Gents,
Hope everyone had a good Thanksgiving! RE: '98 Heritage, stage 1 installed & aftermarket pipes.
It is still warm enough to ride here in Baltimore (mid 50's). Experiencing a lot of carb coughing even when warmed up. Bought the bike used in July and it ran great all summer. Seems to cough in the lower 1/4 of the throttle. Is this on the pilot jet circuit? I'll be pulling of the carb this weekend. The shop manual says to pull the tank off to remove the carb. Seen some posts about guys loosing the rear tank bolts and raising it up a little. Any comments on that? The fuel mixture screw is out 3/4" turn. My patience is wearing thin and I'm getting ready to ****-can the CV and buy a Mikuni. Who has experience with the Mikuni? Is the jetting good out of the box ? There are a lot of posts on this but they mostly pertain to the TC. Do any of you East Coast guys that have Mikuni's have any problems when riding in the mountains? Thanks Guys!!

 

When changing pipes on a carbed motor,a rejet is usually done as well.Should you feel the need to toss the CV,the Mikuni is an excellent choice.Should you go with the 45mm then a rejet should be done,not sure about the 43mm though.The S&S is also a good easy to work on carb for the EVOs.Good luck & let us know the outcome.

 

Idle mixture is probably set too lean. Nothing wrong with the CV carb on lightly modified street bikes. Mikuni and S&S both make good aftermarket carbs, but for the money I'd either screw around with the CV or find someone with a dyno that knows how to tune one and go that route.

 

My .02 - Rejet you stock CV.
A Mikuni 45 is to big a carb. The Mikuni HS42 or 40 is better suited to an 80". I ran a Mikuni for years and it was a great performer , but it was more work to dial in. I run an S&S E on an 80" evo, the gas milage is great, the performance is great and it is stone cold simple to dial in compared to the Mikuni or CV.

 

Generally, on a CV cardb, the pilot jet is in use from idle (slide closed) to about 1/8 - 1/4 throttle (slide begining to open), at which point it becomes a mix of pilot and main, increasing to main, depending on float level, needle height and needle taper.

If you mixture screw is not providing enough range (toward rich, in this case), you might consider increasing the pilot jet size and / or raising the needle (add or swap washers as needed). If you do move the needle, watch for rich conditions in the 1/3 to 1/2 throttle range. Performing plug checks may be a PITA, but it is accurate and still about the best way to get a carb "dialed in".

It's all about proper floatlevels, jetting, needle height and needle taper. Makes no difference if it's a CV or mechanical slide (flat, round or hybrid). CV type carbs (note, this is not a brand, but then I'm sure you already know this ) when properly setup, work very well.

It is unlikely that you would buy a non-CV style carb (or any carb for that matter) that is ready to go, right out of the box, and it not require some adjustments.

Good luck and remember that the reward of patience is satisfaction.

 

Tucker, get yourself a carb kit with adjustable needle. Change the slow jet to a 45, 170 mainjet. Set your a/f screw at 3 turns out from lightly seated. Get the bike at operating temp and adjust the a/f screw in or out very slowly until you get your hightest smoothest idle. That cv carb can be re-jetted to run very smooth, no spitter's.

 

I have an S&S Super E on my 91 Ultra. It works very well, but if it hadn't been installed by the previous owner I would have kept the stock CV and had it re-worked since my bike only has better exhaust, ignition, and intake. I would've bought a cam ahead of the S&S carb. When I worked at a Harley dealer, it was amazing how good our mechanics could get a CV to run. We tried all kinds of different carbs and modifications but couldn't see much of an improvement on the CV until the motors were quite highly modified.

A recipe that worked well was to get a good A/C, exhaust system, ignition, and cam, with rejetting the stock CV. We recommended more displacement, more compression, and better heads or porting before considering a bigger or "better" carb. The stock, reworked CV ran great at this stage too, but gave up just a few HP over a bigger carb. One of our bikes dynoed at 93 HP with a reworked CV and ran beautifully.

If your bike ran great all summer but now doesn't, it seems likely that a careful inspection and perhaps rebuild/rework of your carb (if the carb is actually the problem) would restore its previously good driveability.