Carb tuning after adding a head and MSD enhancer

[oxnard111]

I'm trying to settle a debate with my buddy. He wants to add a 35cc ADA head and an MSD enhancer to his ski. His current setup is a this

- Stock 62T 701
- Riva Single Carb conversion manifold
- Single 46 MM SBN
- B-Pipe with limited chamber


He thinks he'll be able to just richen the fuel mixture and not change any jetting, needle and seat, or pop-off.

I say he's wrong. What do you guys think?

I'm basing my knowledge/opinion from what I was told when I added a timing advance to my SXR a couple years ago.

The MSD advances the timing right?

 

[B-Roy]

I say richen high speed 1/8-1/4 and he'll be good to go.

 

[Matt_E]

Why would he need to rejet?

A moderate compression increase shouldn't require rejetting.
The enhancer doesn't change the motor characteristics enough to require jetting, either.

I'll bet he doesn't even have to touch the screws (unless they're already off)


PS: The higher rev limit of the enhancer might require a bit higher hi-speed, but it should already be dialed in.

 

[marz831]

I have never had to rejet after adding a head before. An increase in compression doesn't necessarily affect the air/fuel mixture. As far as the MSD enhancer, I am not really sure but again you are not changing the air/fuel mixture so I would say a rejet is not necessary. Someone correct me if I am wrong.

By the way, my vote is to "not touch anything"...that wasn't an option in your poll

 

[oxnard111]

Well after just a few responses I will admit that I was wrong.

I thought the MSD would advance the timing enough to warrant being concerned over pre-deto conditions. But I guess it doesn't advance it as I thought.

 

[Matt_E]

Even if that was the case...carb jetting won't fix that.

 

[WaveDemon]

I agree, bolt and go. no jetting.

 

[oxnard111]

So what is the purpose of adding an MSD enhancer? Just up's the revs?

 

[marz831]

Stronger spark, adjustable rev limiter...and i thought it did advance the timing also, maybe I'm wrong here

 

[Matt_E]

Supposedly better curve. I don't know, I can't tell a difference.

 

[oxnard111]

Supposedly better curve. I don't know, I can't tell a difference.

That makes sense. I though that it dramatically advanced the spark. Guess not. I think that is where I was initially mistaken. Thanks guys. You rock!
I love the X. Full of knowledge from the best of the best and best of the worst (being me :biggrin: ).

 

[bluegtate]

Thanks for all the info guys. I am going to bolt everything on and run it

 

[FLY6584]

Supposedly better curve. I don't know, I can't tell a difference.

I definitely noticed a difference when installing mine recently. The main difference was the throttle was MUCH crisper and snappier of the bottom. It didn't make the boat pull harder, but I really liked what it did to the crispness. I also noticed a huge difference in not hitting the rev limiter. I never realized how much I hit the Rev limiter until I put on an MSD Enhancer. Lastly I noticed a change in the sound.

 

[SUPERTUNE]

Bolt on and go shouldn't need much adjusting, as most 46 single setups are a bit on the rich side out of the box. MSD enhancers have a marginal improved spark output and the curve set they come with is not very aggressive at all, Matter of fact I've seen a lot of them on a timing light and are not impressive. Most MSD cdi boxes didn't even do as much as they say they should do and a 3 degree retard rate is not much of a performance gain. So about the best gain you could get would be to time it so it retards to like 20-21 degrees. So IMO... It's just a fancy rev limiter.

 

[h2odesperado]

So IMO... It's just a fancy rev limiter.

I've been toyin with gettin one, you just saved me 150 bones :arms:

 

[Matt_E]

I definitely noticed a difference when installing mine recently. The main difference was the throttle was MUCH crisper and snappier of the bottom. It didn't make the boat pull harder, but I really liked what it did to the crispness. I also noticed a huge difference in not hitting the rev limiter. I never realized how much I hit the Rev limiter until I put on an MSD Enhancer. Lastly I noticed a change in the sound.

Good for you, I guess.

I've tried two different ones, back to back with stock CDI. I couldn't tell. :dunno:

 

[spdwrx701]

I noticed a very nice improvement in bottom end and crispness as well.... I think it is a must have on a modified boat unless of course you want to shell out for an Advent, Wax or TL........

 

[Superjetjim]

I noticed a very nice improvement in bottom end and crispness as well.... I think it is a must have on a modified boat unless of course you want to shell out for an Advent, Wax or TL........

Me too - MSD was way better than stock - with a B pipe and the stock Ignition I kept hitting the limiter and 'landing with the brakes on' - fitted the MSD and its ace (still limits when it needs to but its not 'nanny state' like the stock ignition) - running the same one for the past 5yrs fault free (damn shouldn't have said that!!:haha: )

 

[Matt_E]

I'm TL spoiled.