Author Topic: CB750K2 How easy is it to set the carb float without removing the carbs? (Read 3722 times)

jeremyillingworth · « **on:** July 19, 2015, 07:02:27 PM »

I pulled a float bowl off to change a leaky gasket and noticed the float was rather crooked with one side hanging down far more than the other. I suspect I hit it pulling off the bowl; when I put it back together it doesn't run as well, leading me to believe it's not set right anymore.

How easy is it too set while it's still on the bike or will I have to remove the whole lot of them?

jeremy

harisuluv · « **Reply #1 on:** July 19, 2015, 07:07:07 PM »

Not easy to do.

Possible? Yes. Practical? No.

Faster than taking them off and being able to easily access everything? Probably not!

As good as off the bike? Good luck getting clear access to everything and using a float gauge even, probably wouldn't even fit with the next bowl screwed down next to it. Plus you're upside down, and have inches to work and use all your tools.

jeremyillingworth · « **Reply #2 on:** July 19, 2015, 07:09:54 PM »

I guess I'm doing them off the bike. Can a combination square be used to set the height?

ekpent · « **Reply #3 on:** July 19, 2015, 07:19:31 PM »

Yep its a bench job, that one time you clean things up well and put them back together in spec and hopefully if done right move on to other things knowing the carbs are dialed in correctly

seanbarney41 · « **Reply #4 on:** July 19, 2015, 07:25:25 PM »

Quote from: harisuluv on July 19, 2015, 07:07:07 PM

Not easy to do.

Possible? Yes. Practical? No.

Faster than taking them off and being able to easily access everything? Probably not!

As good as off the bike? Good luck getting clear access to everything and using a float gauge even, probably wouldn't even fit with the next bowl screwed down next to it. Plus you're upside down, and have inches to work and use all your tools.

totally disagree...it does take some careful attention to detail and some very steady hands and delicate touch. Don't use a float gauge, do the clear tube test. Don't try and adjust float tang with it still in the carb. Pull the float pin, remove float and catch the needle with your other hand as it will fall out. Adjust, insert needle into seat, hold it there with your pinky, put float into position, remove pinky, and insert pin...check fuel level with clear tube, repeat as necessary. It does help to remove the bottom half of the airbox. I can reset float levels on 4 carbs in a half hour or less this way.

harisuluv · « **Reply #5 on:** July 19, 2015, 08:25:11 PM »

it's a 750, not a 550, i agree it's a totally different story with the bowls that you can just unclamp.

Thought it was a 550 therefore reference to bowl screws.

mystic_1 · « **Reply #6 on:** July 19, 2015, 08:44:37 PM »

Quote from: seanbarney41 on July 19, 2015, 07:25:25 PM

Don't use a float gauge, do the clear tube test. Don't try and adjust float tang with it still in the carb. Pull the float pin, remove float and catch the needle with your other hand as it will fall out. Adjust, insert needle into seat, hold it there with your pinky, put float into position, remove pinky, and insert pin...check fuel level with clear tube, repeat as necessary. It does help to remove the bottom half of the airbox. I can reset float levels on 4 carbs in a half hour or less this way.

I have done it exactly this way several times, most recently this past spring. It's a little more back-and-forth than setting them on the bench, and it's a bit more of a pain to do the inside carbs, but it's definitely doable.

mystic_1

Flyin900 · « **Reply #7 on:** July 19, 2015, 08:55:51 PM »

Check first with a small mirror to see if possibly the float pin has moved out of one side of the two mounting posts and is causing the float to be crooked.
If this is the case it should be easier to get the pin back into the mounting post and get the float oriented correctly again.

lrutt · « **Reply #8 on:** July 20, 2015, 08:13:33 AM »

do it right or do it over.

Just 50 years experience talking here.

flybox1 · « **Reply #9 on:** July 20, 2015, 08:36:31 AM »

the airbox is always a hurdle.
removing its bottom half first, makes it measurably easier.

jeremyillingworth · « **Reply #10 on:** July 28, 2015, 08:33:51 PM »

I just rolled the bike into the basement and took it apart properly. It was pretty quick and easy.

My plans to use a combination square were frustrated by it's large size and I didn't want to spend thirty dollars on a gauge or wait for shipping so I whipped up a wooden one. It's not perfect but within a millimeter.

Setting the floats was actually easier than a was dreading. They overflowed a bit on installation but stopped.

jeremy

rddcw · « **Reply #11 on:** July 28, 2015, 09:11:59 PM »

Jeremy, Nice float gauge. Would you care to Post the dimensions and how you made it?

mrbreeze · « **Reply #12 on:** July 28, 2015, 11:08:38 PM »

I just did mine last month with clear tube. It wasn't a big deal. They were pretty much on except #3 which wasn't too far off.

jeremyillingworth · « **Reply #13 on:** July 31, 2015, 12:59:24 PM »

The gauge is three and a half inches high and two and three quarters inches wide. The legs are obviously 26mm long with an extra half inches in the center section, which is also half an inch wide. The legs are an eighth wide leaving two and three eighths in-between.

I just stood the piece up and ran out through the table saw with the blade at the right height. I didn't feel like getting out my dado set so it took twenty or so passes.

przjohn · « **Reply #14 on:** July 31, 2015, 01:28:18 PM »

Quote from: lrutt on July 20, 2015, 08:13:33 AM

do it right or do it over.

Just 50 years experience talking here.

Yup, couldn't have said it better. One of my first jobs was after school at a gas station. This is when gas stations repaired cars instead of selling hot dogs rolling for days under a heat lamp. The mechanic there taught me something that has stayed with me my whole life. "If something is in your way, or has to be removed to gain access to the problem you are working on, just do it, in the end it will be easier, and a better job done"

jeremyillingworth · « **Reply #15 on:** July 31, 2015, 01:56:39 PM »

When you check it with a clear tube do you run one end into the bowl drain and hold it up? What size tube?

seanbarney41 · « **Reply #16 on:** August 01, 2015, 07:25:55 AM »

not on your bike...you have to rig up the tube out of the drain screw hole

mystic_1 · « **Reply #17 on:** August 01, 2015, 10:52:00 AM »

On some bikes, the overflow tube and the float bowl drain screw are connected, so that when you loosen the drain screw, fuel flows out of the overflow ports.

Not on these carbs, though. The drain screw is a separate passage, so to properly do the "clear tube" test, you have to rig up an adapter as seanbarney said by either drilling out a drain screw and soldering in a nipple, or milling it down, to accept some clear tubing:

Others have also had some luck with partially melting the tubing, stretching it so that it gets thinner, then trimming it off at the narrow part so that it has a taper to it. Then the tubing itself can be screwed into the hole in the float bowl and seal well enough to perform the test.

mystic_1

jeremyillingworth · « **Reply #18 on:** August 02, 2015, 06:21:03 AM »

Next time I'm ordering parts I'll get a spare drain plug and drill through it. It looks easy enough.

mystic_1 · « **Reply #19 on:** August 02, 2015, 07:42:16 AM »

I've had some good success just buying a short metric screw of the proper diameter and drilling THAT, cheaper than using a brass drain screw, and then you can use solder to add a short piece of tubing instead of having to braze. Also, it's totally possible to overheat the brass ones with a propane torch and melt them down into slag. Ask me how I know

Add a small o-ring to the screw afterwards and you're good to go for just a couple bucks.

mystic_1

jeremyillingworth · « **Reply #20 on:** August 02, 2015, 06:56:53 PM »

That sounds like an even better idea. Do you counter drill the tube into the screw?

mystic_1 · « **Reply #21 on:** August 02, 2015, 09:03:10 PM »

Yes exactly, drilled the through-hole, and then stepped up to a bit size that matched my tubing and counterbored about half way into the screw head.

mystic_1

jeremyillingworth · « **Reply #22 on:** August 03, 2015, 07:25:19 AM »

That's genius. Next time I'm out in the car I'm taking a bolt with me to match up and getting a brass coupler from Lordco. From what I've read aquarium tubing seems to be the most readily available clear tube variety.

flybox1 · « **Reply #23 on:** August 03, 2015, 08:48:21 AM »

Quote from: jeremyillingworth on August 02, 2015, 06:21:03 AM

Next time I'm ordering parts I'll get a spare drain plug and drill through it. It looks easy enough.

Its easier and cheaper to heat/stretch/taper a section of tubing and just turn it into the drain screw hole

Spend the effort mocking up a nice carb stand on your bench. Something to hold them still while you work on them.

jeremyillingworth · « **Reply #24 on:** August 03, 2015, 07:22:44 PM »

Any pictures of such a stand?

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Author Topic: CB750K2 How easy is it to set the carb float without removing the carbs? (Read 3722 times)