Boyer problem?

Greetings-I have a bit of a head scratcher going on with my 75 850. A while back I started noticing that after the engine was warmed up, I would get a 200-300 increase in RPM at idle. It also seemed to be a little sluggish-not a lot but noticeable. Checked valve clearance, went through the carb (single Mikuni VM-34) - no improvement. Checked the cam chain and it seemed a bit loose so I adjusted and then set the timing again. Got a marked improvement for three or four rides and now it seems to be acting up again. I run a Boyer, with about 8800 miles on it. The last trial, the RPM was up about 400 and I was also getting a little hiccoughing and popping. It always starts and runs beautifully before it gets warm - about 12 miles. I am beginning to suspect the Boyer. Are there any checks I could make or is replacement the only way to test? Any ideas on where else I can look? Any sage advice would be greatly welcome.

Very happy to find this site and this forum. I don't feel so alone anymore. Thanks.

RL

RD,

Sound more like a dirty carby, are the carby manifold bolts tight ?.

short of dry joint in the boyer, changing the advance when it heats up, I would go over the carbs first, looking for manifold air leaks. Try spraying WD40 or equivalent near the joints upstream of the carb. My experience on Boyers is go or no go. Apart from on a Trident where a blown fuse made the boyer retard, but triples have the ign trigger above the alternator.
good luck, cheers Richard

Thanks for the advice. I did check the manifold and went through the carb and all seemed well. I very stupidly forgot to mention one other factor in this little mystery. I have noticed that at times (not always), after getting back to the garage and the bike was warm, I was picking up a distinct clatter - to me it sounded like valve clatter and that is why I checked them. All seemed OK. I can't seem to localize the noise but thought it was coming from the area around the camchain which was why I tightened. I thought it might have been getting loose enough after warming up to cause a little change in the timing at idle. I did think I had it fixed for a while afterwards but, as I said, it becomes an enigma again. Many thanks for the responses.
RL

My experience on Boyers is go or no go

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I respectfully disagree. I have had the stator wires fail, twice. There have been numerous posts on this site indicating the same problem. The wires to the stator coils are definitely a problem with the Boyer. The soldered connection is very prone to failure. Its an easy fix, though. Unsolder the wires and put two small bolts to use as studs. Crimp ring connectors to the leads going to the Boyer box. Its important you do not solder these connections.

I've also had rotors lose magnetism--if the rotor won't cling to a ferrous screwdriver blade and support its own weight it won't reliably trigger the black box



Tim Kraakevik
kraakevik@voyager.net

I too had Boyer trigger wires cause intermittent starting and running very rough, twice, until I got Greg Fauth's trigger wire upgrade kit and found ya can't put two thin nuts behind the Boyer plate or magnets strike them to cause wild advance and glowing headers to the muffer in a few seconds. When I followed instrutions kit worked as intended w/o any more failure.
If Boyer copper broken inside the insulation it can work fine until engine heat softens the insulation then goes nutzo. BTW the primary and the cam chain get quite a bit tighter when hot, better double check the cam chain tension. Too loose a chain or a flattened cam lobe chain jerk/slack will also cause Boyer brains to go bonkers, ugh.

Stokie,

I misread you post about the Boyer being go or no go. Since it was morning, too early for me obviously, I mistook your post to read: Boyers go on and on.

Although Boyers are famous for firing one cylinder only.

For any of you running a Boyer and are experiencing a misfire below ≈3000 rpm, check the wires for a separation inside the insulation near the stator coils. Bear in mind the old adage, 95% of carburetor problems are electrical.

An increase of idle speed due to the engine warming is due to engine oil thinning and reducing the drag.
Very common on boyer analog and rita due to the nature of the advance curve...as they are similar.
Even worse on a rita...one of the technical deficiencies why I decided not to repop them.

One of the best diagnostic analog Boyer techniques is with plugs out on head and key on, plink,plunk,poke,push,pull everything in power path and trigger leads and listen for a snap/spark. Do not do in gear.

Thanks all. Looks like I've been visited by the Boyer broken wire I've heard so much about. Gonna do the the ring connectors on screws fix. A big help having all your advice.

RL

I was perpetually chasing a stable idle with the Boyer. Fitted a Tri-Spark and no more problems, hot cold, whatever.

Just another one;
Sometimes, if the battery voltage drops a little too low the Boyer can start to advance and that will increase revs. If the voltage gets lower the advance can get out of control and cause that miss and pop.

Best of Luck,

Cash

Hi all. New to site. Aquired 850 mk3 from father. Replaced boyer.k3 with boyer mk4...appare tly stops kickback. My simple question is where best to locate unit. I have it in the space below engine hanger underneath frame downtube. Bike started easily but now harder to start and when running it is misfiri g on lhs. New amal carbs fitted 10 yr ago and has only done 200 miles since. Any advice appreciated..simon in liver pools

"I was perpetually chasing a stable idle with the Boyer. Fitted a Tri-Spark and no more problems, hot cold, whatever."

Concur re trispark.

Re the Boyer - it's a location issue that frequently causes the problem. It should NOT be located on the bike; a trash can is a good location.

I never figured out how a system that wasn't as good as the oem points/AAU performance-wise became known as an "upgrade." Good marketing, I guess.

40 years ago the Boyer was the dog's bollocks. Getting rid of the sticky POS AAU ('72 Combat were the worst) was a huge improvement. I was relatively happy with my Boyer all that time. Although the idle was not all that reliable when sitting at a light it was still better than points. Technology has marched forward with idle stabilization and better advance curves. I switched to the Pazon Altair two summers ago and the idle is wonderful. Boyer needs to wake up if they want to stay in the game.

dynodave said:

An increase of idle speed due to the engine warming is due to engine oil thinning and reducing the drag.
Very common on boyer analog and rita due to the nature of the advance curve...as they are similar.
Even worse on a rita...one of the technical deficiencies why I decided not to repop them.

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I'll be damned...that's the technical reason why my '72 750 with RITA idles faster after warming up. Not really a problem as long as the idle is set hot. Always assumed it was the carbs allowing more air in as they got hot.

batrider said:

Technology has marched forward with idle stabilization and better advance curves. I switched to the Pazon Altair two summers ago and the idle is wonderful. Boyer needs to wake up if they want to stay in the game.

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Many BB ignition systems still in current in use will be the old Micro MkIII analogue units which sold in their thousands and could easily be 30+ years old, as well as being relatively old technology so things need to be kept in perspective.
I don't necessarily think Boyer Bransden need to wake up, as they introduced their Micro Digital and Micro Power ignition systems years ago, well before Pazon and Tri-Spark ignitions were around. The Micro Digital is a considerable improvement over the old Micro MkIII analogue ignition in my opinion, however there still appears so be a significant market for the less expensive Boyer (now Micro Mk IV) system as it would seem not everyone is prepared to pay out 300-400+ (pounds, dollars, whatever) for electronic ignition, so dealers still continue to sell the popular cheaper alternative.

Anyway...to get back to the original subject.

Simondean said:

My simple question is where best to locate unit. I have it in the space below engine hanger underneath frame downtube.

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One usual place would be under the coil bracket between the coils where the condenser pack and ballast resistor would originally have been fitted (unless they are still there?) however, it's placement isn't critical as long as it's reasonably well isolated from vibration.

Simondean said:

Bike started easily but now harder to start and when running it is misfiri g on lhs.

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That is unlikely to be caused by the electronic ignition if the problem only affects one cylinder. If it is an ignition related problem, then it's more likely to be the spark plug, cap, HT lead or coil of the cylinder in question. You can try swapping over those parts individually and see if the misfire transfers over to the R/H cylinder, if not, then the fault could be carb related (perhaps a blocked pilot system) or the problem may be inside the engine (rings, valves, etc..)

LAB you are right about the higher end Boyer units. I forgot about them. My inputs seem to shut off when the price goes out of my range.

I swore by my old Boyer for years and was one of the first to buy one when they came out. But as an engineer I really like trying out newer technology and in this case it was an improvement. All my bikes will idle with no hands now. (My new Harley is really good at it!)

Russ

I think the trispark is great for a triple but on my commands, I blew up 3 of them. I think perhaps the vibration of a big twin was not as compatible as it could have been.
They are fantastic to set up, don't get me wrong but thre failures and the towtruck drivers no: on speed dial was it for me. I ended up buying him a bottle of rum for Xmas we got that close!!!
All the units were replaced under warranty which was also very re-assuring but again, my daily rider needs to work every day!!
The issues varied from fried black box to internal circuits failing and I can't even remember the last one. Each issue was isolated to the sexy little red gemstone behind the points cover.
One issue saw the bike idle perfect then within 5-10 mins, would just jump to 5000rmp or stop altogether. That was the last issue. Sent back to trispark, he was nice and said it was the unit and commented that I wasn't having a good run eh!!!
He personally put together a unit for me and sent it assuring me it was brand new and there would be no further issues with the trispark unit for me.
I popped it on eBay.