Boyer Bransden quetstions

WacoBrian

WacoBrian

XS650 Junkie
Messages
527
Reaction score
2
Points
16
Location
Waco,Texas
i picked up an 81 with a blue box Boyer Bransden kit in it, guy had it put in at a shop awhile later the piston developed a hole, this guy telling me the boyer is to hot for a #1 piston, could this be true or is there some other issue?
now i know about stock points and pamco but i know nothing about the boyer bransden. thanks to everybody who makes this site happen :thumbsup:
 
I have used the BOYER setup for over 20 years on Triumph BSA and XS650 plus other bikes and never heard that or had that problem. First you have a single fire ignition and unless your motor is repased both will burn not one. Sounds like its a old motor that just needed pistons.I have run motor with electronic ignitions on 118 octaine and with Nitro and destoryed parts but never popped a hole in a piston.Buy a good set of pistons and call it a day.
 
cool thanks for the info

I have a fresh points motor I want to put in it, I will just swap the necessary parts then call it a day.
 
Based on my experience installing a blue-box BB on my '82 last summer, I'll take a wild guess: whoever installed it did not time it correctly and it was over-advanced. The BB install instructions that came with mine do not show how to time it in the '81-'83 models, which do not have a full-advance timing mark like earlier 650s have. You have to make one yourself, as shown in the attached pic, which Michael Morse emailed to me while I was on the phone asking him how to do it. Done right, full advance is 39 degree BTDC; done wrong, anybody's guess. :shrug:
 

Attachments

  • timing mark for Boyer Brandsen ignition system.jpg
    timing mark for Boyer Brandsen ignition system.jpg
    163.1 KB · Views: 341
If you assume that the timing plate is in the right position and hasn't been moved, you're asking for another holed piston. Verify alignment of the TDC mark.
 
The Boyer uses a wasted spark system , what color was the other plug, it can not be too hot for one cylinder as the timing is the same for both, more likely an air leak on the inlet or carbs not balanced, than a problem with the Boyer on one cylinder.
 
jay760 said:
The Boyer uses a wasted spark system , what color was the other plug, it can not be too hot for one cylinder as the timing is the same for both, more likely an air leak on the inlet or carbs not balanced, than a problem with the Boyer on one cylinder.
Click to expand...

that's what my friend told me when he fond the bike down the street from him,
this is kind of what I was looking for, thanks
 
There is NO WAY timing is going to put a hole in your piston. The boyer or any other electronic systems don't have that type of spark. What you had like i said before was a motor that is over 20 years and may have had pistons that were also that old with tons of miles. It takes many many hits from a valve to crack a piston and you would have had other problems first. I had a xs650 that ran its ass off and when i broke it down to refresh it for a customer it had a dime size hole in the piston and still ran. Bike was over reved many times and valve was hanging up and piston was shutting it closed and if you would have rode this bike you would have never know it. So there is something else going on with your motor. Tap the other piston and see if it breaks easy. I just think you need a new set of pistons and look at your valves . If timing was off that far and the motor and pipes were tuning red the rings would have seized first. Just a bad or old cast of pistons.
 
A too advanced timing can hole a piston. The too advanced timing causes detonation. This detonation can and will burn a hole in a piston.
Leo
 
I never seen one so if you did i got to beleave you. I have built many street and race motors and have seen valves poke holes in pistons but never seen a ignition system blow a hole in a good piston. That motor would have too glow on the outside for that much heat. So Leo may be right if he has had that happen so double check your timing.
I have had motors blow up but it was always a piece of something eles that broke and went into cylinder. When you take it apart show a picture of piston if you can and were they original?
 
Sounds like you haven't torn down many dead XS650 motors, "Daddy." I've taken down quite a few with no valve train issues and a dime-sized hole in one piston--usually the right, probably because the primary side runs a little hotter. Every time--we're talking around half a dozen motors here--the ATU was either trashed due to improper securement or worn, leading to excessive advance and detonation. It isn't just a matter of how hot the engine gets, either. When the spark fires so far advanced that the crank can't respond--well, you figure it out. You stand corrected.
 
I''ve holed an mx bike piston before due to incorrect timing. Bike was not running properly I checked the timing (appeared to be set correctly) & took it for a ride - holed the piston in no time. The owner had replaced the stator rotor with some random rotor with incorrect timing marks & I didn't pick it up. Let's just say I learned my lesson - check your timing.
 
I did about 30 and never seen that happen and its very odd that only one piston would have a hole when they both fire together. I have been doing motor since 1969 and i am going to say i never seen one due to ignition . It was always a old wise tale that Mags would get so hot that they would melt the top of a piston and i ran them on Triumphs and Hondas and never seen that either. I have ran Nos Nitro Alky and straight 116 in motors and never made a hole in a piston. So as old as i am you learn something everyday but its got to do with the age of pistons and the miles. I just can't beleave a new set of pistons and your timing off and you burn a hole. Like i said before i had a XS650 with a dime size hole in the piston but ran fine. Couldn't beleave it ran that good but it was the exhaust valve that had a little bend in it and the rocker opened it and the piston slammed it closed. Thats the only one out of 30 that i seen a hole in. Live and learn and i have done many many motors over the years and got to say never saw it.
 
thanks guys for all the great info, no how in the world am I going to be able to set the timing? I have a 79 motor that im going to swap parts over to go on this beast.
 
Use the search function at the top of the page, search for timing. While you are there search for a manual and get reading.
 
Gonna say it again--piston holing due to preignition has nothing to do with how hot the spark is and little to do with how hot the motor gets (though preignition will be more severe in a hotter cylinder, which is, again, why the primary side usually takes the damage; are you reading it this time?) It has to do with combustion occurring at the wrong time due to excessive compression for the fuel used, incorrect ignition setting, lean fuel mixture, or a combination of all three. Preignition knocking is called "detonation" for a reason; it blows material off the piston crowns, which is why guys with bad hearing need to look for aluminum flecks on the spark plug insulators after a plug chop.
 
a lean mixture can also cause pre-detonation in a cylinder. Too much air (air leak) or too little fuel (octane etc)

Have you ruled out the fuel mix to that cylinder ? What does the skirt of the pistons ,cylinder head , valves and the spark plugs tell you about the fuel mix and detonation characteristics between the cylinders prior to failure?
 

Similar threads

peterg
Boyer Bransden Micro Power Kit Wiring with an M-Unit
Replies
9
Views
1K
peterg
peterg
1
need help with wiring!
Replies
2
Views
964
650Skull
650Skull
2ManyHobbies
77 xs650 won't start after mods
Replies
19
Views
554
sleddog83
sleddog83
B
No Start - Voltage Drop While Cranking
2 3 4
Replies
68
Views
4K
Jim
Jim
Mailman
Boyer Bransden Ignition installation on my XS2
2 3 4
Replies
70
Views
11K
JRay77
JRay77
Back
Top