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Old 07-13-2010, 03:28 AM   #46
Lornce
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Quote:
Originally Posted by StephenB
Yeah, looked at that but the "A" hi-comp pistons are not a good match to the "C" Nikasil barrels, too loose.
Ah ha.

I'm forgetting the dimentional differences between A, B and C cylinders. What were they again? A couple of tenths of a thou?

It's been a while since I looked at that stuff...

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Old 07-13-2010, 03:35 AM   #47
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Originally Posted by Lornce
Ah ha.

I'm forgetting the dimentional differences between A, B and C cylinders. What were they again? A couple of tenths of a thou?

It's been a while since I looked at that stuff...

You have to match them. They are tolerance grades. The largest possible A piston will fit in the smallest possible A jug. Etc. Mix grades and if you get unlucky you will either have interference fits and a seized engine or too loose fits and broken rings.
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Old 07-13-2010, 04:16 AM   #48
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Originally Posted by Plaka
You have to match them. They are tolerance grades. The largest possible A piston will fit in the smallest possible A jug. Etc. Mix grades and if you get unlucky you will either have interference fits and a seized engine or too loose fits and broken rings.
Yeah, I know all about the why's. But do you know the numbers? The actual production tolerances ascribed to each "grade"?

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Old 07-13-2010, 04:30 AM   #49
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Originally Posted by Lornce
Yeah, I know all about the why's. But do you know the numbers? The actual production tolerances ascribed to each "grade"?

I imagine they are in my SNAB book. The inspection tolerances are in the service manual which gives the relative differences between them.

Fortunately the engineers marked the jugs and pistons A, B or C so you don't have to worry about it. Very handy.

I know the routine you are thinking of playing. I don't recommend it with a "points" guy. They're fearful sorts (no offence to the OP, but really)
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Old 07-13-2010, 06:27 AM   #50
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Quote:
Originally Posted by Lornce
Ah ha.

I'm forgetting the dimentional differences between A, B and C cylinders. What were they again? A couple of tenths of a thou?

It's been a while since I looked at that stuff...

A B and C pistons are nominally 1/100mm (4/10 tho) apart: A 93.96, B 93.97, C 93.98 I believe. But (big but) last time I checked my "S" piston it measured 93.88 (with 93.96 being nominal), but I could have bodged that measurement. It was clearly rattling in the C barrel, you could have thrown a couple of tho's through the gaps ...

Barrels have a tolerance band of their own. Mixing and matching A B and C pistons and barrels is of course possible as long as the piston-to-cylinder and other relevant tolerances/clearances are in spec. It's all in the Clymers or Haynes's ... you must have one of those.
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Old 07-13-2010, 06:29 AM   #51
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Originally Posted by Plaka
I know the routine you are thinking of playing. I don't recommend it with a "points" guy. They're fearful sorts (no offence to the OP, but really)
I am interested in the routine you're mentioning that would make "points" guys shudder. Never met one but I'd love a good scare !
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Old 07-13-2010, 07:46 AM   #52
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Originally Posted by StephenB
It's all in the Clymers or Haynes's ... you must have one of those.
Somewhere...



Thanks, Steph. That's the sort of thing I was wondering.



byam, a couple tenths of a thou here or there won't matter too much with the pistons as long as the rings are well spec'd.



awaiting the purist storm de merd
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Old 07-13-2010, 08:04 AM   #53
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Always measure the pistons anyway. I got a pair of C's that were well over 93.98, so had to send them back. Too big even for the hogged out used barrels.
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Old 07-14-2010, 02:49 AM   #54
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can someone summarise their thoughts on why the motorad electik is superior to the stock can?I need to either replace the Hall sensor or think about an alternative(89 R 100 gs)
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Old 07-14-2010, 05:33 AM   #55
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ease of maintenance

other significant differences are ball bearings vs. bushings and solid state ignition advance vs. centrifugal advance.

I went through a spare can last night, it's not as difficult as one might think.
http://www.motoelekt.com/alpha.htm
http://robfrankham.co.uk/bike/replac...ect_sensor.htm

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Old 07-14-2010, 05:45 AM   #56
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The part of the stock can that's failure prone is the hall sensor. If it goes you can't replace it without power tools so a lot of people carry an entire spare can on their bike. That's a $300 piece of electronics bouncing around in your panniers for years. Rick's alpha ignition uses a big snap ring and a commonly available hall sensor from Honeywell. Most Radioshacks will have it.

Also, the stock can uses springs and bob weights for the advance. They can get dirty or sticky and affect the advance. Rick's is an electronic advance.

The stock can is really half-electronic rather than a full electronic ignition.

Rick's system uses the stock ICU which is the same ICU on most Volkswagen Jettas. You should be able to get a spare from most auto parts stores.
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Old 07-14-2010, 06:02 AM   #57
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Quote:
Originally Posted by bgoodsoil
The part of the stock can that's failure prone is the hall sensor. If it goes you can't replace it without power tools so a lot of people carry an entire spare can on their bike. That's a $300 piece of electronics bouncing around in your panniers for years. Rick's alpha ignition uses a big snap ring and a commonly available hall sensor from Honeywell. Most Radioshacks will have it.

Also, the stock can uses springs and bob weights for the advance. They can get dirty or sticky and affect the advance. Rick's is an electronic advance.

The stock can is really half-electronic rather than a full electronic ignition.

Rick's system uses the stock ICU which is the same ICU on most Volkswagen Jettas. You should be able to get a spare from most auto parts stores.
+1 on all of that. Plus these bikes mechanically will last a life time, electronically not so much. I am a self professed cheap bastard and I think most if not all of Rick’s upgrades are worth the money if you ride everyday and need to rely on your bike. I have been super pleased with my new bean can and the new diode board is very impressive looking and works great. My charge light doesnt even come on at stop lights anymore. Small things like LED brake lights help as well, because what I understand is that those regular lights draw a bunch of current. My next purchase will be the Omega 450 Alternator and maybe new coils. I figure after that, the bikes good for another 40 years of riding. I have 2 old Hall cans, one is in pieces and one intact, wish I knew someone who could convert those to the points in a can version (which I have just as a back up) reasonably...
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Old 07-14-2010, 07:39 AM   #58
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I thought the Hall sensor was actually the robust part. It was everything else in there that went all warbly. Thats why Rick kept the Hall part and changed everything else.
A spare Used one might be $300 but a brand new one from BMW is $500. Rick's is half that, brand new. Plus his advance is now only susceptible to heat, rather than heat and every other possible intrusion.

Is it really the Halls that go bad? I couldve swore the springs and advance and all that crap went bad first.
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Old 07-14-2010, 08:39 AM   #59
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I've always heard it's the hall sensor. roadsacallin's bike went dead because of the hall sensor.

Isn't that why Matt's trying to put 2 hall sensors in your can?
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Old 07-14-2010, 09:14 AM   #60
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Quote:
Originally Posted by Stagehand
I thought the Hall sensor was actually the robust part. It was everything else in there that went all warbly. Thats why Rick kept the Hall part and changed everything else.
A spare Used one might be $300 but a brand new one from BMW is $500. Rick's is half that, brand new. Plus his advance is now only susceptible to heat, rather than heat and every other possible intrusion.

Is it really the Halls that go bad? I couldve swore the springs and advance and all that crap went bad first.
The advance units can gum up and stick open causing high-idle issues, easily cured with brake cleaner and silicone lube. Happens fairly often on high mile bikes.

The hall effect transistors *can* fail on and off as they thermally degrade over time. That *can* become a show stopper. A fairly rare occurance.

I'm curious to know about the guts in the replacment marketed by ME. Most everything he sells is mfg'd in Taiwan, and there's nothing wrong with that. But I've yet to see a Tiwanese electronic ignition on the market for airheads.

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