TG50 carb hookup...?

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guzzispree
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TG50 carb hookup...?

Post by guzzispree » Fri Nov 29, 2019 8:03 pm

I'm in the very last stage of putting my '86 Gyro back together - and I'm confused about where the various lines attach. I can see at least three hose barbs. I think I have the oil line on correctly ((I'm going to run premix, so I've plugged that hose). Can anyone point me to info as to exactly what lines attach where? I can't find it in the shop manual, nor through a search here. Is the barb alongside the oil barb simply for an overflow line? Does the fuel line attach to the rear-facing, uppermost barb? Thanks for any help!

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Re: TG50 carb hookup...?

Post by vintagegarage » Fri Nov 29, 2019 10:47 pm

Sounds like you have the wrong carb and the wrong service manual. There is no rear facing barb on the carb. If there were, it would foul in the intake pipe cover. There are plenty of photos of the carb in the service manual in section 4 and the photo at the bottom of 4-8 shows the main fuel inlet barb on the side of the carb. Compare your carb to the one in the service manual and let us know what you find.

The service manual is here:

http://www.motorscooterguide.net/manual ... Manual.pdf

In the exploded view of the carb, on page 4.0, the barb at the top on the side of the carb going away from you is the main fuel inlet. The smaller barb between the air mixture screw and the idle speed screw and pointing at you is just a vent/overflow tube, and the barb at the bottom of the carb float bowl pointing toward you is the drain tube. Gasoline flows out the drain tube when you open the screw right next to it on the bottom of the float bowl.

In the exploded view on page 5.0, the upper hose is the fuel hose, the lower is the oil hose. There are no barbs on the carb for an oil connection. The oil hose out of the pump goes to the barb on the intake manifold.

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Re: TG50 carb hookup...?

Post by harleyracer59 » Sat Nov 30, 2019 2:57 am

sounds like he has a nb50 aero carb

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Re: TG50 carb hookup...?

Post by guzzispree » Sat Nov 30, 2019 11:32 am

Gyro carb.JPG
Gyro carb.JPG (92.89 KiB) Viewed 212 times
vintagegarage - thanks for putting so much work into this. I have the same manual you've provided a link too...I've looked at all the references you've provided...and what I have isn't what I'm seeing in the pictures. Without pulling off the rear fender unit for a more complete look at my carb, here's the best I can come up with in terms of a photo. This picture was taken from the right side of the bike. The clear hose I'm touching, is what I called my rear-facing barb. I'm assuming it's the fuel hose. The blue hose was an oil line going off to somewhere (the oil pump?). Just to the left of that blue hose, is a barb that I can't figure (though the more I look at it - the more it doesn't look like a hose barb, but maybe some sort of open tube that just sits there). Is this even the correct carb for a Gyro?

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Re: TG50 carb hookup...?

Post by guzzispree » Sat Nov 30, 2019 11:34 am

I just realized - the "blue line" I've referred to, doesn't show up as blue in the photo. It's the hose coming off the fitting in the right hand lower corner of the photo. Sorry for the added confusion.

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Re: TG50 carb hookup...?

Post by vintagegarage » Sat Nov 30, 2019 11:41 am

Somebody has chopped up your intake cover so that the rear facing barb on your non-TG50 carb can be used. Your carb is clearly not a TG50 carb..

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Re: TG50 carb hookup...?

Post by vintagegarage » Sat Nov 30, 2019 12:16 pm

My bet is that your carb is something like this one:

https://www.ebay.com/itm/1985-1986-HOND ... SwG-1WukUK

While the listing claims that it is a carb for a TG50, it clearly is not.

This might be a TG50 Carb:

https://www.ebay.com/itm/Honda-Gyro-S-T ... SwI-ddOeqr

The main fuel nipple is missing, but the same passageway that a rear facing barb would go has been plugged by the factory with a "BB". The main barb feeds the same passageway, but comes in from the left (when viewed while you are sitting in the seat facing forward). You can see where it goes in the second photo. It is the only threaded hole in that photo. What doesn't look right with this carb is the size and position of the idle mixture screw hole when compared with the blowout (Page 4.0) in the workshop manual. The vent near the idle speed and mixture screws also doesn't have a barb, but rather is just a tube. The pictures on Page 4.6 in the workshop manual show the position of the idle mixture screw to be more like the one in the ebay ad, than the one in the blowout, however. I do not remember the idle mixture screw being larger in diameter than the idle speed screw, but it may be.. I just don't remember. I think that this carb is very likely a TG50 carb.

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Re: TG50 carb hookup...?

Post by guzzispree » Sat Nov 30, 2019 1:47 pm

vintagegarage...I removed the muffler/fenders to get a more complete look at the carb. Yeah - I don't think I have an OEM carb on there...it has "I S O Performance" cast onto it - "PA" on another part of it. No "Keihn Japan". I think I have the multitude of hose connections figured - the confusion was a result of some unclear thinking. There's an hose barb on the base that's clearly an overflow pipe connection. the "three" barbs on the top - one is NOT a hose connection - seems plugged, as you described. One, comes off the bystarter chamber Which leaves the third clearly necessary as the primary premix supply. Part of my confusion was not understanding that the oil pump fed into the intake, NOT the carb. Dumb me. So I have only question - doesn't the fuel line need a fitting that splits the gas feed to BOTH the bystarter and the fuel bowl? Thanks for all your very patient and able help.

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Re: TG50 carb hookup...?

Post by vintagegarage » Sat Nov 30, 2019 2:02 pm

There is no thinking about it.. you don't have a TG50 carb. The dead giveaway is the location of the main fuel barb. It must be at the side, and not at the back.

You also have some sort of Rube Goldberg clamp holding in your rear facing barb. That, plus cutting away the intake cover raises red flag as to the quality of the PO's mechanicing skills.

And no, you don't need a fitting to split the fuel. The bystarter bowl fills through a tiny hole at it's base. The main fuel feed fills the main float bowl as fuel passes through the float valve. As the main float bowl fills, gasoline leaks through the tiny hole at the base of the bystarter bowl, filling up the bystarter bowl.

Time for someone else to jump in here.. I can help you with understanding a TG50 carb, but not the carb you have. I don't understand either why you chose to use premix instead of the Honda oil pump.. that makes no sense to me. Maybe meatball or harleyracer can take over..

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Re: TG50 carb hookup...?

Post by guzzispree » Sat Nov 30, 2019 10:20 pm

...not using premix? Only reason, was my not wanting to trust the pump. In terms of the carb. Any suggestion on what carb to use? My guess is, a $25 Chinese carb would probably be a poor choice. And a used OEM carb looks like it has no parts support.

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Re: TG50 carb hookup...?

Post by harleyracer59 » Sat Nov 30, 2019 10:29 pm

the insides of the gyro carb are just like the aero af05e except that fuel inlet. I have an aero carb on one of my tg50s. I just didn't install that manifold cover that the PO of your gyro cut... and any spree, aero, elite up to 94 will bolt right up. on the tg50 a rear facing inlet isn't that big of a deal. on the nn50 the muffler is right there backed up against the carb so you really do need that side facing inlet

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Re: TG50 carb hookup...?

Post by guzzispree » Sun Dec 01, 2019 10:50 am

I've learned plenty here - thanks for all your help! Just one last question...that barb situated near the base of the carb slide (you can see it in the lower right corner of my photo - it has a length of hose pushed onto it that I added for no particular reason)...what in the world attach to that barb? I have my fuel line attached; my overflow line, also. I can't figure what that barb is used for.

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Re: TG50 carb hookup...?

Post by harleyracer59 » Mon Dec 02, 2019 12:31 am

that is also a drain/ vent for the carb bowl. don't plug it. you can leave your hose on there as long as the other end is open.

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Re: TG50 carb hookup...?

Post by nateberrier » Mon Dec 02, 2019 12:49 pm

harleyracer59 wrote:
Mon Dec 02, 2019 12:31 am
that is also a drain/ vent for the carb bowl. don't plug it. you can leave your hose on there as long as the other end is open.
Correct me if Im wrong, but hes talking about the one with the hose already on it, which would be for oil injection. The barb to the left of that is the vent, which doesnt have the hose attached. The pipe on the housing for the slide is for oil injection, some of the motors using PA carbs (AF16 for example) would use that to inject oil. Others would have oil injection from the intake barb and that barb would need blocked off. The other barb that is cast aluminum is just a vent that could have a down turned piece of hose attached.
https://www.treatland.tv/OEM-honda-NB50 ... a7-701.htm
1986 Aero White -- Af16 Swap + Keli Var + NCY Pipe
1985 Aero Red -- Af05 Malossi BBK + Keli Var
1985 Aero Red -- Parts bike that will be fixed soon

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Re: TG50 carb hookup...?

Post by harleyracer59 » Tue Dec 03, 2019 9:23 pm

I think you might be correct. its hard to tell from that angle. that barb looks more forward than the nb50 carb. that carb has to be some kind of hybrid? because the dio carb has a wider bolt pattern than the others. both gyro models, both aeros and spree all have the same bolt spacing.
in stock configurations, the gyro's have an oil injection barb on the manifold. do if you run oil to the carb or go premix, make sure the barb on the manifold is capped off.

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