GM HEI: Cheap and Extremely Effective Ignition Upgrade

If it's broken or just needs tweaked

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Pinhead
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Sun Jun 12, 2011 11:15 pm

RitcheyAuto wrote:But where did you guys mount the coils? Can someone post some pics?


I got 'em stuffed under the tank on my '79. I'll try to get some pics tomorrow if it's not raining.

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Mon Jun 13, 2011 10:40 pm

Just wanted to briefly update my progress. All soldering joints are completed on my control modules. I have finalized most of the wiring up to the coils. The 1982 Nighthawk has almost no room under the seat for ignition control modules so I moved the mount location to just below the rectifier/ volt regulator.

I removed the factory toolbox and used some aluminum bar stock to fabricate a fairly clean little bracket set. I have no vice and no real fabricating tools aside from a Dremel tool and a hand drill so everything was fairly freehanded. My workbench was the ground with some cardboard set down so as not to ding up my bits.

Last night late I did some temporary test wiring with some alligator clips to test my setup. Nice fat blue sparks arced from the coil to the kickstand and that was before hooking in the starter boost circuit. That was also on a nearly dead battery (discovered the ignition switch has a slight short in it).

Anyway I am excited to see where this goes. It's a labor intensive project but I wouldn't say that it's very difficult to figure things out once the initial idea is out there....

Anyway not sure if I will have any room to mount the coils under the gas tank. If not I will have to do some more clipping and drilling to come up with a satisfactory mount point.

I will post some pictures of my setup as soon as time allows. Doing most of the work at night to avoid apartment property managers who are kind of mean about working on stuff outside.

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Tue Jun 14, 2011 4:34 am

If I can find my camera I will post pictures of what I have done. Got everything wired up and got some good spark. Didn't finish in time to get to NAPA to get the plug boots and high tension terminals. Tomorrow I believe will be the night of truth.

If I can find my darn camera I will post what I've done and how I've done it. Basically any monkey with a Dremel tool and a hand drill and a soldering iron could duplicate what I've done. Gotta love the simplicity and modesty of this modification.

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Wed Jun 15, 2011 5:41 pm

OK so last night I put together my coil brackets, wire things up and the bike jumped to life for a split second and died. Spent the rest of the night trying to figure out what died and where my spark went.

Then today I charged the battery and tried to figure out what the hell had happened. After an hour with a multimeter I stood up to stretch my legs and scratch my butt and see the kill switch nestled in the "off" position. My buddy must have bumped it last night when we were messing with hit. Flip to "On", and bike coughed to life on 3 cylinders. Hooked up the number 4 wire and within I'd say 15 second the throttle response was crisp as my EFI suzuki TU250. I have to tie some wiring away from the heat before I run it for any extended period of time but my hopes are really high for this project at this point...

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Wed Jun 15, 2011 6:37 pm

So a quick test ride around the block....

No problems with ignition system. Power is much smoother though the revs. No more loading up and dying at a traffic light as it once did. It's a hot day out and no choke was required for starting. Bike is probably jetted on the rich side - I live in Flagstaff AZ which is about 7,000 feet MSL elevation. Nothing that is carbureted runs quite the same up here.

I did not reset the plug gap (still running.028 gapped NGK DR8ES-L spark plugs). I hope to go with some iridium spark plugs...

The booster circuit hooked up makes a significant difference on the cold start behavior of the bike.

Anyway love this mod. Three cheers for Pinhead for posting this up. :) Thanks! New coils would have been $160. I brought this one home for right around $100 in brand new parts. Could've gone even cheaper! All are lifetime warranty from Autozone too!

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Volker_P
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Thu Jun 16, 2011 1:48 am

Sounds like this upgrade really improves things, especially cold starting. Now this seems rather an ignition but an intake ports issue.
I'd suppose iridiums won't make a difference any more. Typically they seem to help most if something is wrong with ignition.
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Pinhead
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Thu Jun 16, 2011 3:02 am

Volker_P wrote:Sounds like this upgrade really improves things, especially cold starting. Now this seems rather an ignition but an intake ports issue.
I'd suppose iridiums won't make a difference any more. Typically they seem to help most if something is wrong with ignition.


Agree.

But what do you mean by "an intake ports issue," btw?

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Volker_P
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Thu Jun 16, 2011 3:19 am

Just a consideration. The CB650 typically starts cold incredibly bad compared to the other fours and moreover needs choke much longer than any other bike I am aware of. On the other hand the intake ports are supposed to be the most advanced ones in the whole SOHC four history.
So I assumed poor cold properties of these ports being responsible.

Now it looks like that the points ignitions of the earlier fours may still have some (low rpm) advantages compared to the electronic/CDI ignition. Which I guess was still the first generation of electronic ignition in series Honda bikes at all. In this sense it seems no more surprise that the stock ignition is easy to beat with any nowadays (or not really ancient) electronic ignition.

Maybe the stock ignition itself not that bad at all, however it came together with the poor charging at low rpms.

Does the upgrade still show significant improvement without the start booster? I know my (1993) dirtbike CDI has a starter pin which probably does something like that.
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Pinhead
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Thu Jun 16, 2011 4:28 am

As I understand it, the "start booster" only helps boost the trigger signal coming from the reluctors at low RPM and doesn't directly increase the power of the spark.

The "start booster" is only active while the starter button is being pushed, as it is designed to offset the voltage drop caused by the starter motor. Once running the ignition definitely shows an improvement on "cold-bloodedness," as the motor can come off the choke much more quickly.

I found that without the start booster (and 7-pin modules) the bike starts up about as quickly and easily as with the stock ignition, but runs better once it's started. With the booster the engine fires and starts at the first spark event.

This may be a little off the topic of ignition but...

When it comes to the ports possibly contributing to the poor cold start and cold running behavior, you may be on to something.

The port shape is much better than any of the earlier SOHC4's. This would have a positive effect on cold-start and definitely overall performance.

However, the 650's ports are much smoother with fewer casting irregularities than the earlier SOHC4's. It is known that smooth intake port can cause the fuel to attach to the walls and flow into the chamber without being broken up into the air stream. This causes large drops of fuel, which are very hard to ignite and contribute very little to horsepower, to feed into the cylinders.

Many racers "rough up" the intake ports with sanding scrolls to help reduce this problem. I prefer to take it further by cutting "PowreLynz" into the intake ports (as shown in my 100 mpg thread).

So as you have suggested, the improvements made in the ports could be contributing to the cold start behavior.

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Volker_P
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Thu Jun 16, 2011 4:59 am

Pinhead wrote:...as shown in my 100 mpg thread...
Good catchword. Last thing I read there was that you still had to do some fine tuning to the carbs and fix the accelerator pump or so. Any progress, already first mpg results?
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Pinhead
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Thu Jun 16, 2011 2:44 pm

Volker_P wrote:
Pinhead wrote:...as shown in my 100 mpg thread...
Good catchword. Last thing I read there was that you still had to do some fine tuning to the carbs and fix the accelerator pump or so. Any progress, already first mpg results?


For fear of running this thread too far off-topic I'll update that thread. :)

HERE

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Fri Jun 17, 2011 1:49 am

Forgive my input here as I am far from a complete expert on all things spark plug and ignition related but I have to jump in a little...

As I understand it the iridum plug like the Platinum and double platinum plugs are mostly here to reduce the phenomenon of gap erosion common to copper and nickel alloy plugs. In addition Iridum and Platinum in the correct alloy form are extremely resistant to oxidation - a phenomenon common in the combustion chamber environment.

The primary performance increases would be seen in increasing the gap of the spark plug I should think, which would improve the spark profile and thus promote more effective combustion. This is one advantage of the GM DIS HEI ignition used in the Cavalier and other models. 60K volt spark with a wide gap (factory .060) double platinum element spark plug allow for more efficient combustion. Spark voltage of 60k volts versus a system capable of 35k volt can promote similar energy levels across a larger gap. The same amount of energy spread over a larger surface area means less unburned gas and better overall performance. Relatively simple high school chemistry teaches that the correct activation energy is necessary for a chemical reaction to occur completely.

Now also to consider is that DIS by nature promotes a reverse or waste spark whereby the spark jumps from the center electrode to side (ground) electrode on the incident cylidner but also jumps from the side (ground) electrode back to the center electrode on the non-incident cylinder. According to some, this promotes much faster gap erosion when you do not use double platinum and iridium tipped spark plugs.



On to my problems... Now of next concern to me is that the bucking problem I had been fighting before returned tonight. Only at relatively low RPM under high load. Verified all my connections to the coil packs, verified all wiring was still OK. I do believe though that the ignition switch is not totally reliable on this bike and I further feel that when I gapped the pulse generators one of the screws on pulse #2/3 was stripped out of its base. I suspect pulse generator gap has shifted out of spec again. Gonna have to come up with a fix for this one but not sure what yet. Drilling and tapping could well yield the same problem short term. All I can say is that I put about 80 miles on the bike since gapping the pulse generator and it wouldn't shock me if it rattled loose again...

Anyway I still feel the HEI is a big win. As Pinhead commented, the booster circuit only helps boost the input from the pulse generators when the starter button is depressed. I've noted that the bike starts better when it's hooked up rather then when it's not. It still takes my buddy's tired old nighthawk a try or two to get her going but again, still the stock gap DR8ES plugs and it still needs much more work before I can call the engine in "good" tune for its age. Valves are a clicking a little and I suspect tightening up the valves a little, syncing the carbs, and soldering the rest of my electrical connections will yield incremental improvements to the bike.

Anyway I definitely do not intend to drag this topic to "fix up craig's nighthawk". In the grand scheme of things, I can demonstrate with confidence that this modification made a positive improvement on an old, tired, and out of tune 650 nighthawk.

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Volker_P
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Fri Jun 17, 2011 2:09 am

cdg wrote:On to my problems... Now of next concern to me is that the bucking problem I had been fighting before returned tonight. Only at relatively low RPM under high load.

Which means relatively low rpm? You should not ride at load below 3000rpm at all because you don't have full oil pressure here.
Another issue is the transmission. I've seen many bad 4th and 5th gearwheels (including mine). So the transmission won't like torque at low rpm and this should be avoided.

The CB650 is a somewhat high rpm bike which can stand that perfectly as long it is warm and there is enough oil. Lowering rpms significantly makes no sense and will rather be destructive and cost much more than you may ever save by a possibly higher mpg.
I learned to accept that after my first transmission replacement and had no more engine related trouble since then. I hesitate to install an improved ignition because the option of low rpm power includes the temptation to make use of it.

In summary I'd say problems at load at low rpms are rather a feature but a bug for a CB650! 8)
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forum links to common technical issues

cdg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby cdg » Fri Jun 17, 2011 6:42 am

Low RPM roll on the throttle to me on this bike mean a dead spot between 3000 and 4500 RPMs. I don't deliberately lug the motor. Just basic climbing a hill in taller gear situation leads to the bike lurching rather abruptly. The bike is still a bit more cold blooded than I'd like to see too and as I mentioned, as I was adjusting the pulse generators I did notice that one of the pickup screws was stripped out of the back plate. I plan to fix by threading a machine screw through the back side of the generator, using epoxy to secure it and securing the pickup coil with a nut. This way I will avoid having to buy a new pulse generator backing plate or an expensive tap or die.

I do recognize the higher strung nature of this bike though.

Pinhead
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Pinhead » Fri Jun 17, 2011 1:33 pm

cdg wrote:...Verified all my connections to the coil packs, verified all wiring was still OK. I do believe though that the ignition switch is not totally reliable on this bike...


You should verify that your coils are getting battery voltage with no drop while the engine is running. Usually the factory harness will drop a volt or two at the coils which will obviously reduce ignition performance.

I wired a relay that gives the coils power straight from the battery. One of the original coil power wires switches the relay on when the ignition is turned on.


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