Author Topic: New to Me 1978 CB750A (Read 5197 times)

limerence · « **on:** June 19, 2014, 07:43:59 PM »

Hi Folks,

Been lurkin on here for quite some time. Just recently finally was able to get a 78 750A. I was looking for quite some time for a blue one. Found one last year on the east coast, set up transport, but the seller ended up selling it the day before pick up.

So even though I am not a father yet, the wife was out of town this past Sunday, and decided to get myself a father's day present and pick this one up locally. Shes red, but I figured she will be the learner bike I get to work on until I find a blue one.

The cool thing was that I bought it from the original owner. It has 6,400 miles on it. However, it is in rough shape since its been sitting since 2002 due to owner's health. Even with my unknowledgeable hands, I plan to bring her back to life. I also promised the family I would send pics to them once complete.

I had borrowed a friend's truck to pick up the bike, and drove back to my house and waited for him to swing by after to help me unload it. The pics above were taken at that point. I went inside to eat breakfast only to have a neighbor knock on my door and ask me if that was my red truck. He said there was smoke coming out of it. I grabbed the fire extinguisher and dashed out, in my mind thinking the bike caught fire. When I got outside, it was coming from inside the cabin. I opened the driver's side door with the extinguisher on just in case the fire would flare once it got oxygen.

My friend arrived soon after. I had mentioned to him that everything was totally fine when I left the truck and I didnt use the radio at all. He mentioned that it was installed a couple months prior. We checked the engine bay and it was fine. He said he was fully covered insurance wise so everything should be ok. I said I could pay for his deductible if that helps any. Although dismayed, he said there couldn't have been anything I did that would have caused it. I felt so bad. Only good thing that came out of it for me is that he has a little girl. I am glad that it happened to me rather than him with his little girl inside the truck.

But yeh, I plan to to tinker with the bike soon. She's not running at the moment. Here's the list of stuff I am thinking of getting:
- Deka ETX-18L battery - on order
- Shinko 230 100/90-19 front tire - on order
- Shinko 230 130/90-17 rear tire - on order
- Parts Unlimited K22-2519 Countershaft Sprocket (Thanks Stu!) - on order
- JTSprockets JTR284.48 Rear Sprocket - on order
- EK 530 SRX X-Ring Chain 120 links - plan to buy soon
- Pamco electronic ignition - plan to buy soon
- CB750K carbs - plan to buy soon. going this route since the current carbs need to be rebuilt. as opposed to investing more money for the current set up, I figured I would go the K route after reading KandRtech's Performance Mods thread.

Don't exactly know how to put everything together yet but I figured everyone has to start somewhere. Will get the factory manual soon and hope to start playing around with her soon. I am sure I will have tons of questions so hoping you guys will bear with me.

Thanks in advance for the guidance.
John

BIKE · « **Reply #1 on:** June 22, 2014, 05:02:35 AM »

Very nice, good luck!

dhall57 · « **Reply #2 on:** June 22, 2014, 07:04:31 AM »

Welcome from North Carolina. Don't visit this site much but looks like a nice original 750A. Hate it for your friends truck, but at least the fire didn't get to your new to me bike before having any insurance coverage on it.

Don't know how much he visits this site anymore since selling his super nice 750A. but forum member Stu(chickenman_26) Im sure could answer any question you had about these bikes.

limerence · « **Reply #3 on:** June 22, 2014, 08:53:45 AM »

Thanks guys.

I did reach out to Stu for the 630 -> 530 chain conversion and he was very helpful. After reading your message above though, I looked at his posts and saw that he sold his bike recently due to health reasons. Hope he gets better soon.

And I got manual yesterday and trying to read through and make sense of all of it. Getting anxious and thinking about the easy stuff I can do. Can anyone point me in the direction of how to remove the gas tank and front/rear wheels? I bought vinegar and baking soda to try to clean out the inside of the tank. And I got tires coming that I want to take to Cycle Gear to have them mounted.

Thanks,
John

Stev-o · « **Reply #4 on:** June 22, 2014, 09:54:51 AM »

Welcome. That is wild what happened to the truck. Was it the radio that caused the fire?

Tank is very easy to remove, disconnect fuel line from petcock, then pull back on the rubber mount at the very back of the tack, then lift up the back and pull back and up.

Here is a good thread to clean/derust your tank. Good Luck!

http://forums.sohc4.net/index.php?topic=106169.0

limerence · « **Reply #5 on:** June 22, 2014, 09:46:51 PM »

Thanks Stev-o.

It was getting dark and I wanted to look over the tank with your instructions in mind. Went to just lift off the tank and it was already totally loose. Seems like there is gas inside and I gotta drain it out somehow. Once I drain it out, I will do this method (http://forums.sohc4.net/index.php?topic=64952.0) that I saw in the thread you referenced. Got 4 gallons of vinegar and some baking soda from Walmart. Thanks!

-John

Stev-o · « **Reply #6 on:** June 22, 2014, 10:09:20 PM »

Unscrew the petcock with an adjustable wrench, the gas can drain out then. You also need to inspect/clean the petcock.

POPS 911 · « **Reply #7 on:** June 23, 2014, 07:41:21 AM »

JOHN: DRAIN GAS FROM TANK WITH A HOSE into a gas can from the petcock. Then you can remove tank. Those stock carbs work fine if you can get someone local to ultra-sonic clean and clean the plugged up jets [ gas from pass years ] that was setting in bowls. My stock 1976 with 11,000 runs just fine on these stock carbs that are like brand new. I have a great set of those carbs off a 1978 that I DO-NOT USE because my 750a are DRAG BIKES with CV carbs from a XJ750R SECA YAMAHA w/ K boots. Get the bike to running then start adding parts and new set ups.
Make sure the plugs are firing then work on fuel system. FUEL-SPARK- AIR as I saw one lately that had a mouse nest built in the air box from sitting in a shed for about 3 years = NO AIR GETTING IN TO CARBS, PACKED SOLID WITH GRASS ,STRAW AND JUNK. PM me if you need more info.

limerence · « **Reply #8 on:** June 23, 2014, 10:59:05 AM »

Quote from: POPS 911 on June 23, 2014, 07:41:21 AM

Get the bike to running then start adding parts and new set ups.

You're right. Getting too eager and looking at other stuff like spin on filters already. Always happens when I get a new toy. Need to slow down and just focus on the basics for now: fuel spark air. Thanks Pops.

POPS 911 · « **Reply #9 on:** June 24, 2014, 11:24:46 AM »

CALIFORNIA 750A: [ My son lives in Livermore but spent 15 years in Fremont been to SAN JOSE airport many times ] You will pull the carbs off that 750A and probably break the boots = 37 year old rubber is hard and brittle. PROBLEM: You CAN-NOT FIND THESE CB750A BOOTS and Honda quit make them long ago but you can buy new K-F boots for 75-78 and buy some carbs from a F-MODEL [ bigger carbs and boots ] or like I do put on a set of Yamaha XJ750R SECA CV CARBS that can be pushed in with STP on rubber boots and carb mounts. I got your PM and will send you a e-mail = that kick starter, I bought the last NEW ONE that HONDA had in stock at their factory store here in Marysville, OHIO...... MIGHT HAVE A OLD ONE from the other 5 part bikes.

limerence · « **Reply #10 on:** June 24, 2014, 11:53:13 PM »

Pops, in regards to the carbs, I didn't know the best approach to take. The grandson of the PO said the carbs will have to be rebuilt. I wasn't sure if that was the best way to go given what KandRTech said about the performance improvement in using the K carbs, and what you just mentioned about the lack of even finding replaceable parts for the A carbs.

I'm still trying to wrap my head around this carb stuff I am reading, but in the end, I am just trying to put the bike together to a point where it is reliable with easy/low maintenance (even better if theres a perf gain too). Although I am eager just cause its a new toy, I'm not really in a rush. So if it takes quite a bit of time to get her put together, I'm ok with that. I just don't want to rework/redo things cause I didn't think it through, and thus waste money in the process. Hoping that guys like yourself that have worked on these a ton, can point me in the right direction on some things and smack some sense in me if I'm goin at it all wrong on other things.

Thanks,
John

POPS 911 · « **Reply #11 on:** June 25, 2014, 08:48:23 AM »

JOHN: You can try to get carbs of those boots as I use a hair dryer [ not a electric heat gun ] on the rubbers and spray PB BLASTER at the edge of the boots and pull carbs out of those boots = maybe no broken boots ? Remove air box and gas tank first , flip carbs over and pull the bowls, get online to DENNIS KIRK AND ORDER NEW MAIN JETS and SLOW JETS. Sirus on e-bay has rebuild kits for CB750A and new rubber bowl gaskets. In time e-bay will be your parts book for parts. Do not mix carb parts and check floats and jets , clean with carb cleaner and air gun all parts. Remember those jets are BRASS so be careful. When you go to put carbs back in boots heat boots with that hair dryer again [ buy a Blue bottle of STP ] and take a small brush and that slick sticky STP an rub around in side of boot, spread a coat on the carbs mounts and those carbs will pop in the holes.

FIRST : PULL THE PLUGS ,TURN ON KEY, CRANK ENGINE OVER WITH PLUGS TOUCHING A GROUND ON THE HEAD = ALL 4 HAVE BLUE SPARK then you got spark. Put in new plugs. SPARK=FUEL=AIR then motor will run

POPS BK911 NHRA

limerence · « **Reply #12 on:** June 26, 2014, 06:08:47 AM »

Thanks Pops. Out of town currently but get home today. Watched youtube videos on checking for spark like you mentioned. Will install the new battery and will try to check it soon.

POPS 911 · « **Reply #13 on:** June 26, 2014, 10:59:05 AM »

Mark those plug wires 1-2-3-4 left to right. Seen folks pull off 4 wires at same time and put back on the wrong plug. When you put in new plugs make sure you use anti-size on the threads = steel plugs in a aluminum heads can freeze and pull the threads in the head. Turn out slowly and start screwing in [ by hand ] with a rubber fuel hose over top of plug = stops cross threading.....

limerence · « **Reply #14 on:** June 26, 2014, 05:16:14 PM »

Out of curiosity, what plugs are people running. The manual says NGK D8EA. However, in scanning the web, the best upgrade for that plug is the NGK DR8EIX? Is that true? If so, what are they gapped at and are there any special considerations that need to be made for the upgraded plugs? (I am planning on getting the Pamco Ultimate Ignition Kit later)

Thanks,
John

limerence · « **Reply #15 on:** June 28, 2014, 10:11:02 AM »

Woke up early and did a couple of things today.

- Installed Deka battery
- Installed the Randakk spin on filter adapter
- Installed Purolator Pure One oil filter
- Put in Shell Rotella T6
- Installed a new Emgo Air Filter - turns out there was a new Uni one in there. Didn't know which was better so I put in the Emgo
- I have the gas tank with vinegar sitting in there for about 4 days now. Still see like a tanish varnish inside the tank and on the gas cap chain. (Does that stuff come off?)
- Checked for spark on the plugs. Saw spark in 1,3, and 4 plugs. Not sure if it was because I was in the sun, but plug 4 seemed really faint. I couldn't seem to get plug 2 out to check for spark. They look to be all brand new D8EA plugs so no need for me to get new plugs.

It started to get hot outside so I rolled her back inside. Was hoping to try to figure out how to take off the wheels to have Cycle Gear mount the tires and put on the new sprockets but I'll leave that for another day.

Although I only just started, I probably might spend more money on this bike than if I bought one already fixed up and ready to go, its been rewarding learning this stuff with you guys' help. Thank you for that. I know alot of this stuff is very basic for folks on here, but I'm not a wrencher so taking myself out of my normal confines and trying to DIY this stuff myself is something I look forward to in the morning (wife has been whining that I am spending more time with this project than her. oops). Never knew how to diagnose what a motorcycle needs in order to start up, or how to check for spark, etc. Hopefully this journey ends well.

POPS 911 · « **Reply #16 on:** June 29, 2014, 08:38:31 AM »

Spray some PB BLASTER [ BUY at Auto parts store or WALLMART ] IN THE #2 HOLE on the plug [ REMOVE PLUG WIRE FIRST ] and let soak for a day. # 2-3 plugs are hard to get at because of the angle and the frame down tubes use caution to not pull the threads while removing. Put plugs back in using fuel line hose [ Or clear PLASTIC hose from HOME DEPOT, TAKE A PLUG WITH YOU TO MAKE A GOOD FIT ] ] that can slip over the white insulator, Put ANTI-SIZE on threads and gentle screw into the hole with rubber or plastic hose = then use the RIGHT PLUG WRENCH. A DYNA ignition for the 750a is the best and have use these on many drag bikes or street bikes over the past years. For the tank use KREEM fuel tank liner kit= tank wash, conditioner and fuel tank liner. The rust is in the outside edges of tank as water is heavier than gas and this water sets in the seams at the bottom of the tank..... buy on e-bay and read the directions.

limerence · « **Reply #17 on:** June 29, 2014, 04:56:00 PM »

Thanks Pops.

The thing about plug number 2 is that for some odd reason I can't get the socket to grab hold of the plug. Seemed like it was too small for it but even when I went bigger in size, couldnt find one that would grab it. I think maybe I was doing it at the wrong angle. As you mentioned, its hard to do it due to the lack of visibility. I'll be out of town for about a week but will try again when I get back.

Going to let the vinegar sit for another week or so and then take it out. I just want to make sure it eats up as much of anything in there as much as possible. As soon as I dump it, I was going to wash it with water and baking soda. From your post, I'll pick up some of the Kreem stuff to follow that up.

Ignition system wise, I have tried to find a clear cut winner but have not been able to. I've read threads on Pamco, Dyna, Daytona, and Hondaman's. I still can't get my head wrapped around any of them but I did see some threads where folks were having issues with the Dyna units so I thought I would take that off my list. Hondaman's still kept points so that one dropped as well. Last two was the Pamco unit and Daytona. I contacted "JayHawk" on here who has the Daytona on his clean bike and he thinks its a very solid unit in design. I was leaning that way until further searches revealed that his thread was the only thread on sohc4.net that used the Daytona. Not that that is bad or anything, but I figured that the more folks that have a certain unit, the more that would be able to help me if I screwed something up. Plus, it seems as though PamcoPete has a good record of customer service.

POPS 911 · « **Reply #18 on:** June 30, 2014, 11:19:09 AM »

JOHN: I know the folks at DYNA and for year have used their coil and ignition systems and their DS1-2 for HONDA 750 2 VALVES works well for me and for years I ran their DS2-1 IN ALL OUR KZ drag bikes COILS,WIRES,TWO STEP,REV-LIMITERS,SHIFT COUNTERS,SHIFT LIGHT , VOLTAGE MONITOR AND CHARGE MONITOR.
Just found 4 carb boots for the 750A number 1-2-3-4 IN MY STORAGE BUILDING LIKE " NEW " came off a head I did for a guy that keep his bike inside forever with 6,000 miles on motor...................... might have to keep for my 1976!!!!

limerence · « **Reply #19 on:** June 30, 2014, 06:18:45 PM »

Quote from: POPS 911 on June 30, 2014, 11:19:09 AM

Just found 4 carb boots for the 750A number 1-2-3-4 IN MY STORAGE BUILDING LIKE " NEW " came off a head I did for a guy that keep his bike inside forever with 6,000 miles on motor...................... might have to keep for my 1976!!!!

Teasing me Pops.

POPS 911 · « **Reply #20 on:** July 01, 2014, 09:50:21 AM »

JOHN: If you take off carbs, drain fuel from bowl with screw in the bottom of the bowls = then use a HAIR DRYER to soften up the boots then spray PB BLASTER AT THE LIP OF THE BOOT WHERE IT MEETS THE CARB SIDE and gently pry out with a large flat blade breaker bar = little on # 1 [ left ] then on #4 [ right ] each side [ outside carbs ] one at a time. UNHOOK all the tubes and wires and mark with colored zip ties so they go back on their proper place = take a picture.

jweeks · « **Reply #21 on:** July 01, 2014, 07:44:39 PM »

Cheap intake manifolds for K carbs come from cruzinimage_co on Ebay for $35. Kenosha Kid (Ebay)has occasionally K intake manifolds from Germany. Much better than stock and cheaper also. If you need a stock oem set, I've got one that I can sell you. (message me) You'll like the K carbs. Dyna makes a good points eliminator setup. Their ignition box (with 5 different advance curves) had reliability issues. It can be challenging to find in a search all that has been discussed in the past on this stuff. Good luck with your restoration!

limerence · « **Reply #22 on:** July 04, 2014, 07:49:56 AM »

Bought the Pamco unit a couple days ago at CB750 Supply. They have a 5% off sale now if anyone is looking to buy stuff from them.

POPS 911 · « **Reply #23 on:** July 14, 2014, 04:20:25 PM »

Well is it running

limerence · « **Reply #24 on:** July 14, 2014, 04:35:32 PM »

Hi Pops,

Not yet. I was out of town and the wife moved the tank that had vinegar in it. It was sitting on three buckets to balance and just in case it leaked, something would catch the vinegar.

Unfortunately when I got home, one of the buckets was almost full of vinegar. While moving it, I think my wife loosed teflon ball I had plugging the pet cock hole. I dont think it happened when she moved it, or else she would have told me. But basically vinegar came out and then came the flash rust. So I had to redo what I did before and it is now sitting with vinegar in it now again.

Any tricks on how to remove the vinegar out of the tank quickly and completely? I know flash rust happens within minutes so I'm trying to see how to drain it quickly, put in water and baking soda, and then dry it out. I have acetone I can swirl around if theres still a little liquid in there but I just wanted to see how everyone else does it.

Also got the Pamco ignition kit but havent had time to even crack open the box to look at it yet.

-John

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Author Topic: New to Me 1978 CB750A (Read 5197 times)