Dohc Cb750f: possibly a valve issue

SquidHunter

Active Member
Ok. Rode the bike today for about 5-6 hours. Here’s what I found out. With the ignition cover on, it will break down. With it off, it will run perfect indefinitely. This leads me to believe it’s a heat issue and not a noise issue. The bike isn’t any hotter than it would normally be. It is an oil cooled bike, but I still feel like it’s a faulty ignition module.

I rode today, all day, with the cover off but that’s not a good permanent solution


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teazer

Well-Known Member
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Isn't it an optical system which would tend to have issues if it's not covered or at least shielded from ambient light? Maybe drill holes to improve air flow in a way that keeps out the light.
 

SquidHunter

Active Member
teazer said:
Isn't it an optical system which would tend to have issues if it's not covered or at least shielded from ambient light? Maybe drill holes to improve air flow in a way that keeps out the light.
It’s an optical sensor. Seems to be similar to an abs sensor, like on a ktm duke. Ambient light doesn’t seem to effect it.


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Pete12

Member
teazer said:
Isn't it an optical system which would tend to have issues if it's not covered or at least shielded from ambient light? Maybe drill holes to improve air flow in a way that keeps out the light.
Optical sensors generally use infrared technology which is unaffected by ambient light
 

teazer

Well-Known Member
DTT BOTM WINNER
That's interesting. Lumenition and Newtronics both say to keep them covered up and people have all sorts of horror stories about Newtronics and ambient light. Maybe because ambient includes the whole range of light from red to blue.

I'm no light engineer. Just passing on what I have read.
 

SquidHunter

Active Member
Now they are sending me a diode to wire in. This is supposed to eliminate all noise possibilities. If that doesn’t work, then we’ll see what happens I guess. Gary at power arc seems to be in denial that there could be a problem with the ignition.


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SquidHunter

Active Member
The diode didn’t work. I spliced it in today, and the bike still breaks down with the ignition cover on. Take the cover off, and no problems at all


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SquidHunter

Active Member
Here’s my next test. Since the bike runs with the cover off, my theory is it’s a heat problem. I’ve drilled out a cover I had laying around


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teazer

Well-Known Member
DTT BOTM WINNER
Time to buy a nice simple DYNA S and see how that goes.

BTW. how hot is the ignition when it fails?
 

SquidHunter

Active Member
teazer said:
Time to buy a nice simple DYNA S and see how that goes.

BTW. how hot is the ignition when it fails?
I may end up doing just that. I haven’t taken a temperature reading, but it’s not any hotter than the motor would typically get. I live in the city, so traffic and redlights are the norm.


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crazypj

Split personality, I fake being smart
Looks like seller of ignition thought it may be power spike although I don't see how a bridge rectifier would help. If he actually developed ignition *and isn't just marketing something) I would have thought a simple diode bridge and capacitors would work better. It's more than likely one of the 'Military Spec' components is either breaking down or simple turning off when it heats up. Manufacturer should eb doing more to help you out, so far it's a good advertisement to avoid them at all costs
 

SquidHunter

Active Member
crazypj said:
Looks like seller of ignition thought it may be power spike although I don't see how a bridge rectifier would help. If he actually developed ignition *and isn't just marketing something) I would have thought a simple diode bridge and capacitors would work better. It's more than likely one of the 'Military Spec' components is either breaking down or simple turning off when it heats up. Manufacturer should eb doing more to help you out, so far it's a good advertisement to avoid them at all costs
You hit the nail on the head. The diode was the last effort to eliminate electrical issues. THE WHOLE TIME I’ve been saying it’s a heat issue with the ignition. It’s very obvious. The problem is power arc doesn’t want to admit there’s something wrong. Ken at cycle x has been the one trying to figure it out. Now it’s been drawn out long enough the warranty is no good, so I’m basically screwed out of 600 bucks. I’m over all the back and forth. I just want it to run right. I need dependability over performance, because I’ll be traveling on this bike. I have been traveling on this bike.


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SquidHunter

Active Member
pidjones said:
For dependability, I'd go back to the original Honda system.
I could do that, but it’s hard to believe that nobody has designed anything better. The erratic behavior of the stock ignition, paired with the stock charging system is nerve racking. My stock charging system failed three times since I’ve owned the bike. I went to the cycle x charging system, then my stock ignition failed (whilst riding 600 miles from home). Then I went to the power arc ignition from cycle x, and I haven’t been able to achieve reliability since.

The bike runs great, until it breaks down. I’ll check the spark. No spark. Take the ignition cover off..... boom, instant spark. I can ride all day and night with the cover off.

Ken at cycle x tells me he’s got one in the shop with the same set up, and he can’t even make it fail. I believe him. I just don’t know what’s different on his bike than mine. I have to believe it’s a difference in the wiring, or perhaps because I’m running an agm battery?

I’ve got to pull everything apart anyway, so I’m thinking I may try wiring the coils straight to the battery, instead of through the ignition switch. I read through some information that suggested that. Apparently the ignition module shuts the coils off with the kill switch, and it isn’t necessary to run them through the switch. Power arc even suggests this, due to fluctuations in voltage through the switch. That still doesn’t explain why it runs great with the cover off however.


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crazypj

Split personality, I fake being smart
Haven't read all your post yet so may amend this. There is nothing bad about stock ignition system as long as bike is running. It does have problem when ignition is left on and engine isn't running, ignitors overheat pretty quick as they never had a timer or shut off. I would probably get the trigger units and use any of the aftermarket boxes. (even GM can be used at about $20.00 each and about $50.00 for 'high temp' versions) Only time I've seen issue with stock charging systems is when they are used to charge 'dead' batteries.(even brand new ones that were not prepped properly) The charging system can put out about 20 amps but only for very very short period. If the regulator /rectifier tries to maintain high output the internal regulator burns out then the diodes start overheating and often short circuit. Battery goes flat and new battery gets fitted which discharges through charging coils burning off the insulation. A battery will fail if left discharged (10v or less) for about 30 days. You need to get back on Power-X and get them to test ignition at 220f (then get them to replace it when they say it's 'fine') I would also make a lot of noise on their Facebook site (pretty sure they will have one, 'they all' like free advertising) Itonly took 48 hrs for Yahoo to fix my problem when I was locked out, other people had been complaining for 3~4 months and getting run-around with automatic replies I guess negative results on Facebook do carry some weight?
 

pidjones

Well-Known Member
The voltage regulators in old 50's, 60's cars were electro-mechanical relay type (many had adjustable voltage control), and often lasted for several decades. It's hard to understand why solid state devices can't hold up as well. All they have to do is sense the voltage and turn the field current on/off to maintain it. The diodes in the rectifier could always be uprated.
 

SquidHunter

Active Member
I’m generally good with mechanics. I understand motors, and I work meticulously. Electrical on the other hand...... blows my mind every time. Especially the technical side of it. Absolutely a pain in my ass. This is the main reason I’ve stripped everything off my bike and made it as simple as possible. That’s also the reason I’ve chosen the components I have. Simple.

I’m still suspicious the battery I’ve chosen may be the root of my problems. Reason being, these components were designed to work with a lead acid battery. I chose a agm battery (for the warranty, mainly), and didn’t really do the homework before hand.


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VintageMBike

New Member
I think you and i conversed about this. I have a 900f pictured below.

When I first bought it, batteries kept dying, all sorts of shit.

I bought the Cycle X 3 phase thingy (its really a brit charging system) installed it myself with a new battery, and havent had a problem since (well, the battery DID die thereafter when I had to ride 2 up with a friend whose bike broke down in the dead of night. With my headlight on and the extra load, it died just as we got where we needed to go. I ran it a while after with the headlight off and it was fine).

There maybe be an issue in your particular bike that is causing this.

\
 

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