Tech Articles

BASIC TROUBLE SHOOTING:

Before a person can begin to fine-tune the internal combustion engine, many people have issues with their 30 plus year old project bikes. We can talk about a lot of fun topics like exhaust systems, carburetion, ignition systems, etc…. but troubleshooting is sometimes annoying without a systematic approach. We at Cycle X have a system we follow every time an ill running bike is in our shop.

THE POWER TRIANGLE:
The power triangle is nothing new but needs to be remembered when the going gets tough diagnosing poor running bikes.
Motor must be in good, sound condition. (Duh.)
Ignition must be in good, sound condition. (Duh.)
Carburetion must be in good, sound condition. (Duh.)

MOTOR:
Valve adjustment should be checked or adjusted. Reminds me of a story. We had a drag bike with big, overlapped cams and it had 16-to1 compression. Because of the cam profile we had a little over 120lb’s compression. But the compression increased with the RPM of the motor. (It’s a cam thing.) We could alter the compression readings by setting the valves looser. (Cutting back on duration.) The looser we set the valves, the faster the bike went. And the compression changed also. So, if you want an accurate compression reading. Make sure to set your valves.

CHECKING COMPRESSION:
Open up throttle. Turn motor over 4 times and record readings. Do not be concerned with the readings being high or low. Be concerned that the readings are within plus or minus 5 percent of the average. Remember the cam profile story. NOTE: Over-head cammed motors compression readings can be affected by cam chain stretch also. NOTE: An abundance of oil in a cylinder will raise compression. (If you’re motor was upside down or on its side.)

IGNITION SYSTEM:

We like modern high-powered ignition systems for obvious reasons but if you have points and stock coils here are some tidbits of info. Stock coils produce approx. 10,000 volts. Internal combustion engines need 14,000 to 18,000 volts to complete the burn properly. Points start to go out of adjustment after about 200 miles. Points have also been the primary cause of detonation in higher performance motors which connecting rod breakage has been seen.

DO’S AND DON’TS:
Solder all connections. 1/10 of a volt can be lost with each connection without soldering.

Check spark plug caps. 5K ohms is good.
Clean and set points to .015-point gap.
Lube advance unit cam lobe. If you don’t, your ignition timing will retard.
Check charging system. Low battery = Low spark.
Use a timing light. We time to the full advance marks. Timing lights can be used to detect misfires in your ignition system. If you suspect a problem… Hook up a timing light to your bike. Start the bike and flash the timing light on your leg or arm. You will see and here the misfire.
Never splice spark plug wires to get more length.
Modern ignition systems have big spark, consistent timing and zero maintenance.

Now that you have addressed your motor and ignition system the carburetion system will hopefully be a breeze.

CARBURATION:
Check needle/seat and float adjustment. The amount of fuel in the float bowl will have an affect diagnosing rich or lean conditions.
Check for intake manifold leaks. Spray carb cleaner around the intake rubbers to detect fluctuations in the motors RPMs. (We see this problem a lot.)
When jetting carburetors start from the bottom (Idle.) and work your way up.(Main jet.) Check your jetting at ¼, ½, ¾ and full throttle. This jetting thing is part common sense and experience. Mikuni has a very detailed book on jetting carburetors if you run into trouble.

Remember… Motor first. Ignition second. Fuel last when diagnosing your bike.
The seasoned mechanics that read this article might find it basic knowledge but we hope this helps the others.

Slick's Note: Once again, Ken and I are in total agreement on this. I can't say enough how important this little mantra is.... POWER TRIANGLE, POWER TRIANGLE, POWER TRIANGLE.... OR.. Compression, Spark, Fuel, not enough of one and the other two don't work. Often times people forget that the ORDER of checking them is as important as all three of them being present. With Low compression your carburetors will not work correctly. They need to be checked just as stated...

1. Compression

2. Spark

3. Fuel

Remember if your new to bikes, and you are learning. Print out a copy of this and hang it on your garage wall,,, it will save you TIME AND MONEY in the long run....

again, Thanks for the great article Ken, If anyone has a question for ken or your looking for some parts feel free to drop him a line stop by his web page at Http://www.cyclexchange.net

The 70’s (Exhaust and Tuning).

For those of you that are to young or cannot remember, here is my opinion. Bike building in the 70's was very simplified; there were over a dozen catalogs to buy custom Honda parts, ranging from gas tanks, frames, wheels, front ends, exhaust systems, etc. We look at bikes from that 70’s era and can identify most every part as an aftermarket purchase. Now-a-days Hondas are much harder to build; every part must be hunted down or made from scratch. So the people who are building Hondas now-a days deserve a lot of credit.

Exhaust systems from the 70’s.
Many systems claimed horsepower increases, but many achieved minor gains by the fact less restrictive exhaust will show gains. Many systems used automobile collectors welded to there 4 into 1 system to save money. Primary exhaust tube diameter was a major issue with many systems, almost duplicating the factory diameter.

In my opinion, any 4 into 1 system is better than drag pipes and most other cool looking systems. Exhaust systems open up a world of theory, debate and experiences in tuning the internal combustion engine. The 4 into 1 system have been published as being tuned with velocity, shock waves or sound beats and the perfect amount of something engineered into them. When a cylinder fires and pushes exhaust down the pipe into a collector, the exiting gases are pulling exhaust gas from the other cylinders. So the 4 into 1 systems work well on muti-cylinder machines. Smaller primary pipes have been known for midrange punch. Shock waves or sound beats have been advertised as being the latest scientific breakthrough. We need to reflect back to our 2 stroke racing days to speak about sound beats. High performance 2 strokes live or die with shock waves. Some pipes are high RPM and some have torque characteristics. I remember cutting and shortening a brand new exhaust system to find higher RPMs for racing purposes. Finding the window of available horsepower getting smaller and smaller. So at what RPM did the exhaust system sold make horsepower?

We custom builders are in a unique situation. We want looks and we want horsepower with ground clearance. We do not have the luxury of shopping for a multitude of different pipes like the 70’s. Here’s my point… We built a bike we call the superbobber and the motor is highly modified (Compression, long duration cam, etc…) and the pipes are extremely long which we did for looks and shock value. We had never tuned or even seen a bike with pipes this long. With the combination of performance parts in this superbobber the normal train of thought would be to give this high performance bike a more generous amount of fuel. So the tuning process begins. Jetting, checking timing, adjusting valves, etc. The jetting process took longer than we anticipated because of a forgotten fundamental mindset needed to tune altered or modified motors. The mindset is if you go into a tuning process with a preconceived idea how a motor should be jetted, you will be wasting a lot of time. Example: Long duration cams help to pull in fuel, and the 4 into 1 exhaust is helping to pull exhaust out. Pressured intake systems help with an incoming charge of fuel. This would mean the bike needs a lot of fuel Right?
The superbobber is now tuned and the jetting is same as a stock motor. Most people find the final jetting on the superbobber unusual.

Back to exhaust systems. Due to the fact we have very few exhaust systems to select from. The only logical thing to do is select an exhaust you like and tune your bike as needed with a open mind. Honda 750s have a great potential to make power with the right combination of aftermarket parts. And have potential to run far better than the factory offered back then. There are a lot of theories about the internal combustion engine. But remember: Webster’s dictionary says: THEORY is a speculative plan, a conjecture, and a guess.

Thought maybe you would like to hear the superbobber story and maybe the preconceived jetting mindset might help you someday. Maybe you have an experience you would like to share?

Slick's Note: This is one of my favorite articles by ken and applies to ALL motorcycles. I have had the exact same experience with motorcycle exhaust and tuning. Especially when related to Jetting the Carbs. Simply do not ASSUME!!! Each and every motor will act differently. What works fine for one person might not even be close for another. I've had identical bikes set up with identical drag pipe exhaust and identical air filters that took completley different jets. To correctly tune a bike you MUST understand how to read spark plugs and understand how a motorcycle engine and its components work. So in conclusion, don't just hop into a chat room and say "i've got a stock 1973 750 with mac drags and K&N intake, what jets do I need"........you might get lucky and get a correct ball park range, but chances are all you will be is in the area of where they should be. The same goes for exhaust. Exhaust effect the whole bike, its acceleration, midrange, carb tuning, timing ect...

Great article Ken and thank you, I'm looking forward to more in the future. If you would like to get ahold of Ken, or are looking for any parts, stop by CYCLEXCHANGE.NET

Carburetion Designed From Experience

Every time I walk into a motorcycle dealership, there is always a proud father buying his son his first new, expensive mini motorcycle. That’s when I start to reflect back to my childhood. Remembering walking down an alley and seeing a Briggs and Stratton lawn mower engine someone had thrown away. Taking the engine and getting it running with the intension of building a motorized something. My father was not to keen on the mechanical aspect of anything. No tools, no interest, no money, no messing up the garage. So my project was to be secretly done elsewhere. This project (Go-kart.) was made from wood. A washing machine belt drove the kart and pulleys. The wheels were found somewhere. The governor was wired wide open and off we went driving down the road going faster than we should of. Then it happened… Busted by the old man.

Many years later, I got a job working on motorcycles (The 70s.) Honda 750s were the shit. The boring bar was running constant. Boring Honda cylinders to 836, 900 and 1080cc. Cams, headwork and the whole performance thing. The one thing I will always remember is after doing performance or minor changes. (Pipes & air filters.) The carbs were a pain in the ass. 30 years later Honda 750s are hot again and people are reliving their youth. Not being able to afford one of those v-twin bikes or whatever the reason.

So here we go again. Big bore kits, cams, headwork, etc… and there are those carbs again. I said to myself, “I’m not going through this carb thing again.”

Introducing our new carb system:

Thru years of experience we have taken into account velocity, atomization, carb size, fuel to air ratio, distance from the cylinder head, etc… And developed a carb system that we are proud of. The development of the manifolds was not rocket science. No computer generated images. No elaborate Nasa space shuttle testing facility. Just experience and determination. (“Persistence wears down resistance.”) The manifolds were lengthened, opened, angled, shortened and everything you can imagine. We knew we must get the intake runners equal length. Then we had to test quite a bit to get the intake runners the perfect size. (Inside diameter.) Not to big. Not to small. They had to flow like water. Flow like water? Yes, bigger is not always better. Just like cylinder heads, velocity and direction of the flow means everything. Think of the intake flow like a garden hose. If you squeeze a garden hose the water moves faster. If you have a great big garden hose the water moves slowly. We knew we could gain a lot of torque and some streetable horsepower if we pushed the carbs away from the head a little, but we also knew that the carbs had to feel a signal, or pulse from the motor at low rpm. Some of the carb systems we have seen in the past have a long intake tube or something with the carb or carbs attached to it .We have found this theory impossible to work in the real world. All the carbs feel is vacuum at low rpm, not a signal or pulse. Remember, carb tuning should be done from the bottom up. (The main jet is last.) We tested 30, 32, 34, 36, 38 and 40mm carbs. Bigger carbs made more power on top rpm, but we were determined to build a system that worked at all rpms. Because we wanted to build a system that covered all possible applications, (Custom frames, pipes, air filters and altitudes.) we were not focusing on high performance. After testing, testing and more testing, it was time to DYNO test the bike. Mainly for proper fuel to air ratio. When we check fuel to air ratios, we like 12 or 13 to 1 ratios for good power. Sometimes with lower cooling abilities we like 10 or 13 to 1 ratios for cooling. (Richer). We never make lofty horsepower claims because there are so many variables involved to achieve max horsepower. (Exhaust, cams carburetion, ignitions, etc…) Lets just say, if you have your fuel to air ratio correct your motor has reached its potential and the horsepower is there. Once again, we like to leave exaggerated horsepower claims to bar stool mechanics, but if you want to have some horsepower facts here you go.

Our test bike went from 51 to 58.8 hp. (Rear wheel) The bike gained significant torque. We were pleased, because it does not hurt to have extra power. This carb system took us about a year to develop. (Yea right.) Because we also have a full service department. Honda high performance engine program, custom frames, and other custom stuff. The carb system was put on the shelf now and then. There seems to be a lot of speculation on how this system makes power and how this system actually works when so many other systems have failed. Lets think about a couple of theories. Webster’s Dictionary says: “THEORY [The principles of an art or science rather than a its practice][A conjecture, a guess.” 4 into 1 exhaust systems work well because as a cylinder fires the exhaust helps pull exhaust gases from the other cylinders, so the cylinders are working together extracting exhaust and pulling fresh fuel in the cylinders. With that in mind lets talk about the intake system we have developed.

You will notice there are two separate manifolds. One manifold is for number 1 and 2 cylinders and the other manifold is for number 3 and 4 cylinders. Lets talk about number 1 and 2 cylinders. While number 1 cylinder is pulling fuel in the cylinder, number 2 is not pulling fuel. We feel just like the 4 into 1 exhaust theory, by number 1 cylinder pulling fuel in the cylinder this helps number 2 cylinder with a waiting incoming charge of fuel almost pressurizing the intake manifold. This almost makes you think that a 4 into 1 intake manifold might work also, but do not forget, you must jet the carbs from the bottom up. And the carbs must feel a signal. Seems to me there is also a lot of speculation on which is better. One carb per cylinder or an intake system like ours. I believe at very high rpm, maybe one carb per cylinder might make more power, but Honda sohc motors do not rpm that high. Before you go spending money for a carb system, remember this system is not a cure all solution for other problems. You will also need basic skills to install and possibly tune the carb system. Consider the power triangle procedure we at Cycle X perform on all ill running motorized vehicles. Motor must be in sound condition. (Compression, valves adjusted, etc…) Stretched cam chains will affect your performance.

Just like a race camshaft that has not been degreed could cost you a half a second through the quarter mile. (Drag racing.) Ignitions must be powerful and ignition timing perfect. (Honda ignitions are suspect even new.) And every unsoldered electrical connection may cost you approximately 1/10 of a volt loss. Then lastly, the carburetion is addressed as necessary. Most of the fuel purchased now days is causing some problems with older hot rod motors. We recommend to jet up a bit for pinging and detonation. Each carburetor system is prejetted for your particular needs. Altitude, motor modifications, exhaust system, handle bar size. (7/8 or 1 inch.) So, there you go. Some insight on developing products and a few tech tips. Hope you like.

Slick's Note: Ken has included a title in with every article that he has sent me. After all it just plain makes sense to give a article a title so that the reader knows what there in for. This article did not come with a title. There was a reason for that too. This was a Tech Sheet never intended for this site when it was originally written. Ken was asked by Chopper Underground to write an article about carburetors and his new carburetor system. Ken came through with his end of the deal "as he always does" but Chopper Underground went "UNDERGROUND" for good. Ken and I were talking about the article and I asked him to send it to me. He said no at first because he thought it would seem like a blatent advertisement and that is not the intent of this section of Slick's Choppers. But I kept pestering him about it until he gave in and sent me a copy of the article. Once I read the Article I could only think of One title that would make sense... and that title is above.

I have PERSONALLY used Ken's Carb system and would recommend them to anyone. If your motor is good and your mechanics are sound, this carb system runs GREAT!!! I will buy another carb system from ken, and will continue to recommend it. Thanks for the great article Ken, and thank you for taking the time to design a carb system for our old bikes...If you need a carb system,,,, click on the photo of one of the koolest looking carb systems around.