Topic: Help getting this bike running please.

[Logan80]

I haven't remounted the carbs yet. I still need to buy plugs and an air filter also, but yesterday was payday, so I'll be tinkering with it more this week. I want to adjust the cam chain since the carbs are off and it's accessible now.

I had the plug wires on correctly, I pulled, snipped, and reinstalled each one by one. But when the carbs came apart, two of them had totally plugged idle jets, so no surprise on the poor/non-existent idle.

I'm hoping to have the bike running/idling smoothly within a couple days. Then and only then, will I spend the money to rebuild brakes and replace tires/tubes. Not going to spend another $4-500 on this thing just to find out I needed that money to rebuild the engine 

[Old75_ratafe]

Yea I hear ya I basically was in the same boat when I got mine years ago.  I've owned this bike for almost 5 years and am just now getting to the point of ridding it.  I had the clogged idle jets too.  and fyi I was running on two cyl after the rebuild... new plugs and runs like a champ now.  Good luck man post a vid when u get it going.

[Logan80]

Well, I have the carbs all back in the rack and bench synched. Choke adjusted also. The only problem is I can't find those damn tiny cotter pins to hold the choke linkage together. I think I'm going to need to use a small amount of safety wire and do it that way.

I also got my new plugs, NGK D8EA. I'd really like to replace the carb-intake boots, but they are very pricey, I might just try to restore mine with the wintergreen oil trick. Although they are still semi-pliable, probably usable as they are.

I still want to set my cam chain tension before I put the carbs back on. Seems like a good time to do it with all that room available. Anyone have tips on setting the tension on a CB750? Should I remove and clean/grease the tensioner while it's accessible?

I spent tonight cleaning and organizing my garage. It's a disaster with my CB750 and a friend's XS650 both in there and both in pieces. I really just needed to pick up some stuff and build a shelf and workbench. My garage only has ONE light socket, and it's towards the back, so I'm also installing a nice 48" overhead light above my toolbox/grinder/vise area.

[Old75_ratafe]

Well, I have the carbs all back in the rack and bench synched. Choke adjusted also. The only problem is I can't find those damn tiny cotter pins to hold the choke linkage together. I think I'm going to need to use a small amount of safety wire and do it that way.

I also got my new plugs, NGK D8EA. I'd really like to replace the carb-intake boots, but they are very pricey, I might just try to restore mine with the wintergreen oil trick. Although they are still semi-pliable, probably usable as they are.

I still want to set my cam chain tension before I put the carbs back on. Seems like a good time to do it with all that room available. Anyone have tips on setting the tension on a CB750? Should I remove and clean/grease the tensioner while it's accessible?

I spent tonight cleaning and organizing my garage. It's a disaster with my CB750 and a friend's XS650 both in there and both in pieces. I really just needed to pick up some stuff and build a shelf and workbench. My garage only has ONE light socket, and it's towards the back, so I'm also installing a nice 48" overhead light above my toolbox/grinder/vise area.

I'll let u in on a tip from my rebuild logan... that choke linkage in the # 3 I think it was (or 2) with the two adjustable pieces the adjuster is side specific too me a min to figure out why even though I set it the same way the choke was all off... I had swapped them and then had to readjust everything.

[cobra2411]

The only problem is I can't find those damn tiny cotter pins to hold the choke linkage together. I think I'm going to need to use a small amount of safety wire and do it that way.

I think they're like 1mm cotter pins. The smallest I could find was 1.6mm (1/16") so I just used a 1/16" drill and opened them up. It was a lot easier then I thought. I bought a couple drills thinking I would break them or tear them up and it was like 1 minute to open up all 4.

Also when I first remounted my carbs I only had 1 & 4 running. Turns out that the float was stuck closed on 2, and the slow speed jet was still clogged on 3... Then I remounted them again and 4's float stuck open... Grrr...

Runs like a top now and I haven't even changed the plugs or points... It's been too fun to ride. I've got new cables coming and I'm going to do it then. It was a little snotty above 5k but it's cleaned up as I've been riding. I was out with my buddy on Sunday and he was on his R1. I decided to wind the bike out and see what she had and was thrilled. I was shifting at 8-9k and really giving her a good run and my buddy was pacing me. Then he went WOT and instantly was going 40mph faster then me... It looked like I was in reverse.   

Good luck and get out riding. These old bikes are such fun to ride.

[Old75_ratafe]

The only problem is I can't find those damn tiny cotter pins to hold the choke linkage together. I think I'm going to need to use a small amount of safety wire and do it that way.

Also when I first remounted my carbs I only had 1 & 4 running. Turns out that the float was stuck closed on 2, and the slow speed jet was still clogged on 3... Then I remounted them again and 4's float stuck open... Grrr...

I did forget to mention something about my rebuild logan I DID buy the float tool and had to reset two of my floats when I put them back together.  Set those wrong and you get to much or too little gas.

[Logan80]

Well, I did some running around today and one of my stops was the big local Honda dealer. I wanted to ask the parts guys about a few things and to see if they had anything in stock. It was pretty funny when the parts guy told me he's pretty sure that Honda doesn't make anything for these bikes anymore, but he'd look anyways, just to double check. He seemed surprised that they still had push/pull throttle cable, clutch cable, and carb to intake boots all available. However their prices were ridiculous, so I'll likely just go with ebay stuff.

The guy in the service department was really cool, he rides a '77 CB750K and we chatted a bit. He also GAVE me some tiny cotter pins so I can put my choke linkage back on the "right" way, so the trip wasn't wasted at all.

Now to try to soften up my carb boots and reinstall the carbs. They really aren't too bad, I can at least somewhat compress them by hand, but they are certainly not what I'd call pliable...

[Old75_ratafe]

Let me know how the softening goes I bought a "like new set" of feebay and they worked ok but I still have the originals and a spare box so might be cool to get them soft again.

[Logan80]

Well, I bought some wintergreen oil on Amazon.com and boiled/cooked my boots in it tonight. Both the airbox and the head side. Both seem to have turned out well.

I used http://www.amazon.com/gp/product/B000NWGL6W/ref=oss_product oil to do it. I filled a pot of water to just cover the boots and used 4oz of oil. Cooked the airbox boots for 15 minutes and the head boots for about 25 minutes. Hopefully they stay soft for awhile. If you choose to do this, make SURE you do it outside. I used the sideburner on my BBQ and the smell is still VERY intense outside and even in my house some. Smells like a TicTac factory lol! Also beware that the fumes/steam was very strong and made breathing difficult when it wafted into my face. Make sure you have plenty of ventilation.

[Old75_ratafe]

Hmm wonders if your exhaust will be minty fresh after this 

[Logan80]

Well, I put the carbs on, and tried to start the bike. No air cleaner and just MAC headers, no muffler yet. It just cranked and cranked then BOOM! A huge backfire. I also had one float that was set wrong apparently, and leaking, I managed to reset it while on the bike and it's fine now. Cranked it a bit more and BOOM! Another backfire...I replaced all the plugs with properly gapped, new NGK D8EA plugs, verified point gaps, and timing by eye (no test light yet). The points start to open right near the 'F' mark.

More cranking and no firing, so I'm giving it a rest for the night.

I'll have to try again tomorrow after work. It was getting late and there is a church across from me and a few lots down with people outside. Don't need this thing making a racket at 9pm...

[Old75_ratafe]

I'm guessing its cause you've got no air box or muffler on.  Could be timing too.

[Logan80]

Ok, so I reset the points and timing. Also had the coil wires (blue and yellow) plugged into the wrong mates. Blue to yellow, and yellow to blue. Swapped those around and it fired up. It idles like #$%*, and smokes a bit, but it's alive! Been sitting for 15 years, so I expected the smoking, and it's not that bad. Will probably just have to break itself back in again. It does need a muffler and the airbox put on for sure though. I think both of those will help quite a bit.

Next up is finishing my engine for my car, then buying brake pads/shoes, caliper and MC rebuild kits, tires, tubes, etc. Plus a LOT of cleaning and painting. I'll keep posting as I go.

[Logan80]

Well, it DID run...Now time to clean it all up, fix all the "pecker tracks" in the wiring, and paint.

[Logan80]

So I pushed the bike outside today and started cleaning. Pulled off the wiring harness and battery box. Used a lot of simple green and some brake/carb cleaner to eat away the years of grime. The area around the front sprocket was really nasty. I then discovered some sort of rubbery silicone in there in front of the sprocket on the case. My heart sunk. Could someone REALLY have tried to do what I think they did?



Yeah, they did. The chain must have broken at some point in the past and bashed a hole in the case. The PO must have figured filling it in with silicone would fix it. Clearly it hadn't, since the area was REALLY nasty and grimy from it leaking still.

Now what? Hopefully my friend, who welds for the Navy, can weld this back up without me having to totally strip the engine to pieces. Not really looking forward to an engine rebuild. Although it probably would be the smart thing to do....

[eastoak]

So I pushed the bike outside today and started cleaning. Pulled off the wiring harness and battery box. Used a lot of simple green and some brake/carb cleaner to eat away the years of grime. The area around the front sprocket was really nasty. I then discovered some sort of rubbery silicone in there in front of the sprocket on the case. My heart sunk. Could someone REALLY have tried to do what I think they did?



Yeah, they did. The chain must have broken at some point in the past and bashed a hole in the case. The PO must have figured filling it in with silicone would fix it. Clearly it hadn't, since the area was REALLY nasty and grimy from it leaking still.

Now what? Hopefully my friend, who welds for the Navy, can weld this back up without me having to totally strip the engine to pieces. Not really looking forward to an engine rebuild. Although it probably would be the smart thing to do....

who was saying that this rarely happens? this is the 4th or 5th one i see here...

[Stev-o]

Some guys have made a similar repair w/JB Weld.

Get it cleaned up real good.

[Logan80]

I'm going to weld it. Or, more accurately, my friend is going to. I need to clean it real well and pull the pieces out and clean them also. Then bring it to his place and we will weld it up. Still very very frustrating.

I bought what I THOUGHT was a mostly stock 1972 CB750, and found out it was not even close to what I was hoping for. There have been a lot of discoveries made already, and probably more to come. But I won't give up. I NEED to ride this bike. It's become a personal mission