ViragoTechForum.com :: Yamaha Virago XV Forums That Rock!!!

ViragoTechForum.com » Tech Articles » Easy Start and better gas mileage bonus

#1:  Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Sun Oct 16, 2005 1:57 pm

In 1983, when I heard for the first time, a Japanese bike that did not sound like a lawn mower, a 1981/750 Virago with Jardine slip-ons, and after a short ride, I fell in love with it, traded my spouse Triumph Tiger 650 on the spot, and married the Virago. But like any marriage, after a couple of years, the problems started. At this point you have two choices, live with them or divorce. A lot of Virago owner’s did in fact divorce. The beloved lady gave a good ride, but she was hard to start. So me and my friend, who has a 1983/920, decided that the ladies would not wear us out, and that we we’re gonna have the last word. And man, having the last word with a lady, is a hell of a decision, and getting her started on a quarter turn is also quite an enterprise.
For those who are not to familiar with engine mechanics, the basics are divided in three groups. The engine itself, the fuel and the ignition.
-The engine itself is basically a pump, an compressor to be more precise, well let’s say that half it’s cycle is. All it does is suck an air/gas mixture and compresses it. So in order to duplicate our result, the pump has to be in good working order (good compression, valves adjusted, ect) and, of course, the starter problem must be resolved, if you want to get her started on a quarter turn. We’ve solved that problem, once and for all, five years ago.
-The fuel is a mixture of air and gas at a very precise ratio. That the carburetor’s job. Again this issue has to be resolved. Your carb has to be in top shape, clean and properly adjusted. Now I mean properly adjusted, not by ear or by feeling, properly adjusted. We tune our carburetors electronically with a voltmeter, there is no other way.
-The ignition is composed of a pick up coil, a TCI box, coils and spark plugs. Their job is to ignite, that’s why it’s called ignition, the mixture that as been compressed at a specific point in time.
So for the purpose of this topic, the ignition is the issue. Again the basics have been dealt with. I mean your battery is ok and the charging system is working properly. All wire have been check and there is no corrosion on any of the multiple plastic connections. This is very important, we are dealing here with bikes that are anywhere from 10 to 25 years hold, that have been left outside, in the rain, in the snow, etc. And even if you did go through all your wires and connections last year, this is something you’re gonna have to do on a permanent basis, check all your connections regularly.
All of this being said, we’ll take for granted that the pick-up coil and TCI unit is working fine and that the ignition coils are also in good working order. That does not leave much hey? Well we’re getting to heart of the problem. Yes, spark plugs and wires. Some of you must have guest it, but have done something? Well we did not take for granted that the builders of this bike knew what they were doing. Mind you they did a great job on the engine, but on the rest? Just take the starter as an example.
There is also another thing that has to be taking in account here, is the fact that the engineering around the conception of this bike dates from the late 70’s. That guys is 25 years ago. There were no personal computers back then, well maybe the Commodore 64 or the famous Atari, and who would ever think of the idea to able to communicate worldwide at a clic of a mouse?

PART ONE: SPARK PLUG
The recommended plugs for all Virago’s is: NGK BP7ES, the Champion equivalent is: N7YC. Now you will noticed here that Yamaha does not recommend the BPR7ES (RN7YC) which is a RESISTOR type. What’s it’s purpose, a resistive element (hence the term resistor plug) is used to help reduce radio interference in most cars and gap erosion. This resistive element (typically 10,000 ohms) changes the initial resonance characteristics of the ignition's secondary circuit, thereby reducing the initial high-frequency, high-current capacitive phase (i.e., less high frequency radio noise) of the arc discharge, and as a byproduct helps to reduce the erosion of the gap. The ensuing low frequency, low current inductive phase of the arc is minimally or not affected by this element. So for our Virago’s it’s useless, unless you converted your bike to a Goldwing.
The problem that we have with our bike is closely related to the design. The newer V-twin engine use a decompressor to ease the stress on the starting motor. By ease of stress, I mean less current drawing from the battery, and this is THE VIRAGO PLAGUE. Yes guys, now we are dead center on the problem. When you start your engine, sorry I meant trying to start your engine, the starter is pulling so much current that there’s nothing much left for the plugs, hence the hard starting. The solution? Well read the following explanation:
What makes good ignition? Ignition occurs in a modern automobile when an arc is struck and current flows between the electrodes of a spark plug, or when current migrates across the conductive medium in a surface gap plug. While that may sound simple at first, the process becomes progressively more complicated as engineers try to optimize the type of spark plug with the ignition system generating the required voltage.
The amount of voltage necessary to arc the electrode gap is set by the following characteristics:
· The size of the gap... arc-over voltage is roughly proportional to the gap size
· The air/fuel ratio within the gap... the richer the air/fuel ratio (more gasoline vs. Air), the lower the required arc-over voltage
· The compression at the moment arc-over is to occur... the higher the compression, the higher the required arc-over voltage
· The composition of the electrode... certain metals for all the same conditions stated above will require less arc-over voltage than other metals. For example, platinum requires less arc-over voltage, all other things equal, than does steel
· The shape of the electrode... the sharper and more jagged the shape, the easier it is for voltage to jump
· The amount of fouling deposits trying to remove the electron flow from the arc... more fouling deposits and lower resistance to ground pulls more energy out of the spark gap.
While it may therefore seem desirable to lower the required arc-over voltage, since without arc-over there is a total misfire and no ignition, low arc-over voltage produces low spark power because spark power is directly proportional to arc-over voltage. That is, by doubling the required arc-over voltage, you double the instantaneous peak spark power, and the higher the spark power, the better the ignition.
All ignition is, therefore, a balance between the requirement to have sufficient arc-over voltage and increasing peak spark power for better, quicker ignition.
What benefits to specialty plugs bring to this mix? One popular specialty type is platinum plugs. The primary advantage of these plugs, especially when used in an OEM ignition system (especially an older system, which may not be producing as much voltage as when it was new), is that platinum will require less arc-over voltage and therefore, particularly in a weak ignition, allows the gap to be jumped a higher percentage of the time.
For example, if at factory gap and with steel electrode plugs, it requires as much as 18,000 volts five percent of the time to jump the arc... due to the changing engine environment and running conditions... and if the OEM only produces 17,000 volts, then it follows that five percent of the time there would be a misfire.
Now, if one installs platinum plugs, which may only require, say, 13,000 volts to arc, the five percent misfiring with steel plugs would be eliminated. Since the ignition output on OEM ignition rolls off as rpm increases, platinum plugs in this case would allow the motor to reliably turn to higher rpm, thereby giving and increase in performance and possibly gas mileage.
The disadvantage of this method of reducing misfires is that the higher arc-over voltage, the better the spark when it does fire. Therefore, platinum plugs will show a performance improvement with a weak ignition because the benefit from reducing the percentage of misfires more than outweighs the loss from reduced spark power.
Well that’s what we did, we started out, four years ago with NGK BP7EVX. There is also the newer BP7EIX which I’m testing this year. Our bike are a lot easier to start, specially when the engine is hot (with premium gas of course, but that’s another story). We’ve tested these plugs on many other bikes and there was always a gain in gas millage, from 10% to 20%. Now did we encounter any problems with these plugs? Not really, but as stated before, everything else has to be in top shape to duplicate our results. In fact the only problem we had were some wet fouled plugs. The plug is not a fault here. Read the following NGK tech note on this:
FOULING
Will occur when spark plug tip temperature is insufficient to burn off carbon, fuel, oil or other deposits.
Will cause spark to leach to metal shell...no spark across plug gap will cause a misfire.
Wet-fouled spark plugs must be changed...spark plugs will not fire
Dry-fouled spark plugs can sometimes be cleaned by bringing engine up operating temperature
Before changing fouled spark plugs, be sure to eliminate root cause of fouling
And finally,
PART TWO: THE PLUG WIRES
I will be brief on this one. The carbon type wire, found on almost all motor, were developed to reduced the radio interference in automobiles years ago. Unless you converted, as stated before, your Virago into a Goldwing, these wires do not help our starting problem. The solution: steel core wire. You’re local car parts stores have that in either a kit or by the foot, and it’s usually yellow. Plus these new wire will have the newer silicon insulation.

Gook luck, and keep the rubber on the ground

#2:  Re: Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Sun Oct 16, 2005 2:01 pm

Here's a couple of tech pics on spark plugs

Keep the rubber on the ground



NGKIridiumIXwithLeaderLines.jpg
 Description:
 Filesize:  7.94 KB
 Viewed:  4598 Time(s)

NGKIridiumIXwithLeaderLines.jpg



NGKcharttempfiringend.gif
 Description:
 Filesize:  18.62 KB
 Viewed:  4591 Time(s)

NGKcharttempfiringend.gif



NGKchartheatratingflowpath.gif
 Description:
 Filesize:  10.74 KB
 Viewed:  4606 Time(s)

NGKchartheatratingflowpath.gif



#3:   Author: zbiker Post Posted: Sun Oct 16, 2005 9:50 pm

This was very instructive thank you so much!

#4:   Author: P.O.L. Mafia Post Posted: Mon Oct 17, 2005 7:16 am

I still do not like NGK, they are junk in my book and always will be. I have replaced them when they fouled with anything, even re,,,,,,never mind. I won't get into a pissing match. I will leave it as this, in my experience of 15 + years, I have found NGK to be the most unreliable plug bar none. Good reading though.

#5:   Author: turtlspd Post Posted: Mon Oct 17, 2005 11:26 am

Well there was some good information there, (once I got past the Drama) I like it much better when tech posts are kept brief and to the point.
Thanks for your input cr_roger...

#6:   Author: P.O.L. Mafia Post Posted: Mon Oct 17, 2005 12:11 pm

Sorry for the drama. My apologies. Very good info. Did not mean to take away from the post. That’s from a different situation, didn’t mean to,,,,,,,,, aaa bull. Sorry CR.

#7:   Author: cr_roger Post Posted: Mon Oct 17, 2005 12:42 pm

turtlspd wrote (View Post): › Well there was some good information there, (once I got past the Drama) I like it much better when tech posts are kept brief and to the point.
Thanks for your input cr_roger...


I agree with you, the post is too long. But since to main topic is wrenching secrets I wanted to be as clear as possible. Sorry.

#8:   Author: cr_roger Post Posted: Mon Oct 17, 2005 12:48 pm

P.O.L. Mafia wrote (View Post): › Sorry for the drama. My apologies. Very good info. Did not mean to take away from the post. That’s from a different situation, didn’t mean to,,,,,,,,, aaa bull. Sorry CR.


No problem there, all I wanted to do is put the reader in perspective that my result where from a long time period and not just a puff of smoke. I see that you don't like NGK. The info applies to Champion, Denso, Bosch, ect.. Equivalent fine wire plugs from these guys will generate the same results. As for your NGK fouling problem, was it wet or dry fouling?

#9:   Author: P.O.L. Mafia Post Posted: Mon Oct 17, 2005 1:51 pm

Yea I agree that info is not by any means just NGK, that little rant came from, reading INTO a discussion while having “aggressive negotiations” with someone who ironically doesn’t even ride, or a member of this forum. Need to learn to not do that. But in answer to your question, I don’t remember, I changed to Bosh Platinum years ago and never had another problem. When I get a problem with a customers vehicle, the first thing I see is if they are NGK, it’s the first thing I jerk out.

#10:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Mon Oct 17, 2005 2:35 pm

Thanks cr_roger for a real in depth article! I just love it! Beers
As a teacher in physics and a motorcyclist the info is great stuff!

#11:   Author: cr_roger Post Posted: Mon Oct 17, 2005 3:12 pm

P.O.L. Mafia wrote (View Post): › Yea I agree that info is not by any means just NGK, that little rant came from, reading INTO a discussion while having “aggressive negotiations” with someone who ironically doesn’t even ride, or a member of this forum. Need to learn to not do that. But in answer to your question, I don’t remember, I changed to Bosh Platinum years ago and never had another problem. When I get a problem with a customers vehicle, the first thing I see is if they are NGK, it’s the first thing I jerk out.


Which Bosch platinum do you use? See, even if the manufacturer makes a cross reference between his plug and a competitor, that does not mean that the heat range is the same. If the Bosch works where the NGK fails (with fine wire type), I suspect the NGK being too cool and that the engine is on the rich side. That's a deadly combination for plugs.

Keep the rubber on the ground.

#12:  Re: Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Mon Oct 17, 2005 3:18 pm

lassesand wrote (View Post): › Thanks cr_roger for a real in depth article! I just love it! Beers
As a teacher in physics and a motorcyclist the info is great stuff!


Thanks. I made a small error when I said that in the NGK designation, ES stands for Electrode Standard. E stands is the reach but S is for standard. All my regrets.

Keep the rubber on the ground

#13: Question Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Tue Oct 18, 2005 1:19 pm

If the goal is to get a better spark, why not plug in a stronger coil? In Sweden we have a company; BILTEMA (www.biltema.se) where you can by a coil that has a claimed output of 36000 Volt naughty at 1000 rpm, 12 Volt in and at 20Âş C. I asked the thech -guys if it would fit my bike with the TCI-igition; OK they answered! It looks reasonably small and should fit in the same space as the oem's. Waddayasay?


coil.jpg
 Description:
 Filesize:  3.88 KB
 Viewed:  4497 Time(s)

coil.jpg



#14:  Re: Easy Start and better gas mileage bonus Author: geo Post Posted: Tue Oct 18, 2005 8:54 pm

i have the ngk irridiums in my bike for two seasons now (same set) and i LOVE them! my cars get only bosh platinums. champions? do-do

#15:   Author: geo Post Posted: Tue Oct 18, 2005 8:56 pm

yep, thats about how my car ran on them

#16: Question Re: Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Tue Oct 18, 2005 9:55 pm

lassesand wrote (View Post): › If the goal is to get a better spark, why not plug in a stronger coil? In Sweden we have a company; BILTEMA (www.biltema.se) where you can by a coil that has a claimed output of 36000 Volt naughty at 1000 rpm, 12 Volt in and at 20Âş C. I asked the thech -guys if it would fit my bike with the TCI-igition; OK they answered! It looks reasonably small and should fit in the same space as the oem's. Waddayasay?


That a very good point. Coils are the third element in the high voltage ignition circuit. The first being the plug and the second, the wires. In theory, those coils could work. There are two potential problem that would have to be put the test. First, Virago coils are weather protected, and there quite exposed to elements. The one you show does not look to be well protected. Secondly, to charge up to 36,000 volts (that almost double what it is now), at the same voltage (12 volts), this coil is gonna need twice the current. I don't know how the TCI is gonna react to that or even be able to supply that increase in current. We'd have to put that to the test before implementing that conversion.

Keep the rubber on the ground

#17:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Wed Oct 19, 2005 4:46 am

"Secondly, to charge up to 36,000 volts (that almost double what it is now), at the same voltage (12 volts), this coil is gonna need twice the current. I don't know how the TCI is gonna react to that or even be able to supply that increase in current. We'd have to put that to the test before implementing that conversion. "

Yes, I don't want to fry the TCI! flame If I measure the resistance in the primary winding (PW) they should be 2.7 Ohms +-15% (2.3-3.1 Ohms) according to the service manual. I'll have to bring my multimeter to BILTEMA and check!
The question is how low resistance in the PW can the TCI cope with before it breaks???

#18:   Author: Matthew Post Posted: Wed Oct 19, 2005 10:14 am

Yea, the TCI is a negative trigger system.
Which means you can feed it all the juice you want by the positive. But in reality the juice flows backwards.

Maybe have the TCI just control mini RC like micro switches or a big amp relay for a stereo system. That would trip a switch for better coil without any of the load going through the TCI?

#19:  Re: Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Wed Oct 19, 2005 12:29 pm

The other point concerning the TCI is that the amount of current remains the same in the low circuit while on the high voltage sides it doubles, the current will then be reduced by half (total wattage (voltage x current) has to be equalize somewhere). The question then is, will you get a better spark?

Keep the rubber on the ground

#20:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Thu Oct 20, 2005 2:25 am

I haven't got a clue how a TCI is built but there has to be some transistors of some kind involved. On what info do you base this:
"The other point concerning the TCI is that the amount of current remains the same in the low circuit " ?
I'm curious cause I want to understand how the TCI works!

I had an old SAAB with mechanical breaker points where i built (kit) a gadget with electronical components (transistor or tyristor etc) that took the load of the points so they lasted much longer. A small current trough the points were amplified in the gadget and then sent to the coil. I was able to have a high output coil without burning the points.
Perhaps the same gadget could work here (but then I'll need 2...)?

#21:   Author: geo Post Posted: Fri Oct 21, 2005 7:22 pm

that is what i was thinking before i read your post. you would need two devices but i see no reason it shouldn't work.

#22:  Re: Easy Start and better gas mileage bonus Author: cr_roger Post Posted: Sat Oct 22, 2005 11:21 am

lassesand wrote (View Post): › I haven't got a clue how a TCI is built but there has to be some transistors of some kind involved. On what info do you base this:
"The other point concerning the TCI is that the amount of current remains the same in the low circuit " ?
I'm curious cause I want to understand how the TCI works!

I had an old SAAB with mechanical breaker points where i built (kit) a gadget with electronical components (transistor or tyristor etc) that took the load of the points so they lasted much longer. A small current trough the points were amplified in the gadget and then sent to the coil. I was able to have a high output coil without burning the points.
Perhaps the same gadget could work here (but then I'll need 2...)?


Sorry, I meant "if the amount of current remained the same in the low circuit". See, a coil is basically a transformer. The amount of current flowing is dependant of the load. On this case the load is the high voltage cirucuit. If you double the voltage on the high side, the load demand could also double. Since the voltage remains the same on the low side, that would mean that the flowing current would double. If this is the case, will the circuit in the TCI take that? Or will it fry? Or will it overheat after a little while? Get the point?

Keep the rubber on the ground

#23:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Sat Oct 22, 2005 1:41 pm

Yes I get what you mean. The culprit (right word?) should be to know how the TCI is built and works. In what span the current/voltage can be.
Anyhow, when I was young and owned a brand new TR1. (1981) I did put on to heavy duty car-coils to see if it should work better. I didn't notice any difference and the TCI didn't fail. Maybe I was just lucky or didn't drive long enough to fry it. I will try to investigate the high output coil -alternative this winter.

#24:   Author: cr_roger Post Posted: Sat Oct 22, 2005 3:32 pm

That's a good idea. I'll do the same. What we're looking for is a higher voltage so we can optimize the platimum plug's performance thus getting easier starts and good fuel economy. Basically, it's the difference between cars today and the ones from the early 80's.

Keep the rubber on the ground.

#25:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Sun Oct 23, 2005 2:55 pm

I've been stydying the combustion chamber on the xv's. They are a bit more compact that the old hemis from the 60's. They also have a slight offset of the valves thus promoting a slight swirl-action to enhance (quicken) combustion. Perhaps there are some squish band effects to?

(To my knowledge the Zuzuki twin-swirl combustion chambers are near the optimum.)

An interesting experiment would be to take two 4-valve head from Yamaha thumpers an graft them on a Virago or TR1! Presto, modern compact combustion chambers and good breathing without extreme cams!

#26:   Author: yamahog Post Posted: Tue Oct 25, 2005 12:28 pm

So, and I apoligize in advance, I have little to no knowledge of electronics...so, could you run two coils in line, a small one to sort of step-up to the big one, so it got enough juice without drawing it through the tci and thus possibly damaging it?

#27:  Re: Easy Start and better gas mileage bonus Author: lassesand Post Posted: Tue Oct 25, 2005 12:50 pm

The gadget was a Welleman-kit and worked like an amplifier. My idea is that the signal from the TCI triggers the gadget that triggers the coils. Sorry to say I've probaly has trown the little bugger away... Yoho!!! If found it at Velleman.be; Transistorized ignition
All the specs to!! It can take 4 amps; more than enough for this use as a trigger for a high perf' coil Beers
I think 2 kits can be connected like in the pic. It's a guess so I won't give any guarantees...



velleman.gif
 Description:
 Filesize:  13.3 KB
 Viewed:  1024 Time(s)

velleman.gif



scheme.gif
 Description:
 Filesize:  10.81 KB
 Viewed:  1024 Time(s)

scheme.gif



#28:   Author: Matthew Post Posted: Wed Oct 26, 2005 2:44 pm

I got some good info on a solution. Straight from the #1 ignition man in the world. Dead serious on that, what he says goes. Don't even think to question him.

But I am gonna ask about timing curves.

"XS550 were an inline transverse 4 cylinder, used two, two lead coils, have two separate circuits inside the boxes, and can trigger any coil with the correct primary resistance rate for....Capacitor Discharge setups.

I'd trigger one of those boxes with the Virago pickups and use single lead coils for each cyl.

It wouldn't be weak after that, and it'd be all Yamaha.

The 550 was the ONLY one of the inline 4's to have capacitor discharge systems."

#29:  Re: Easy Start and better gas mileage bonus Author: makeityours Post Posted: Wed Oct 26, 2005 8:45 pm

Uh Oh,try to get those on eBay now.I can just hear the bids going now.

#30:  Re: Easy Start and better gas mileage bonus Author: blacks Post Posted: Mon Jan 16, 2006 10:29 am

ok

#31:  Re: Easy Start and better gas mileage bonus Author: pachakutek Post Posted: Thu Nov 09, 2006 2:00 am

cr_roger wrote (View Post): › Your carb has to be in top shape, clean and properly adjusted. Now I mean properly adjusted, not by ear or by feeling, properly adjusted. We tune our carburetors electronically with a voltmeter, there is no other way.


Nice write up... I know is a bit out of topic, but how do you use a voltmeter to tune a carburetor?

#32:   Author: Matthew Post Posted: Thu Nov 09, 2006 2:04 am

With an oxygen sensor. Just need a volt meter to read the output and see wht your fuel ratio is.

#33:   Author: pachakutek Post Posted: Thu Nov 09, 2006 2:22 am

Do you plug the O2 sensor to the exhaust? like in a car?..
What's the appropiate fuel ratio?

#34:   Author: Matthew Post Posted: Thu Nov 09, 2006 2:47 am

Yep it goes in the exhaust where it can reach op temp. They don't need juice or anything, they put out juice by some reaction that will tell you your fuel ratio. Just hook red of volt meter to red of 02, black the same and it will read once up to temp.

check old links, near bottom, carb tuning the scientific way

#35:   Author: Matthew Post Posted: Thu Nov 09, 2006 2:51 am

I wish someone could find some mini low profile 2 wire O2 sensors that could be put in the virago exhaust some where and not be seen or in danger of touching ground.

#36:  NGK crap Author: srinath Post Posted: Wed Nov 28, 2007 6:41 pm

P.O.L. Mafia wrote (View Post): › I still do not like NGK, they are junk in my book and always will be. I have replaced them when they fouled with anything, even re,,,,,,never mind. I won't get into a pissing match. I will leave it as this, in my experience of 15 + years, I have found NGK to be the most unreliable plug bar none. Good reading though.


Oh man, I never thought I'd hear anyone else say this.
Total POS and I believe sometime in 2003 they started slipping in quality.
I have plugs from before that still alive, but newer than that busted.
I currently use autolites in my virago. Platinum I believe, but I also like champions.
The virago is the hardest and most finnicky on plugs but my GS500 and my savage also hate NGK's.
Cool.
Srinath.
Links monetized by VigLink
Join VigLink