Sreter's '73 CB750 Cafe Project

decided to ride the bike to the gym yesterday (only about a mile away) and on the way there it bogs down on me bc it wasn't getting fuel... tank was maybe a quarter filled (maybe a little less) and somehow it wasn't enough (BTW, the PO idiotically welded the factory petcock up and welded in a little 90* elbow tube on the left side so i have an inline fuel filter with an inline petcock). From there, I was able to just swish the tank around and get some fuel in the line enough to be able to turn around and go to the gas station like a quarter mile down the road...

so back on the road and its obvious it needs a carb sync/tune bc its just not delivering power and slows down alot on the one small hill before coming up to the light I have to turn onto for the gym... I do my thing at the gym (about an hour or so) and get back on the bike to head home. Turns on normally, I drive off and everything feels as it did before and half way home (luckily only about a half mile from home) the bike just all the sudden shuts off and rear wheel locks up. Luckily my first reaction was to pull the clutch so nothing bad happened and there weren't any cars right behind me. Pulled over, and try to start it back up but the battery is dead and the starter just barely makes a noise...

to my understanding, these alternators/stators on these bikes are "bullet proof" according to a discussion I read on the SOHC4 forum and usually a recharging problem comes from a bad rectifier or Vreg. My issue is that I have a new ricks motorsports reg/rec... unless i have some wiring for the alternator that is corroded, disconnected, or broken, do I have that unusual case of a bad alternator/stator?
 
Probably just a drained battery that finally breathed its last breath. Happens pretty easily if your bike has been just sitting for a while and the battery isn't on a tender. Grab a cheap multimeter and start pluggin'!
 
coyote13 said:
Probably just a drained battery that finally breathed its last breath. Happens pretty easily if your bike has been just sitting for a while and the battery isn't on a tender. Grab a cheap multimeter and start pluggin'!
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its a new Shorai LFX. its been fully charged up twice. First charge when i got it then it sat for a couple weeks while i had a valve adjustment done and seat hoop welded and then charged back up and used maybe 3 times since then. It read normal power when it charged back up and dropped only a few Volts over the next 2 or so days till i rode the bike again

could that lithium battery have died or been damaged that easily?!
 
well... this project has taken a turn I really was dreading... after charging the battery back up from the scenario of the other day mentioned above I pulled the bike out of the garage yesterday, pushed the starter button and the starter just makes noise and spins... no turning over at all. Tried giving the kick starter a kick and nothing... its completely stuck. Oil tank has plenty of oil in it. I'm thinking this ticking/knocking noise was in fact a bent rod and from that short ride, it finally gave out and seized up on me...? not entirely sure since this is a first for me but looks like I'm in the market for a new motor. I'm assuming a rebuild with some necessary internal machining to fix any damaging from this will probably cost the same (or possibly more) than just buying a motor in good working condition and just doing the swap myself. Any advice is much appreciated!

Such a tease too... my new Hagon shocks come in the mail today and Barbers is right around the corner :'(
 
CB750 motors are pretty common around here, I'd source a new motor and tear down the one you think is bad, rebuild at your leisure. You can swap those motors around in a day!
 
DesertKZ said:
CB750 motors are pretty common around here, I'd source a new motor and tear down the one you think is bad, rebuild at your leisure. You can swap those motors around in a day!
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around here as in you're also in the Birmingham, AL area? if so, can you suggest a source to find a motor? I was told today to check out Midway Cycle Salvage in Madison and I've been suggested previously to check out Motorcycle Sports in Munford. Gonna be giving them a call soon but more options would be great.
 
Sreter said:
well... this project has taken a turn I really was dreading... after charging the battery back up from the scenario of the other day mentioned above I pulled the bike out of the garage yesterday, pushed the starter button and the starter just makes noise and spins... no turning over at all. Tried giving the kick starter a kick and nothing... its completely stuck. Oil tank has plenty of oil in it. I'm thinking this ticking/knocking noise was in fact a bent rod and from that short ride, it finally gave out and seized up on me...? not entirely sure since this is a first for me but looks like I'm in the market for a new motor. I'm assuming a rebuild with some necessary internal machining to fix any damaging from this will probably cost the same (or possibly more) than just buying a motor in good working condition and just doing the swap myself. Any advice is much appreciated!

Such a tease too... my new Hagon shocks come in the mail today and Barbers is right around the corner :'(
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Damn, that sucks bro. That IS such a tease. But with your determination I'm sure you'll be back on the road in no time.
 
As previously mentioned, my Hagon suspension came in the mail yesterday and these shocks look so nice! As much as it is a tease, I'll be installing them this weekend most likely as well as pulling the motor to start the teardown.

also got a caliper from a fellow DTT forum member so I can actually have front brakes now. Brake hoses came in a few days ago and a new set of levers and reservoir are on their way.

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Sad I wont have the bike running for the festival this weekend but I just got my ticket for tomorrow! Super excited to spend the day at Barber! Also wish I were bringing the bike so I could meet some fellow DTT members... kinda hard to know what I look like without the bike hahaha
 
PS: if any of you that follow my thread would like some pics of the bike(s) you're bringing to Barber tomorrow, let me know what you've got and I'll do my best to find you and snap some pics. I'll be bringing my gear with me taking pics all day.
 
So the Barber festival was amazing! Felt like a kid in a candy store but it definitely made me sad not being able to ride the bike there and it would've been so much fun to ride through the whole place in it... I think the coolest thing for me were the vintage races. Loved seeing the old Thriumphs, Nortons, etc ripping around the track. Also super glad it was a nice day out bc when I left my place it was pouring and I live only 20 minutes away from the track.

Anyways, here is my album of photos that I took as I walked around the festival on Saturday. Enjoy!
Barber Vintage Motorcycle Festival 2014 Photos
 
Been very MIA for the past few months due to lack of funds because my student loan repayment started up in January but was able to find someone locally selling a motor. According to them, it was running smoothly for a short time and then the carbs flooded with gas and it shut off. The motor has now been taken off the bike and has been sitting for some time. They want $250 for it so i'm going to take a look at it tomorrow. Hopefully it checks out and its good enough I can get something working on my bike soon while i take apart and do a full 836cc build on the old motor that seized up.
 
Had one of those lucky breaks this weekend with this motor purchasing thing...

Went to take a look at the motor this guy was selling and ended up leaving with the motor, gas tank, oil tank, side covers, and 4-1 headers for FREE... yup haha. It was an older guy with 2 badass custom HD Sporter show bikes, VW dune buggy project, VW Beetle project, and a real nice house so needless to say, $250 wasn't a worry for him. He really just wanted that motor out of his garage. Basically told me to take it, pay him later if it works, keep it for free if it doesn't run when I swap it in.

Old motor will be coming out hopefully this coming weekend so I can start doing work on this "new" one. It looks a little beat from the outside but according to the guy, it was running real smooth before it came off the bike. Hopefully my lucky streak continues and I can get this one running properly soon enough to have something to play with while I build up the old one ;D
 
HolyRoller said:
Any updates?
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unfortunately, not yet. new motor has just been sitting in the garage... honestly just been really lazy haha but now that its getting warm out I'm itching to get started on the swap. hopefully this weekend!
 
Well, the good news: I didn't pay for the motor i picked up a little bit ago....

the bad news: that motor is garbage... tore it down this weekend to find that cylinder 2 was rusted in place, 2 wasp nests inside the head, horrible scoring on the cam (bearings were non existent), stripped bolts everywhere, rusty rockers and valve springs.... it was REALLY bad

so yea, super happy I didnt have to pay for the motor and it ended up being a good learning experience on engine tear down and inspection. Several parts will be salvaged as spares for my original motor and the rest that is in decent shape will either be sold or just thrown away.

I guess I will now take out the original motor and just rebuild it. maybe even do an 836cc kit while I'm at it, not sure yet.
 
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