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Post by jimmyflawless on May 21, 2022 8:15:27 GMT
Hi all, New member of this site here. I bought an old Superdream in February as a project. It is a 1981 model and hasn't run for at least 10 years. High mileage as well, but it looks like it's got decent compression. I have refurbished the carbs (thorough cleaning and replacement of seals and jets). Unfortunately I have no spark. When I hit the starter button, the starter motor is turning the engine, but there's no spark at the plugs. I have replaced the spark plugs, spark plug caps and ignition coil. It has a brand new battery. There is a good ground from the battery to the engine. Other things I have tried: - Starting the engine with the black and white cable to the CDI disconnected (in case of any fault with the ignition or kill switch) - Starter solenoid is ok. - I have taken resistance measurements from various wires coming from the stator: - Low speed coils / green and white - 317 ohms - seems ok reading - High speed coil / blue and white - 4.1 ohms - maybe a bit low but ok? - Pickup coil / green and light blue - 144.8 ohms - seems ok - Advance coil / green and pink - 16.2 ohms - seems ok
It could be a faulty CDI but I don't have a known good one to test with. However, I've read that these are unlikely to go bad (no moving parts, all sealed up etc). I'm sure it's probably something quite simple (but hard to pinpoint). Does anyone have any suggestions? I'm only a backyard tinkerer, not a mechanic, so please let me know if there are any easy tests I can try first. Do the stator resistances look ok? I really don't want to have to replace the stator or get it rewound if I can help it. Also does anyone have a wiring diagram in colour that I could refer to? Thanks in advance for any comments.
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Post by BritPete on May 21, 2022 9:33:50 GMT
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Post by buster on May 21, 2022 10:00:11 GMT
rex's speedshop figures for 250 stator
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Post by buster on May 21, 2022 10:13:43 GMT
disconnecting the black and white wire is a good move (for testing) as its the only link from the ignition system to the main harness. is your replacement coil a brand new item? is it suitable for cdi ignition? if so then it could be a cdi issue but as you mentioned they are reckoned to be very reliable on the 250's (nippondenso, three wires). bit of a bugger in australia, here in blighty its easy enough to buy another and rule it out. might be worth taking the spades and their female counterparts out of the connector blocks and giving them a good clean up, theres a little groove inside each connector that you can poke a small tool down and bend the tang flat, the connector should then pull out
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Post by jimmyflawless on May 21, 2022 11:10:05 GMT
Thanks BritPete for the link to the diagram.
Buster: My stator falls (mostly) within Rex's Speedshop tolerances so fingers crossed that's ok. The replacement ignition coil I bought was an aftermarket one suitable for the Honda CB250N. I presume it works with the CDI. I can always order a new CDI but they are quite expensive, so I'd like to be absolutely sure before buying a replacement. Thanks for the suggestion about the connectors. I'll give that a try.
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Post by buster on May 21, 2022 11:18:14 GMT
not sure if the chevrolet beretta was an australian model? the coil off one of those makes a good upgrade or so I'm told.
part number GM10472401
or
AC DELCO #D555
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Post by andy1kenobe on May 21, 2022 16:29:33 GMT
not sure if the chevrolet beretta was an australian model? the coil off one of those makes a good upgrade or so I'm told. part number GM10472401 or AC DELCO #D555 I recall a thread about the coil from a Monterey V6 being suitable. johnjones was the member that brought this up.
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Post by jimmyflawless on Jul 8, 2022 10:34:44 GMT
Hi again all,
Just to give you an update on my no spark issue.
I sent my stator and CDI unit away to be tested and rewound if necessary.
I thought I would have to send them back to the UK (ie Rex's or BB Bike Shop), but there are a couple of places in Aus that offer the same service. Anyway, it turns out that my stator was fine; it was the CDI unit that was faulty (which is quite uncommon I thought). Anyway, I was supplied with a new CDI unit for a fee.
I finally got time to install everything back onto the bike this week, and today (after a lot of messing about with leaky carb float bowls) managed to fire up the engine and get it running. It was quite a relief!
On the face of it, the idle seems fine. However, I am sure there are going to be a lot of running issues, partly because the bike hasn't run in over 10 years, and partly because I've had the carbs out 200 times and might have changed a setting. Although I meticulously cleaned the carbs a few months ago, and replaced many parts with a rebuild kit, I can't guarantee I didn't adjust various screws accidentally. Is there a guide somewhere (either here or on the web), that can help me with the basics of tuning the carb settings on these things? Something for a total layman or a step-by-step guide would be great.
Also, now that I know that the engine is capable of running, I'm going to be doing a full restoration, which will include stripping it down and repainting the frame. Would you recommend I leave all the carb tuning and fiddling until after I get it all back together? Or do you think it's better to get that done first? The bike does need new parts (such as intake rubber boots and clamps) which I haven't ordered yet.
By the way, I can't take the bike for a spin, because firstly it's unregistered, and secondly it's got no brakes!
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Post by buster on Jul 8, 2022 16:35:50 GMT
theres only a few things that can be adjusted with the carbs, have they had new pilot screws/washers/o-rings? that can be well worth doing ( the old o-rings can be fiddly to get out) and from memory the 250 sets initially at 2 full turns out (I'll check that when I find a manual). from there its how good your ears are, I can set the pilot on my XBR by ear but I cant do it on a multi cylinder bike (too many years of circular saws, weaving looms etc), the right results can be achieved with low speed plug chops, say about 3000rpm, and check the plug colour choke butterflies should be ok with a visual check off the bike to see if they are operating together throttle pull cable needs a small amount of slack when fully closed (safety to ensure it fully closes) but I'm sure you know that tickover can easily be set when the engine is warm (and carbs balanced) on the bike as its idling if its not going to live its life at the red line on a race track I'd set the float heights to the higher end of honda's tolerance (done with carbs upside down) to ensure that the float valves shut the fuel off (less chance of leaks, like the one I got on the derbyshire run, still at least nothing dropped off ) balancing, do you have suitable vacuum gauges? this is only done when everything else is spot on and its a bit fiddly on an SD. I cheated with my 400 and set the throttle butterflies by the rack of the eye, seems to work ok but its not really the correct method. as for getting it running before a rebuild, its really up to you, personally I'd like to know that it runs ok as thats what your aiming for when it goes back together, especially if you go the cafe route (trimmed down wiring loom?) it can help with problem solving. hope this helps and keep us posted with the build pics, got to go now cos its salad night
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Post by dick on Jul 8, 2022 18:37:31 GMT
as buster stated the mixture/air screws are 2 full turns out on a 250, although i had to alter mine slightly as she was running to hot [ lean ] with the standard settings, but this will only be obvious when riding the bike probaly a good idea to have the bike running properly before stripping it down [ especially if it still needs new carb rubbers etc ] that way at least you know its in fine fettle before stripping and applying new paint etc brakes...what do you need those for...she wont go fast enough ! [ well ok the silver ones like to pick their heels up ] but the front brakes are rubbish anyway...
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Post by jimmyflawless on Jul 9, 2022 2:37:15 GMT
Thanks all.
I will start a new thread (and read old ones) for any carb/running questions....
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No spark
Apr 18, 2024 19:01:25 GMT
via mobile
Post by nbason on Apr 18, 2024 19:01:25 GMT
I have a '76 CB250T with the same issue, running fine one day, then no spark on either cylindef. The starter motor failed first.
Does anyone know what the resistance readings in Ohms should look like if I'm checking that the CDI's not packed up? Also which colour lead to make contact with the multi-meter (there are 6 I think)?
I've changed the coil for a new one, and taken out the black and white kill-switch wire to no effect.
Welcome, your expert take on this, as CDI aee expensive.
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Post by buster on Apr 18, 2024 20:01:45 GMT
the cdi is a tricky thing to test, its really specialist gear thats needed (charge the capacitor up with say 200v? and then force it to discharge and measure that) I think honda dealers could do it back in the day but unlikely now.
I'd rule everything else out first, so clean all the connectors and contacts from the stator, ditto the cdi and then double check the earth at the coil. where did you get the new coil from? cdi or points type?
if all thats ok and theres still no spark, try the stator test using the green wire (as rex's speedshop suggests) and then repeat using the engine as the green wire.
if everything is looking ok but still no spark then I'd hunt round for a secondhand 250 cdi (I might have one spare, dont know if it works though) hope this helps
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Post by nbason on Apr 19, 2024 6:45:46 GMT
Thanks for the advice, will try what you suggest. The new coil cam from David Silver and tests OK with mutimeter primary & secondary. I'll whip the side cover off and check the stator functionality as suggested
Seems it is the generator Low Speed winding has no reading on the multimeter.
Does anyone have a functioning spare out there?
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No spark
Apr 26, 2024 17:28:44 GMT
via mobile
Post by nbason on Apr 26, 2024 17:28:44 GMT
What's the best way to remove the flywheel/rotor please?
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