Author Topic: Symba Carburetor Jets and Air Fuel Screw Information  (Read 7742 times)

ABray

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Symba Carburetor Jets and Air Fuel Screw Information
« on: May 23, 2015, 07:03:50 PM »
It is my hope to save you some money in buying multiple parts carb jets IOT get it just right. I finally got the Sym running perfect. As a backstory I put up some deets here: http://symforum.com/index.php?topic=11464.0 I had a hard time finding one source for a definitive guide, I ended up ordering a bunch of extra jets at ~$5/piece, for what to buy so here it is.

I took off the bicycle speedo off (not fast enough at updating) and gutting the original speedo. I pounded the original mount flat, turned around the bar mount, and mounted the old speedo back on. https://www.flickr.com/gp/130042194@N06/7sP5oR

For jets I used a 45 for the slow jet http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-74C_slow_27-xxx.htm and 65 for the main jet http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_99101-116_main_round_small_and_38-xxx.htm. This is with the smog stuff completely removed and a K&N RC-0790 pod filter on it. Exhaust and engine is still stock for now. It's kind of temperamental starting the first time you put the empty bowl back on, just take off the filter and plug off the intake with your palm and it will suck the bowl back full of fuel. I'm at 850M ASL.

For the air/fuel screw I used part #23013-Y001 from http://www.ronayers.com/ It was a pain to drill out the original screw, hacksaw a slot into the blank head of the new screw and get adjusted just right. I ended up at exactly 2 full turns out from bottom. I put a blob of silicon on it to keep it once it was all done.

All this being said I was cruising at 100 kph today! It's amazingly smooth and fast now. I can pull against the garage wall and do a steady burnout with no issues. It's perfect! I still need new bars, drop some misc stuff off for powder coating during my next work trip, maybe put on some new exhaust if I end up finding something small and cheap, new tires, and new and fancier rear springs, but it's basically done. I hope you enjoy reading about this, LMK if there's anything you have questions on. I'm calling it the Dreamsickle, for the the orange color and the Honda Dream.
« Last Edit: May 23, 2015, 07:06:01 PM by ABray »

SUNSET KID

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #1 on: May 25, 2015, 11:50:33 AM »
    Holy Cats, you really got that figured out. Although we can't go 100 kph here in the US as we only have mph here.  :D
Finally got some pictures on of my two Symbas.

LisaRae

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #2 on: May 25, 2015, 07:50:08 PM »
Cruising at 100 kph...what does that do to your gas mileage??

LisaRae

ABray

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #3 on: May 26, 2015, 07:09:03 PM »
Cruising at 100 kph...what does that do to your gas mileage??

LisaRae

Honestly, I'm not sure yet. I ran it out today on the way home so we'll see now that I finally have a fresh tank and I was sober when I filled it :) I'm sure it could get decent mileage but the way I ride I'm sure I won't get over 65. Being able to pick my bike up by myself and throw it in a passing truck sure isn't much of a deterrent for watching my gas level. SO much different than my Harley!

    Holy Cats, you really got that figured out. Although we can't go 100 kph here in the US as we only have mph here.  :D

Thanks, I figured most were not US here so I converted. That's ~62 (give or take a few tenths) for us yanks. Fresh gas gave me another MPH today too!

mouserat

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #4 on: July 03, 2015, 10:46:27 AM »
ABray, can you please tell us a little about the climate where you live?  Altitude, average temperature and humidity would be useful indicators of how your jetting works.  It's tempting to go ahead and put the same size jets in my bike, but chances are, I'm in a different environment so it wouldn't work as well for me.  Thanks!

scottmtoland@gmail.com

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #5 on: January 10, 2016, 08:53:04 PM »
Just wanted to bump this issue, thank the op and let folks know what I've had success with. Bought Keihin jets from jets r us. 65 main and 42 slow. SKU 99101-116 & N424-74C. Binned the vapor can. (plugged the 2 holes in the intake) I dumped the exhaust air injector. (plugged the tap on the intake manifold and put a 1/2'' copper plumbing cap on the fitting on the engine). I kept the air box to keep water and such from fouling an open style filter but I oiled the foam and cut the tops off the rubber 'snorkels' on top of the air box to open things up a bit. I dug the glue out of the idle screw, cut a slot into its head and now can adjust it easily. I fiddle with it in 1/4 turns to find good idle and throttle response. Result? Awesome! Smoother and significantly more power. Such a fun bike. And extra fun now.  I'm in Los Angeles btw.

bmwzenrider

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #6 on: January 11, 2016, 11:24:36 AM »
Bought Keihin jets from jets r us. 65 main and 42 slow.


Have you been keeping track of your fuel economy before and after the change in jetting?

HelloPitty

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #7 on: January 14, 2016, 09:02:22 PM »
Oops, found the information above.
« Last Edit: January 15, 2016, 07:01:40 AM by HelloPitty »
2015 SYM Symba * 1981 Honda C70
1982 Honda CT110 * 2006 Vespa LX150
2008 Vespa GTS250

scottmtoland@gmail.com

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #8 on: January 28, 2016, 09:06:15 PM »
Update. After further experimentation I found that the slow 42 was too rich and went back to the stock 40. Running great.

Texasliam

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #9 on: March 05, 2016, 07:54:22 AM »
A little confused.   What's the source and part number fit that 40 slow jet?
 This?
http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-74C_slow_27-xxx.htm
Did sym make this carb or did it come from another manufacturer.  Keihin?  And if so does it have a specs sheet and diagram somewhere else.   It seems like the bike is all about the carberator and it's the only real issue I've had. 
« Last Edit: March 05, 2016, 08:07:02 AM by Texasliam »

bmwzenrider

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #10 on: April 16, 2016, 10:38:15 PM »
A little confused.   What's the source and part number fit that 40 slow jet?
 This?
http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-74C_slow_27-xxx.htm
Did sym make this carb or did it come from another manufacturer.  Keihin?  And if so does it have a specs sheet and diagram somewhere else.   It seems like the bike is all about the carberator and it's the only real issue I've had.


The stock Symba carburetor is a 16mm Keihin model.
The stock slow jet is a #40,
The stock main jet is a #58.

If you wish to buy replacement jets or a different size, here are the links:
Slow Jet:
http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-74C_slow_27-xxx.htm
Main Jet:
http://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_99101-116_main_round_small_and_38-xxx.htm

I am not sure if they buy them from Keihin or build it themselves, but the stock main jet in mine appears to be a genuine Keihin part. 
There is another thread in this forum where I posted an exploded view of the carburetor, but I am too lazy to go look for it right now.  ;-)

Some Symba owners have reported that their bike works better with a #42 or even #45 slow jet and a larger main jet as well.

I bought my Symba used and the previous owner had installed a #42 slow jet, but I have decided that it is too large in my engine.  I can turn the air bleed mixture screw all the way out without effect, indicating that the slow jet is too rich.

motox22a

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #11 on: April 16, 2016, 11:16:22 PM »
I ordered that 23013-Y001 Kawasaki Airscrew as the one that came in the Wrecked Symba I fixed up had been mangled by a previous
owner (And it was still glued in place)....The 23013-Y001 that I received had totally different threads and could NOT be screwed in
without damaging the carb...I wound up taking the stock screw and lopping off the damaged part and then carefully cutting a new
slot for the screw driver with a dremel ...
This was after I used GOOF OFF to remove the glue...So that was $8 wasted on this so called Kawasaki replacement air screw...
The 23013-Y001 Kawasaki Airscrew was NOT a good replacement from my experience.

vintagegarage

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #12 on: July 02, 2020, 07:21:18 PM »
Sorry to reactivate this old topic, but I found it with search, and so others might find it too in the future.  I seem to be the only one buying and restoring Symbas but here is some additional information that may help someone with questions about the Symba carb, vs. the Kawasaki ATV carb.

First, I confirmed that motox22a is correct.  The Kawasaki air bleed screw has different threads than the one on the Symba.  See this photo I took today.  The Symba is on the right, and the Kawasaki is on the left:


I also bought a complete Kawasaki carb and the air bleed screw in it is the same as the 75-23013-Y001 screw, so the number for the screw itself is not an error.    The main jet in the Kawasaki carb is an 85 and the slow jet is a 40, if my vision is correct.  Also, the connector for the wires to the bystarter is different than that on the Symba.  The Kawasaki carb may be a good replacement for the Symba carb, once the Symba carb becomes unavailable, if all you do is change the main jet to a 58, and splice the wires to the bystarter connector.  I have not tried that.  The Symba carb is still available for $290 plus shipping from Scooter Dynasty, and the Kawasaki is $175 plus shipping from Partzilla.

The Symba I have been working on had been sitting in a shed in Florida out of the rain, but nonetheless in the Florida humidity for 10 years.  The previous owner had "cleaned the carb" to get it running for sale.  It sort of ran, but idled on the main jet, and it had a stumble when accelerating after each gear shift.  The main jet said 58 on it, and the spark plug was sooty black.  I decided that it was running rich at speed, and ordered a new 58 main jet and also a 55. I never got to try the 55 main jet as the stumble went away when I installed the new 58 main jet.  I assume that the main jet had been reamed out with a welding tip cleaner sometime in it's past.   

I had to remove the glued in air bleed screw in order to properly clean the idle circuit passageways.  The end of it was already bunged up, so I ended up cutting a slot in it with a Dremel tool and after a lot of work, was able to get the air bleed screw out, and once out, I was able to cut a proper deep slot in it.  After blowing out the idle circuit passageways, and reinstalling the air bleed screw, idle was now perfect, and idle mixture was easily adjustable. 

By the way, the air bleed screw on the Scooter Dynasty replacement Symba carb comes with a slotted air bleed screw instead of the D-head screw in my original Symba carb, and the Kawasaki carb comes with a D-head screw.  That D-head is identical to the air bleed screw on the early Honda Metropolitan scooters and Honda Ruckus scooters.  The Honda tool to turn the D-head screw is available from your Honda Powersports dealer if you ask for it.  I never got the part number for it, but here is a photo of the tool.  It has a flexible end on it so you can get to the D-head screw from any angle:



Bottom line is that I managed to get the original Symba carb working perfectly, and now the engine idles well, and runs well with no stumble.  I'll put the Kawasaki carb on the parts shelf and use it if I come across a Symba with a missing carb. 

I am still buying Symbas in the southeast USA with clear titles.



gorillapimping

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #13 on: November 15, 2020, 09:52:41 PM »
This is such a great thread, I just can't help but restart it further.

I have two questions if anyone can help me out with knowledge:

1) If I change the Jets, do I have to adjust the AF ratio? or is it okay to just reJet it only. Actually I just installed the new jets without changing the AF screw, and it definitely does have more power, however it seems to hiccup for a half second when I'm about midway through the RPM range under load. Anyone have this experience? Maybe this is why I may need to adjust the AF ratio?

2) It seems that some people have had luck with the 75-23013-Y001 screw, others haven't. I've also gotten the impression that some Symbas might have different screws based on the model year, depending if the AF screw is sealed with epoxy or soldered. Anyone have any information on this? if so, which carb does the 75-23013-Y001 screw correspond with?

I'm about to embark on a trip from SF to LA through the airline highway (25 to 198 to 33) with some 200 mi without a gas station and up some steep grades. I hope the rejetting helps me with the grading. Wish me luck.

vintagegarage

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Re: Symba Carburetor Jets and Air Fuel Screw Information
« Reply #14 on: November 16, 2020, 07:11:45 AM »
First, it might be that I am the only one watching this thread who still has a Symba, but I will try to answer your questions.

1. Your first question is unanswerable without more details.  When you say, change the Jets, you need to be more specific.  What were the size of your old jets, and what are the size of your new jets?  When you say adjust the AF ratio, do you mean by screwing the idle mixture air bleed screw in or out, or do you mean changing the air to fuel ratio at speed by changing the ratio of the main jet to the slow jet?  If your question is, do I need to change the setting of the idle mixture air bleed screw if I change the main jet to a non-stock size, the answer may be yes, if you want a smooth idle.  The setting of the idle mixture screw should have no impact on the problem you describe, since your problem is not at idle.

2.  The 75-23013-Y001 doesn't fit any of my Symba carbs, so if you find someone who says it does, you need to get more information from them.  Also, I don't think is possible to solder the screw in place, so I am not sure what you mean by that.  Many had epoxy put on them at the factory.  As the previous post says, the 75-23013-Y001 screw fits the Yamaha ATV carb which is very similar to the Symba carb.  If you really want to know what is what, remove your air bleed screw and compare it to the photo in the previous post.  Please report back what you find.

Good luck on your trip on the airline highway.. please report back on how it went, with photos..

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