XS Charging and Ignition demystified (for newbies) Please read

RustiePyles

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Demystifying the XS650

Charging & Ignition

By: Fletch Hiner

This question seems to come up more than any other regarding new XS owners and builders, so let’s talk about the charging and ignition systems of the XS and what’s available to replace and repair them.

Let’s clear up some myths right out of the gate. NO XS650 was EVER produced with a CDI (Capacitor Discharge Ignition). They were only produced with points and TCI (Transistor Controlled Ignition). The charging and ignition systems are not the “weak link” of the XS, most have lasted 40+ years. That’s a pretty impressive life span for any automotive part. Part of this undeserved reputation comes from the fact TCI bikes will not start by means of kick or electro motion if the battery is not fully charged. People are quick to blame the systems of the bike for poor quality and poorly maintained lead acid batteries. That coupled with the fact that now after 40+ years these systems are starting to fail in earnest, people now associate mass failure with poor quality when it’s simply not the case. Replacement TCI components are not expensive, the TCI box can be replaced for around $20, but more on that later. Points are not better than TCI, The ENTIRE automotive industry did not abandon points in favor of more advanced systems as some sort of ploy to confound shade tree mechanics and advance their scheme for global domination. They were abandoned in favor of better, more precise, and lower maintenance solutions. While it is true that you cannot “fix” TCI ignitions on the side of the road, like can be done with points. TCI ignitions have an exponentially lower failure rate so roadside repairs are simply not needed. And the “roadside fix” theory doesn’t hold much water anyway, if literally ANY other system on your bike fails you’re most likely not fixing it on the roadside, so why should your ignition be any different.

Here are some facts. The XS650 in all its forms [XS-1, XS-2, TX 650, XS650] was produced from 1970-1985 with last model year for US bikes being 1983. The XS650 is a SOC (single overhead cam) 360degree parallel twin, meaning that both pistons rise and fall at the same time and fire on alternating strokes. From 1970-1979 the they used twin CV (constant velocity) 38mm Mikuni BS38 carburetors. From 1980 onward, they used twin Mikuni CV 34mm BS34 carburetors. The XS utilized a brush type alternator for the duration of its manufacture. Bikes built from 1970-79 used a separate rectifier and mechanical regulator, while 1980 and later utilized a combination regulator/rectifier From 1970-1979 XS’s used a cam operated dual point/dual coil on early models and dual point single output coil ignition on later models. In 1980 the points system was replaced in favor of a TCI on us models, but points remained on some non-US models until 1983. The XS TCI was a crankshaft fired transistor-based ignition system.

If upon getting your newly acquired vintage bike home you discover that there is nothing under those lovely domed chrome covers on either side of the rocker box. DO NOT I repeat DO NOT freak out and take to social media to enlist the help of the YouTube certified masses with claims of “help! My bike has no points”. Calm down and ask yourself a few questions. 1) Is my bike currently running? If the answer to this is yes, then there is zero chance you have a magical bike running without an ignition system. 2) Was the motor in my bike produced after 1980? If the answer is yes, then your bike did not come from the factory with points if you’re in the US. 3) Has the previous owner modified the ignition system? If the answer is yes, then they may have removed the points in favor of a more modern ignition system.
 
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RustiePyles

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The points operate by the battery charging the coil(s) with voltage until the one of the points are opened by the lobe on the cam causing the coil(s) to discharge into the spark plug and igniting the fuel air mixture in the combustion chamber. The most notable difference between the XS’s two different OEM ignition system’s is that in 1980 when Yamaha abandoned the breaker (points) system in favor of the TCI they moved the triggering location from the camshaft to the crankshaft. The reason for this is that the cam triggered systems weather they be points or electronic are simply not as precise as crank triggered systems of any type. This means that cam triggered systems are subject to any wear in the valve train meaning that even when the cam chain is properly adjusted the timing is not 100% accurate. And as the cam chain wears and becomes loose the timing becomes less and less accurate. This compounds the inaccuracy of an already inaccurate system. In 1980 Yamaha combined the new TCI ignition with the charging system. They embedded a magnet in the rotor and installed a pickup on the stator. This system operates much the same way points do. By the magnet passing under pickup every 360 degrees in a fixed location. Every time the magnet passes under the rotor it triggers the coils to discharge their stored voltage to the spark plugs. This system proved to be so accurate that no provisions for adjustment of the timing system were made, meaning that if the ignition system and charging system are assembled properly and all components are functional there is no need to “time” the bike or adjust anything. The crank fired TCI was no longer subject the valve train slop and the inaccuracy of the previous points system. Another notable difference between the two system and major driving force behind the TCI was that it contains no moving parts so there were no contact wear items. In a points system the points ride on a lobe on the camshaft and the rotary contact between these two parts causes wear which in turn necessitates the frequent replacement of parts. Not to mention the mechanical spark advance system used in the points was also another point of wear and slop. No components of the TCI system contact any other parts in motion hence no wear items.

The OEM charging systems on all XS650 motorcycles was a brush type excited field (electromagnet) alternator. A brush type alternator produces AC current by spinning the rotor which is an electromagnet powered via the brushes inside windings of the stator. The components of the XS charge system are the rotor, stator, regulator/rectifier, and battery. Without going into too much detail the XS charge system functions as follows. The rotor being fixed to the end of the crankshaft rotates at engine RPM within the stator which is fixed to left case half and contains wire windings and the carbon brushes which transmit the switching voltage to energize the electromagnet. Once the electromagnet is energized (field excited) the stator then sends current to the regulator/rectifier which turns AC current into the DC the bike needs to charge the battery. The regulator/rectifier only charges the battery with this DC power when battery voltage falls below 14.5VDC by energizing the electromagnet thus turning on the charging system. Contrary to popular belief the XS doesn’t run off the charging system, that’s why it’s called the charging system and not the generator. It runs off the battery, and if the battery is not in good shape the bike will not run.

As soon as you get your XS there will be throngs of YouTube certified mechanics screeching at you to immediately replace the OEM charging and ignition systems with aftermarket options. This is nonsense, as stated earlier these components didn’t last this long because their junk, if your bike runs leave it alone. But, Fletch my bike doesn’t run! you say. Ok lets talk about that. First off your charging and ignition systems are not the same thing. Your charging system charges the battery and your ignition system creates spark. They are separate systems.
 
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RustiePyles

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If you’ve come to the conclusion that one or both of those need to be replaced you have a few options. First is to repair the OEM stock system. So, lets talk about that first.

Stock charging system

Rotor= you can replace or repair the stock rotor. Replacements are about $150, or you can have your stock rotor rewound for about $100. To have your rotor rewound please message @Jim here on the forum.

Stator= you can replace the brushes and brush holder in your stator for about $25 whole replacement stators are about $150 but are rarely needed.

Regulator/rectifier= can be replaced for about $40

Stock ignition system (points)

Points rebuild kits are available in a wide range of prices and levels of quality so I won’t get into specifics but you can get a points kit starting around $20<

Since coils are needed for most all system and all cost about the same we can safely assume you’re not going anywhere without one so we wont cover cost on that.

Stock Ignition system (TCI)

TCI box= Can be replaced with a TCI box from a GN250 for about $20 these can be sourced from many places. The details of this conversion can be found at

http://www.xs650.com/threads/tci-replacement-2020-it-works.57388/





Pickup= this is where we run into a little bit of trouble. These are not currently available from anyone that I know of. The good thing is that barring any physical damage they very rarely malfunction. If yours is damaged you can often find them on eBay.

Aftermarket options, things start to get a little hairy here and this is what often leads to confusion among new XS owners. So, I’ll do my best to make it as simple as possible. First, the term PMA gets thrown around a lot but what does this mean. PMA= Permanent Magnet Alternator, it means that unlike the OEM electromagnet alternator the stator does not require any voltage to activate charging but rather relies on its regulator/rectifier to shunt unneeded voltage away until the battery needs it. This type of alternator produces voltage constantly if turning but still only charges when battery voltage drops below 12VDC. This is the most common aftermarket alternative for the XS. So why would you want one of these? Well, it’s the most common way to eliminate the battery. When wired up properly you can actually power most of the necessary components to move the bike down the road. But that’s not without its disadvantages. If you eliminate the battery you will no longer have an electric starter, at low RPMs the voltage output is low and lights can become very dim and ignition can become weak. And a PMA alone does not provide enough power when using the kickstarter to actually fire the ignition without the addition of a capacitor. And even with a capacitor letting the motorcycle sit for even short periods can discharge the capacitor making kickstarting still quite difficult. These can still be quite effective charging systems and are widely used today with and without batteries. The parts for PMAs are widely available from quite a few different sources but do require modifications to the bike to be used.
 
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RustiePyles

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Aftermarket Ignitions, like stock ignitions fall into two categories crankshaft fired and camshaft fired. The modern electronic camshaft fired ignitions are still prone to same shortcomings in precision due to valvetrain wear and slop that the OEM points were. Crankshaft triggered ignitions still offer the highest degree of precision and reliability. The main drawback of these modern crank fired/PMA units is cost at near $600 they are by far the most expensive option. But you get what you pay for.

Cam triggered units

XS-Charge

Boyer Bransden

Crank Triggered Units (These include a PMA charging system)

Hugh’s Handbuilt

Vape



The foremost supplier of these PMA/Ignition kits is Hugh’s Handbuilt. Hugh Ownings (owner/operator of HHB) has spent countless hours perfecting his kit and sourcing quality parts and his customer service is unrivaled. Check him out @ hughshandbuilt.com

The Vape is sold by Hoos Racing who is also well known as quality dealer of quality XS parts and can be seen @ Hoosracing.com Gary Hoos also offers excellent customer service.

Mikes Xs is a place that sells “parts” for these bikes, you can find them on the internet if you’re so inclined.

The down and dirty. XS’s from 1969-79, you can replace the charging system with a PMA without replacing the stock points ignition. Bikes from 1980-84 cannot have their charging systems swapped with a PMA without the addition of another ignition system. If you buy a Hugh’s Handbuilt or Vape its an all in one system. No other system is all in one other than the OEM TCI from 1980-84.

This document was not meant to dive deep into the theory of these systems and how they operate but rather to be a 101 type of primer for new XS owners trying sort out all the info they find on the internet.
 
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XSLeo

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Not abad read even with a few mistakes. The production years of the XS650 started in 70 not 69. Some were produced in 69 but they are 70 models.
In your ignition descriptins the points as mentioned are two seperate systems. One for each side. This gives you one spark coming up on compression. No spark at other times. So not Wasted spark.
On the TCI and many aftermarket ignitions tye coil has a dual out put. The igition firesthe coil every time the pistons come up to TDC. Once on compression, once on exhaust. The spark on the exhauist is where you get a wasted spark.
Most of the other mistakes are in nomenclature. You used the wrong names on things. The stock Alternator is a Felid Excited Alternator. This means the feild coils, in thuis case in the rotor create the magnet feild thsat excites the stator into creating the AC voltage. This rotor as you hinted gets turned on/off by the regulator. The regulator used battery voltage to tell when to turn the rotor on/off. Most rtegulators have a set value of 14.5 volts+/- 5%.
When the regulator reads battery voltage below the set value it turns on the rotor. Once the voltage reaches the setr value it turns the rotor off.
When the rotor is on the stator makes AC current. This current flows to the rectier. The recifier coverts the AC to DC to charge the battery.
On the 70-79 bikes the reg and rec were seperate units. The reg was a mechanical unit. In 8o they combined then into one and used a soild state reg.
This solid state reg has no moving parts to where.this did several thuings. No movig parts it cyled much faster than the mechanical version/ This maintianed the volta to the battery at a much more constant level. This helped the batteries maintain priope vltage and lasted longer.
They lack opf moving p[arts made them much more reliable as well.
On the points ignitions, if the engine recieved proper miantiance the timing was very accurete. As the chain wore the timing did change a bit. it became a bit retarded, but then so does the valve timing.
The TCI did help i this regaurd but it didn't help the valve timing.
Evem with these few thuings this is a good thread for newbies.
Leo
 

Team Junk

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Would also like to add that the change from mechanical to electronic regulator also changed how the rotor is is powered. On the pre 80 bikes the regulator varies the the voltage( and therefore the magnetic field in the rotor). On the later bikes the rotor is supplied battery voltage on one side and the regulator controls the amount of current allowed to flow to ground. The upstart to this is that changing to a later regulator on a early points bike requires a modification to the brush holder.

BTW there are no magnets in the stator. The magnetism is created in the rotor which induces a current in the stator.



+1 on the HHB system.

The one big advantage of of the PMA systems is the elimination of the brushes which is the the only wear part in the stock system. The only other mechanical part of the system are the relays in the regulator.

Hugh has addressed the regulator issues (MOSFET series regulator vs. the cheaper shunt regulators) that have given the PMA systems a bad reputation. The one big advantage of the the HHB and vape systems is that if the engine turns it will make spark. The CDI ignition they utilize is powered by a separate coil in the stator . Same story with the charging. If the engine turns over it will make current. The problem is keeping from making too much current.

The Banshee conversions that Hugh very kindly documented in a thread here is the basis of his current system (pun not intended). The Banshee system originated in the RD/RZ bikes in the 80's and my RZ charged just fine and kept the lights plenty bright at idle.

Thank you @RustiePyles for putting this together and don't let the editors get you down. I've put up with editors for decades and while there were a couple I'd just like to punch generally I type faster than I think( and I don't type that fast)

Jack
 
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RustiePyles

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Ok, I've made the edits. Lots of good info guys, thanks for pitching in. Yes I know not all the terminology is 100% correct, but if someone already knows what an excited field is they are most likely not reading this and looking for information that they don't already have. I was not trying to get to deep in the weeds in theory. The point of this write up was to help new guys understand all the info being thrown at them about systems they have no experience with, not to turn them into Yama-Techs. If anyone sees anything that still needs correcting please let me know.
 
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