I have a 2006 Heritage Softail Classic. It has a TC88 engine with a CV carb on it. Recently, I decided to upgrade my original cam chain tensioner system to the newer hydraulic tensioner system, so I carried my bike to an independent shop and had the work performed. New adjustable pushrods, new lifters, an Andrews cam plate and a new oil pump were installed. I decided since I was upgrading to replace my stock cams with Andrews 21 conversion cams. A S & S Stealth Air Cleaner was also installed, but the stock air cleaner cover was retained. The invoice from the dealer stated the carb was adjusted and listed the intermediate jet as a 50, the main jet as a 190.

After riding the bike for less than 400 miles, I noticed my slip-ons were bluing. I installed the slip-ons myself three years ago, and they remained pristine until the upgrades were made. I suspected this may have been a result of a lean air/fuel mixture, so I pulled the plugs and took a photograph of them.

I then called the shop and explained my situation. The owner asked what type of fuel I put in the bike and I told him 93 octane. He asked if the gas was ethanol free, and I said no. He then blamed the bluing on the ethanol gasoline. I explained that I have always purchased fuel from the same stations, and didn't understanding why the slip-ons didn't discolor until now. He pointed out that I just installed new cams. I asked him if I texted him a picture of my spark plugs if he would look at it and he said no, the picture would be of no value. He accused me of being argumentative and informed me if I was concerned the bike was running lean, I could schedule another appointment and have his shop check it out.

After putting additional miles on the bike, I noticed that if I maintained a constant speed of 70-75 mph, my bike would cough and it actually backfired once. It also felt to me as if there was some surging, as well. The bike accelerated smoothly, wide open throttle was spot-on, and there was no popping on deceleration, just the coughing at 70-75 mph.

Frustrated by the shop owner's lack of concern, I carried the bike to an independent shop much closer to home for dyno testing. The shop's owner stated the bike was running very lean at speed. His solution to my problem was to put two small shims under the needle, but stated the bike was now running a little rich at lower rpm's. There is no longer any coughing at highway speeds, but in town the bike runs rough, and sounds almost as if it is missing. The owner asked me to let him know if I wasn't satisfied and he would do his best to make it right. I believe he will, but I have not carried the bike back to him yet.

I am not mechanically astute, but think paying customers should be allowed to ask questions without being demeaned. Since the coughing occurs around 70-75 mph, I suspected a larger intermediate jet would have been installed, but don't know much about carbs, and virtually nothing about shimming the needle. Your feedback is greatly appreciated.

 

You put cams in it, but did he adjust the timing? Do have an adjustable aftermarket ignition?

Yes you should be able to ask questions, but no he shouldn't have to diagnose symptoms over the phone. He offered for you to bring it back to him to try and solve the issue. Carb tuning is not an exact science and he can change the jets but without it going on a dyno all he can do is test ride it and make the best guess. Then try again.

I say take it back to him and let him figure it out.

 

If you want to learn more about the CV40 carb, go here:

https://cv-performance.com/instructions-guides

The CV40 carb is pretty easy to tune, and to rebuild. Parts are readily available....

It's predecessor, the butterfly carb, was usually replaced by numerous brands... The CV40, I believe is underrated, and suffers from the reputation of it's butterfly predecessors...

For your reference:
I know someone with an 88" twin cam with A21 cams, high flow A/C and exhaust... he ended up with a Sportster needle (#27094-88), 48 pilot jet, and kept the OEM main jet (190). I believe he was two turns with the mixture screw. He kept the OEM ICM, (no spark advance changes).... That bike ran really well.... Fast starting and quick to accelerate.

He originally tried a 50 pilot jet, got poor gas mileage, changed to a 48, and retuned the mixture screw... he got better performance and better MPGs...

I know someone else, who did the same, A21 cams, exhaust and intake on an 88" twin cam... he was 45/190 on the jets, sportster needle, a tad over 3 turns out on the mixture screw (anything over 2.5 to 3 turns usually means it's time to go up a little on the pilot jet), and no ICM changes..... He loved the way the bike ran enough to just keep the 45 pilot jet and the mixture screw at just a tad over 3 turns..

 

Thank you for your reply! I especially appreciate the two specific examples cited, which are the same set up as I have. I have talked to the tuner and he is going to remove the two shims and swap the needle for the Sportster needle you referenced. It seems pretty clear to me there is a problem using the stock needle if modifications are made, however slight.

 

Glad to share the info.... every bike is different, even with the same mods... the VE is always a little bit different... you may still have to play/experiment a bit.... but those examples should get you close..

I know of a bike that also got an adjustable ICM from Twin Tec (TC 88 Twin Cam Ignition module #1008) along with Andrews 21 cams... His bike ran real well also, but not sure it felt noticeably better than those who ran the OEM ICM and didn't mess with timing curves... but I would suspect it would have a better looking dyno sheet...

For an unrelated example.... On my carbed 2001 88" with OEM cams, Screamin' Eagle Air stage I air cleaner and Vance & Hines big shot staggered exhaust... I rebuilt the carb with the OEM jets (45/190), and the N65 needle clone, used in the early CV40 carbs with no accelerator pump. It ran OK, but was a little rich (I think) in the cruise areas. I switched to the CVP Velocity needle (#402-823) and about two turns out on the mixture screw... now It runs and starts excellent..... If it had a kick start, it would be a one kick bike....

I find it kind of fun to play around and see what works best, good luck with the tuning.....