My bike carb converted 4AGE AW11

[jondee86]

Most people find that the 4AGE likes to idle slightly on the rich side, so I usually aim for around 14.2 - 14.3 AFR with a fully warmed up engine. You can get the engine to idle much leaner, but it is liable to be unstable and not as smooth. At 18:1 AFR you are close to the point where the engine will no longer run because the mixture is too lean to support combustion.

Knock is primarily governed by ignition timing and load. Provided you have conservative ignition timing and don't place a high load on the engine at low rpm, you should not have a problem with knock. Using the gears to make sure the engine is not lugging (struggling) under load, is always good practice.

As engine load increases and the engine is working harder, the mixture needs to become richer and the ignition will advance as the engine speed increases. These are the values that you need to tune. If you keep your ignition timing conservative and your mixture slightly rich, you should not have to worry about knock.

At idle there is almost zero load on the engine, and about the only way you could make it knock would be to snap the throttle wide open. Then, if you have too much ignition advance at idle, you might get a couple of knock counts just as the engine starts to accelerate and struggles to overcome its own inertia.

Cheers... jondee86

[mr2mk1hero]

Thanks for the tip jondee.

So I managed to get the tacho to work. Kinda. Here it is: https://www.youtube.com/watch?v=ORNW...ature=youtu.be

The needle bounces a bit, and the rpms on the tacho seem to kinda lag behind the actual rpms, maybe. Disregard the knocking that's a kitchen range hood hose on my exhaust so I don't suffocate. Disregard the clicking, that's my bike carb fuel pump. The engine dying half way through the video happens when I turn off the choke.

Here's the weird thing, I got it to work with the old setup. This one:

I'm obviously on the right track, now it's a matter of figuring out whether this can be improved. All suggestions are welcome .

[jondee86]

I can see how that circuit is working, but I wouldn't be prepared to say that it was a good idea or predict how well the tacho will work or for how long. This is the circuit suggested by NODIZ in their product manual, which is in line with the suggestions from several other sources...



I'm not an electronics engineer, so I can't do the calculations to figure out what is really happening in your circuit, or suggest improvements. If the tacho is working well enough to be useful, you could probably leave it as it is while you are tuning the carbs. But I think it would be a good idea to make the signal converter with the transistor to install when you have the time.

Cheers... jondee86

[mr2mk1hero]

I can see how that circuit is working, but I wouldn't be prepared to say that it was a good idea or predict how well the tacho will work or for how long. This is the circuit suggested by NODIZ in their product manual, which is in line with the suggestions from several other sources...



I'm not an electronics engineer, so I can't do the calculations to figure out what is really happening in your circuit, or suggest improvements. If the tacho is working well enough to be useful, you could probably leave it as it is while you are tuning the carbs. But I think it would be a good idea to make the signal converter with the transistor to install when you have the time.

Cheers... jondee86

So I tried this too. And it seems to work perfectly so far, the needle behaves exactly as it did stock while trying to start the car. I haven't seen it in action as I haven't been able to start the engine again for some reason, even though I haven't changed anything since it ran last time. Engine sputters and almost manages to start but can't "catch".

I did change the bike fuel pump but I have checked that fuel delivery is good, there's fuel in the carb float bowls. I took a look at the spark plugs, and here's the weird thing, cylinders 1 and 4 looked fouled, cylinders 2 and 3 looked great. I then took a look through the spark plug hole onto the pistons, and pistons 1 and 4 have carbon deposits and look dirty. Piston 2 is absolutely spotless, like the day I installed it. Piston 3 is also really clean but not as perfect as cylinder 2.

Since I first started the engine here's what I have been doing with the jets. I started out with 45 pilot, 160 main, 1 factory shim and 1 thick nylon shim on jet needle. I ran very rich like this at idle. 9-10:1. So I installed 40 pilots and installed only 2 thin factory shims on the jet needle. Ran stupidly lean after this. 15-16:1. So I went back to 45 pilots and 3 thin factory shims on the needle. I ended up at 13:1 on the idle, which is the best result so far. I adjusted the throttle to be part open at idle and I am idling around 1500 rpms, so it isn't plain old idle. These are all values of cylinder 4 exhaust runner only as that's where my wideband sensor is right now until I build a custom exhaust manifold.

I am now thinking to leave the 45 pilots in cylinders 2 and 3 and go with 42 pilots in 1 and 4. I am leaving the three factory shims on the needle and getting 165 and 170 main jets as the afrs go lean when I blip the throttle a bit more. I haven't touched the float bowl height or the idle mixture screw and the carbs are all synced.

[jondee86]

I adjusted the throttle to be part open at idle and I am idling around 1500 rpms, so it isn't plain old idle.

Don't know if this will help, but carbs rely on vacuum to suck gas into the airstream for vaporisation. They are not like EFI where the fuel gets injected under pressure. So cracking the throttles open may have reduced cranking vacuum to the point where the mixture is not rich enough to fire the engine properly ?

Just by way of an aside, my Honda XR650R motorbike would not start if the throttle was open by any amount. It would only start with the use of the choke lever and/or the air screw, depending on how hot the engine was when kicking it over.

Cheers... jondee86

[davew7]

First you need to verify the float level and seat function on each carb. My guess is that the main problem between the cylinder mixtures. Initial off idle enrichment is controlled by the slide cut-away. Richer mixture would require a lower/smaller cut-away. You can also try blocking off the top one or two holes on the emulsion tubes to enrich off idle condition. A temporary fix would be to put a small metal band around the top holes to block air and enrich the mixture, to see if that improves the condition. Davew7

[mr2mk1hero]

Don't know if this will help, but carbs rely on vacuum to suck gas into the airstream for vaporisation. They are not like EFI where the fuel gets injected under pressure. So cracking the throttles open may have reduced cranking vacuum to the point where the mixture is not rich enough to fire the engine properly ?

Just by way of an aside, my Honda XR650R motorbike would not start if the throttle was open by any amount. It would only start with the use of the choke lever and/or the air screw, depending on how hot the engine was when kicking it over.

Cheers... jondee86

So I closed off the throttle completely and opened the choke, but it didn't start, sounded like it had less of a chance to start then before. Replacing the spark plugs and trickle charging the battery didn't help either. I am considering spraying starting fluid into the intakes to try and get it to start, but am also thinking to remove the carbs and install new jets that will arrive soon and take another look at everything and then put them back on and try again, because even if I manage to start it with starting fluid I really won't gain anything as I definitely need to re-jet.

[mr2mk1hero]

First you need to verify the float level and seat function on each carb. My guess is that the main problem between the cylinder mixtures. Initial off idle enrichment is controlled by the slide cut-away. Richer mixture would require a lower/smaller cut-away. You can also try blocking off the top one or two holes on the emulsion tubes to enrich off idle condition. A temporary fix would be to put a small metal band around the top holes to block air and enrich the mixture, to see if that improves the condition. Davew7

I haven't verified the float level as I assumed it was good but will do that. The folks at six sigma jets from where I got my jets suggested to block off the air jets on the front of the carb to get a richer mixture off idle. Here's a picture from the manual that came with the jet kit:

[jondee86]

You are at the start of a pretty steep learning curve with your carbs Were I in your position I would be looking for a motorcycle shop or mechanic to help me get the basics sorted, and get the car to the stage where it can be safely driven.

Finding a workshop that can dyno tune your car might also be a bit of a mission, as these days the tuners work almost exclusively with fuel injection and electronic engine management. You may have to end up doing a lot of your tuning on the road, searching for the settings that give you the best performance.

But when it is all done, and you are driving around with a grin from ear to ear, you will have learned a lot of new stuff and have the satisfaction of knowing that you have done something different

Cheers... jondee86

[mr2mk1hero]

You are at the start of a pretty steep learning curve with your carbs Were I in your position I would be looking for a motorcycle shop or mechanic to help me get the basics sorted, and get the car to the stage where it can be safely driven.

Finding a workshop that can dyno tune your car might also be a bit of a mission, as these days the tuners work almost exclusively with fuel injection and electronic engine management. You may have to end up doing a lot of your tuning on the road, searching for the settings that give you the best performance.

But when it is all done, and you are driving around with a grin from ear to ear, you will have learned a lot of new stuff and have the satisfaction of knowing that you have done something different

Cheers... jondee86

I had an army of people telling me not to do the carb thing. I am fully aware that fuel injection is superior in terms of performance, but I'm not chasing dyno sheet numbers here, I'm having fun doing what I want and learning along the way. You are one of the few individuals who actually understood that. Thank you.

[davew7]

You do not want to block off the air jet hole. That will affect the full range vs off idle. It will be way to rich at WOT. One option would be to decrease the air jet size, but will effect the full range. You could also change needles, i.e. smaller initial dia. but that could get $$$ when you start buying and trying needles for 4 carbs. DaveW

[LittleRedSpirit]

This might give you inspiration for your tacho. On the ae71 and ae86 there is a known method to modify the tacho board to make it work. I was able to adapt the ae86 method to ae71 by simply looking at the 2 boards and making similar changes on the ae71 board. http://www.ae86drivingclub.com.au/fo...odern-ignition

I found addition of a variable resistor lets you tune it as well, as some earlier corollas already have from the factory.

There are dyno tuners that will know carbs, just focus on someone from the old school that dynos a lot of classic rally cars. Once you get it to run and rev out, its simply a matter of testing the car once, seeing what the afrs do at different moments, as different jets take over at different times and conditions, and a fairly insightful tuner will be able to make these decisions pretty mathematically based off one or two pulls. At least you have electronic ignition, so you can find as much power as possible.

The thing I would really miss about being on carbs and not efi, would be the inability to have idle control and over run control, basically everything that gives you creature comfort. Throttle response should be as good as possible though. Being that you have an ignition computer you can probably add a rev limit to save the engine from spinning too fast.

[mr2mk1hero]

So bit of an update.

I figured out why the engine wasn't starting. It was getting flooded. I couldn't figure it out because it would get flooded within seconds. One failed start and it gets flooded.

So I removed spark plugs, which were wet with fuel, cleaned them up and let them dry out. I also let the fuel evaporate from the cylinders for about an hour. I drained the oil. It was pretty black and smelled like gasoline. Not completely dilluted, still felt oily but I'm glad I didn't attempt to start it anymore, Hope I didn't cause too much wear.

After an hour I pushed the throttle to the floor, held it down and it started right up. No choke. But it ran really rough.

Jets in it right now are 42 pilot and 170 mains. 2 shims on needle.

Here's a little video of the afrs. https://youtu.be/oUB49zoOUmQ I recorded it with a cellphone but it should be good enough. As you can see they are kinda all over the place with the new fuel pump. With the old Chinese one they were a lot more stable. They also go lean when I blip the throttle, this was the case before as well. When I blip and then hold down the throttle the afrs kinda catch up and go really rich, especially at higher throttle. I'm thinking about cutting the diaphragm springs a bit to maybe improve the response?

I also tested compression. 165 psi on 1, 2, and 3. 170 psi on cylinder 4.

I am suspecting the new junkyard fuel pump. It's either pumping too much or too little fuel. Too much in the sense that it might be blowing past the float valves or something. If I turn the choke on, it won't start and floods the engine during the start attempt. The engine will start only with the choke off and throttle held wide open. It is hot here now, so choke off I guess makes sense? It will stall if I let go of the throttle. So this lead me to believe that it's pumping fuel past the float valves. So with the float bowls filled with fuel and the pump disconnected I tried to start it....but it won't start. Also, the rpms would randomly spike up sometimes without any throttle input, which also sounds like a crappy pump symptom to me.

Here's another weird thing about the new junkyard fuel pump. It never stops pumping. The Chinese one would pump and then stop when it built up the pressure, this one never stops. To confirm it just isn't pumping fuel past the float valves I tightened down one of the fuel lines with a vice and started the pump, and it would still keep running like crazy.

The problem is the old Chinese pump has failed and I don't want to spend another month waiting for a new one. Will try to repair it.

I also ordered a carburetor balancer.

[jondee86]

If you want to work on getting your carbs tuned while waiting for a replacement pump, you can rig up a temporary gravity fuel supply as shown from around time 2:00 minutes in this video...
https://www.youtube.com/watch?v=eoaYmNZtlis

Just suspend the fuel container about one metre above the carbs and you will have constant pressure without needing a pump in the supply. That's how bike shops do it when they have the tank off a bike for repairs.

EDIT: Some interesting reading in this thread...
https://cbrforum.com/forum/cbr-600f3...-relay-101822/

Cheers... jondee86