Topic: Jet Needle clip height after carb rebuild

[Ausmithe]

I have a 72 500/4 that was running rich enough to completely foul the plugs within about a tank of gas. From looking at the plugs they were more fouled on the 3 & 4 carb, but not by much. So I've begun the work to do a carb rebuild and need some advice on setting the clip for the Jet Needle height. My setup is pretty much stock with the exception of the exhaust which is 2 into 1.
I've read as much as I can find on the forums, and I know that the stock setting is in the middle, or 3rd down from the top. Mine were set to one notch below that, but the clip setting wasn't the only factor in the over-rich problem I was having. Once into the carbs, I found that the emulsion tubes were crudded up, and some of the jet gaskets were badly in need of replacement. The carbs looked fairly clean otherwise inside.

In this post http://forums.sohc4.net/index.php?topic=7401.msg67249#msg67249 which is originally from Hondaman, he mentions that the 70s inline fours all came from the factory with the jet needle set too high, except for the 500/550 which were too low. This makes me question if the factory clip setting was 3, and it should have been 2, then should I move mine up to 2 or even 1? Does my 2 into 1 exhaust make enough of a difference to be considered in my jet needle clip height?

Any help would be appreciated, this is my first carb rebuild and would like to make sure it's as close to right as I can get it.

[lucky]

You did not tell us  all of the information.

The needle clip position stock is 4th from the top.

Need all of this filled out.
1972 CB550
Main jets ?  Stock #100
idle jets ?    Stock #38
Slide needle clip position 4th from top.( Always say from the top)
Mixture screws 1.5-2 turns out.
Float height 22 mm.
Exhaust 4 into 2
Intake ?

There is about 4 members of this forum working on this same problem right now.

[Ausmithe]

Okay, I probably should have mentioned I'm new to this, sorry for not including enough info.

My bike is a 1972 CB500
Main jet is 100 ( just replaced )
Idle jet is 40 ( my manual says that is stock )
Slide needle clip position is 2nd from the top, not 4th ( I'm assuming the slide needle is the same as the jet needle.)
Mixture screws are set to 1 turn out. I read to start there, so that was my plan.
Float height is 22mm
Exhaust is 4 into 2.
Intake? Not sure how to answer this one.

My carbs are not back on the bike yet, and my question was asking for a recommendation on needle jet clip height considering the 4 into 2 exhaust.
I've replaced all the jets, and the jet needle, as well as the adjuster screw basically doing a full rebuild on the carbs. I've pulled and thoroughly cleaned my emulsion tubes. Essentially I'm ready to put it all back together and was just hoping for some insight as to a recommended change, if needed, for my jet needle clip position.

[Deltarider]

Standard setting for the CB500 needles clip in Europe was the middle (3rd) position which makes sense. Only in an American Honda booklet we find 4th clip denoted. IMO that's the max and on the rich side. It's probably there to compensate for the exceptional 2 turns out of the airscrew (standard in Europe is 1 turn out). That 2 turns out is exceptional. We do not find that setting in the Honda documents. Probably American Honda had to achieve a lean idle to please legislators.
For experimental reasons I've put my needles clip in 4th, but bike runs a bit on the rich side now.

[Ausmithe]

Thanks for the updated info. My jet needle clip was sitting in the 4th position from top when I pulled the carbs apart, but it was also running way rich. I guess the question is: Would 4 into 2 exhaust warrant a clip position move on it's own, and if so which direction?
My thought was that stock was 3 from top and I was too rich at 4 from top, maybe I should go to 2 from top. But now with your feedback I'm more inclined to go back down to 3 from top as long as the exhaust isn't enough to suggest a higher position.

[iron_worker]

Try 3rd from the top. If that's not enough then try 4. You will have to experiment a bit since your bike is not stock.

Also, by intake he means if you are running the stock air box or if you're running pods or some other after market part. The intake mods make a huge difference to how these bikes run and need to be tuned.

IW

[Ausmithe]

Thanks for the suggestions. I'll move to 3rd from the top and then update the post once I have them back on the bike. I ordered new bowl drain screws as mine were all beat up and two of the four o-rings on them were torn. I don't expect them to come in until next week, so it may be a bit before I can post results.

[Deltarider]

 

I'll move to 3rd from the top and then update the post once I have them back on the bike.

Not a bad idea. After that you may have to adjust the airscrews to one turn out ⁺/_-¹/₈ to ensure driveability.
Next time I have my carbs out I'll return the clips to 3rd notch and will try to shim them with a little ring so needle will be within 3rd and 4th (gasoline today is not the gasoline of the 70s).

[Ausmithe]

Well, it's running even more rich than before I started down this road. Before I pulled and re-built the carbs, it would foul the plugs in about 35-50 miles of ridding. Now, it left me sitting at a gas station 1 mile from my house. I had to call the wife to bring my tool bag so I could add new plugs to get it home. Which it didn't make. In fact after a bit more than a 1/3 of a mile it completely fouled the new set and I ended up picking it up on a trailer to get it home.
So, this is the next day and I'm wondering where to start. Here's an update of the stats.
72 CB500
Main Jet is 100 and Needle clip position set to 3 from Top
Slow Jet is 40
Emulsion Tubes cleaned
Valve seat replaced with new
Float pin - reused the ones I had since they were the rubber tipped kind and my carb kit came with all metal pins. But they looked good under a microscope.
Floats set to 22mm
Air mixture screws and springs replaced, and currently sitting at about 2.5 turns out. (I started 1.5 turns out but was increasing the air mix to lean out...to no avail)
Airbox is stock. The type that has a foam filter you coat with oil. It was recently cleaned and re-oiled, like within the last few miles prior to my starting on the carbs.
Exhaust is 4 into 2.

I attempted a sync but was having trouble getting them to be all exactly the same. Seems that adjusting one up or down affected the other three. I got it close, but not sure close enough. The other thing is I noticed that one of the tubes that draws the mercury up (rigid plastic tubing like the air lift tubes on an aquarium) was cracked. Now sure if it happened after I was done with trying the sync or if it was like that during and was the cause of the difficulties in synching.

So based on the other threads I've been reading the advice would be to verify that float level is in fact 22mm. I'm going to look up the clear tube method mentioned and try that before pulling the carbs off again. Another suggestion I've had was to pull the air filter and see how it works. Beyond those two, what are my most likely culprits for such a rich setup?

[lucky]

"BINGO"!!!! There it is...

"Float pin - reused the ones I had since they were the rubber tipped kind and my carb kit came with all metal pins. But they looked good under a microscope."

But you cannot see the inside of the float seat where the tip of the needle contacts the seat. The two angles have to match. The float needle is one of the most important parts of the carb.

Those are called float needles not float pins.
You cannot use rubber tipped float needles in the metal float needle seat.
I think the rubber tipped float needles are larger in dimeter than the metal ones.

But what I would do is get the correct float needles and seats BRAND NEW and install them and recheck the float height. Your problems should be solved.

It would certainly explain this over rich condition.

OR...
You meant you used rubber tipped float needles and seats, instead of the metal float needles and matching seats.
I do not know if that would work because of the design of the float tang.
The metal kind the tang rests on the spring loaded pin. On the rubber tip kind the wire brings down the float needle by force if the rubber cone gets stuck from suction or any other reason. So the tangs could be different designs.

Click on the photo for a larger version.

[Ausmithe]

EXCELLENT!!
That has to be it. I had no idea that the angles would be different on the two different needle types. I'll be swapping out those needles tonight, as I have the new float needle seats in the carbs already, they came with the kit I purchased for the rebuild.

I will note that the rubber tipped needles that I have do not have that wire on the bottom. So their method of action is the same as the full metal needles. At least this is the way they were installed in the carbs when I opened them.

Either way, I'm anxious to get home and try out those new needles. I will probably be a couple of days before I'll get to to update this post as I won't have time tonight to get it all done, but I'll definitely post an update for any other noobs out there that might make the same mistake. This forum has been an invaluable resource to me as I feel my way into the world of motorcycle maintenance and I really appreciate all the giants that go before me.

[lucky]

Do not forget to check the float heights like the books shows you, before starting up etc.,. 1.023 thousandths or ONE inch and twenty  three thousandths.

twenty thousandths=3 pieces of copy machine regular paper.

[Ausmithe]

I was able to get the float needles swapped out, double checked my float levels and a bench sync done yesterday. After putting it all back on the bike, it fired up and idled well right off the bat. Huge improvement over what I'd been experiencing. I ran out of time to be able to actually run it down the road or anything with it being the holiday so that will have to wait until tonight or tomorrow. I am confident though that the float needles were the major problem.

So huge thanks to Lucky for spotting my mistake in re-using the old float needles. Lesson learned!!

I'll post a final status once I've gotten a chance to really ride and check it out.

[Ausmithe]

I wanted to post a final status on this topic. My bike is running well and it's definitely better than when I started. I have good color on the spark plugs and just need to do a carb sync. That will have to wait until I can get a manometer, but the bench sync got me pretty close.

Thanks to Lucky for spotting my mistake and thanks to other folks for their advice as well.