Topic: New to forum, looking for some advice

[xdistancex]

Hello all, I'm new here and i apologize for the long winded explanation. I'm sure there are a lot of members that start this exact way, so i hope to not be repetitive.  I have been searching and reading posts for a couple weeks now before i decided post myself.  I picked up a 77' Cb750 fourK spring of 14, it started great, rode great, and i loved it... and then it just started stalling out on me, it would restart and then stall once i put it in gear and tried to ride off.  I decided to take it to a shop i had been following online for a while, i explained everything to him and told him i wanted it rebuilt completely so i wouldn't have this issue again.  so after 3 months, engine rebuild carb rebuild, forks, brakes, new cables, and even me helping with exhaust wrap and a little lowering... i picked it up, but when i did he had issues installing the exhaust because of the kickstand not fitting with the wrap, so the exhaust wasn't installed. the bike started right up at the shop even without the exhaust twice, i got it home figured out the exhaust, proceeded to start the bike, it started and ran on choke for a few mins, then idled out slowly, i figured it was maybe out of gas... couldn't get it to start for a couple days. Today i was moving it into my garage and it started up but only ran with the choke on, as soon as the choke was let out it stalled but would start back up with choke. The shop owner told me to check the fuel lines and install a filter. Could that be causing this, or is it something different?  figured this may be a good place to look for some knowledge and advice. thank you all in advance!

[vames]

Very nice looking bike.

You had the entire engine and chassis rebuilt just because you wanted to fix a stalling problem? You might get some #$%* on this site 1) because rebuilding the engine and carbs might or might not have solved the problem and 2) because it's akin to knocking down your house and building a new one just because there was a stuck window. Just sayin' -- go into this with a thick skin and people here will berate you a little and help you a lot.

And about your "mechanic" -- even if the rebuild was done correctly, all he did was take a bike with one set of problems and hand it back to you with an entirely different set of problems. If what you wanted was a perfect turn-key bike handed back to you, then why did you settle for getting back the bike without the exhaust not installed and the engine not in a perfect state of tune? And for him to try and prove to you that it was all running well by starting it without the exhaust on it is kind of dishonest (false implication that if it runs well without an exhaust, it will run perfect with one). And for him to then tell you that the problem is that it needs a fuel filter is outright stupid (it might very well need one, but I don't think that's your main problem here). And what was it that you figured out about the exhaust that he couldn't figure out? Based on the description, this "mechanic" really stinks.

People are going to tell you that now that it's been rebuilt, you need it to be in tune. Start with the 3000-mile tuneup set out in the factory manual. Since it seems to be fully stock (except maybe the exhaust) it would probably make sense to get it all to stock specs and start from there.   

[BobbyR]

+1 on what Vames said.  If you need the choke to run the bike, it is very lean and a filter will not solve that. Before you start ripping things off get a can of carb spray, you will need it anyway later. Start the bike and spray around the carb rubber carb insulators one at a time. If the sound of the engine changes you have found and air leak. you have a 77 so you have screws in the carb bodies to attach a synch guage, make sure they are all there.

My guess this genius did a quick spray down on the carbs and did not properly go through the internal passages with a strand of copper wire and then spray out the debris. You will see it written that the slow jets are pressed in and cannot be removed. They can be removed, cleaned and put back in place easily. Keep us posted on what you have done and we will take you further. Down load the shop manual from a link on this site.

[DaveBarbier]

Welcome to the forum, nice bike and nice beard.

Yeah it seems a little extreme to rebuild everything just for a stalling out issue. Might have just needed a carb clean which would have been free. What was the mileage before rebuild? What was actually done to the motor? Was it a complete tear down and split cases or just a top end re-ring, hone and valve lap? Are you still in the break-in period?

What was done to the carbs? Just replacing rubber parts and cleaning the rest or all new jets (OEM or aftermarket)?

You should know where the bike stands as far as exact work that was done and what specs carbs were left at like jets and float height, air screw, etc. And +1 to what Vames mentioned about the 3k mile tune up.

Pretty much since you got it rebuilt and it's still not running well then you need to second guess this mechanic's work. But all's good. With some work you can get this thing running like a top (or an angry sewing machine is what I've heard people describe what the sound of a good running SOHC4 should be). Good luck and be vocal on the forum, don't be a stranger!

[70CB750]

Welcome.

[jaguar]

Modern fuel has a life of less then 14 days in a bike.
If it sits, bad things happen.

EVERYONE that owns/rides a vintage bike should become comfortable with some mechanical work.  Carb cleaning is one of those things.

[madmtnmotors]

Wow. 

I mean... damn. 

Did I say wow? 


If it was running "great" before, then an engine "rebuild" was way over the top. Did they provide receipts for the "new" parts? Did they return your "old" parts? I'm afraid you got hosed. 
Any mechanic worth his salt should have suggested a simple tune up to begin with. This may have been all that was done anyway, unless all of the hard parts that were replaced were returned to you (i.e. pistons, clutch plates, timing chain tensioner components, etc.)

These are very hardy machines. My approach to this, or any other misbehaving means of ICE locomotion would have been:

>A full tune up. This is quite likely all that was required. Don't overlook the fuel filter. The later models (77/78) have the fuel filter up in the tank where the petcock attaches. These usually require some deliberate effort to remove after they have been in there a while and are often overlooked. A clogged in-tank fuel filter or a clogged fuel tank vent in the filler cap (least likely) can starve the engine of fuel and cause stalling.
>If that didn't solve it, then a thorough carb rebuild and sync. This should have been "worst case".

You are now back where you started, and I would suggest proceeding with the two steps mentioned above and report back. The "full tune up" should now probably include a compression test. As suggested in a previous post, check for vacuum leaks at the carb boots too.

These motorcycles will go 100,000 miles easy without a "rebuild", even those that are treated badly. Treat them well, and these engines can reach 200,000 before cylinder sealing really starts to become an issue. Look up posts/threads by members "Hondaman", and especially "ofreen". I think ofreen holds the high mileage crown.

Where in Michigan are you? You might consider reaching out to other members in your area, we have several members throughout Michigan.

Good luck and keep us posted.

[flybox1]

Distance,
Welcome to the forum.
Bummer you had all that work done at a shop, paid all that $$ and still have issues.  Its a song sung before 'round here.
But the good thing is you are finally in the right place.
The collective wisdom and good people here is invaluable.

Carbs - Learn them. Know them. Love them.
I can almost guarantee that the 'rebuild" the guys did on them was half-a$$'d, probably included the use of crappy aftermarket jets and such, if they even got past the surface cleaning with a can of carb spray to make them LOOK rebuilt
You're going to want to get them off and check everything.  Become familiar with their innards, and how the systems work.  Its not as hard as you think.  start a thread, post pictures, and ask questions.  the forum will help.

Im certain your issue lies with your carbs.  you are the best one to discover why.  we will look over your shoulder.

~fly

[przjohn]

told him i wanted it rebuilt completely so i wouldn't have this issue again.  so after 3 months, engine rebuild carb rebuild, forks, brakes, new cables, and even me helping with exhaust wrap and a little lowering... i picked it up, but when i did he had issues installing the exhaust because of the kickstand not fitting with the wrap, so the exhaust wasn't installed.

This is the part I don't get, it took 3 months and you had all this work done. You get it back and the bike doesn't run. What did it cost you, and why are you not taking it back to this shop?

[Sgt.Pinback]

I assume she doesn't get enough fuel.

[Gene]

Start the bike and open the fuel cap - see if it runs better.  Plugged cap vent maybe?  Cheap check.

[xdistancex]

I am sure that my decision to rebuild everything was probably overkill... and i agree with you all the mechanic should have talked me out of that and into what needed fixed... i did see some of the work in person as i went to the shop during to see it, and also have a couple pics that were sent to me from him. (attached) which when i was there we discovered the bike had been taken care of and had a dyna ignition already. but why i have not taken the bike back or why i took it before it was done to my standards were that he was moving his shop from MI to IL, i believe, and the day i picked it up was his last day at the shop. so now I'm here.. but the plus side is when i do get it running there shouldn't be many issues in the future haha  ohh and i am currently in Bay City MI.
i will def be trying some of your suggestions this week, and i will keep everyone posted on the results, thank you all for your advice and compliments on the bike, and beard! i def appreciate it!

[madmtnmotors]

Wait a minute....

I thought we were talking about a CB750. The pictures of the engine under construction is not a CB750. What bike are we talking about here?

Just curious. Regardless of what engine we're discussing, the same principles apply.

[NobleHops]

Wait a minute....

I thought we were talking about a CB750. The pictures of the engine under construction is not a CB750. What bike are we talking about here?

Just curious. Regardless of what engine we're discussing, the same principles apply.

Oh no way. Could be an honest mistake by the shop, sending the wrong pics, but...

[flybox1]

yeah....engine pics dont match the pics up top   

[RevDoc]

yeah....engine pics dont match the pics up top   

Yeah, that made me do a double take as well! The carb rack looks like the PD46Cs on Angie and what I can see of the head pic looks like the head on Eva!

[harisuluv]

Looks like the ol "cruzinimage" carb kits.  Cheapest possible ebay special.  You will not find a cheaper carb kit.  Installing all that brass will probably do more harm than good.  From everything I've seen I think you probably need to find a different shop.

What are these pictures from, pictures you took or the shop took?

If you REALLY want to actually pinpoint and solve your problem, you are going to have to provide us with data.  You are the only one with access to the bike and therefore we already have second hand info.  We need pictures, pictures, pictures, pictures.  And seriously, taken with something better than a potato, well lit, that actually SHOW something.  Carburetors, engine, inside of fuel tank, multiple angles.  Taking these pictures will literally take minutes. 

If you can handle some pictures, maybe you can hit "record" and give a small video of you trying to get it running.  We need to see what you are doing when you start it--SHOW US.

What you are describing could literally be DOZENS of different issues.  You don't have to figure out what exactly is wrong, we will be able to tell you, but we need data to do so.  But if you do provide us with media, we will always be here and always help you.  Otherwise you will just flail around from one suggestion or possibility to the next and you will maybe get lucky or not.

[xdistancex]

It is a 750, 77' four K,  the last 3 pics i posted were the pics the shop sent me, but the carbs were in the same place as the pics when i got there so the pics should def be of my bike, but i really don't know..
I will have some time off work this week and i will take some more pics of the actual bike and some videos of whats going on so that you all can better understand whats going on. I appreciate everyones help and suggestions as i am pretty lost when it comes to doing anything more then cosmetic stuff on this bike...

[madmtnmotors]

Looks like the ol "cruzinimage" carb kits.  Cheapest possible ebay special.  You will not find a cheaper carb kit.  Installing all that brass will probably do more harm than good.

I can vouch for that. The rubber bits aren't any better either. After one week of exposure to fuel laced with 10% ethanol the rubber bits (rubber tipped float needle and bowl gasket) in my freshly rebuilt carbs on my 78K turned to goo and the carbs started spewing fuel out the overflows. The C.I. kits do not use Viton rubber, which is absolutely necessary for ethanol blended fuel.

Hurts to see that your mechanic is not using JIS screwdrivers either. Get yourself a set of JIS Philips screwdrivers before you try to do any of this work yourself.

[DaveBarbier]

Hurts to see that your mechanic is not using JIS screwdrivers either. Get yourself a set of JIS Philips screwdrivers before you try to do any of this work yourself.

Just to clarify a little. All the Phillips screws on these bikes aren't Phillips, they're Japanese Industrial Standard (JIS). Phillips screws and drivers are designed to "cam out" to not apply too much torque. This results in stripping the heads for screws that are slightly stuck. JIS drivers don't do that and they even feel way more locked in to a screw. Much less chance of rounding out the heads. Getting a set makes things much easier.

[Stev-o]

Sounds like carb issues.   The mechanic is either an idiot or a scammer telling you a fuel filter will solve your issue.