Ta200 Carb Tuning

[AllanB]

I have been trying to figure out whether the fuel/air mixture screw on my Phantom, has an air screw or a fuel screw.

Fuel screws are normally located at the engine end of the carb, air screw at the filter end, which would make the the Phantom carb be of the fuel screw type. However, the carb make is, I believe a "Mukuni" type, which is an air screw design.

Most confusing,

Does any know for sure, I am hoping it has an air screw or my carb is buggad.

Also does anyone know the normal setting, or base point?

[NeverSure]

Your Mikuni has both. First, make sure your air filter and fuel filter are clean.

The air screw is the one turned by a screwdriver, probably a phillips. The fuel (pilot jet) is below it, turned with a small wrench.

Both turn in (tighten) to lessen flow and turn out to increase.

You really should google for some Mikuni tuning instructions. You have a slide valve with numbers, and the number you set to should match the number you choose for the fuel needle valve. You also have a choke setting which could mess up everything. Then it's also easy to set the float level, which could also mess up anything else you do. You also could have some dirt in the jets.

It really isn't difficult and I can think of no better carb than the Mikuni. Just don't tell the Harley owners that their trick Mikuni carbs are Japanese, hahaha.

In sum, I would say to either google and get some good step by step, or take it to a good shop.

[AllanB]

"In sum, I would say to either google and get some good step by step, or take it to a good shop". Are you kidding the bike shops around here are crap, they don't have torque wrenches or feeler gauges, or bike stands, they tighten chains like a bow, don't clean things properly, etc.... It is too hot for me to work here, but I have to now, as I can't rely on anyone. I just got it back from a major overhaul and the plug is heavy black from driving 5km, so way too rich.

Now looking closely at the carb, it only has one adjustment and as I stated previously there is a contradiction between it's position, of being next to the engine and it being an air-screw. I found this page regarding tuning, but it covers parts which are presumably already preset by Honda. http://www.iwt.com.au/mikunicarb.htm

Is it not the case that the fuel screw is not preset?

[wantan]

Stupid question: Isn't it a Keihin carb on the Phantom? Guess it would be useful to name brand and model. Or maybe even a picture to make things clearer

Edited February 6, 2013 by wantan

[NeverSure]

Please look again at fig. 2. There's a pic showing both the air adjustment and the fuel adjustment jets. In the text it mentions both of them, and also that slide valve I told you about. You just aren't seeing the fuel valve. It's below the air valve which adjusts with a screwdriver, but adjusts with a small wrench.

Quote:

"Both the pilot air screw and pilot jet affects carburetion from idle to around 1/4 throttle. The slide valve affects carburetion between 1/8 thru 1/2 throttle..."

Where are you located? There was a thread saying that an independent opened a shop in Chiang Mai and said he's really good.

You really need a better "manual" than that site. You need something with pictures, and step by step.

[NeverSure]

Stupid question: Isn't it a Keihin carb on the Phantom? Guess it would be useful to name brand and model. Or maybe even a picture to make things clearer

No, that's a good question and may be his problem although Mikuni is really popular aftermarket.

[BSJ]

So there are no mistakes....can you photograph the carby and post it here? Closeups of each side.

[AllanB]

How do I post images?

[wantan]

Reading the help may help?

http://www.thaivisa....lp&do=01&HID=24

EDIT:

Did you click on the "More reply options" button? Then you should get an upload function titled "Attach Files".

Edited February 6, 2013 by wantan

[AllanB]

Yes, of course, didn't scroll down to find this...doh!

When I got the bike back, the plug was black, this screw was 1 turn out, just put a new plug in took it to 3 turns out and still sooty black after 5km.

[NeverSure]

It says Keihin right on it. Let's start over.

[CBR250]

Please don't write off all Thai mechanics. There are lots of shonky ones, but there are some good ones too. Sure, many don't have the sophisticated equipment of western workshops, but they make up for it with resourcefulness born from experience.

My favourite Thai mechanic is a gem. Works on many big bikes as well as scooters. Excellent with carbs too - if you need some help and are in the Chiang Mai area pm me and I can provide contact info. One of his best attributes is that when he is not too busy he is happy to let you sit and learn how to set up your own carbs while he fixes them.

[NeverSure]

Edit. I'm going to step back. I don't know those carbs.

Edited February 6, 2013 by NeverSure

[wantan]

Allan, iirr you reported that you need 1l oil on 1000km. Is that still an issue or has it been fixed?

I dnt know a lot about adjusting carbs. But maybe there is also a screw from the bottom. But you should not turn any screw without knowing what its for. And you should write down the initial settings when you start, so you can go back to zero

[VocalNeal]

I think it is a Keihin CVK so at the front (engine side), underneath in the centre is a screw. It is a plug. Under that plug is the pilot jet. On some bikes there is, literally, not much room for adjustment.

Oops sorry took too long so the screw is not at the bottom it is the one on the (engine side) in the first picture.

Start bike and go for a ride to warm it up. Stop the engine.

Screw that screw in very slowly and very gently and note how many turns it takes to stop. Usually between 7/8 of a turn to 1 1/2. Write this down for future reference. Screw it back out to where it was.

Go around to the otherside of the bike. Start the engine and set idle using the adjustment under where it says Keihin to a bit faster than normal. (turn the screw in or upwards)

Go around the other side of the bike and adjust the screw (in the 1st photo) both in and out about 1/8 turn at a time until you get the fastest idle speed, then turn in the screw in a very little (1/16 turn) until the idle speed drops a very small amount , then adjust the idle speed back to normal.

Edited February 6, 2013 by VocalNeal

[AllanB]

I found this vid

looks helpful.

[NeverSure]

OK, the first thing I'd do with it running so rich is to see if the choke is actually wide open when you set it to "off." I can't imagine the idle circuit doing this blackening thing so fast, but...

Take that black hose off between the carb and the engine. Turn the choke off and on and look into the hole in the carb to be sure the choke opens clear up when off. There is nothing a whole lot more frustrating that to have a choke on or partly on when you turn it to off. If it's a problem, it's just a linkage adjustment. That now, would turn your plugs black real fast.

[AllanB]

OK, the first thing I'd do with it running so rich is to see if the choke is actually wide open when you set it to "off." I can't imagine the idle circuit doing this blackening thing so fast, but...

Take that black hose off between the carb and the engine. Turn the choke off and on and look into the hole in the carb to be sure the choke opens clear up when off. There is nothing a whole lot more frustrating that to have a choke on or partly on when you turn it to off. If it's a problem, it's just a linkage adjustment. That now, would turn your plugs black real fast.

There isn't a black hose between carb and engine, just a plastic manifold, the plastic hose is between carb and airbox. See 3rd photo. In order to remove this I must first remove the plastic hose and then the carb from the engine. Is that what you mean?

Edited February 6, 2013 by AllanB

[NeverSure]

OK, the first thing I'd do with it running so rich is to see if the choke is actually wide open when you set it to "off." I can't imagine the idle circuit doing this blackening thing so fast, but...

Take that black hose off between the carb and the engine. Turn the choke off and on and look into the hole in the carb to be sure the choke opens clear up when off. There is nothing a whole lot more frustrating that to have a choke on or partly on when you turn it to off. If it's a problem, it's just a linkage adjustment. That now, would turn your plugs black real fast.

There isn't a black hose between carb and engine, just a plastic manifold, the plastic hose is between carb and airbox. See 3rd photo. In order to remove this I must first remove the plastic hose and then the carb from the engine. Is that what you mean?

OK, The more I look, the more I think that just your basic model CV carb, and they are way easier to tune than a Mikuni.

So if there's a rubber hose on your left (toward the rear) then see if you can remove that. What I think you need to do is to look into the carb, into that hole, and see if the choke is completely open, leaving no restriction in the hole thru the carb (the venturi) when the choke lever indicates the choke is off. You may have to give it wide open throttle to see the choke. I can't recall. Just make sure that at wide open throttle (engine off) and choke clear off, there is a clear round hole through there with nothing more than some plates turned sideways. If that venturi is blocked at all, it won't get air and it will run rich and give you your problem.

A plugged air filter or any restriction in that intake area of the filter would do it too.

In everything when repairing, always start with the easiest and most obvious first before you tear everything down. This is just #1.

[NeverSure]

AllenB, for sure quickly blackening plugs are a sign an otherwise healthy engine is running too rich. It's either getting too much fuel or not enough air or a combination of those.

This is why I keep repeating check the air cleaner and passageway, check that the choke isn't cutting off air - see if anything could be blocking air.

The next suspicions will go toward too much fuel which could be something like float level or bad float or a bad needle valve that's attached to the float or some dirt keeping that needle from closing or...

If it was running rough and hot and the plug was white, we'd be looking at a lean condition but that just isn't happening here.

[NeverSure]

AllenB, I'm all bad and should have stayed out of this. I forgot that your carb doesn't have a choke. It has an enrichener valve, so when you pull the "choke" you're actually opening that valve.

This is a carb I don't know and I'm sorry. I'm outta here. Can't help.

[VocalNeal]

Allen,

Are you using the correct spark plug? NGK DPR8EA 9 ? Could it be that someone has installed a convenient one not the correct one?

Yes the enrichment device could be stuck open but in Thailand I suspect as from your pictures there is no enrichment device as it not necessary here. ( manual says there is but... TIT) If there is one take it out and inspect the rubber end. But if it was stuck open the bike would run rough, when hot. Also if there is one just operate it a few times and make sure it is pushed home.

As has been said . Air filter clean and check.

[AllanB]

AllenB, for sure quickly blackening plugs are a sign an otherwise healthy engine is running too rich. It's either getting too much fuel or not enough air or a combination of those.

This is why I keep repeating check the air cleaner and passageway, check that the choke isn't cutting off air - see if anything could be blocking air.

The next suspicions will go toward too much fuel which could be something like float level or bad float or a bad needle valve that's attached to the float or some dirt keeping that needle from closing or...

If it was running rough and hot and the plug was white, we'd be looking at a lean condition but that just isn't happening here.

Lifting the jet plunger up and opening the throttle butterfly, I can't see anything, so will have to remove the carb, but I can already see the manifold is only effectively held on with one bolt as the washer is missing from the bottom bolt and is doing nothing except retain the gasket.

Hells-bells...........

So I removed the carb and the choke control doesn't operate a butterfly valve, it operates something in the fuel system within the carb. In which case the cold start mixture is increased by increasing the fuel, rather than restricting air flow.

Looking at the choke cable, the outer part is broken and I think there lies my problem.

[AllanB]

AllenB, I'm all bad and should have stayed out of this. I forgot that your carb doesn't have a choke. It has an enrichener valve, so when you pull the "choke" you're actually opening that valve.

This is a carb I don't know and I'm sorry. I'm outta here. Can't help.

That's okay mate, all ideas are welcome and i understand that all carbs are different, I assumed that all mixture screws were on the fuel, never heard of an air-screw, I have now. Thanks for your help.

As long as I get it fixed, that is the important thing.

[NeverSure]

AllenB, for sure quickly blackening plugs are a sign an otherwise healthy engine is running too rich. It's either getting too much fuel or not enough air or a combination of those.

This is why I keep repeating check the air cleaner and passageway, check that the choke isn't cutting off air - see if anything could be blocking air.

The next suspicions will go toward too much fuel which could be something like float level or bad float or a bad needle valve that's attached to the float or some dirt keeping that needle from closing or...

If it was running rough and hot and the plug was white, we'd be looking at a lean condition but that just isn't happening here.

Lifting the jet plunger up and opening the throttle butterfly, I can't see anything, so will have to remove the carb, but I can already see the manifold is only effectively held on with one bolt as the washer is missing from the bottom bolt and is doing nothing except retain the gasket.

Hells-bells...........

So I removed the carb and the choke control doesn't operate a butterfly valve, it operates something in the fuel system within the carb. In which case the cold start mixture is increased by increasing the fuel, rather than restricting air flow.

Looking at the choke cable, the outer part is broken and I think there lies my problem.

That would do it all right. Yes, in an earlier post I apologized and said I had forgotten that your carb doesn't have that choke butterfly that I asked to look for. It does indeed have (or should have) and enrichener valve which instead of cutting off air as a choke does, adds fuel. Either method enrichens the mixture ie more fuel to air ratio.

VocalNeal is right on. If that enrichener is stuck open, then you'll get a bunch of fuel you don't want. It will go unburned and cause the black and fouled plugs.

You have probably found the problem. If the "choke" cable controlling the enrichener is broken in any way, that could be the whole deal right there. It probably is.

[AllanB]

Now bearing in mind the Khon Kaen Honda dealer who screwed the bike up (and I told them so) is now not my very best friend, they will probably rip me off for the part and I don't like dealing with shitbags anyway. Are there any mail order places I could get a choke cable assy, preferably run by a non-Thai, so I don't end up with a toilet roll holder?

[wantan]

Our sponsor Sumet?

LOL

Edited February 6, 2013 by wantan

[NeverSure]

I can tell you that this carb was standard equipment on Harleys from 1989 through the 90's until they started going with fuel injection. Even then they stayed with a carb model for several years into the 2000's. It's a common carb. These bike manufacturers mostly didn't make their own carbs so you'll see a lot of those CV style carbs around.

I know nothing about your area but those are my hints, and what's wrong with buying a used part from a Thai who parts them out?

[VocalNeal]

Is the enrichment device held shut with a spring on the cable or is the spring internal under the nut that holds the plunger inside the carb? If as I suspect the later you can take the "choke" cable off and throw it away. It doesn't get cold enough in KK to ever need to use it?

Must have a new one where is your nearest Honda main dealer?

[NeverSure]

Is the enrichment device held shut with a spring on the cable or is the spring internal under the nut that holds the plunger inside the carb? If as I suspect the later you can take the "choke" cable off and throw it away. It doesn't get cold enough in KK to ever need to use it?

Must have a new one where is your nearest Honda main dealer?

I think the enrichener wants to stay closed or "off." To activate it when the bike's cold, you pull the cable. The cable actually has a tension adjustment to cause it to stay put when you pull the "choke" "on."

The reason I've never been into one is because I have a fabulous indy who tricks them out. There are a couple of places to drill holes, and of course there is jetting... All comes with leaning a bike out with freer exhaust and intake and bigger valves and more duration etc. So the indy has a tail pipe probe for mixture and a dyno for power, so I would be a fool to mess with one.

But, from running them I do know that the enrichener wants to stay off and you have to pull it on against spring tension, and occasionally adjust the friction to keep it on.