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Old 11-06-2013, 01:06 PM   #1
lphil OP
lpihl
 
Joined: Apr 2012
Location: Shaky Christchurch,New Zealand
Oddometer: 5
Question regarding Boyer ignition on R75/7

Hi all ,
I have a question regarding mainly bikes with a Boyer ignition.
A little history first, I acquired the bike over a year ago and slowly going through it. Bike never idled properly, but that was due to numerous reasons, leaky valves, carbs etc.
I got to check the timing dynamicaly and found that it was way over advanced, however i have to say that the bike did feel spirited.
I retarded the timing as per instuctions, max advance at 4k or there abouts(dot stoped advancing). From what I have read and the curves I have seen the boyer runs a little more retarded compared to stock. Furthermore a lot of users on this forum claim that the optimum advance is at 30-35degr.
Bike feels a bit hesitant at 2k onwards, though i know most of the riding is at 3k, plus it feels like its running a bit warmer..
I just want to gauge other riders with a similar ignition and if they have experienced similar behaviour.
My next step is too advance the timing slightly...
Finally does anyone know approximately the difference in degrees when watching the fast dot in the window from the center to the edges.
THanks all, I have being reading this forum for a while and it has being a great resource.
Phil
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Old 11-06-2013, 01:22 PM   #2
190e
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Quote:
Originally Posted by lphil View Post
Finally does anyone know approximately the difference in degrees when watching the fast dot in the window from the center to the edges.
THanks all,
Phil
A little over 3 degrees.

If you know or can find out the number of teeth on the flywheel it might be helpful to calculate degrees per tooth.
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Old 11-06-2013, 02:30 PM   #3
disston
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The number of teeth on an Airhead with the 9 tooth starter is 111, I think. The 8 tooth starter is 97 or 98 , I think.

Wish I knew for sure. I have been lost in the Tech Pages for the last 20 mins trying to find the answer. Hopefully I get it before the end of the night or somebody else could post the answer and save me?
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Old 11-06-2013, 03:05 PM   #4
190e
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I'm not certain of these figures either but as best I know 8 tooth starter was matched to a 93 tooth flywheel and a 9 tooth starter to a 111 tooth flywheel except for R45/R65 which was 107 tooth flywheel.
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Old 11-06-2013, 03:45 PM   #5
disston
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OK. The 9 tooth starter has a 111 tooth flywheel. The 8 tooth stater has a 93 tooth flywheel. In addition there are changes in the crank bores and thread for the flywheel bolts. Some 93 tooth flywheels will take 10mm bolts and some will take 11mm bolts. There are early, shorter, 10mm bolts and later, longer, bolts but the bolt length is determined by the crank bore and doesn't effect the flywheel. Some of the earliest /5 flywheels were very heavy.

I'm not sure about the 93 tooth flywheel coming in 10 or 11mm bolt sizes but I did see some labeled as such. All clutch carrier bikes that do not have a flywheel still have a ring gear for the starter and they would be 111 teeth.
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disston screwed with this post 11-06-2013 at 04:07 PM
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Old 11-06-2013, 03:56 PM   #6
Rob Farmer
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Phil,

Is it the black box Boyer or a micro digital?
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Old 11-06-2013, 04:31 PM   #7
Plaka
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Quote:
Originally Posted by lphil View Post
Hi all ,
I have a question regarding mainly bikes with a Boyer ignition.
A little history first, I acquired the bike over a year ago and slowly going through it. Bike never idled properly, but that was due to numerous reasons, leaky valves, carbs etc.
I got to check the timing dynamicaly and found that it was way over advanced, however i have to say that the bike did feel spirited.
I retarded the timing as per instuctions, max advance at 4k or there abouts(dot stoped advancing). From what I have read and the curves I have seen the boyer runs a little more retarded compared to stock. Furthermore a lot of users on this forum claim that the optimum advance is at 30-35degr.
Bike feels a bit hesitant at 2k onwards, though i know most of the riding is at 3k, plus it feels like its running a bit warmer..
I just want to gauge other riders with a similar ignition and if they have experienced similar behaviour.
My next step is too advance the timing slightly...
Finally does anyone know approximately the difference in degrees when watching the fast dot in the window from the center to the edges.
THanks all, I have being reading this forum for a while and it has being a great resource.
Phil
First, if it runs good--starts well, idles, progresses, don't knock---then this is good. Don't mess with it. if you make changes, take notes on what you had, what you're doing, what your's shooting for.

max advance at 4k is a little high for a single plug engine. See where your static mark is at idle (1000 rpm).

max advance is good, (again single plugged) at 32 degrees. This is not some BMW thing. It applies to all engines and you are correct on that 30-35 thing. The question is, what RPM for max advance? The advance mechanisms in different electronic advance Boyers have different ranges. The early Boyers used the original mechanical advance. Dunno what you got.

The advance mechanism only has so much range so the idle and max advance are bolted together. On your /7 you want the idle (or static) timing at 6 degrees. Gives good starting and idling. The S mark on the flywheel is at 6 degrees. I think. Check your manual.

To answer your question, if you know the degrees of that S mark just measure between the S mark and the OT mark and you know the number of degrees/cm on the flywheel rim. This info is also on a lot of websites. See Snowbum for instance. The timing page.

getting a good reading on the RPM for max advance can be tricky. The problem is the tach. You don't say what instruments you are using.

I would begin your tuning by getting your S mark in the window on the line at idle. Use your strobe light. Then see how it rides. I can't armchair it--I don't know your compression, the kind of gas you have or how you ride. But if you start from the stock setting you have a known place to begin. Modify from there depending on how it drives.
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Old 11-06-2013, 05:29 PM   #8
lphil OP
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Quote:
Originally Posted by Plaka View Post
First, if it runs good--starts well, idles, progresses, don't knock---then this is good. Don't mess with it. if you make changes, take notes on what you had, what you're doing, what your's shooting for.

max advance at 4k is a little high for a single plug engine. See where your static mark is at idle (1000 rpm).

max advance is good, (again single plugged) at 32 degrees. This is not some BMW thing. It applies to all engines and you are correct on that 30-35 thing. The question is, what RPM for max advance? The advance mechanisms in different electronic advance Boyers have different ranges. The early Boyers used the original mechanical advance. Dunno what you got.

The advance mechanism only has so much range so the idle and max advance are bolted together. On your /7 you want the idle (or static) timing at 6 degrees. Gives good starting and idling. The S mark on the flywheel is at 6 degrees. I think. Check your manual.

To answer your question, if you know the degrees of that S mark just measure between the S mark and the OT mark and you know the number of degrees/cm on the flywheel rim. This info is also on a lot of websites. See Snowbum for instance. The timing page.

getting a good reading on the RPM for max advance can be tricky. The problem is the tach. You don't say what instruments you are using.

I would begin your tuning by getting your S mark in the window on the line at idle. Use your strobe light. Then see how it rides. I can't armchair it--I don't know your compression, the kind of gas you have or how you ride. But if you start from the stock setting you have a known place to begin. Modify from there depending on how it drives.

Its the red micro digital.
I started messing with it because it was hard to start, which led to me to checking the timing. At the time, at idle i was way past the 6degrees and uppon acceleration the fast timing mark would disappear from view. This is why I chose to reset the ignition according to the instructions.
With the Boyer you dont have to rely on the accuracy of the rev counter, I am also using a separate one that wraps around the ignition wires for reference. The timing marks now are currently lining up but as I explained earlier bike seems to run hotter and less lively.
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Old 11-06-2013, 05:44 PM   #9
Plaka
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Quote:
Originally Posted by lphil View Post
Its the red micro digital.
I started messing with it because it was hard to start, which led to me to checking the timing. At the time, at idle i was way past the 6degrees and uppon acceleration the fast timing mark would disappear from view. This is why I chose to reset the ignition according to the instructions.
With the Boyer you dont have to rely on the accuracy of the rev counter, I am also using a separate one that wraps around the ignition wires for reference. The timing marks now are currently lining up but as I explained earlier bike seems to run hotter and less lively.

My bike ('83 r100rs ) has stock idle (S mark) timing at 6 degrees. I bumped the compression and dual plugged it. Then played around with that idle timing. It still wanted 6 degrees. Getting away from that either gave me hard starting or some hesitation rolling on from 2k RPM. So 6 it is.

I've changed the advance range and RPM for max advance considerably. But that's for the dual plug setup.

I would set it up as stock as you can get it for timing. Then dial in the carbs. Then go back to the timing maybe. For example, if the carbs are set too lean, it'll run hot and less lively. Someone may have tweaked the timing to try to resolve this not understanding the carbs were the real issue.

So, check you have the correct jets and needle position. Check for worn o-rings in the carbs, a sucked enricher gasket and air leaks in the manifold downstream of the carb. Then balance them nicely with particular care with the idle air setting. Set timing stock and see where you are.
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