it and no one knows when it was changed or if ever.

The wiring is a mess. 40+ years of people modifying it and it looks like a rats nest behind the front headlamp. I assume it was stock to have the wiring harnesses all gather and connect there? I have several wires that are unconnected and of course no colors match. A mix of butt splices and crap clips some I believe are stock. I am planning to do a decent amount of electrical work with it. Going to LED, changing almost all of the lamps, changing the gauges, and possibly a bluetooth ignition system. Is it worth trying to fix and correct the current harness or just buy a replacement and start over?

I have ordered the Clymer manual for the bike, so it will help with a lot of the detailed instructions, but people with experience I find know where the common jerry rigs are and the hassles to fix em

Any help or opinions anyone has would be much appreciated. BTW, this bike is not going back to stock, looking to make a classic looking cafe racer style with modern electrics and delete as much gauges, switches, knobs as possible without going to an ECU.

Thanks!
Pie

piefairy · « **Reply #1 on:** April 30, 2018, 08:32:37 PM »

Well after a few more hours of messing with the wiring... I decided I'll just cut to the chase... I might as well do what I want to... motogadget blue ordered.

scottly · « **Reply #2 on:** April 30, 2018, 10:03:27 PM »

Quote from: piefairy on April 30, 2018, 05:24:22 PM

The neutral sensor light is always on, I have disconnected the switch itself and it still stays on and I cant find anywhere it may have been bypassed, but I dont know if its a normally open or normally closed circuit.

The neutral switch is closed when the trans is in neutral, and open when in gear. It provides a ground to one side of the light when closed. The other side of the light is "hot" when the ignition switch is on.

MauiK3 · « **Reply #3 on:** April 30, 2018, 11:12:55 PM »

If you really want to fix the bike you need Hondaman's book. No question.

Yamahawk · « **Reply #4 on:** May 01, 2018, 03:27:03 AM »

Sounds like a nice bike to start with! There are plenty of custom/cafe racer builds on this forum, so you have a lot of ideas there. The M-Unit Blue will do all you want and more. It will give you an opportunity to ace the butchered harness and start rom scratch, just follow wiring logic for the unit, and the push buttons, and you will be fine.
I don't have it, but Hondaman's book is a great wealth of info, as he is also! He is a blessing to the SOHC community. Good luck, and welcome!
Charlie

calj737 · « **Reply #5 on:** May 01, 2018, 03:38:43 AM »

Welcome. Any chance you're pals with Harrison? If not, you and he are nearly neighbors and he's in the middle of a rebuild on his 750 and a 550. And Wilbur is not too far away either. Both are local, knowledgeable guys with good hands, and great hearts.

BPellerine · « **Reply #6 on:** May 01, 2018, 06:18:20 AM »

you will never make a honda sound like anything other than a honda,it will be a loud honda or a quiet honda,just saying.bill

cb_n00b · « **Reply #7 on:** May 01, 2018, 08:24:36 AM »

The m-unit blue is sweet. Probably the best money I spent on my bike, other than maybe completely rebuilt '76 super sport carbs.

I'd also agree that there's not an exhaust that I've come across that will make it sound unlike a Honda....You can basically vary how much volume and rasp you can stand.

piefairy · « **Reply #8 on:** May 01, 2018, 01:59:27 PM »

Thanks for all the replies. I don't know either Harrison or Wilbur but I'll keep an eye out for the locals

For the exhaust, I'm looking for a quieter sound, without effecting power as much as possible of course. Any particular brands to go with or avoid? I use to be big into sport bikes, but the crossover to vintage classics doesn't seem to carry to many of the names I know. I would like to keep the headers it has for now to save money, I'm trying to make it reliable and ride-able before I go down the looks side. Ideally I would like to go back to a 4-2 system but that may be a bit down the road.

When I saw the M-unit, I just had to go for it. I hate messy wiring and a new harness would be almost half the price of the unit. Plus it will help me delete many of the switches, buttons and gauges.

I did manage to drain the battery yesterday while going over the "wiring", the bike went from starting and riding strong to the starter not even trying to turn over in 30 minutes. I hooked it up to a charger this afternoon and its gone from 35% to 90% in under an hour... That seems awfully fast to me and has me thinking the battery may be on its last leg. Any thoughts? Also, what are the thoughts on going to a LiPo system?

Thanks for the warm welcome!
Pie

Bankerdanny · « **Reply #9 on:** May 01, 2018, 02:02:30 PM »

Depending on whose exhaust you have you can often just add baffles to quiet it down. Another post or two and you should be able to add photos. Take some pictures of your bike and add them to this thread, that will help us provide more accurate answers.

piefairy · « **Reply #10 on:** May 01, 2018, 02:16:40 PM »

Ill post up as soon as I can. Anyone have any experience with Cycle Exchange? I ordered my shocks and forks from them, got billed, but I am having a hard time getting in touch with anyone on the status.

piefairy · « **Reply #11 on:** May 01, 2018, 02:18:41 PM »

Images

piefairy · « **Reply #12 on:** May 01, 2018, 02:30:09 PM »

For those with the M unit, did you have any issues registering in M.ride? I keep getting an error when I try.

calj737 · « **Reply #13 on:** May 01, 2018, 02:35:17 PM »

Quote from: piefairy on May 01, 2018, 02:16:40 PM

Ill post up as soon as I can. Anyone have any experience with Cycle Exchange? I ordered my shocks and forks from them, got billed, but I am having a hard time getting in touch with anyone on the status.

They are a small shop, work LONG hours, but are as good to their word as Gold. Don't worry.

Quote from: piefairy on May 01, 2018, 01:59:27 PM

When I saw the M-unit, I just had to go for it. I hate messy wiring and a new harness would be almost half the price of the unit. Plus it will help me delete many of the switches, buttons and gauges.

Also, what are the thoughts on going to a LiPo system?

The m-unit won't eliminate all these things unless you use your phone for the "gauges". You'll still need headlight, turn, horn signals, etc. Yep, it does clean up the wiring a great deal, but that's the easy part.

A good quality AGM battery (Scorpion is a popular brand) should satisfy your needs if you're sticking with a stock-ish bike and seat.

Next time you go about troubleshooting your electrical, pull the headlight fuse and disconnect the ignition coils. With the key ON, you're burning up those elements and drawing a heavy load while you tinker.

Bankerdanny · « **Reply #14 on:** May 01, 2018, 02:50:35 PM »

I think that is just a MAC exhaust. You should be able to buy a baffle kit from them to quiet it down.

piefairy · « **Reply #15 on:** May 01, 2018, 03:04:33 PM »

Calj737

I should have pulled the fuse, but got into it and when I saw the rats nest, I went straight to fix it mode. Its odd though since the headlight only turns on if the left turn signal is on... right turn signal gives power to the horn.

I know it wont clean it all up, I bought 2 of the M-switch 3 switch sets to cover the controls and I am looking at the Motoscope Mini for the MPH/Tach. Headlight will be the Bikemaster LED headlight with integrated turn signals.
https://www.dimecitycycles.com/black-motoscope-mini-digital-multifunction-gauge.html
https://www.dimecitycycles.com/bikemaster-led-headlight-with-integrated-turn-signals-5-3-4-amber.html

piefairy · « **Reply #16 on:** May 01, 2018, 03:34:43 PM »

Quote from: Bankerdanny on May 01, 2018, 02:50:35 PM

I think that is just a MAC exhaust. You should be able to buy a baffle kit from them to quiet it down.

Thanks for the tip, Ill have to chase it down.

piefairy · « **Reply #17 on:** May 02, 2018, 04:15:52 PM »

Spent some time with the bike, found some oil on the fins of the engine, not sure where it may be coming from. Photos attached.

Also, I went to replace the petcock today and the new replacement looks completely different from what is currently on there. Am I missing a part?

Some genius decided to replace the allyn screws on the clutch casing with philips... of-coarse they are stripped. I got all but 3 out. Any suggestions? They are aluminum and just fall apart when you try to undo them. The fact that someone painted over them doesn't help.

Last question. What is this? Am I to replace it with Ricks Regulator?

piefairy · « **Reply #18 on:** May 02, 2018, 04:18:22 PM »

calj737 · « **Reply #19 on:** May 02, 2018, 04:37:45 PM »

Stock screws are NOT Phillips nor were they Allens, they are JIS. Knuckleheads use Phillips drivers to remove JIS screws and you now have the result of that. Use a drill bit, 5/32 will do, and drill the center and knock the head off. Remove the cover. The shank will then turn straight out.

piefairy · « **Reply #20 on:** May 02, 2018, 04:51:16 PM »

Weird. Seems all the photos I have seen have had allens heads. But your right, I just looked at the image in my Clymer book and it does show a JIS.

Also, I looked at the petcock in the book and its different than the replacement I received from DCC as well.

piefairy · « **Reply #21 on:** May 02, 2018, 04:53:13 PM »

It seems the 3/4 inch thread that my tank has is the preferred method. Should my petcock have 1 or 2 fuel lines out or does it matter?

calj737 · « **Reply #22 on:** May 02, 2018, 05:39:37 PM »

There’s nothing on your bike that’s Imperial. Everything is metric so your 3/4” thread is wrong.

Bankerdanny · « **Reply #23 on:** May 02, 2018, 05:46:32 PM »

Quote from: piefairy on May 02, 2018, 04:51:16 PM

Weird. Seems all the photos I have seen have had allens heads. But your right, I just looked at the image in my Clymer book and it does show a JIS.

Also, I looked at the petcock in the book and its different than the replacement I received from DCC as well.

Allen head conversions are very common. My 550 came with them. These days when I am removing OEM screws I just go directly to the impact driver (the kind you use a hammer with). I have a set of JIS screw drivers and will make one attempt to remove them, but it isn't unusual for the screws to be seriously stuck and the impact drives the bit solidly into the head and it usually only take one or two good whacks to get it loosen it so that it comes right out.

You can also get JIS bits for impacts, I just haven't done that yet.

seanbarney41 · « **Reply #24 on:** May 02, 2018, 05:48:46 PM »

That paint color, if original, was only offered in 1976. That small petcock is also for a 76. Your brand new petcock is correct for 69-75.

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Author Topic: 1974 CB750, new bike, new owner, new user, and new questions :P (Read 10049 times)