80 cb750 buildup with nitrous -which ignition system and coils to use?

Closing in on a 3.5 year long project and now it's time to get the right ignition for it. Read a bunch of info but the real scoop from the Ton readers is what we are after now!

Looking for impute on choosing the right ignition system and coils for this project. Leaning towards the Dyna 2000 system and a matching set of coils. Need to be able to retard the ignition when the nitrous is in use, but can't seem to find the right set of Dyna coils to use. Most of the information we find is talking about the 3 ohms, but no real information to speak of on the variety of coil options they offer and what fills the need best.

Now before anyone chimes in about Cycle Exchange's version of ignition -not really interested. I've already spent a small fortune with them with the Mikuni twin carb kit with intakes and other assorted cool parts, and cannot get any tech support to speak of out of them!

So even though I like their stuff, this is just too much money and important info to consider to chance on not having support if needed! That leaves us with just the Dyna stuff...

So here's the deal, for now we are running a stock cb750, eventually plan to add cb900 cams maybe a few more goodies. For now though we need to get her up and running.

My wife calls the bike a Frankenstein mainly because it's evolved to something completely different than the original cafe bike plan. Not sure what to call it now, guess a "Street tracker" fits the best. Attached is a photo, right before tear down.

The bike now is back from the powder coater and features the frame done in Tangelo Oange House Of Kolor pearl. Left to do is the wiring, the ignition system and paint of the sheet metal -which is also going to be done in Tangelo pearl...

If anyone has suggestions as to what the best coil choice would be from Dyna or ignition system of choice would or will be, please fill us in on your opinion, be happy to hear any and all suggestions!

Thickmc


Bike photo: http://thickmc.com/bikeside.jpg

I don't know of any ignition systems that can handle (out of the box) what you're after. You may have to roll your own or locate an engine management system (Megasquirt?) you can adapt.

Unrelated... but are you running only two carbs?

Cycle Exchange sells the two carb setup for right at $500. Read MANY people who love them but often have some jetting issues. Those that did that I read about before buying them myself -claimed Ken the boss at Cycle Exchange, got on the phone and hooked them up with the right jetting information.

Now that hasn't been my experience, although the engine hasn't been fired up as yet -the tech questions I have is just on their recommendation on where the nitrous solenoids should be mounted, which has gone UN-nswered to date, doesn't have me wanting to rely on them for ignition info...

From what we've read so far the Dyna 2000 system has the ability to be set so that when the nitrous is activated the ignition can be retarded the needed amount. Problem is we can't find the specific coils by Dyna that best fit our needs. Since the Dyna system seems to be popular with 750 riders, I thought the best place to start in getting opinions and recommendations on choosing the right stuff was right here at dotheton.

Hoping those using the coils will throw some info our way!

Thickmc

trying to make up for the strangling of 2 carbs with nitrous ? :-\

Not sure you could think of it as being "strangled" -these are BIG carbs, if anything I'm worried about not having enough cam out of the box to handle all the fuel air these things can push. All the fuel and air is of no use if we can't fire it off and do so without turning the engine into an instant grenade...

We kicked around going the turbo route, but really wasn't all that feasible, so we figured we'd go with the nitrous and later add the turbos if needed.

Thickmc

you need 4 carbs like in the stock configuration to get max top end
it is ALL about moving air you cannot do it with 2 giant carbs on a long split manifold
too much loss in drag, velocity drops hence strangled

this is what you need if 2 carbs were good they woulda done it then,ya think?

Juice on the twin vm 34 kit cyclex or mine is going to result in some serious carb icing even 36s will ice up

expect your motor to not return to idle below 4000 rpm after using the nitrous till the carb thaws

run pure gas if you can that does help ood luck and stay safe

The solenoids on a wet shot NO2 setup should always go after the carbs, in the manifolds between the carbs and head. What are your plans for fuel pump and fuel injection?

Sonreir said:

The solenoids on a wet shot NO2 setup should always go after the carbs, in the manifolds between the carbs and head. What are your plans for fuel pump and fuel injection?

Click to expand...

This is what I was going to say.
Why would you spray before the carbs? That makes not sense. Spray into the manifolds after the carbs to avoid freezing and disruption of AF ratio.

im not sure but isnt the poster asking where he should put the solenoids not the nozzles?

solenoids should be mounted in a cool location

and the manifolds better have hold down brackets so they dont spectacularly blow off going down the track

Well thanks for the advice and impute so far!

Current plans are to locate the NOS nozzles right at the intake manifold just after the rubber boot close to the carbs. Using one nozzle per intake manifold.

For fuel we added an extra fuel bung in the Suzuki GS tank. The fuel tank is heavily modified, with the gas cap being moved up towards the forks (originally to gain more room for the airbrush work), and we now are using a popup flush fitted cap.

We've got a 7psi electric fuel pump, going to a filter then to a pressure regulator / gauge rated a 3-8psi and then running to a fuel pressure safety switch rated at at 5psi. then out to the NOS solenoid.

Not really worried about top end speed at all, this thing is built for red light work (squirt gun racing), and tight twisty stuff. We've got a 150-80-16 Dunlap on the back... The front end is off a 09 HD Dyna narrow front end. We machined a new stem to make it all work.

We went ahead and ordered the Dynatek 2000 setup with coils today with the PC management software. This should allow us to retard the timing as needed for the NOS hits.

Outstanding questions now are how big a shot to feed it and the amount of timing change will be needed to keep it breathing.

Suggestions?

Thickmc

Shouldn't take much. Two or three degrees. Maybe none at all if you're running race gas.

How do you plan to run the nitrous switch?
WOT switch or push button or?
What I'm getting at is how will the dyna know it's time to retard the timing?

i have way way more v8 experience than air cooled 4 but rule of thumb is 1-1.5 degree per 50 hp sucked off the bottle

than said i have a concern that the dyna 2k will be to coarse for you the

from a recent turbo mtr i built using one the dyna retard mode allows for 5.7.or 10 degrees

i think using it willl rob you of power as it will over retard

Hmmm, I didn't even think about how much retard it offered. I should have asked that question before hand!

Too much would definitely be as big a problem as too little. Probably wouldn't have mattered since the Dynatek system was the only game in town...

Any suggestions on a work around if this proves to be a problem? At over $400 for the Dynatek system, I'm stuck for sure making it work in some way.

Didn't plan on using race gas... If this is a problem, race gas would be the only way I could get the advance up enough to allow the Dyna system to retard it to a suitable level for nitrous. Dang' now this has got me wound up for sure...

May be time for a call to Dyna tech support and see what the software can actually do. At any rate thanks for bringing it to my attention!

Thickmc

yes give them a call

the only ignition i have used on a four cylinder sohc or dohc so far that ran juice and a blower is a msd system the mc4

the box is a bit bigger but the scope of what you can do with it is amazing like it has a retard control of 0-25 degrees

in as little as 1/4 degree increments

Well! Looks like a call to Dynatek is in order. Since they are likely the only ones who can answer the amount of retard available and increments of retard when using their system. Can't find anything on online documentation about it.

CXman was the first to bring the MSD option to our attention. I can see now that we should have asked for help on this long before we started cutting checks and buying parts!

Thickmc

Have you looked at Ignitech.cz ? I'd also be surprised if a DYNA 2000/4000 doesn't do what you need it to do.

see section 11

http://www.dynaonline.com/skins/downloads/instruct/DDK1-11.pdf

Quick follow up for those that are following this thread...

Got with Larry in support at Dynatek. Talk about a fellow who knows his Dynatek products! Explained the issue and he came up with a workaround utilizing certain unused wires to allow more specific amounts of retard to be dialed in with the Dynatek 2000 system. I was impressed. Especially since we didn't have the unit in hand at the time.

The system arrived today, with the exception of no real method of mounting the main controller on the bike, the whole kit was impressive and complete. We also purchased the PC management software and cabling to hook up to our laptop, so we should be set when it comes to dialing everything in.

We appreciate everyone's help on getting this sorted out!

Thickmc