High Performance Questions 96 Sportster

[WhipLash96]

hello to whole community. I have a 1996 883 Sportster that I converted to a 1250. I have some SE heads that I am looking to get ported. I am curious as what the approximate flow numbers of the heads? They are 55cc SE Sportster heads. I am also looking for the cfm rating of a 40mm CV? I am curious if the 40mm with sufficiently flow enough cfm after I get the head work done?? If not, will the 44mm be sufficient??

[PC_Hater]

The 40mm CV is reckoned to work well on motors up to about 90hp. Beyond that the carb starts to limit the output. Depending on what cams you are using you could well be at the limit after your heads are flowed. It is cheapest to try it out on a dyno and see what it gives. If you can live with a bit less power at high revs so much the better!

The HD 44mm CV is obsolete now. There is a thread about it in the Dyno Tuning section. Jets, needles etc are just about impossible to get. So be sensible and don't use the 44mm CV unless you find one very cheap!

Then we get to the problem of what to use instead.
I would choose Mikuni first, then S&S, but do some research on the S&S carbs, to me they sound primitive and a pain to set up properly.

[WhipLash96]

I am pretty sure that I will be able to find parts for that 44mm, but to be sure, are you talking about the HD SE 44mm carb? I just looked in the SE carb and it is still available as far as the catalog goes.... I am going to take your advice and put my bike up on the dyno. I have this nagging feeling that I am a little lean on the main circuit. However, I am not going to adjust that until I get some afr readings from the dyno. OH, just to tell you, I am running .497/.497 lift and 256*/256* duration SE cams..

[PC_Hater]

The quote below is by mayor in the AFR and Tuning Zone thread 'how do you adjust the VE's on a carbed bike' started by mayor.

"The other issue is the CV44 needles are no longer available as an individual item.  Since they are now obsolete, there isn't a huge stock for custom sanding needles until you find one that works."

I think that means you can buy a nice new SE CV44 from HD but will have trouble buying parts for it. Check before you buy!   

[mayor]

the CV44 carb is still available (for now at least), but as PC pointed out the individual tuning components are now obsolete.  What this means is if the stock needle jet combination supplied with the carb doesn't work for your build, you will likely not be able to find a supply of new jets/needles.  This might not be a problem if you need less main jet or less pilot jet, since lower values of these are still available....but if you need larger than what they come with stock (48 pilot/220 main/L-needle), you may be out of luck.  The main isn't so much of an issue since you can always drill it larger, but the needle is a different story.

I like the cv44 carb, but I have to agree with PC that Mik42 may be a better option since the tuning components for them are still available.  The benefit that you have is the Mik will work on your stock intake manifold, where the CV44 needs a different manifold.

I am also looking for the cfm rating of a 40mm CV?  I am curious if the 40mm with sufficiently flow enough cfm after I get the head work done?? If not, will the 44mm be sufficient??

here's some posted flow numbers for all three carbs mentioned:
Carb Shoot Out 3: CV40, CV44, HSR42, HSR45 (by B Woltz)


to say whether or not a cv40 will be suffeicent really depends on how well all your components are working together.  I was able to get 83 hp with a cv40 on a 1200 (n8's/Buell T-storm heads).  I never ran the bike on a dyno after I switched to a Mik42, but I doubt it went up that much....if any.  I have seen 1200's hit low 90's with a CV40.  I have also seen 1200's hit mid 70's with a cv44...it all depends on how well your set up works together.

here's a good thread that's related (although twin cam values) that will give you a better idea of how carb choice is affected by head flow (read page 9-12):
HD TC Heads: Flow Bench Study

[WhipLash96]

Thank You very much for posting that information, that was really helpful. I am not that familiar with what is available for the motorcycle aftermarket as far as performance goes, nor do I know who is most reputable. That "G" that was discussed, is that an S&S Super G intake?

I could see that the Mikuni 45 seems to be the better flowing carb according to how the test was performed. Then this leads to another question. How by looking at dyno numbers can I determine that I need a different carb? Do I need to look at afr or just look for HP and torque drops at a certain rpm??

[mayor]

First, don't just focus on CFM flow numbers.  If you do that, you will end up putting the biggest carb that you can fit on the manifold and you will end up with lots of driveability/tuning issues. 

Second, a G is way too big for a sporty.....see the first item again    I really don't think the average sporty build needs a Mik45 either. 

The thing to keep in mind is the biggest gains from switching from a cv40 to a larger carb will likely be in areas that you may not personally hit very often.  The power output may not see much change in areas below peak torque, it's the areas after peak torque that might get carried further with less restriction through the carb.  The key is matching components, not maximising the components values.  The question really is what are you trying to accomplish? do you want a good running everyday bike, or are you building a racer (or dyno superstar)?  I personally wouldn't build the two the same. 

one additional thing to note.  There's two basic types of carbs that we are discussing: constant velocity (CV) and mechanical (Mik, S&S).  You may get the exact same performance out of a CV that you would a MIk, but the Mik has less lag in response. Even if the power was exactly the same between a CV and a Mik, the Mik feels stronger because you have instantaneous results when you twist the wick.  The problem comes in when you over twist the wick for what the engine can take at that particular time. The CV is easier to tune, and is much more forgiving of the operators over wick twisting tendencies...plus they are more friendly to environmental changes. 

[Hillside Motorcycle]

hello to whole community. I have a 1996 883 Sportster that I converted to a 1250. I have some SE heads that I am looking to get ported. I am curious as what the approximate flow numbers of the heads? They are 55cc SE Sportster heads. I am also looking for the cfm rating of a 40mm CV? I am curious if the 40mm with sufficiently flow enough cfm after I get the head work done?? If not, will the 44mm be sufficient??

I lean in the direction of a 42 Mik, or an S&S E, with a Thunderjet.
Scott

[WhipLash96]

I think that I may need to give my engine specs so you can better understand my set up. I am sorry if it sounded like I was going to rush out and get the MIK45 right away, not my intention. The following is my engine set up.

SE 55cc Sportster Heads
SE 10.5:1 Flat Top Pistons
SE Perfect Fit Push Rods
SE .497/.497 Lift and 256*/256* Duration Cams
SE Selectable Ignition
40mm CV Carb with  a46 pilot and a 185 main
D&M Custom Cycles Spike Series Air Cleaner and intake

First off I understand that "bigger" is not always better, that is why I was asking about flow numbers. I want to be able to have the best set up. I am looking into doing some performance head work on the SE  heads. I am looking at doing some port matching intake/head, 5 angle valve job, having the chambers measured for trueness to advertised chamber size etc. any suggestions?

[mayor]

I'm not trying to be coy, but there really isn't a specific answer.  Read the tc head flow study I posted the whole way through.  One thing a bigger carb does is allows for more airflow potential of the heads, this was eveident in all heads tested that had more than stock flow rates.  The more the heads flowed, the more all carbs would allow flow to go through the carb.  There was no point (at least with the heads tested) where the flow reached a maximum cfm through the cv40, but the amount of flow potential loss in percentage increased as the head flow potential increased. 

If I was running that build, I would choose the CV44 (but...I have a box full of jets and needles...and two other bikes running a CV44    ).   If money is a little tighter, I would choose the Mik42 (since you can use the stock manifold).  Do I think that either of these carbs will produce higher HP than a CV40 on that build?  yes.  How much?  dunno    Do I think that you will notice a difference below 4,500....no.  The Mik will likely feel stronger though, but it wil be because the carb is mechanical and not CV. 

[WhipLash96]

Ok, How about this, do you want to sell any of the needles and jets?  Actually, I am pretty serious about that??? OK, what about boring the CV 40mm? is that really a possibility and do you recommend it?

BTW, thank you for being straight to the point, that is much appreciated. I will look at that information on the head flow numbers.. I thought it was real interesting for what I did read.

[mayor]

Ok, How about this, do you want to sell any of the needles and jets?  Actually, I am pretty serious about that???

no thanks   afterall, carb tuning components are becoming increasingly obsolete.

OK, what about boring the CV 40mm? is that really a possibility and do you recommend it?

yes, there is folks doing that and no, I don't think it's worth it.  The cost vs. gains makes this less than an attractive option than just buying a Mik42. 

I will look at that information on the head flow numbers.. I thought it was real interesting for what I did read.

yea, I'm not sure the author has a clue what he's talking about...but it does give some interesting data to think about.   

[WhipLash96]

Can you direct me in the direction to where I can start looking for parts for the 44mm? If Harley sells that carb, don't they support it with parts available through MoCo?

[mayor]

I'm not sure, but HD may still sell an all in one kit that has all the needles and jets.

here's a chart with HD CV carb part numbers (the jets fit both CV40 and CV44, the needles are exclusive to the CV44):

I have since found out that the caliper used to measure the needles may not be accurate...so take the values with a grain of salt. 

[Hillside Motorcycle]

Ok, How about this, do you want to sell any of the needles and jets?  Actually, I am pretty serious about that??? OK, what about boring the CV 40mm? is that really a possibility and do you recommend it?

BTW, thank you for being straight to the point, that is much appreciated. I will look at that information on the head flow numbers.. I thought it was real interesting for what I did read.

CV carb mods/boring?? www.woodcarbs.com
Scott

[jimlibo]

"I have some SE heads that I am looking to get ported. I am curious as what the approximate flow numbers of the heads".

I don't have the flow rates in front of me now but do remember that those SE  heads actually flow a little LESS air than stock late model XB pattern and 2004 up XL heads on the intake side and alot less on the exhaust. They'll still be  better than your stock 96 XL heads though. A 42 Mik or S&S E would be far better carb choices with those heads and that cam. The Mik would favor mid and top power at the expense of some bottom torque and the S&S kind of the opposite of that.

BTW I'd recommend getting those big block chevy beehive springs out of those SE XL heads way big seat and nose pressure and they wallow all over the place in the spring pad area for starters.

[WhipLash96]

"I have some SE heads that I am looking to get ported. I am curious as what the approximate flow numbers of the heads".

I don't have the flow rates in front of me now but do remember that those SE  heads actually flow a little LESS air than stock late model XB pattern and 2004 up XL heads on the intake side and alot less on the exhaust. They'll still be  better than your stock 96 XL heads though. A 42 Mik or S&S E would be far better carb choices with those heads and that cam. The Mik would favor mid and top power at the expense of some bottom torque and the S&S kind of the opposite of that.

BTW I'd recommend getting those big block chevy beehive springs out of those SE XL heads way big seat and nose pressure and they wallow all over the place in the spring pad area for starters.

I have never had anything of mine on the flow bench or ported. Should I open the exhaust valve up or just the port going to the pipe?? But just to be clear, are you suggesting that I have a bad set up???  Most people I have spoken to about my head really like them. I have talked to two head porters that post on this site, or a t least one and they like the heads.... Just saying.

[jimlibo]

then run them. 'nuff said.

[WhipLash96]

Ok guys and gals, here are some dyno sheets that I just had done. I am not overly impressed with it and am willing to listen to suggestions on what it is that I have to do to fix the problem.. What is the problem???

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[WhipLash96]

Here is another..

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[WhipLash96]

Another

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[WhipLash96]

another

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[WhipLash96]

and the last...

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[WhipLash96]

then run them. 'nuff said.

I always like to improve on things...

To anyone who would like to see, I posted my initial dyno runs in that section.. Check it out...

[rigidthumper]

What is the combo? Displacement, year, mods, etc. Tuner used? Carb/injected?  Hard to say anything other than you are a little rich about 1 second in, and way too lean from about 4 1/2 seconds out to the end.