Topic: At this point.........(MAGICAL ASS RAPE FAIRY STRIKES AGAIN)

[jtb]

Matt,
You've got 2 choices.

1.  Bring the bike to Bham and give it to me.
2.  Pull the carbs and work on them again.

I went out for breakfast yesterday on my 77, filled up right after I left the house.  It rained while we were in the restaurant, but had quit by the time I started home.  When I cranked the bike up, it was running on 2.  After a while, it got to going on 3, and the 4th cylinder would kick in and out.  (Really fun, since the road was WET, and a brand new tire on the back).  I figured I was in for a stint of trying to waterproof the coils and wires, (probably still am).  It poured on me the last 2 miles (great morning).  After I got out of the hot shower, and got dressed, I realized I could smell gas.  Went to the garage, and it was pouring out of the air cleaner housing.

Any way, I'm going to have to take my carbs off for the first time (this year ).  I'm sure some piece of debris got into one of the float valves.

Actually, I probably had them off at least 5 times in the first year I had the bike.   I know how you're feeling, just take a breather for a couple of days, and do something else.  The upside is that now I can take them off, disassemble them, clean them and have them back on in less than 2 hours.  I'll be thinking about you when I start in on them tonight.

John

[MosquitoJones]

The magical assrape fairy stretches my o-ring.

Is this some sort of euphemism?

There's nothing magical about assrape, OP, nothing at all 

[ev0lution7]

well i got one for you....

went to town after i rebuilt my harness and everything seemed fine stop by a friends house to brag about my bike and we started it ran it he sat on it and then i went to leave and then he said OMG you got smoke comming from your seat i took the side cover off and my regulator wiring was almost on fire my green wire was completely melted! it was crazy!!!

[gregimotis]

The magical ass rape fairy drinks your milkshake.

[PJ]

Fbomb, how are you making out bro? Any progress to mention?

[cb750fbomb]

The float was stuck. After whackin' it a couple of times it stopped draining. I'm about to go out and start it with a fresh, new battery.

[PJ]

Sometimes they will hang on the side of the bowl if they are bent out of shape, sometimes I think they don't float evenly too but that could just be paranoia of the worst kind

[cafebob]

What would I need to do to get a set of those carbs set up for my bike besides change jet sizes and what jets would I got to?


see my thread on the 83, 84, and 85 CB650SC carbs.  For a stock the 83/84 ones would probably be fine (they are 29mm) The should fit right on your stock boots (they fit my 78F head no problem, needed a little rubber mallet taping at first, now after 50 miles, they are fine.)

Jetting is hard to say, they come with 35 slows and 115 mains.  Might be fine for a stock bike, as they have about the same HP.  With my 836, with pods, 40/122 @ 5280ft is working very nice right now.  Also, there is a Dynojet jet available for them for about 120$. (I do not know what comes in the kit though)

I think you're crazy (ton cafebob).
The 1st gen carbs are the easiest to tune, jet, or otherwise work on, of all of them. They also work wonderfully.
I would change them, however, for whatever they were using on the late 70's kawis, were it an easy swap.


As to being crazy, my bike with them on it is very smooth.  It is probably the best idling, and around town driving 750 I have ridden.  I know alot of you think it is blasphemy, but IMO they are much nicer than the stock ones.  And as to the stock ones being easy to work on and working wonderfully, I think this board is a testament to that not being the case. There are many, many reports of the various problems riders have with these carbs.  I think every owner has wanted to through a set in the trash at one point or another. 


Just my 2 cents.

CB

[baldy253]

Hi there fbomb.  Just found this thread. Have been a member with this group for only a little while. You had asked about what it would take to change your 77 carbs to maybe the 69-75 style? I am just now finishing up that swap on my 77CB750k. Ya have to get the carbs, carb boots(head to carbs) 77's are not the same. You also have to change to the earlier style throttle cables. The 77's are 3" too long. Not a big cost there. Anyhow, I decided to do the swap for many of the simple a** reasons  mentioned here. The early carbs are easy to work on, and tune. The hold their sync, and if ya talk to a few old timers, some will tell you that they can flow air as well as those $700 CR smooth bores.

Just some food for thought. If ya decide to go this route, get in touch with with me, and I will help as I can. Plus, I am also trying to finish my 70 CB750 Cafe.

Later  T

[mick750F]

  And as to the stock ones being easy to work on and working wonderfully, I think this board is a testament to that not being the case. There are many, many reports of the various problems riders have with these carbs.  I think every owner has wanted to through a set in the trash at one point or another. 


Just my 2 cents.

CB

   I have to say that that is an inaccurate blanket statement about the 77/78 750 carbs. They can be disassembled, cleaned and rebuilt just like any other carb. If people aren't doing the job thoroughly or cutting corners it doesn't make them bad carbs. Maybe the board being a testament to them being problematic is because people tend to post when they have problems rather than when they have success? Need a success story? A few years ago I COMPLETELY disassembled my carbs, cleaned them like there was no tomorrow with Yamaha carb cleaner and air, replaced all gaskets/o-rings using Honda carb kits, reassembled, installed, synced and...no problems, they work great.

Mike

[mlinder]

I think he was saying that about my statement concerning the first gen, 4 cable carbs that came on the k0 and some k1's.

[cb750fbomb]

I posted this as a seperate post, but I've gotten no replies:

I got her running, but the idle is real inconsistent. The throttle is weird too. I'll rev it and it will stay reved up to 3k-4k rpms, I adjust the idle and the rpms drop out and she'll stall if I don't idle it back up. Runs with choke on or off. I sprayed carb cleaner on the boots and noticed that #3 is still leaky with new boots and new stainless boot clamps. Narrowed it down to the carb side of the boots by spraying carb cleaner on engine side with no change. I spray on the carb side and it idles up a lot. The boot is seated flush to the carb. Anyone possibley run into something this before and it stemmed from something that wasn't so obvious? I'm going to be checking the carb body for a crack or cracks as soon as it stops raining and I know this isn't a lot of input, but any ideas would be great.

Also, does anyone have a good source for washers for the sync screws? That could be part of the problem. The local Home Depot doesn't have anything.

[Frankenkit]

Should be able to run with choke on or off, but 'on' will likely be boggy and rich. 

Could also be a matter of how tight the airbox is connected to your carbs and ... those connections from carbs to head are tough.  I don't think I could attach them without some kind of engine guard on.  What I do (and it's different for everyone) I brace a knee against the guard (maybe the frame?) and grab the carbs, (top and bottom, for each side) and while tipping them up and down a little, apply pressure pulling toward me to pull the carbs into the boots until they 'pop' into place. 

Cracks can and do happen, though, especially if the PO was especially hamfisted and used a pry bar or something on the carbs.

Any way your throttle cables could be dirty/tight (same for the linkage) could be sticky slides, bad gas, voodoo, being out of synch, etc. 

For those washers, you might want to bite the bullet and order them from the Moco.  Other option would be buying a carb rack from the boneyard so you have a whole rack of 'spare parts' just in case.

[cb750fbomb]

Should be able to run with choke on or off, but 'on' will likely be boggy and rich. 

Could also be a matter of how tight the airbox is connected to your carbs and ... those connections from carbs to head are tough.  I don't think I could attach them without some kind of engine guard on.  What I do (and it's different for everyone) I brace a knee against the guard (maybe the frame?) and grab the carbs, (top and bottom, for each side) and while tipping them up and down a little, apply pressure pulling toward me to pull the carbs into the boots until they 'pop' into place.

I have pods. The carbs never "popped" into place but they look to be flush.

Cracks can and do happen, though, especially if the PO was especially hamfisted and used a pry bar or something on the carbs.

[/quote]Any way your throttle cables could be dirty/tight (same for the linkage) could be sticky slides, bad gas, voodoo, being out of synch, etc.[/quote]
The cables are new and are well lubed, but I hadn't thought until now to try the throttle with the tank off to see how that works. I would also bet money that they're not in synch. I synched them with a 1/8 allen wrench since I didn't have anything else


[/quote]For those washers, you might want to bite the bullet and order them from the Moco.  Other option would be buying a carb rack from the boneyard so you have a whole rack of 'spare parts' just in case.
[/quote]
What's Moco? I googled the hell out of it and found nothing but marketing info and vague forum posts.

Thanks for the input. It really helps getting the gears in my head moving to discuss the problem. I thought of a few things just reading your post.

[Frankenkit]

'the moco' is another way of saying 'the motor company'.

[cafebob]

Ah yes another satisfied stock carb customer....


For the boots, I made a little "pressure cell" out of 2 metal plates, some air fittings, and a pressure gauge.  I sandwich the boots in a vise between the two plates, one of which has a valve stem and a pressure gauges in line on it. pump up the cell and see how well it hold pressure.  good ones for me hold 10 psi over night. bad ones are at 0 by morning.  doesn't work 100% of the time, but if yours are hard, and you can't see cracks, it is a good way to test them.   works better than spraying starting fluid on the boots while the bike is running.  That tends to only find the big ones.


My local performance cycle shops have plastic multi welled boxes of various carb parts from all the major manufactures.  Jets, springs, washers, clips....if you ask nice sometimes they will let you kind of flip through the box.  Other times you just show them the part and they pull out the box and get you something real close.  May not be the exact one, but it has always worked for me.

If you have a pick and pull recycle yard for bikes getting what you need off of a bank of dead carbs is the trick....these days though, good luck finding any 1st gen 750 parts on a bike in the yard....my local place has 10-15 of them last time i looked, but they are really picked over....but you can always try to find what you need of a similar age set of carbs too.

[cb750fbomb]

I did the old 2X4 and a strap with a ratchet trick and there are no leaks at the boot. I'm still trying to figure out why, as it warms up, I'll give it gas and it will hover around 3k rpm for a little while. The cables don't seem to be pinched or anything and the action on the carbs seems to be nice. Everything looks to be moving fine since I pulled and cleaned them the last time. My dad was over and he was agreeing with me that everything seems to be snapping back as it should. Ignorance is frustrating. I think syncing them would do a lot of good.

[Spanner 1]

Bomb is the man !!. I aint #$%*tin', he aint quittin' with his bike.......it will run like a champion, believe me, 99 per cent there.....