Oldmanracing,
Yes I am running the stock CDI. Here is my thoughts on aftermarket CDI's.
1. I have read several cases of them trashing starter. I don't want that.
2. If the motors peah HP is around 7000 7400 rpm, why change the rev limiter aboove that? The power curv is on the way down?
3. Reliability. I do not want to give up any reliability, it is very important to me.

Can you dispell any of these?

 

I have a 2001 with a ProCom that has ran well for 3 years.
My sons 05 has the new Big Gun, only on for the last 3 weeks.
All aftermarket cdi's draw more voltage. They state it on the package.
The 01 started hard and required a fully charged battery.
Any DS with a low battery will lug and backfire. Thus hurting the starter.
I installed a ProCom reg/rectifier, not for more hp but for more voltage during starting and
better charging of the battery. For over a year it starts better and can sit longer betwen rides,
without the battery becoming too weak.
Older DS's have a voltage draw even when not being ran.

If running the stock CDI, I would recommend you run lower octane fuel.
I ran 87 for a few years with no problems. Changed when I with with new cdi's.
This is free horsepower. Please try it.

 

It's funny you mention the lower octane fuel . I have noticed that it DOES seem to run better on 87-91 octane. I need to dyno it both ways. To see if it is all in my head.
I like the 111 because it seems to run cooler and cleaner. I'll go back to 97-89.
About the starting issue with the CDI, is it due to the more agressive timing at start-up?

 

The aftermarket CDI's draw more voltage because of design, not timing.
To get the cost as low as they are, the circuitry must be using eproms that
draw more current. This is not alot, but enough that even though your motor is spinning decent,
there is not enough left for the spark plugs.

On the gas issue, too much cooling hurts performance and makes your motor appear to be running rich.
Your motor may be cooler, but rich will thin your oil and add extra wear to rings.

 

I understand all that (Professional ASE Certified Mechanic for 15 years). From what I understand, the timing is too fast at idle causing extreme load on the starter. The current draw from the CDI can't possibly be that great. I would like to see specs on the Big Gun CDI as far as timing curves. Know where any are?

 

The timing for a stock cdi is 10 degree's with an advance of 16 degree's, for a total of 26.
I mechanically advanced the timing 4 1/2 degree's(01) and starting was not affected.
I have talked to the head engineer at ProCom and he says that the timing curve is only
changed in mid to top. Total timing is still 26 degree's.

The RW cdi is 16 at idle and has a aggressive curve. Total timing of 32 degree's.
They have no starting problems. No rev-limiter and pricey.

What causes the ProCom units to draw more voltage is something they will not state.
I like the customer service at Big Gun and the 1 year warranty.

Getting aftermarket company's that make cdi's to show their curves is a big secret.

 

hey oldman. i had a thread refering to the noise that come from the starter when starting fails. i have a 00 ds and the only mods i have done for performance are hmf, ported intake, uni filter, 175 main, and a hi-comp piston. i DO NOT HAVE A AFTERMARKET CDI. i have the horrible noise sometimes and its got me worried . why is this happening.?????? i have been wanting a big gun cdi but iam scared to buy one.

 

I'd like to give thanks to you Oldmanracing for posting many times all you've learned from experimenting with the stock carb. This is really the kind of thing that makes the forum great when people post solid info they worked hard to obtain without trying to sell something. I used to post my recomendations like this but got tired of butting heads with people with other agendas.
I fully recommend the dynojet needle, I'm a dynojet defender. For a wide open dyno run maybe the stock needle is best but I'd never give up the crisp response of the dynojet needle.
I run a filter under the seat through a piece of metal tubing to the carb with only mild bends, something like an aftermarket intake tube. I think this helps to straighten out the airflow as it really seemed to improve the topend.

 

Oldmanracing,
Man you are a welth of information. Thanks for the GREAT information on the CDI's. Ofter reading your posts I think I will try one. I have heard many good things about the Big Gun so that is what I think I will order. DOes thye Big Gun change your rev limit? What can I expect it to do to the torque curve? I have noticed (while riding and on the dyno) it seems to have moved up the RPM range. Will the CDI move it up even further?
This is a great thread I hope people are following it. Thanks for answering my questions. I hope to make these mods and get it back onthe dyno quickly and get some results posted. It will be interesting!

 

Good Morning Mystereid,

Posting in the middle of night, you are either a second shifter or a very early riser.
Thanks for reading and appreciating the post. I am not a dealer. Just a old gearhead who
is always looking for an edge.
I see that many of the predator guys are using a Honda civic intake to control air flow.
Your idea is a good one. With a cv carb you need to control turbulence before the carb.
Air swirling or tumbling before the butterfly, in carb, will cause not only poor flow but cause havoc with pressure control.
The large snorkel going into the carb is like a large velocity stack, it is trying to straighten out the air. Its size is overkill, MrHP uses it on motors putting out 80+ hp.
I like your idea and would like to make a few suggestions.
You state that you notice more improvement on top. Your tube is moving air at a higher velocity. Please make mods to slide/spring. I would only drill the 2 extra ports to 1/16”.
This will greatly improve your bottom end.
To reduce air turbulence I would install, at filter end, on your tube a divider, about 1 ½-2” long, horizontal(same direction as butterfly in carb) across center of tube. It is the same theory that Scaryfastracing.net is using. A divider close to carb is great for a 2 stroke, but I have not seen any great improvements for a performance 4 stroke. For a cv carb, air going thru filter and into the tube would be immediately straightened and would go thru the carb at low and high speeds great. I was going to try this theory out, but to stay in stock class we cannot modify the intake snorkel.
Straightened air, high velocity and a few carb mods, Let me know what you think.