I have been trying to tune my 2001 SG from day one. When I got it, it had some performance Hooker 2-in-1 pipes and CV performance parts in the carb but I could not tune out the decel popping and backfiring...and I hated those pipes so I tried Samson Wildcat 2-in-2 pipes...but I still could not get it tuned just right so I replaced all the CV Performance parts with new OEM parts and the Sporty needle valve. Much better performance but still not "just right".

I was disappointed with the performance from the 2-in-2 Samsons and replaced them with new (hard to find) Screaming Eagle Pro II pipes and changed the jets to 46/185 but it was still sluggish mid-throttle and flat on the top. So upped the main to 190. Better top end but still flat in the middle and it took way too many turns out to stop the decel popping and backfiring.

Upping the slow jet did not move the adjust which indicated vacuum leaks. No matter what technique I used, propane or carb cleaner, I just could not verify any leaks. Seals are cheap and it ain't that big of a deal to replace them so I replaced the intake seals but still could not get it to tune right. It still showed symptoms of a vacuum leak.

During this process, I got a family deal on a good SE-44 and intake with flanges ($75). It had been sitting around in my garage for awhile so I rebuilt it and put it on with my original flanges but it ran worse than the 40 and would not tune either. Again, symptoms of a vacuum leak. Now I am focused on finding a vacuum leak.

I pulled it all apart again and started taking a closer look at everything and discovered that my original intake flanges were warped...vacuum leak #1. Probably been that way for a long time and I had just been fighting a loosing battle trying to tune it all that time.

Replaced the flanges with the ones that came with the CV-44 only to discover that they were an aftermarket brand, not marked Front or Rear. They were not warped so I put them on anyway with a different style of intake seal and accomplished nothing. I broke it back down and put it back together with OEM seals and still had the vacuum leak. I pulled it all apart and really looked it over again and discovered that the aftermarket flanges did not align with the head port correctly...causing yet another vacuum leak...vacuum leak #2.

Sometime during this process before I installed the CV-44, I noticed fuel seeping from the vacuum petcock and when I went to drain the tank and rebuild the petcock I discovered the petcock leaked vacuum...vacuum leak #3.

My rebuild on the petcock was successful with fixing the vacuum leak but had a heavy fuel leak around the new diaphragm and I could not get it to stop so I replaced the vacuum petcock with an earlier model manual petcock...and promptly discovered that the carb float was not properly adjusted when it overflowed and leaked out. Not a problem with the vacuum actuated valve because the fuel supply was automatically shut off when the engine was not running.

I got new OEM flanges at the local dealer yesterday and I am headed out to the garage to put them in and work on the float adjustment, and I will go back through this again...and again...and again until I get it right.

EFI maybe more reliable when they work right, but carburetors are more fun...and work even when they are not just right.

 

First off, I am a carb guy myself. I wouldn't call myself an expert by any means, maybe an expert tinkerer if that's such a thing. If you are running a relatively stock 88 then you will have fits with that CV44, too big of a throttle body to detune for your needs. On your CV40 I would have a good look at the diaphragm. It's cheap enough to replace and it will come with a virgin slide that hasn't been drilled out which can cause some issues in the mid-top range.

 

I'm also a carb guy. Got my bike dyno tuned and it runs just great! There is only so much we can do in our backyard, so it often helps a lot to use an expert, if only occasionally.....

 

I replaced the vacuum piston assembly and spring when I discovered that they had been modified.

The CV-44 came off of a stock 88 on a 2004 Electra Glide. It did not run well WOT on my SG with 200 main jets so I reinstalled the 220. It is not the carburetor that is the problem, it is the vacuum leaks. Once I get that remedied, I should be able to tune it just fine.

I think the aftermarket flanges were used when my nephew rebuilt his 88 and put SE heads on it...They are probably for a later model or larger heads. The intake manifolds are the same diameter at the heads, it is the carburetor diameter that is larger. The aftermarket flanges shifted the intake at the 10:00 and 4:00 positions, moving it toward the 4:00 position and offsetting the intake-to-head fit and didn't line up correctly. The correct flanges for my engine will fix that problem.

You are probably right about the CV-44 being too much carb for a stock 88, but it is designed to work and so it should. I also got the same deal on cams but I have not tried to put them in yet...maybe later with some mild headwork.

 

I have been told (by an indy and local dealer) that dyno tuning a carb is hit-and-miss at best. They both recommended just keep tuning and reading the plugs until it is right.

I started out just trying to reduce/eliminate the decel popping and backfiring. I am pretty sure the carb was way mistuned with the CV parts and other modifications when I got the bike and had a manifold leak. I think this because to reduce the decel popping and backfiring, I had to turn the mixture adjustment out way too far, 4+ turns. Replacing the exhaust pipes and the CV parts with new OEM parts and putting in the new vacuum piston was a big improvement but the idle adjust was still around 4 turns out. Increasing the size of the slow jet did not move the adjustment very much. That is when I replaced the intake seals. I think the flanges were warped then but I did not know to check that so I did not fix the problem with the new seals, I made it worse. Using the aftermarket flanges created a whole new problem with the same symptoms.

I now have OEM new flanges for my ride, new OEM seals and boot, and lots of experience changing them out, and a known good carburetor and intake...

If I have to go back to the 40, I will, but the 44 should work just peachy when I get it installed and tuned correctly/

 

I'd better tell my favourite tuning shop they don't know what they're doing!

Or perhaps you need to find better shops to talk to.....

 

I am not trying to say that dyno tuning is not a good way to tune a carb, I am just repeating what I was told that dyno tuning a carb is convenient, but is expensive and the results are not anymore effective than reading plugs. I have experienced nothing to dispute their opinions.

When I first started down this road, I had the dealer dyno tune the bike but $200 later, I was not pleased with the result. I was told that it was the best it would get with the CV parts and Hookers. I was new with this procedure and maybe the tech didn't want to mess with an old carbed Super Glide with aftermarket parts in it. (Now, I am thinking that it had the intake leak from the warped flanges and he never caught it or just didn't want to bother) I replaced the parts in the carb and took it back but the manager told me that they, "...could not get to it for a week," so I took it to an indy who said he would run it on the dyno but that it was just as easy and effective (and a lot cheaper) to tune the carb using the procedure called out in the manual so that is what I have been doing. It was the indy who told me to start looking for vacuum leaks. I have learned a lot about the CV carbs working on this problem under the patient guidance of this old-skool indy

I have been dealing with the creeping crud this week and not working on the bike. I will return when I fix the float adjustment and replace the flanges and let y'all know how it went.

Once I get it where it will tune, I may just take it back and have it dyno'd again and see how close I got.

 

Update:

I got the new flanges installed and that made a world of difference. It was pretty obvious that although the CV-44 setup worked well, it was running way too rich at WOT with a 220 main jet but would not perform well off-idle to WOT with a 200 jet. Final verdict, the SE big bore CV-44 is not a good match for a stock twinkie and so I put the CV-40 back on. I will save the SE big-bore carb setup for when I put in the cams and open up the head flow.

I took my time and the final results are promising. The CV-40 is setup with a 46/190 jet combo, I polished the slide, and installed the N65 needle jet with two washers. Initial mixture set at 2.5 turns and it took another turn to eliminate the backfiring...still got some decel popping until it gets warm, but after that it idles and runs great.

I still need to make some hard runs and check the plugs, but it is running far better now than it ever has...

 

The CV40 is a great carb, to a point, it's best attribute being vacuum chamber controlling the needle lift can deal with elevations (assuming the carb was setup to begin with). It's downfall is...flow. It just doesn't flow at high rpms.
I lived with one for 10 years on my Glide, and tuned it as best as I could. It served me well, but it's no match for a Mikuni.
Throttle response anywhere in the rpm zone with a Mik is way outside the CV's capabilities.

 

Final update:

I did a spark plug read run and the mid-range was a bit rich so I took one of the two washers off the needle valve and ran it again...the results are right where I want and by the book.

Now, seriously, should I pony up $80-$150 for a dyno run to fine tune the mixture or just ride it...