Ignition Timing

[Anthony Duffield]

Seeking guidance regards Commander advance/retard

Before the temperature reaches approx 70 degs the engine has a steady tick over, as the sensor closes the circuit the engine speed drops and begins to run very poorly it is very difficult to get anything like a steady tick over, it revs and pulls well and seems to be OK I just cannot get a steady tick over.

I first noticed this problem after the engine was overhauled about two years ago, I suspected the original Boyer so fitted a system from Startright, same effect so I went back to the Boyer.

I have done several thousand miles since then.

What puzzles me is that below 1000 it is supposed to be retarded but runs poorly, if I disconnect the sensor so in effect running it retarded it runs fine.

Both ignition boxes are the same, below 1000 rough running above no problem disconnect the sensor and it has a steady tick over, by the way with the sensor disconnected it runs and pulls well.

I'm sure the ignition boxes are doing something to the timing so that below 1000 the ignition is causing the engine to run really poorly.

Is it not just a simple, retarded below 1000 and advanced above or it there some other clever stuff going on?

One thing I have not done is to check the sensor for earths, just in case.

All suggestions/observations gratefully received.

Tony

[johnbirchjar]

Hi Tony,I have exactly the same problem ,but what puzzles me is the Ignition System and Carbs are the same one's I took of the Air cooled engine , and the idle then was perfect ,lovely and smooth at 800rpm,and something else I noticed is that Water Cooled Rotories seem to "Hunt" on tick over,(especially the F1's and F1Sports,)perhaps someone can explain the reason for this phenomenon.
I may disconnect the Sensor Wire and see how the bike performs,I will report anon,ride safe,J.B.

[Richard Negus]

Hi Both,
Boyer and TT1 ignitions have a built-in retard curve dependent only on engine speed.
Above about 2000 rpm they run at full advance until the rev limiter is reached. At that point a huge retard effectively causes a bad misfire at about 9,000 rpm.
Below 2000 rpm, the ignition gradually retards until about 800 rpm where typically there is 45 - 55 degrees of ignition retard. Careful setting of the idle air screws will give a smooth idle at this speed, all other things being equal. Commanders, with their heavy flywheels, are usually very simple to adjust. F1's, with much lighter flywheels, can be a pain.
However, if the engine is not in top mechanical condition with good compression, it won't idle smoothly.
The temperature switch, or original thermistor on a Commander, tells the ignition unit whether the engine is 'cold' or 'hot with the changeover point being reached at around 65 C. Below that, the ignition unit runs at full advance and will idle around 1200 rpm. When the switch closes, it reverts to the retard curve and should idle at 800 rpm on a closed throttle. The thermistor gives a slow change from full advance to full retard; the temperature switch gives a sudden change. Original Boyer thermistors had a high failure rate and many Commanders now have a temperature switch, with zero failure rate.
Disconnecting the switch/thermistor fools the ignition into believing that the engine is always 'cold' and gives full advance at all engine speeds even when the engine is really 'hot'.
If both your engines idle well at full advance, then they are almost certainly low on compression - either worn apex seals, worn seal springs, or scored engine plates.
If the plates are scored, you may find idling gets worse, hot re-starting more difficult, and eventually impossible.
Worn apex seals and/or springs will show a more gradual decline.
R.

[Anthony Duffield]

Richard,

Thank you for your reply helping me to properly understand whats going on with my Commander.

As the engine starts instantly and pulls well just now I will now plan an overhaul for next winter.

Thanks again for your help with this

Regards
Tony

[Richard Negus]

Tony,
I forgot to mention a significant difference between Boyer and TT1 boxes.
With the switch/thermistor connected and a hot engine, the Boyer is at full retard at cranking speed which makes re-starting difficult sometimes.
The TT1 was designed such that, under the same starting conditions, it gives full advance for 25 revolutions of the engine before reverting to full retard.
That's a clever feature that gives the engine a boost for hot re-starting.
R.

[Anthony Duffield]

Richard,

Thanks again, excellent information.

I have set up the connections on both ignition units so that I can change them on the side of the road if I had to, I may swap back to the TT1 to check out the difference.

Thanks and Regards
Tony

[johnbirchjar]

Thanks for that Richard.
I assume that the TTI Ignitions are the ones made by Julian?
I havn't disconnected my Thermister yet so I can't compare tick overs(not quite sure what colour the wire is )
I checked the compression before putting the engine in the Classic frame,seemed nice and high,and no probs: at all with starting a hot engine ,rgds,J.B.

[Richard Negus]

John,
Julian developed and makes the TT1 boxes. Compared to the Boyer, they're modern technology with a re-programmable chip so you could, if required, have one with a different rev limit or different retard curve.
This is the thermistor:-

4002-03-2.jpg

A temperature switch fits in exactly the same place.
With a Boyer box, disconnecting the thermistor with the hot engine idling at 800 rpm, it should immediately increase speed to around 1200. If it stays at the same speed, then the thermistor is duff.
A TT1 box has no reaction with the same test. You must first switch off, disconnect, and then re-start.
R.

[johnbirchjar]

Thanks for the info Richard,but I will leave well alone 'cos having "Tweaked" the Idle Rod(and ditto the Idle Air Screws) I have got the old girl ticking over just like the Classic's Air cooled used to .
BUT,I still have a fluid leak from the front brake master cylinder ,the actual piston & rubbers all seem dry,but fluid leaks round the brake lever pivot,not copious amounts,just enough to "lubricate" the pivot bush and splash a bit on the Fairing & petrol tank(which will probably cost me about five/six hundred quide to get re-sprayed and sign written )The brake pipe union is also dry,as is the joint at actual filler cap,(the later "Coffin" shape) so I am at a bit of a loss,any ideas anybody?J.B.

[Mick Taylor]

Hi John, if your master cylinder is the Yamaha FZ750 / FJ1100/1200 etc version and is of typical Japanese design then it's hard to imagine the fluid is coming from anywhere other than past the piston seals assuming the banjo bolt, cap seal and fluid level window are all dry.

There are a number of used ones on ebay (this one is just up the road from you in Chelmsford).....

https://www.ebay.co.uk/itm/YAMAHA-FZ750 ... Sw5UVa4bm4

Substitution might be cheaper than leaking fluid all over your tank......but there is always a lottery element with used parts.

Mick.

[johnbirchjar]

Thanks Mick,I'll try another repair kit first,(the one on offer is half the price of the one from A/N)I will report anon,J.B.

[Richard Negus]

John,
Take care with cheap seal kits! I think it was on another thread that I mentioned a manufacturing fault with a pattern, ie branded Tourmax, seal kit. The piston secondary seal, which should stop fluid escaping from the reservoir when the lever is pulled, doesn't fit tightly on the piston and could allow fluid into the rubber bellows on the piston. That bellows is not meant to be a fluid seal, just keeps road dust away from the piston and primary/secondary hydraulic seals. That is probably where your fluid escape is happening.
For a safety critical item such as brake systems, I would avoid anything that isn't the genuine part, regardless of cost.
R.

[steve traynor]

try Fowlers in Bristol very helpfull

[Mick Taylor]

try Fowlers in Bristol very helpful

Definitely one of the best Yamaha parts suppliers.

Failing that......believe it or not, Wemoto also supply genuine Yamaha parts, (and others I believe) they turned up obscure parts for my XS1100 when I had it that I couldn't find elsewhere.

http://www.wemoto.com/

Mick.

[johnbirchjar]

Thanks for the warning Richard.
The replacment seal kit I have just fitted was purchased from A/N,(I also imagine that if the rear seal was fitted"back to front"it would leak!!)I will dismantle it, just to make sure,and will report anon,J.B.

[johnbirchjar]

Hi Richard,returning to the Thurmistor Switch,If the Temp:Guage switch is in the same position,(as is with my bike)where is the Turmistor re-located to?J.B.

[Richard Negus]

John,
I haven't got a better photo to show you where things are in that area.
.the fan switch is the big brass lump with a 22mm hexagon and two blade terminals
.alongside that is either the thermistor or the temperature switch, fixed to the engine by two small screws.
..the thermistor is an aluminium cylinder with black wires about two inches long, terminating in a white two-pin plug
..the temperature switch is smaller and has two blade terminals
.the temperature gauge sender is located below those two and has a mushroom-shaped head and a single wire connection to the harness
R.

[mfremlin]

rotary 1 (2).JPG

Hopefully if upload worked...........

Mark.

[Richard Negus]

"A picture's worth a thousand words"

Well done.

[johnbirchjar]

Thanks Mark,"All has now been reveiled" .Moving on.Richard,as in Marks photo the wires from my Thurmistor are Blue,and I assume that they go directly to the TTI Box?(Julians)where the procedure of "Kill engine,wires off,re-start engine" apply?
The Temp sender is fine,(did you know all new Temp Gauges have a Sender sold with them and "Tuned" as a pair?so any old Temp:guage will not do .)
I am having difficulty working out how the Fan Sender works with just two wires, (a manual switch is easy,four wires,two for power in,two for power out to the fan,)but the sender only has two blades(wires presumably to the fan?)so where does the power come from? a puzzled J.B.

[Richard Negus]

Brown wires to the switch, as in Mark's photo, are power in to the switch
Blue wires is power out to the fan.
At the fan connection, you'll find a black wire which is ground for the fan motor.

If memory is correct, the standard production loom had orange wires at the fan switch; could be wrong though.

Not wrong; just looked at what I know is a standard bike and the wires to the fan switch are both orange and, to the fan, they are one orange and one black.

4063-40.jpg

Yours, John, is probably different again.
R.

[johnbirchjar]

Thanks for that Richard,as you surmised, my bike is different,(A)the wiring loom is ah la Classic ,and(B) the Fan is "foreign"(and is 9"wide )but the wires are black and orange .
I shall do some "re-wiring" and report anon,thanks again,J.B.

[johnbirchjar]

Sorry to pester you Richard but "It don't work"(Mind you,the switch could be duff)would a simple"Two wires and a Bulb Holder"test if it's ok?(power to the switch,connect both test wires to both switch terminals,run the engine to 90/95o and see if the bulb lights up .
Why are there two power wires to one terminal,is there another "sender" in the system?
If the switch is duff,have you the part No for a new one(or are all switches the same?)rgds,J.B.

[Richard Negus]

I'm struggling to remember what Mark's bike looks like and why it has two brown wires to the fan switch, and the single blue output to the fan.

But, in the standard set-up, the fan has a dedicated fuse with an orange wire from it to the fan switch and then another orange wire from the switch to the connection to the fan itself.
So, the wires at the switch are both orange and those at the fan connection are one orange and one black (ground).

Mark's set-up looks like it doesn't have a dedicated fuse and uses the generic brown wire (which is 12 volts via the ignition switch) for power to the fan switch and the second brown wire then feeds something else.

First you should check that you have 12 volts at the wire to the fan switch.
If ok, then connect that to one of the switch terminals, get the engine very hot, and check there's 12 volts at the other switch terminal.
If not, then the switch is duff. Norton part number 55.1144, originally from a Volvo 740.
If ok, then connect the blue fan wire to the switch and the black fan wire to ground.
If the fan doesn't then work, then connect it directly to the battery.
If it still doesn't work, then the fan is duff.
R.

[johnbirchjar]

Many thanks Richard,you have confirmed what I had more or less worked out for myself,so the switch is duff ,and I know the fan is ok 'cos at the moment it is operated by an "On/Off" switch on the handlebars ,thank again,ride safe,J.B.