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Post by dick on May 26, 2022 15:51:28 GMT
i was reading an article in the january 2022 edition of " classic bike guide " where a chap was tring to figure out the running issues he had with a honda cb750.. his problems were poor starting, or only starting on 3 cylinders, and starting on differant cylinders, the bike being sluggish etc...he had tried everything he could think of, such as fueling issues, cleaning the carbs multiple times, replacing the coils, checking the timing, new plugs filters etc.. he spent 7 years chasing this issue, only to find out that the problem was down to using both the resistor spark plug caps, and the resistor spark plugs, he kept the resistor spark plug caps, but replaced the spark plugs for non-resistor versions....and the bike was transformed, no further issues...he has a grin as wide as a football pitch, he said the bike was completly transformed ! i know what the plugs in the 250n are resistor types [ BR8ES ] and noticed that the plug caps on my bike are also resistor types XD05F -R with a 5k ohm rating an interesting article, so anybody having similair issues [ not nessesarily with a superdream ] for £2 a plug..its something worth checking, before replacing eveything on your bike  |
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Post by buster on May 26, 2022 19:09:49 GMT
now thats genuinely interesting, I'v recently touched on resistor and non resistor type plugs when researching DC CDI units (got one on the way) theres a dire warning with those units that you must use resistor type plugs. I also confess a certain ignorance in what the difference is, I tried to read up on it online but nothing I found got to the point and I gave up, I understand the basic principals of the coils/plugs ie fire approx 24000 volts into one end of the plug and it sparks at the other end but the resistor is obviously quite important.
also worth mentioning the earlier dream 400 bikes were recommended a non resistor plug (D8EA I think) and the later bikes a resistor type plug (DR8ES)
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Post by johnfcbn44dx on May 26, 2022 21:09:41 GMT
I would like to understand the difference as well, as that earlier dream plug may be the same as the CB400F2...
Found a couple of bits of text extracts from the archives....
"SPARK PLUG CAPS
In a motorcycle system, these caps serve two purposes.
--They connect the plug wires to the spark plugs.
--They also add about 5k ohms of resistance to this path to suppress RFI and EMI effects.
But how does adding 5K of resistance cut down on these effects? Well, it was not too easy to find someone who really knew, but here is the explanation I found.
As we have seen when volts in the kilovolt (thousands of volts) range start to push from the center electrode in the plug tip, gas atoms become conductors and the "infinite" resistance of the plug gap simply goes away. What is needed is some resistance before the air gap to cut down the amount of current flow, that is, the amps. With less current flow, the magnetic and the electro fields generated are smaller and less powerful, and so produce less interference for radios and electronics. That, I am told, is why the 5K ohms are there and how they do their job."
"SPARK PLUGS
.......
.......
--Plugs have different heat ranges. "Cold" plugs dissipate more heat into the cylinder head (which is also hot, but always cooler than the plug tip) than do "hot" plugs. The lower the number, the hotter the plug.
The basic design tradeoff is this: you want a plug that runs hot enough to burn off carbon and oil deposits. But you want a plug that will run cool enough so as not to burn up its electrodes (or suffer from something called "oxide fouling"), and thus have a short and unhappy life. Or worse yet, start to glow and cause "pre-ignition" (pinging) which can damage the engine. The proper heat range will encourage the plug to keep itself nice and clean, but also allow it to last a long time.
A good operating range for the tip of a plug might be between 450 and 650 degrees C (roughly 850-1200 F). Starting with an understanding of the operating temperature range of the engine (which can differ significantly between engines), engineers specify a plug that will run within the desired heat range.
One phenomenon that some riders experience is this: a cylinder fails to fires, or fires badly with the cap on the plug. But when the cap is pulled just slightly off the plug and the cylinder lights up and runs. Why would this happen? Well, my best guess is that there is a problem somewhere in the system that is causing a weak spark. By adding an additional air gap, the coil is forced to reach a bit higher voltage before the two jumps can occur, thus making for a strong, hotter spark. The basic problem still needs to be found.
When riders start to foul plugs, a typical reaction is to try a hotter plug to burn off the built up carbon. This really isn't the way to go, in my opinion. You shouldn't be trying to solve fuel mixture or ignition problems by changing heat ranges. Get your carburetion and ignition right, and run the right plug."
......
So I presume that if you had no resistor caps, and no resistor plugs, the discharge would be so rapid in may not leave your capacitors/transistors in the CDI in the best of health? I'm also thinking folk that say they are testing for a spark from HTlead to the engine could be frying their CDI components?
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Post by andy1kenobe on May 26, 2022 21:10:07 GMT
There's a bit of geeky stuff on sparkplugs.com
I find it quite interesting the stuff they have in their learning centre and it's worth a look. It's not just about spark plugs either. For spark plugs go to learning centre - product information - then scroll down to view info about the different type of spark plug, resistor, inductive resistor and pulse. Keep going through the pages and there's loads of info.
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Post by dick on May 26, 2022 22:00:11 GMT
according to the article... " resistor construction to minimise electromagnectic interferance with electronic equipment by flattening and reducing the ignition spark " basicaly in his case he had resistance in both the spark plug and the cap [ so he had 10k ohm instead of 5k ohm ] leading to a poorer spark, having only one 5k ohm resistance in the circuit cured his problem instantly..the owner of the cb750 thought that the " r " on the spark plug stood for " racer " as opposed to resistor
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