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#579878 - 01/08/15 8:55 am Re: where do the coil wires go on dual plug heads? [Re: NickL]  
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Running from demons in WNY
Nick,the operator of the dyno shop I use for the race bike has a very simply mechanical device to detect detonation. A short length of a small diameter copper tubing is mechanically fastened to the engine head. it's connected with rubber tubing to a set of "headphones" just like a doctor's stethoscope.The sound of detonation can be heard clearly over the normal engine clatter.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#579890 - 01/08/15 11:34 am Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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that's a really useful suggestion.

kevin cameron once wrote that detonation sounded like smacking rocks together underwater, hard. i've heard that in my motor before using poor quality gasoline in an emergency, but the continuous knock that you can't hear because of pipes and concentration would be extremely useful to detect.

there's too many variables to keep track of it all if you're running a motor at the edge, especially fuel blending.


Into the distance a ribbon of black
Stretched to the point of no turning back
A flight of fancy on a windswept field
Standing alone my senses reeled
A fatal attraction is holding me fast how
How can I escape this irresistible grasp?
#579904 - 01/08/15 12:48 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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And piezoresistive chips are used to plot cylinder pressure under varying loads. But all of this is theory and the problems I see day-in-day and day-out are more of a practical nature. As Kevin Cameron is fond of saying, you must toughen you engine to prevent detonation and pre-ignition long before your offer fuel to the engine. The first thoughts about detonation should be in the workshop, not the gas station or the dyno room. It is way to late to make any meaningful changes.

Unlike BSA and Norton, who have by some measure almost modern combustion chambers, Triumph's hemi combustion chamber design was abandoned by engine designers years ago. It is a relic from the distant past. The design is further inhibited being air cooled, very minimal in mass and with no where adequate fining for what some people expect from the engine.

While static compression and intake cam closing are a starting point they are just that.
Just as important are:
Valve margin thickness, margin shape and seat widths.
Removing all sharp edges from the piston, spark plug hole, and blending valve pockets.
Selection of the proper grade of spark plug.
Selecting cams, and timing those cams, with the intended use in mind.
Of course timing and fuel mixture.
Matching individual gear ratios and overall gear ratios for the engines power band and intended use. There is a reason Triumph provided wide ratio transmissions on their dual-purpose models.
Selecting piston ring thickness that matches the engine design. Thin rinshould not be ones first choice for street engines using pump gasoline.
Making sure rings seat during initial start-up as 75%, or more of the heat in the piston is removed through the rings. Those low tension thin rings have there place, but it is not always in one of these motors.
The over all gear ratios are matched to the intended use and riders ability. There is a reason Triumph provided wide ratio transmissions on their dual-purpose models.
And while those early light flywheels worked well for the likes of Eddie Mulder on the soft sand, they provided more opportunity for combustion mischief with the novice rider. At low rpm they lack the kinetic energy

There is a lot of talk about squish and "swirl" helping control detonation. You also hear talk about about squish this, and squish that about Triumph heads. While there might be flat areas near the edge of some Triumph pistons and heads are thought to be squish bands the only head that comes near having a true squish band is the early unit 500 twin. And although the physical parts are in place, the gap between the piston and head is such that it is a squish band in name only. It is too wide to be effective. If you are not measuring and setting the gap in the .035" range it is of no benefit in creating enough swirl to help control detonation.

In the end Triumph did two things that were an effort to help prevent detonation, but it was very late coming. The T140D head with the parallel ports and the constant velocity carburetor. The T140D port design dramatically increased swirl improving combustion and lowered combustion temperatures to a point where it required running spark plugs 2 ranges hotter to prevent fouling. The CV carburetors prevented high dynamic cylinder pressures caused by rapid opening of the carburetor while the engine is under even a light load (often referred to as lugging).

Before Triumph started to use the CV carb the rider had to remember to shift to a lower gear when he sensed that the bike did not respond with an increase in speed as the throttle was opened. While your car does this without you thinking about it, with your Triumph you have to remember to do this. And when you sort the motor a lot of the detonation, and even modern engines designed to use current fuels will detonate, can be managed with intelligent use of the throttle and the shift lever. Modern cars have a computer... your Triumph only has you.


#579916 - 01/08/15 1:42 pm Re: where do the coil wires go on dual plug heads? [Re: John Healy]  
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Originally Posted By: John Healy
And piezoresistive chips are used to plot cylinder pressure under varying loads. But all of this is theory and the problems I see day-in-day and day-out are more of a practical nature. As Kevin Cameron is fond of saying, you must toughen you engine to prevent detonation and pre-ignition long before your offer fuel to the engine. The first thoughts about detonation should be in the workshop, not the gas station or the dyno room. It is way to late to make any meaningful changes.


In my opinion you have to be on guard for detonation when testing on an engine on the track or in the dyno room.Especially hobbyist builders like me who don't have years of experience on a Triumph engine to know the limits.
All might be fine with the engine build but a bad or mislabeled fuel load could turn the pistons inside out....

Last edited by Hillbilly bike; 01/08/15 1:43 pm.

650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#579937 - 01/08/15 3:46 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Quote:
All might be fine with the engine build but a bad or mislabeled fuel load could turn the pistons inside out....


I am not totally unfamiliar with detonation! But over some 50 years of preparing Triumph engines for racing of all sorts, I have learned not to wait, but to anticipate these kinds of problems. Most of the failures I personally have experienced have been of my lack of understanding, not the fuel's.

And my post was not inspired by your previous post...

This is where I like to start:

These are the piston blanks we use when setting up an early 500 squish band head so it works.


#579939 - 01/08/15 3:51 pm Re: where do the coil wires go on dual plug heads? [Re: John Healy]  
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Originally Posted By: John Healy

There is a lot of talk about squish and "swirl" helping control detonation. You also hear talk about about squish this, and squish that about Triumph heads. While there might be flat areas near the edge of some Triumph pistons and heads are thought to be squish bands the only head that comes near having a true squish band is the early unit 500 twin.


hi john

i'm used to seeing much better squish bands on old two-stroke cylinder heads than i've ever seen in a triumph. i didn't even recognize one being there the first time i looked.

are there modifications that one can do to a stock triumph T120 head that can significantly increase swirl? maybe my question includes increasing velocity in general, as it seems to me that one would help the other.


Into the distance a ribbon of black
Stretched to the point of no turning back
A flight of fancy on a windswept field
Standing alone my senses reeled
A fatal attraction is holding me fast how
How can I escape this irresistible grasp?
#579942 - 01/08/15 4:17 pm Re: where do the coil wires go on dual plug heads? [Re: John Healy]  
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JH,I saw that photo of yours recently and meant to ask...Why are the rings located so far below the piston crown ? It appears the they be moved up quite a bit before fouling the valve relief. All modern piston designs seems to have the ring package pushed up as high as possible to eliminate unburned gases remained in the 'dead space"



650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#579946 - 01/08/15 4:50 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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I don't think the rings can go much higher, when you look at the complicated shape of the crown.


Amateur Loctite enthusiast.
#579947 - 01/08/15 4:53 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Quote:
are there modifications that one can do to a stock triumph T120 head that can significantly increase swirl? maybe my question includes increasing velocity in general, as it seems to me that one would help the other.


No, the 650 head, or the late 500 for that matter, does not lead itself to having a squish band without a lot of work, and expense. The 750 twin can be worked to have a squish, but requires different pistons and some work.

Increasing air velocity through the ports seems counter intuitive. Because drawing air into the cylinder is a timed event, air velocity is more than a consideration. In a lot of tuner's eys it is where a lot of the magic comes from. The common thought is to increase the port diameter, but in my experience with the 650 it is too big for a street engine to start with. For street work the early 9 bolt head with the small non-unit ports and valves makes for a more useable, easy to tune, and more rideable street bike with a good wide power range suitable for the standard 4 speed gearbox.

The same port as the late 650 works real well with the large bore of the short rod 750. Unless you know exactly what you are doing I would leave the ports alone, but concentrate your time and money to the area around the valve seat.


#579951 - 01/08/15 5:15 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Quote:
JH,I saw that photo of yours recently and meant to ask...


They are blanks - you chuck them up and machine them to match the squish band in the head. The final shape, after some nibbling away the parts I don't need, is not unlike the ones the factory used in the T100 and Triple racers.

As the area under the dome is also not machined you can vary the top of the dome for improved flame propagation and final compression ratio. You need to put them in a piston vice and go at them in the Bridgeport. This also allows you to vary the piston weight to fine tune balance.


#579973 - 01/08/15 8:12 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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I think there is a little misunderstanding of my previous comment here, the sensors I was talking about are typically known as 'Knock-Sensors' on later cars. These sensors are able to detect frequencies into the ultrasonic range, way beyond human hearing, this is where the onset of detonation starts. They generate a voltage generally in the micro volt range which can be amplified and used within the ECU to proportionally retard timing thus preventing the onset of the pinking you can hear within the human range which is up to about 12khz at our age if we are lucky! I was not referring to pressure type sensors which also employ a similar material and which have a varying deflective resistance.

Joe, whilst your guy at the dyno shop has a great idea with the length of tube and earphone set, he would be better off getting his dog to listen on the 'phones as his hearing will detect detonation well before us and if prevented at that point little or no damage may be done. (only joking)

A couple of guys at Cos****h in the uk did huge amounts of work on this in the 90's. I think they ended up with the mob that build the F1 ECUs. IE. Money is no object.

Anyway......Whats wrong with the advance/retard lever on the 'bars? It was good enough for our fathers and they had to contend with crap fuel.



#579985 - 01/08/15 8:53 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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No, Nick no misunderstanding here. And they also have sensors to measure dynamic cylinder pressure under no-load and full-load. These can be used to predict abnormal cylinder pressures that can lead to detonation.


#579997 - 01/08/15 9:48 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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I worked the squish in a different way. Instead of squishing around the edge of the piston into the centre, I put the squish opposite the spark plug so the charge is pushed around to the plug. No detonation problems with this on pump fuel.

#580012 - 01/08/15 11:56 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Triton Because of the size of the valve cutaway on the intake side of this piston if the rings aren't set a bit lower than normal the valve pocket cuts right into the ring groove. Not ideal, but it seems to work out. Except for the valve pockets the whole dome of the piston above the ring grooves is solid when I get the pistons. The head is machined and measured and the dome cut to match. Then the inside is cut leaving a dome thickness in the range of .125". Do the same with the 750 we ran for years.

David - Nice "another way to skin the cat." KB pistons have been making a piston for sportsters with a similar dome configuration for quite a few years now. It is a whole new world when you find out you can get partially finished pistons and match the pistons dome to the head. SOme people create a trough across the top of the pistons in an effort to improve combustion. Still some small signs of detonation. It seems you exercised the throttle some, or were beginning to loose a valve spring, with that right cylinder exhaust valve kissing the piston - was it worth it? DId you win...


#580013 - 01/09/15 12:44 am Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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That was probably when I was following an RG500 with my Wenco framed R3 racer on PCH coming back south from Laguna Seca. He could not out accelerate me coming out of the corners. If the throttle cable doesn't need adjustment periodically you're not turning hard enough, yes?

Last edited by DMadigan; 01/09/15 2:33 am.
#580089 - 01/09/15 2:17 pm Re: where do the coil wires go on dual plug heads? [Re: John Healy]  
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The T140D head with the parallel ports and the constant velocity carburetor. The T140D port design dramatically increased swirl improving combustion and lowered combustion temperatures to a point where it required running spark plugs 2 ranges hotter to prevent fouling.

hi John, very interesting info as ever.
But I still cannot understand how you can have "improved combustion" and lower temperature at the same time? Is it because they had a very lean carburation and very low CR?

#580111 - 01/09/15 4:32 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Simply stated - the swirl from the incoming mixture seems to mix the air/fuel mixture better than the "splay port" resulting in a better burn or "improved combustion" = little or no detonation.

no-detonation = lower combustion chamber temperatures - and the "explosion" isn't pushing past (blowing away) the protective boundary layer that insulates the head from the heat of combustion.

With lower compression, which they had already done in previous years, you compress the incoming charge less. As a result the fuel air mixture does not heat up as much as it did with a higher compression. It is all a balance of controlling pressure in an effort to control heat. You want the fuel/air charge to burn and not explode.

The constant velocity carb prevents the rider from taking a handful of throttle at low rpm. Doing so, you can drive the dynamic cylinder pressure, and gas temperature with it, to the point that when the spark plug fires the additional pressure created by combustion pushes the end gas (un-burnt gas opposite flame front) to a point where it will self ignite. You have just created a case of severe detonation. In a CV carb the slide responds to manifold vacuum, and not just to throttle position and prevents the rider from causing the carburetor from delivering a big gulp of air when it cannot handle the dramatic increase in cylinder pressure it causes.

A good example of this is checking the cylinder pressure with a gauge. Leave the throttle closed and you get a very low reading - There is no air through the carburetor to compress. Open the throttle and the engine takes that big gulp and the needle jumps up over 100 pound and more. That is dynamic cylinder pressure - it changes with slide position.


#581391 - 01/17/15 2:57 pm Re: where do the coil wires go on dual plug heads? [Re: John Healy]  
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Originally Posted By: John Healy
Simply stated - the swirl from the incoming mixture seems to mix the air/fuel mixture better than the "splay port" resulting in a better burn or "improved combustion" = little or no detonation.

no-detonation = lower combustion chamber temperatures - and the "explosion" isn't pushing past (blowing away) the protective boundary layer that insulates the head from the heat of combustion.

With lower compression, which they had already done in previous years, you compress the incoming charge less. As a result the fuel air mixture does not heat up as much as it did with a higher compression. It is all a balance of controlling pressure in an effort to control heat. You want the fuel/air charge to burn and not explode.

The constant velocity carb prevents the rider from taking a handful of throttle at low rpm. Doing so, you can drive the dynamic cylinder pressure, and gas temperature with it, to the point that when the spark plug fires the additional pressure created by combustion pushes the end gas (un-burnt gas opposite flame front) to a point where it will self ignite. You have just created a case of severe detonation. In a CV carb the slide responds to manifold vacuum, and not just to throttle position and prevents the rider from causing the carburetor from delivering a big gulp of air when it cannot handle the dramatic increase in cylinder pressure it causes.

A good example of this is checking the cylinder pressure with a gauge. Leave the throttle closed and you get a very low reading - There is no air through the carburetor to compress. Open the throttle and the engine takes that big gulp and the needle jumps up over 100 pound and more. That is dynamic cylinder pressure - it changes with slide position.
I get a great education when I examine some of these discussions. Taking this in a slightly different direction, It seems that most if not all the comments here apply to highly modified machines. I am no stranger to mixing fuels to reach necessary octane levels.My 1969 BSA owners handbook shows a minimum octane requirement of 98 ( I'm thinking RON) for a stock 9:1 A65. HB provided two good links,the Sunoco one I am familiar with. The other brought out something that seems to be lost on some people-that a slightly lower static compression ratio with a factory engineered timing curve is better than a retarded timing curve with high(er) compression ratios and is the better way to get our old -stock- iron to run on 91-93 octane pump premium.The article mentioned a 1 to 2% loss in torque with lowered compression. Didn't the majority of T140's have an advertised compression ratio of 7.9:1 in preparation for lower octane unleaded and the phasing out of super premium leaded fuel? With A65's or T120's I was never satisfied with the performance of retarded timing so as to operate on sub-standard fuel.The engine is so much happier with 100 octane and the factory settings and so am I.SO my question is, would quality forged pistons-not cheap- that provide a lowered 8:1 compression ratio for otherwise stock A65,T120,etc. machines be marketable, and if not why not? Hoping for a lot of feedback.


1969 BSA A65T w/A70 engine
1970 Royal Enfield Interceptor S ll
#581392 - 01/17/15 3:07 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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My 76 T140V at 7.9/1 would run on lamp oil


When given the choice between two evils I picked the one I haven't tried before
#670447 - 10/08/16 9:26 am Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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Transgarp calling John Healy smile

I dismantling the engine of the T120R in May
According to this Web site, the wear of my conn-rod bearing confirms the detonation caused by a gasoline of too low octane or a too high C.R., here 9.5:1 with 750 Morgo kit
http://www.agkits.com/bearing-failure-analysis.aspx

My bearing wear:
http://transgarp.dyndns.org/motorcycle/0800/20160000/20160521_04.JPG

The last year 2015, I ride under this configuration :
750 Morgo kit CR 9.5:1
28 full-advance
21 teeth front sprocket, 46 rear
Detonation

In August 2016 I reassembled the engine with this configuration :
750 Routt kit CR 8.9:1
38 full advance
22 teeth front sprocket, 46 rear
No detonation

All my problems of detonation disappeared, while riding with the same super gasoline of Shell and more power all rpm smile

You surely wonder why I have enlarges the front sprocket.
Not the choice because of the necessary release of the chains to the top of the front of the swingarm considering which I installed the complete back suspension of a Honda XR650L on the frame of the T120R

http://transgarp.dyndns.org/motorcycle/2000/20161001/17.JPG

http://transgarp.dyndns.org/motorcycle/2000/20161001/08.JPG

#673622 - 11/06/16 2:32 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
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What do you know, I have an A65 that has the primary side rod brgs that look just like that. Spitting image. However, I have no information on the motor or how it ran when it was a complete bike. I know it had under 10,000 miles on it and the throws and bush are factory clearances. I assume it was all stock. It is a 1971 engine and everything else is specking out as should be. Maybe it had some bad spark knock hey? detonation? I don't know, but I have never seen a brg look like that except in books. I have seen automotive engines like a big block Chevy that was ran very hard at high speeds for several miles then shut down right afterwards and had a slight knock in the morning after cool off, when torn apart one rod or rather one rod with the bearings must have been to hot at shut off and stuck to crank, when it was disassembled it looked similar to what you have. No harm to rod or crank, could only figure one defective bearing that lost its integrity and stuck to crank. Reassembled and fine good to go. Sometimes you do even get defective parts from factory, I know this BSA engine has never been apart so maybe a bad one. Ive seen several bearing failures from vandervill in the past 25 years.

#673909 - 11/09/16 7:07 pm Re: where do the coil wires go on dual plug heads? [Re: Keane Lucas]  
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Originally Posted By Keane Lucas
Originally Posted By John Healy
Simply stated - the swirl from the incoming mixture seems to mix the air/fuel mixture better than the "splay port" resulting in a better burn or "improved combustion" = little or no detonation.

no-detonation = lower combustion chamber temperatures - and the "explosion" isn't pushing past (blowing away) the protective boundary layer that insulates the head from the heat of combustion.

With lower compression, which they had already done in previous years, you compress the incoming charge less. As a result the fuel air mixture does not heat up as much as it did with a higher compression. It is all a balance of controlling pressure in an effort to control heat. You want the fuel/air charge to burn and not explode.

The constant velocity carb prevents the rider from taking a handful of throttle at low rpm. Doing so, you can drive the dynamic cylinder pressure, and gas temperature with it, to the point that when the spark plug fires the additional pressure created by combustion pushes the end gas (un-burnt gas opposite flame front) to a point where it will self ignite. You have just created a case of severe detonation. In a CV carb the slide responds to manifold vacuum, and not just to throttle position and prevents the rider from causing the carburetor from delivering a big gulp of air when it cannot handle the dramatic increase in cylinder pressure it causes.

A good example of this is checking the cylinder pressure with a gauge. Leave the throttle closed and you get a very low reading - There is no air through the carburetor to compress. Open the throttle and the engine takes that big gulp and the needle jumps up over 100 pound and more. That is dynamic cylinder pressure - it changes with slide position.
I get a great education when I examine some of these discussions. Taking this in a slightly different direction, It seems that most if not all the comments here apply to highly modified machines. I am no stranger to mixing fuels to reach necessary octane levels.My 1969 BSA owners handbook shows a minimum octane requirement of 98 ( I'm thinking RON) for a stock 9:1 A65. HB provided two good links,the Sunoco one I am familiar with. The other brought out something that seems to be lost on some people-that a slightly lower static compression ratio with a factory engineered timing curve is better than a retarded timing curve with high(er) compression ratios and is the better way to get our old -stock- iron to run on 91-93 octane pump premium.The article mentioned a 1 to 2% loss in torque with lowered compression. Didn't the majority of T140's have an advertised compression ratio of 7.9:1 in preparation for lower octane unleaded and the phasing out of super premium leaded fuel? With A65's or T120's I was never satisfied with the performance of retarded timing so as to operate on sub-standard fuel.The engine is so much happier with 100 octane and the factory settings and so am I.SO my question is, would quality forged pistons-not cheap- that provide a lowered 8:1 compression ratio for otherwise stock A65,T120,etc. machines be marketable, and if not why not? Hoping for a lot of feedback.


Rather than the expense of custom pistons just run a thicker head gasket and/or get a base gasket made.
You may see the difference on a dyno, but i doubt you would notice it anywhere else.
For a road bike relying on supply of decent fuel whilst out riding are risky, i run both my old irons on the safe side as timing and mixture goes. The 0.5 second 0-60mph or 2/3 BHP lost are worth the security of not holing pistons etc.



#675272 - 11/22/16 10:42 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
Joined: Mar 2011
Posts: 78
linker48x Offline
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linker48x  Offline
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Joined: Mar 2011
Posts: 78
Alaska
Not sure if the original post and original questions are still relevant. But to respond, my AHRMA road racer T140 engine has 11.5:1 pistons, has a twin plug head done many years ago at John Healy's suggestion by Dana Johnson at Import Machine Service in Mass., and uses a crank-driven twin plug ignition I got from Rex Caunt (modified PVL with little twin lead coils). When I first did this, I used a Boyer Powerbox, and John Healy suggested to me to place each of the two wires from each coil on opposite cylinders to get better spark, and I have continued to do that, it seems to work the best that way. To answer the other questions I saw above, I use 32 degree fork lead, and 110 race gas. The effect has been to make the engine run cooler and smoother and make more torque--the combustion chamber shape and flame front were obviously issues with a single plug and this very high compression. Runs great! Doubt twin-plugging is necessary on the street with 9:1 or so, though.

#678816 - 12/24/16 3:29 pm Re: where do the coil wires go on dual plug heads? [Re: kevin roberts]  
Joined: Dec 2013
Posts: 3,262
kevin roberts Online content
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kevin roberts  Online Content

BritBike Forum member

Joined: Dec 2013
Posts: 3,262
ohio, usa
i twin-plugged my old street bike when all i could get was 89 unleaded. these days i use 110 leaded premium and run the timing back to 30 BTDC.

i'm running 11.75:1 now on another machine that is single-plugged at the moment, because i'm using an old ARD. but i'm using VP 108 C12 in it

http://www.racefuel.com/vp-c12-racing-fuel-108-octane/


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