Author Topic: cb550f running at 10mpg  (Read 537 times)

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Offline Bru-tom

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Re: cb550f running at 10mpg
« Reply #25 on: October 11, 2018, 09:59:36 am »
Good call on the 1000 coils. Better would be GL1500 coils. Modern, reliable and you can get 3 for a song.
I had a brand new, ill-fitting Emgo air filter. If you have one, throw it in the neighbor's yard and get an OEM. Night and day.

thanks for the heads-up.

would this also require a ballast resistor as Deltarider mentioned? i guess the best thing to do is measure and see. I have done a ton of reading about coils and leads and discharge time of original and aftermarket performance coils, i think with the higher output voltage, ballast resistor and 5k plug cap to increase discharge time, it will be a nice upgrade with the new points iv ordered :D

Offline spotty

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Re: cb550f running at 10mpg
« Reply #26 on: October 11, 2018, 05:29:31 pm »
when i saw the title of this thread i wondered if maybe you had accidentally put a vmax engine in.....
and here was me thinking I'd kicked the honda habit........silly me

Offline tlbranth

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Re: cb550f running at 10mpg
« Reply #27 on: October 11, 2018, 05:48:49 pm »
Good call on the 1000 coils. Better would be GL1500 coils. Modern, reliable and you can get 3 for a song.
I had a brand new, ill-fitting Emgo air filter. If you have one, throw it in the neighbor's yard and get an OEM. Night and day.

thanks for the heads-up.

would this also require a ballast resistor as Deltarider mentioned? i guess the best thing to do is measure and see. I have done a ton of reading about coils and leads and discharge time of original and aftermarket performance coils, i think with the higher output voltage, ballast resistor and 5k plug cap to increase discharge time, it will be a nice upgrade with the new points iv ordered :D


I'm quite sure you won't need a ballast resistor with GL1500 coils. Guys have used them on GL1000's and CB's direct. Good thing to check though 'cos I've been wrong before. I'm pretty sure you'll need to do some 'customizing' to get them mounted. I'm sure there's someone here on the forum who's done it.
1970 CB750 K0
1975 GL1000
1999 GL1500
2002 VT750-CDA ACE - Momma's bike
Terry

Offline TwoTired

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Re: cb550f running at 10mpg
« Reply #28 on: October 11, 2018, 07:09:14 pm »
My understanding is that Goldwing coils hav 2.4 ohm primaries.  These will draw twice as much current through the points, which will shorten their useful life.

Further, these are actually 6V coils that only run on 12 V during engine start on the Goldwing, after which they operate with a ballast resistor dropping the voltage down to 6V or so for normal run operation so they don't operate too hot.

Can you get way with a direct swap into an SOHC4?  Probably.  Does it follow good engineering practice?  I'd have to say no.  There's going to be some trade offs, like point life, taxing the charging system, and possibly shorter coil life due to higher heat operation.

I'd do it in a heartbeat after the apocalypse to keep the machine operable.  But, if proper parts are still obtainable, not without additional alterations.

Cheers,

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline scottly

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Re: cb550f running at 10mpg
« Reply #29 on: October 11, 2018, 07:54:25 pm »

My filter set up is a custom one. I have modified the plenum intake to house a custom filter box. I have removed it entirely and there is no change in this rich condition :o the surface area is exactly the same as original, so with no filter attached it should break just as well as the original setup would....
Sooty spark plugs ARE NOT caused by ignition problems! No fire, no soot. ;) Once carbon fouled, there will be no spark, but the original cause is an overly rich condition, not an ignition problem. Since you have a "custom" filter, this would be a likely suspect. Please post a picture.
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Offline tlbranth

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Re: cb550f running at 10mpg
« Reply #30 on: October 11, 2018, 08:18:21 pm »
 I looked at the ignition wiring diagram in my GL1500 shop manual and saw no ballast resistor but the primary resistance is 2.6-3.2 ohms. My CB750 shop manual doesn't specify primary resistance so I'll defer to 2T.
If the 1500 coils will only work with a resistor, I'd just buy 2 Dyna coils. Oh wait, that's what I did. They bolt right up and you can get the primary resistance you need.
1970 CB750 K0
1975 GL1000
1999 GL1500
2002 VT750-CDA ACE - Momma's bike
Terry

Offline scottly

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Re: cb550f running at 10mpg
« Reply #31 on: October 11, 2018, 08:29:42 pm »
Terry, I'm guessing that the GL1500 isn't a points ignition. ;)
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline TwoTired

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Re: cb550f running at 10mpg
« Reply #32 on: October 12, 2018, 12:50:52 am »
Terry,
The stock SOHC4 coils are 4.8 to 5 ohm primaries that are switched by points.

Dyna offers coils in both 3 ohm and 5 ohm primaries.  The 3 ohm ones are intended to operate with their dyna ignition triggers.  But then, 3ohm and dyna-s draws too much power for use on SOHC4 bikes smaller than the 750.

Fyi

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Thinking:  It's like reading with your own mind

Offline dave500

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Re: cb550f running at 10mpg
« Reply #33 on: October 12, 2018, 02:14:24 am »
check the plug cap resistance,bad ones WILL cause sooty plugs full stop.

Offline BomberMann650

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Re: cb550f running at 10mpg
« Reply #34 on: October 12, 2018, 09:39:45 am »
Quote
5km per liter

Quote
11miles per gallon

Figured out why your fuel milage is low..

Pesky metric conversions :p
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75 CB550F codename Bloo
76/78 XS750 triple; trash can.
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Offline robvangulik

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Re: cb550f running at 10mpg
« Reply #35 on: October 12, 2018, 10:45:16 am »
Quote
5km per liter

Quote
11miles per gallon

Figured out why your fuel milage is low..

Pesky metric conversions :p
Liters are consistent around the world, whereas gallons are different depending on where you are... ;D

 

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