DaVinci "Firepower" Super G carb first impressions

[05FLHTC]

I can share a couple of things that are similar & also seemed to be reproducible with mine.

TIMING more of it at cruise has helped smooth out the motor on mine.

The other thing I read & have successfully demonstrated is adjusting the air bleed...is very hard to accomplish without an AFR readout. Yes I did manage to lean down my cruise range by swapping out the 40 for a 60 & I am currently running a 56 bleed.

The conclusions I have arrived at by trial & error still leave me uncertain...so take this info for what this is costing you nuttin.

Things to rule out
Leaks manifold & including the carb end shafts
That dumb ass little O ring that sits on the injector nozzle & bowl gasket
Float level
Pump jet leakage, run it at 2K rpms without the AC & look in the throat for leakage from the pump jet should be NONE

Not sure about yr ignition but I would for certain at least for a trial up the timing & run it.

A very wise man suggested I only change ONE thing at a time. My last improvements came from these changes.

Larger Int Jet on mine really helps my HOT starts
Larger air bleed helped reduce my AFR (at least by plug reads & chrome exhaust tip appearances)  If ya go too big you will be able to tell as you go up the RPM range * nail it...it will give ya a quick hesitation before it takes throttle.

Hope this helps some...I know yr frustration.
   

[11.7to1]

Dude, your old carb was sent out cause you thought it had issues. The one you bought 'seems' to have issues. I would bet you don't have a carb problem. You had a surging issue before right? Now you have low rpm issues right? These are also ignition issues. Keep advancing till it pings then back off one. When I say ping, not at 2300rpms and 3rd gear

[Admiral Akbar]

I would bet you don't have a carb problem. You had a surging issue before right? Now you have low rpm issues right? These are also ignition issues.

Bet they are more than just ignition issues but agree about the carb..

Max

[hrdtail78]

IME the tjet gives you another circuit to tune and allows the main to be smaller and not be the only jet in charge of such a wide rpm range. The size of the engine doesn't matter to get the benefits out of them.  For a street bike on the smaller side the tjet airbleed has to be drilled to make it work right.

I don't believe there is anything wrong with your carb. You just haven't found the correct combo with it.   You have all 4 baffles bent completely?

[rel3rd]

I can share a couple of things that are similar & also seemed to be reproducible with mine.


The conclusions I have arrived at by trial & error still leave me uncertain...so take this info for what this is costing you nuttin..

A very wise man suggested I only change ONE thing at a time. My last improvements came from these changes.

Hope this helps some...I know yr frustration.

Edited down to save the site some bandwidth, but I have read and re-read your threads over a few times, and actually it seems mine is just as finicky, but responding differently to jetting. I 100% agree about one change at a time and live by it. In fact, still haven't worried about the main now that intermediate has seemed to come around...see below.

[rel3rd]

Dude, your old carb was sent out cause you thought it had issues. The one you bought 'seems' to have issues. I would bet you don't have a carb problem. You had a surging issue before right? Now you have low rpm issues right? These are also ignition issues. Keep advancing till it pings then back off one. When I say ping, not at 2300rpms and 3rd gear

No sir, there was no surging issues at all before. The issue with old carb was falling on it's face when I tried to take off WOT. Low speed cruise was fine, WOT was fine, but the transition damn near put me over the handlebars a few times...seriously. I believed that the DaVinci Venturi Booster would solve, or at least tone down that issue and after talking to Dan decided to send him the whole carb and let him go over it. Come to find out, the jetting on it was all over the place...as talked about in UPDATE post below.

Are you saying not to worry about a low rpm/high load ping? It was fine at upper rpm's with no pinging ever heard...

[rel3rd]

I don't believe there is anything wrong with your carb. You just haven't found the correct combo with it.   You have all 4 baffles bent completely?

I think you are right about the carb.
btw...
No T-Jet on the presently installed DaVinci carb.

Yes, all 4 baffles are folded over and it seems to have helped midrange, merging capability a good bit, and no seat of the pants loss of top end power...with either carb.

[rel3rd]

* * * * * UPDATE * * * * *

Against all advice from my indy shop owner, even after he gave me a known good CV carb to try, and after I said "F-IT!" and agreed to buy (and he actually tried to order me) a brand new Mikuni setup, which are on National back-order so there was none available that he could find....I came home and gave it one last try before waving the white flag, lol.

Popped in a 26.5 intermediate jet which was smallest he had, and bike runs 99% better. Not 100% because I didn't put the air cleaner back on for test ride, at first. Didn't want to risk stripping any threads out.

Anyway, here's what it has now:

26.5 intermediate
78 main
40 air bleed
a/f mixture 1-1/4 turns out from seated
accelerator pump 1-1/2 turns, maybe a little less

ZERO dead spot (that you can feel with ass-o-meter) on transition.
Zero popping, bucking, sputtering, surging, or sneezing.
Ran great even with accelerator pump turned off and mixture screw seemed to fall in line too.

Surely may need to play with main jet but plan to do that (test it out) tomorrow on way to work. From idle to WOT is awesome though. Very responsive.

Dan DaVinci actually called (about old carb) right as I pulled up from the test ride and I told him what I did, as far as buying another carb and playing with jetting...He seemed to think that the large spread between the two circuits is nothing to worry about (i.e. Normal) with the booster venturi.

FWIW, My old S&S, that he was pulling apart as he talked to me, and that he's still going to freshen up, had 33 intermediate, 76 main and I forgot what ThunderJet jet, but it sounded LARGE to me.

No wonder the damn thing got 29mpg's....

Thanks a lot to each and every one of you who has tried to help me out with this carb situation. It is greatly appreciated! It's awesome to have so much knowledge around and so many that are ready, willing, and able to try and help a stranger out when they have a problem. I'm going to try upping the timing advance a little and hope to dial in the main jet in the next few days, although as-is, it feels pretty darn good right now. Thanks again! 

I guess I'll have a spare DaVinci modified Super G carb to sell soon. He asked if I wanted him to just send my old one back as-is, but since it had a few issues and was on the bike for a few years I told him to go forward with the mods and freshen it up...

[05FLHTC]

 

[Admiral Akbar]

So this has been a jetting problem all along.. Where is the "slap head" smiley face?? Max

[NCTURBOS]

OK, my turn...    Let me ask??  With the bike warmed up, and at idle in neutral.  If you wrap the throttle real hard/fast, does the bike come right up?  Or does it pop and spit some?

This is the only issue left with my "G" carb. that I have to tune out.  I've tried .295", .031", & .033" int. jets as well as moving the acc. pump all over the place and none has helped.  If I roll the throttle some and then hit it hard it does just fine.  Maybe just my idle is too low, or??

What 'cha think??


K.

[05FLHTC]

OK, my turn...    Let me ask??  With the bike warmed up, and at idle in neutral.  If you wrap the throttle real hard/fast, does the bike come right up?  Or does it pop and spit some?

This is the only issue left with my "G" carb. that I have to tune out.  I've tried .295", .031", & .033" int. jets as well as moving the acc. pump all over the place and none has helped.  If I roll the throttle some and then hit it hard it does just fine.  Maybe just my idle is too low, or??

What 'cha think??
K.

What is yr idle set at?

Have you checked for manifold leaks, assured good gas flow to carb & verified the float level?

[hrdtail78]

Your talking sitting at idle in neutral and opening to WOT as fast as you can?  I certainly would not be changing any jets to be able to do this.  Tune the carb to run down the street.  If you want to make noise in neutral.  Roll it on a little slower. 

[NCTURBOS]

What is yr idle set at?

Have you checked for manifold leaks, assured good gas flow to carb & verified the float level?

Not too sure on the idle.  I'm hoping to have everything to mount my tach/shift light in the next couple weeks.  No manifold leaks, good flow of fuel, have not checked float level.

K.

[NCTURBOS]

Your talking sitting at idle in neutral and opening to WOT as fast as you can?  I certainly would not be changing any jets to be able to do this.  Tune the carb to run down the street.  If you want to make noise in neutral.  Roll it on a little slower.

Well, with it sitting at idle on the lift table and opening the throttle as fast as I can.  You think without having a load on it in gear on the street is why?  I'm not trying to just make noise, but figured if tuned correctly it would be more smooth, no?

K.

[Admiral Akbar]

Try increasing the high map idle timing some.. 1000 and 1500 cells.

Max

[rel3rd]

So this has been a jetting problem all along.. Where is the "slap head" smiley face?? Max

Here ya go...

ME --><-- EVERYONE ELSE

I'm afraid so Max. I surely didn't think I'd need that small of an intermediate jet, but it's much, much better. I may even try the next one smaller since I still have a very slight surge with air cleaner back on. Plugs are clean with just a slight tan shade on the white part of the electrode (which name evades me). Roll-on higher rpm/higher speed throttle is great.

Next I think I'll need to do some tweaking to the air bleed. At steady cruise of 3000 rpm's it has a surge/exhaust gurgle still so I am thinking maybe the main is trying to come in to the party a little too soon. I only have a 40 air bleed.

For the ride home from work, I tried upping the timing to table 36A but almost as soon as I hit the highway, it started raining slightly and I didn't pay too much attention to how it was reacting to that. The few times I rolled on the throttle to get some headway towards home, it felt good, but I can't remember if the slight surge was there this morning, with 4 degrees less timing, or not...

[rel3rd]

OK, my turn...    Let me ask??  With the bike warmed up, and at idle in neutral.  If you wrap the throttle real hard/fast, does the bike come right up?  Or does it pop and spit some?

Today & presently, now that jetting is much closer, I can blip the throttle wide open from idle (sitting still), or from a slow roll, and revs come right up with pretty much zero delay.

[Admiral Akbar]

I'm afraid so Max. I surely didn't think I'd need that small of an intermediate jet, but it's much, much better. I may even try the next one smaller since I still have a very slight surge with air cleaner back on. Plugs are clean with just a slight tan shade on the white part of the electrode (which name evades me). Roll-on higher rpm/higher speed throttle is great.

You may even want to tray a smaller main.. 78 is probably pretty big for that motor.. Especially with the bombsite to help pull fuel out of the bowl..

Max

[rel3rd]

I'm afraid so Max. I surely didn't think I'd need that small of an intermediate jet, but it's much, much better. I may even try the next one smaller since I still have a very slight surge with air cleaner back on. Plugs are clean with just a slight tan shade on the white part of the electrode (which name evades me). Roll-on higher rpm/higher speed throttle is great.

You may even want to tray a smaller main.. 78 is probably pretty big for that motor.. Especially with the bombsite to help pull fuel out of the bowl..

Max

Will do. At least the main is a little bit easier to get to.

What's your opinion on trying one size smaller intermediate?
It seems that is what the bike wants. The light throttle cruise surge now is a fraction of what it was when I started this journey the other day...live-able, but yet still noticeable.

It seemed to have no light throttle cruise surge at all with air cleaner OFF, which is why I am thinking one more step leaner with intermediate before moving on to the main.

[Hillside Motorcycle]

If the throttle plate is open too far at idle the transfer holes are uncovered. This will make it nearly impossible to tune. When setting the mixture screw as the RPM's go up you should be backing off on the idle speed screw. I've seen quite a few that were open too far.
Another problem is cams. Some cams will make it hard to dial in. In this case I drill a hole in the throttle plate. This will allow you to close it further so you can set the idle without reversion problems. Comes off idle nice too. 1/8" is plenty.
3/4 of a turn out means you're either too rich or the throttle is open too far.
Turning off the accelerator pump has zero effect on low speed tuning. If it runs bad with it off you've got another problem.
40 is the standard air bleed size. That doesn't mean that's the right size. I went a lot bigger on a 100" engine to get it to run right.
If the bike ran fine with the other carb your ignition should be good enough to get you going.
Tuning carbs is a lot like tuning fuel injection without the computer. You make adjustments for the entire operating range. S&S carbs were popular because they only had 2 jets to change so everybody thought they could do it. They found out otherwise when putting a G on a motor that wasn't big enough for it.
When the 95 " kits first came out a lot of guys bought them with the Super G. S&S recomended it at the time. When their bikes were running rough some guys just switched to an E. Others were looking for a fix. The DaVinci kit was the fix. The air bleed was the tuning part. S&S has since made their air bleed in the bowl removable so you can tune it better. Some go with a T-Jet. Some with the bomb. Either way it needs to be dialed in. Carb guys are like dyno tuners. Some better than others.

I had thought all along, that if someone owned a dyno, they HAD to know what they were doing. 
Scott

[hrdtail78]

An engine under load will act differently than an engine without load.  Going down the road is under more load than an engine reving freely.  I will debate this... But not really the point.  I would rather set something up for something going down the raod.

[rel3rd]

Agreed 100%

My  bike was perfect example of this. Ran good/revved quick sitting still...moving, not so good.

[gryphon]

You may have nailed the problem. No telling what the seller might have done with the carb between the time he got it and the time he sold it to you. That might be why he was happy to get $300 for it which is a pretty good price. Wait and see what happens with your modded carb when it arrives.

[pwmorris]

An engine under load will act differently than an engine without load.  Going down the road is under more load than an engine reving freely.  I will debate this... But not really the point.  I would rather set something up for something going down the raod.

It's all A/F- When at a dead stop the air signal is very slow, at movement under load, much better.
You simply can't replicate launching a bike from a dead stop on the dyno or sitting in the garage...
Dealing with just that issue right now on my racebike. Launch, I'm running fat, and I am lean up top.
Changed my airbleeds from 80's to 100's to see if that cleans up the launch, and going to go bigger on the mains for up top, as well as pull a few degrees of timing out of 4th and 5th gear. Will find out testing this weekend if that helps.