Topic: Carb problems, somebody help?

[buffaloejon]

I know carb problem threads are a dime a dozen (but to be fair, carbs are a pain!), but I believe that's my problem now.
1976 750K, not 100% sure which carbs, I meant to check before I came to work...

Freshly rebuilt, head was off, new gaskets, o-rings, etc etc, valves are timed, ignition is decently timed, carbs are NOT synced yet...

The bike fires right up (thank the lord), it idles (which it did not do before), and revs up nicely! The problem is, it revs up pretty high within like a 15 degree twist of the throttle. Now this next symptom I'm not sure of, but when I was going to ride it around the driveway, it seemed like it bogged out pretty quickly when I actually put it in gear and tried to move it. So what the heck does that mean?

Thanks for the help!

(Seperately of this, I seem to be getting wheezing from around the sparkplug area (when I turn it over by hand, not when it's running)? What the heck? I noticed it before I took the thing apart, should I have lapped the valves? dagnabbit...)

[lucky]

One problem at a time.

Yes valves should be lapped but it is not the cause of a "wheeezzzing problem.

Lets get back to the carbs.
If it runs and idles but stalls when trying to accelerate we need more information.
Do you have stock exhausts?
Do you have a stock intake?
Did you clean the carbs?
If you did clean the carbs did you make sure to remove the idle jets and make sure you could see daylight through them?

[buffaloejon]

Yes, one problem at a time. Didn't want to make a bunch of threads, but didn't want to forget to ask either haha

I do not have stock exhaust, it's a no-name 4-1 header with a Cycle X supersport muffler, the "quiet" one
Stock intake, but the airbox is pretty beat up... can't make the bottom half seat like it should... (definitely potential for intake leak)
I cleaned the boogers out of the carbs, all jets are clear, carbs are bench synced, and screws are adjusted to one turn out. Should be noted the floats absolutely may not be set at the right height (maybe the culprit?), and float needles probably need to be replaced.

I should say that both the intake and the carb boots are in pretty rough shape... but seem to be seated decently, I'll be checking for intake leaks with WD40 when I get home, but I wouldn't think intake leak would create an engine that behaves this way? But then again what would I know.

If any of these things clearly could be the culprit, then let me know and I guess that's what I'll be spending money on next... just wanted to get it on the road, but it's not exactly rideable like it is.

[buffaloejon]

Alright, well update.

Got home today, and got back on the bike, and fixed the tach-cable, wasn't working, so this time I had a tach.

She idles at about 1900, and quickly revs to about 3000, which isn't terrible I don't think.

Now, the reason why I thought it was bogging down, is mostly because I'm a wimp... however, it's also partly the fact that the friction zone on the clutch is the teeniest part at the very end of the clutch release. I'm almost 100% sure it wasn't like that, or that pronounced, before the engine was removed.

So I'm thinking I somehow maladjusted the clutch on reinstall? (not the actual clutch, just the cable) There is some play in the clutch, about what I would think is acceptable, but like I said, that friction zone is RIGHT there when you pull in the clutch... so it's rideable, but I'd like to know if that's something I should adjust, or something to live with. From my knowledge of other motors, a really short clutch means a really worn one. But I'm not sure how it got that far at the "end" of the clutch lever.

[grcamna2]

It'd be good to do a complete "by the book" clutch adjustment & also check if you're advance unit is moving well and not frozen..or the springs could be too stretched out;check it w/ an inductive timing light.It should start out at low rpm's on the F mark..and progressively move to full advance and back again as you decrease the rpm's.

[lucky]

You are like a squirrel running all around WILDRUN88 LOL....lol
Like I said ONE problem at a time.

Get the carbs right then move on to other problems.

Slide needles do not usually need replacing.
Float levels MUST be correct.
Get new float needles if they have not been replaced.
Do not try to adjust old float needles to get the float level correct.
Put in new float needles and adjust the floats. Then you will never have to adjust them again. BTW it should idle at 1000 rpm, not be screaming away at 1900 rpms.

After that is complete THEN repair the clutch problems.
Then move on to the cylinder head wheezing problem.

Do a repair make sure it is right ,then move on to the next problem.

[buffaloejon]

Ok, I pulled open the carbs briefly today, and I'm wondering if they've already been rebuilt. Everything is extremely clean, new gaskets, and the jets match the jet sizes on this kit:
http://www.rustyriders.net/carburetor-parts/carbureator-rebuild-kits/honda-cb750-carb-rebuild-kits.html

Of course I have no way of knowing this other than a hunch, given the matching 110 jets and the general shinyness of the parts.

I haven't broken the carburetors into components cause they're a little intimidating, but I'm thinking that's what I may have to do.

Seeing as my plugs look like this, I'll be pulling the carbs off and finding some stock 105 jets to put in them.


edit: alright well that's actually a terrible picture, but all four are black, (4 is on the left). 3 is ridiculously black (and I believe thats the overflow tube that likes to randomly pee), and I'm thinking maybe that's the only thing causing the surging (fouling that individual plug). But, when I pull the carbs I'm going to set float height correctly and change the jets to 105s, and see where that puts me.

double edit: Any suggestions of where to buy jets from? And float needles if I need them... are what's called the jet needle in the shop manual the float needles? All the different terms "floating"  around are confusing me.

[grcamna2]

Having the floats all matched in height and sealing correctly may be the best thing you can do to you're carbs !

[buffaloejon]

Alright, well I got the carbs off, and put 105 mains, adjusted float height to 22 mm, made sure they were all level (they weren't), and blew out the emulsion tubes. Reset idle mixture screws, and re-bench-synced.

After idling for about five minutes, using a wet rag, the exhaust pipe on 4 was noticeably hotter than the rest. Pulled the plugs, and they look like this: (1 is on the left)

1 and 2 look quite good I'd say, 3 looks kind of wet with black crap, would that be oil? (which I did just change, and the engine is freshly rebuilt) and 4 is dry, so it's firing, but no coloration like 1 and 2, so is it lean? (which would make sense given the pipe being hotter)

I would've taken it out for a test ride to see how the main jets are performing, but I don't wanna ride with 4 running hot and have a meltdown.

[buffaloejon]

Bump to top of forum, somebody help me please?

I'm really hoping 3 isn't actually oil on the plug, but I'm worried it is... another detail to note, the black on the insulator seemed to be only on one side of the plug. Dunno if that means anything or not.

I guess the next thing to do is take the carbs BACK off, and check needle positions (stupid me, didn't do that before), put them all to whatever position 1 and 2 are, and re-blow out all fuel passages. And then pray 3 isn't being oil fouled. I'll cry if I have to pull the motor again after finally getting it mounted back up.

[curemode2002]

So with the plugs a really black color is rich, really white is lean, you want them to look fairly normal color just a bit on the tan side. With the black wet that is usually oil sometimes you can be really rich but it is usually oil. Also idling you should be rich anyway a better option is to warm the bike up and run around 5000 RPM for like 5-10 minutes that will give you a more reliable plug read. You usually have to do this on the road as the bike will overheat sitting still in a garage.