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Post by dave on May 11, 2022 9:36:10 GMT
Got you. Even though the earth on the battery is earthing to the Fram it does not necessarily mean it's earthing to the engine. I will try this and let you know. Thanks Dave
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Cb250
May 11, 2022 14:45:55 GMT
dave likes this
Post by johnfcbn44dx on May 11, 2022 14:45:55 GMT
Last year I had to renew the top engine bolt on my CB400NC, I buffed away the powder coat on the frame, both sides and added a thin copper washer against the frame. This sorted a problem with less than energetic response, when trying to start it.
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Cb250
May 14, 2022 12:46:42 GMT
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Post by dave on May 14, 2022 12:46:42 GMT
Hi all, tried the battery to earth and it is fine. So to date new coil, re wound rota by Rex's speed shop, new cdi from same place, earth's to notch.any other thoughts please all welcome
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Cb250
May 14, 2022 13:51:11 GMT
Post by andy1kenobe on May 14, 2022 13:51:11 GMT
Any chance you can elaborate a little as to why you felt the need to replace the parts? Was it running before replacing the parts and if so how well?
Maybe a pick-up problem or wiring? Possible break somewhere in the 40 year old loom. At the moment it's all guess work unfortunately.
Where are you located? A member here may be able to help, possibly swapping out known working parts or trying yours on their bike? If you were close to me, I would have no problem helping out.
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Cb250
May 14, 2022 13:59:46 GMT
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Post by dave on May 14, 2022 13:59:46 GMT
I am in Rotherham South Yorkshire. The bike is a restoration project. It did start and run but then would not rev and eventually no spark. I was suggested that due to age the Stata coils could have broken down.had new cdi, all wiring checked, black an white wire checked, stator re wired by Rex's, new cdi from same place, good earth to engine, new coil.nothing else to replace and yet there is still no speak.
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Cb250
May 14, 2022 14:01:23 GMT
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Post by dave on May 14, 2022 14:01:23 GMT
Loom stripped and checked, all new wire from stator to cdi and from cdi to coil.
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Cb250
May 14, 2022 17:15:32 GMT
Post by johnfcbn44dx on May 14, 2022 17:15:32 GMT
I am in Rotherham South Yorkshire. The bike is a restoration project. It did start and run but then would not rev and eventually no spark. I was suggested that due to age the Stata coils could have broken down.had new cdi, all wiring checked, black an white wire checked, stator re wired by Rex's, new cdi from same place, good earth to engine, new coil.nothing else to replace and yet there is still no speak. I've only been to Rotherham once, three decades ago, for a 5 day paint inspection course. These electrics are frustrating, can't think of a specific suggestion, what next.. stop switch is breaking the circuit in the RUN position? I always think the panel and connections under the left side panel are a source of much evil .
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Post by dave on May 15, 2022 10:52:38 GMT
Checked side panel electrics Fuses and all well there to. I have sent the re wound stator and new cdi back to Rex's speed shop for checking. I know they said it was checked before leaving them but there is literally nothe wrong anywhere else, it just keeps coming back to either stator or cdi.
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Cb250
May 22, 2022 13:03:20 GMT
Post by jimmyflawless on May 22, 2022 13:03:20 GMT
Hi Dave, Did you get this resolved? I'm in the same position, although haven't replaced stator or CDI. Resistance readings on the stator wires look ok. CDI may or may not be faulty but I don't want to replace unless I know for sure. This might be a totally amateur question, but is there any way to test for voltage at various points along the ignition system (eg out of the stator, out of the CDI, out of the ignition coil etc)?
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Cb250
May 22, 2022 13:56:27 GMT
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Post by johnjones on May 22, 2022 13:56:27 GMT
When rex do a stator rewind, does that include ALL the ignition wiring/coils, all of them ?
As you know 250 system different to 400.
HT coil must have a good earth, frame to coil mount "towers/tubes" to laminations. The internal earth green wire is only pressing on the laminations rather than spit welded/soldered To a tag.
There are opportunities for an extra earth to engine via frame fasteners and outside flywheel fasteners, but the stator green wire goes to the stator.
The stator is also earthed Via 3 screws AND the 3 larger mounting metalwork screws. Again an earthing opportunity...especially via ign advance 250 horseshoe screws.
Does your multimeter have ac volts setting ?
Increase rate of change ( revs ) increased ac volts output.
Expect some quite high ac volts output from main ign coils, lower outputs from the the others involved with the ign system, but remember revs rise so AC volts rise.
Resistance readings are relevent BUT AC volts are as well.
Those red neon plug caps are very very usefull, get 2 and make adapters...a quick safe ( for the fragile ign system )visual indication of ign HT health. They also prevent hair loss I am told.
Plugs in and starter whizzing engine over, tabulate AC volts.
Repeat with plugs out, compare results.
Using two old but working plugs, weld/screw into metal strip with flying earth lead and croc clip to good earth, for safe ( for the ign system ) but still connected ign system. Just be aware of fire risk/sparks etc....
There is a matrix quoting cdi resistance checks...
One other thing to consider is relative strength of flywheel magnets and air gap..
Remember this system should be able to start a cold engine via the kick start, even if it does not have one.
If you know of someone with a "Mega" tester for insulation checking, ask them to check the stator windings. Don't ask to lone the mega as the response will be expletives !
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Cb250
May 22, 2022 14:10:28 GMT
Post by buster on May 22, 2022 14:10:28 GMT
I looked into testing a cdi but it would seem to be pretty much impossible at home. the system charges a capacitor which then discharges to the ignition coil, its not really something you can replicate and measure without some very specialised kit. the coil on the other hand can be tested (not for voltage output, again your into specialist areas unless you have a 'safe' multimeter with a 30,000 volt scale on it) but primary and secondary resistance can be checked with a basic multimeter I use this scale for primary (yellow to ground) this setting (I think) for secondary (plug cap to plug cap) and these are the given values in the clymer manual (ignore the cmx bit, very different set up)
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Cb250
May 27, 2022 20:02:21 GMT
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Post by dave on May 27, 2022 20:02:21 GMT
Hi all, got the dam thing to start but now have another problem in that it will not rev up without back foreign and spluttering as if timing is out. Stator as now been sorted carbs rebuilt more than once. Why is it doing this. It as also had new cdi. Ticks over all day but misfires when opening the throttle.
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Cb250
May 28, 2022 1:17:03 GMT
Post by dick on May 28, 2022 1:17:03 GMT
Hi all, got the dam thing to start but now have another problem in that it will not rev up without back foreign and spluttering as if timing is out. Stator as now been sorted carbs rebuilt more than once. Why is it doing this. It as also had new cdi. Ticks over all day but misfires when opening the throttle. what did you do to resolve the non sparking issue ? check your pilot and main jets to ensure they are the correct ones, i had an issue with my bike [ 250n ] where somebody had fitted the wrong main jet in one of the carbs, leading to the bike geting to much fuel to air ratio, dont assume that the jets fitted are correct for your bike, whip off the carbs, and remove the float bowls, you will see numbers stamped on the jets, just something to check before going any further i assume you have the correct spark plugs fitted and correct spark plug caps ? [ refer to my spark plug/cap thread ] are the floats set at the right height ? is the air filter fitted and clean ? check the timing [ with a strobe light ] to see if its advancing etc make sure the air screws are set correctly..2 turns out is a good starting point check the vacuum guage screws are tight [ they are located above the inlet rubbers on the rear of the engine ] check and set the valve clearances but if you bought the bike as a project, dont assume eveything is standard, somebody could well have messed about with it...
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Cb250
May 28, 2022 6:26:55 GMT
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Post by johnjones on May 28, 2022 6:26:55 GMT
Red neon plug caps to show loss of HT...
Post a picture of the flywheel at T, and cam sprocket timing lines when flywheel at T...
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Cb250
May 28, 2022 11:45:01 GMT
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Post by dave on May 28, 2022 11:45:01 GMT
Timing lines all ok. T mark on flywheel, notch on cam at 12 o'clock, lines on cam sprocket level as should be.
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