Carb question

[mikeyger]

I was reading on another site where a person was told he could put a harley cv40 on a 1500 and plug some vacume line or something to do away with the tps. Is this so I do not need to do this because i got mine tuned right finally but was hoping Mac or mas Tequelia could answer this question Thanks for your time

[MAS Tequila]

Never heard that one before.

But then I don't pay much attention to carb topics.

MT

[macmac]

I have never knowingly seen a carbed Nomad. I might take a wild guess and say the vac line runs the reed valve the same way it does on injected Nomads. But i don't know that as fact.

My take on the cv 40 is it means cv carb type (constant velocity) and 40 mm bore. I have no idea if the kawii carb is a cv carb, and or what the bore diameter is.

I might guess other carbs can be bolted to a Nomad. Long ago I bolted SU type 4 carbs from English sports cars to harleys. The Su type 4 is sort of the grand pappy to Cv carbs. Back then these were 1 and 3/4 inch bore in the bore size matching HD engines best. Converting that to metric gets 43 mm, so 40 mm is in the balll park.

So far I 'hear' the kawii carbs have real accelerator pumps. I have never seen a cv carb with any accel pump before, not that it can't be done. I 'hear' the carbed Nomad have a electric fuel pump, and don't really understand why. The old way is graveity alone is enough to fill a carb float bowl.

With all this yakkin, I don't really understand what the question is.

Before I did do anything with any vac tubing line, I would want to know where that tubinmg goes. If it just goes to the 'Meducas head' a term I coined for what the thing looks like, a vac pod with 1 vac line that controlls the larger air tubings to just Reed Valves, then that can be blocked on a kawii carb body, and all that junk can come off the bike.

If that vac line is tied into the ECU for spark, then that is another thing entirely. Some very primitive ECU's do have vac lines to them. The only one I happen to be familar with is the one used on 1986 Dodge 3/4 ton vans with 318 engines, since I own one.

[mikeyger]

Mine has an accelerator pump and is a cvk keihin and is water cooled and has a tps that has something to do with the timing. Harleys also has a keihin cv and I did not think it would work without a tps on it That was the question. I also have a electric fuel pump its a 1999 model Thanks men for your time Have a good weekend!

[macmac]

Give that vac line a look some time from end to end, and tell us where it goes and what's hooked into it.

[mikeyger]

Mac I will do that.This something I was wondering about I was thing about a replacement carb at one time because after I took mine to the dealer and then a local shop and lots of dollars and it keep flooding out I finally just took it apart several times and replaced all the parts I finally got it set up right. A new one is close to 7 hundred dollars > I really don't understand how the tps works and I figured I would ask you. Thanks Mac

[macmac]

I don't know how this one works, but if you tell me where that vac line goes I might.

I suspect low throttle tells the ecu to retard ignition time, and because at low throttle there IS vacuum. At wider openings there is less vac which tells the ecu to allow advancing timing.

'IF' there is a vac pod with a switch or rehostate slider of one form or another and some wires that just might be how this is set up. Some set ups have a vac pod mounted directly to the ecu. In this case the ecu is just a spark controll no matter what sized it is.

This can also be more similar to injected tps where the throttle plate opening is measured in a similar way, and the signal usually in milivolts is sent to the ecu for the same things.

On injected systems that are electrical injectors the ecu will also controll injector valve openings for more or less fuel depending.

In your case if the carb was flooding, that usually means the needle and seat inlet have something lodged, and or is worn, so fuel can go by, also a sunk or sticking float. If for some reason the fuel pump was over powering the system with too much psi, that could over power a needle and seat inlet as well.

This is just generalized basics, for many vehicals and just sayin' since I don't know any better.

[mikeyger]

Mac it was trash or something I chanded fuel line and filter It would run ok for a few days and the dealer could not figure it out I change =d the line coming from behind the carb going to the carb The judge bob aid to change the float valve It has been ok now for 4000 miles or more After I done all the pulling on and off and adjusting mixture screw and got it running good I smelled gas and the only thing I did not change was the diaphram and sure enough that was torn But all is well now I wish I new you a few months ago! It says as the throttle is opened and closed the IC igniter recieves throttle angle input to determine ignition timing Huh!

[macmac]

"""It says as the throttle is opened and closed the IC igniter recieves throttle angle input to determine ignition timing Huh! """

Ok, as I still don't know it seems the vac line may not be any part of the ignition timing at all. I sort of suspect it isn't but don't know that.

I thing the tps is a varriable sliding rehostat, but I don't know that either. But if it is there will be a little black box on the throttle plate linkage next to the carb and probably screwed to the carb. Voltage goes IN and comes back out. Probably battery volt at charging goes in and lesser voltage comes out. But it could be milivolts goes in and even less come out.

In the tps there is probably a resistor, and this reduced voltage is free to change in value.

This occures depending on where the throttle plate shaft is in degrees measured in a circle. This of course is limited toaround 90 degrees, since the throttle plate closed is near straight up, and full open is around that 90 degrees. The IC igniter changes when spark time will be.

At idle it will be sparking at less crank degrees that at 5,000 rpm.

IC igniters in general either work or they don't, so the problem is much more likey to have been crudling setting up house keepping in the fuel line above the needle and seat fuel inlet valve. This is common as dirt, and dirt of one kind or another causes this.

The dirt can be from bad gas, a fuel screen breaking down, the tubing itself breaking down, and perhaps remants of a pencil some tech used to stuff up the fuel line, that broke off, or left a splinter from.

I had hell to pay for a pencil point broke off in a fuel line that jammed the needel and seat on a vw bug before. Car went great to 35 mph andf then just accted up bad. Some other tech not in out shop did that feat and the car was brought to me, and I had a bad time finging that pencil point. It still had wood on it and would float back towards the gas tank, and catch up inside the tubing of the fuel pump.

I had another guy turn the key to crank the engine holding the fuel line over a bucket and that pencil point spit right into that bucket.

You have/had something smaller and speck of sand it plenty enough to jam a float at the needel and seat. I have seen several bikes with multicarbs do this too, with bits of the fuel tank strainer screens as the cause. All busted up these bits look like little white hairs.

Neoprean tipped needles can take a set, and fuel will run right around that sort of dent.

Some bras seats get brass disease, a sort of dis-coloring where copper is escaping from the brass which is an alloy. The slight loss of copper can change the shape of the valve seat and gas will run right around that too.

Gas is thinner than water and will need a seal near to air tight.

[mikeyger]

Thanks for all your time Mac. Your right there nothing connected to the carb Just the tps and its wires and one vacume line on the top. Later today I am gonna go see where that vacume line goes.

[macmac]

I am just guessing. I have seen a few things in the past, ans these could be hooked up either way.

[mikeyger]

I talked to the judge (Bob) tonight so I asked him about this carb thing. He said without the tps pluged in it would be like the timing would be advanced all the way He said you could run a carb without the tps and therfore could use a keihin off a harley if you wanted to. He as others do not use there water cooling that goes to the carb. If you remove this do not just plug up the lines but run a line from the pump to the head He said you would have to run hitest gas if you use a carb with no tps Also like you said is that if your bike will run on regular gas you should use it It is better because of the carbon build up from hitest like i have been using I am going to try the lower octane like you suggested and will see how it does

[macmac]

The NO tps would be a problem in full spark advance all the time. I am not sure how one would get around that problem either. Starting would be harder for sure. I would think the tps would need to be altered to work or another whole style of ignition and a way to make the advancer work would be a must do.

Most of the time the spark is not any where near full advanced. Machining in a older form of parts for ignition would be a very steep price.

[mikeyger]

Mac So I agree that the advice given to that guy should not be taken and his carb is a good carb and he may just need someone to set it up for him Thanks Mac!

[macmac]

I thought we were just discussing the carb. Had no idea you were working with another guy, but no he wants a kawii carb on that bike for sure. Making ignition advance work any other way will cost more than a new carb.

Please refresh me on this guys problem. I thought it was you, and had the problem fixed with a removed goober in the needle and seat.