CV Carb

I'm fairly new to the forum so I'm sure this question has been asked before...but here goes. I bought my first Harley (2006 883c) last Fall. Had problems early with carb cough. Pulled the carb apart over the Winter and found previous owner had installed half a DynaJet kit. Bought all the right stuff to make it right again including the adjustable low speed screw. Great improvment but I still get a cough from time to time when I downshift. I have the Scremin Eagle pipes and air cleaner. I also notice this motor seems to be straining some over 60mph. Is that normal because of the smaller displacement. Thanks.

Nope, it's not normal & my "tax paid" 883 (SE slip-ons & A/C) will run over 110 mph without any "carb farts". Toss the Dyno-Jet stuff & go back with factory parts - your baseline is 42 slow jet, 165 main, 2.5 turns out on the idle mixture screw & the needle the bike came with.

Prior to the '04 Sportsters, the needle was the biggest problem, but from what I've seen, the '04-'06 models run just fine with the (different) stock needle & it's just a matter of getting the jetting & idle mixture screw "dialed in". Your bike should have come with a 42 slow, so no need to change there, but I've seen different main jets come in '04-'06 883's.

Yes, the '04-up Sportsters do have the XB Buell type heads, but the 883's still have the same combustion chambers & valve sizes as the '91-'03 models - the 1200 heads are the same on the outside, but not on the inside.

Now in '04, H-D started using the "W" grind cams in all 1200's, which were previously used only in the rare '98-'03 1200S models & somewhere along the line ('05-up ?) they started putting the W cams in 883's too - those cams will change the main jet which works best, but not the 42 slow.

Get rid of the gimmick stuff, get the idle, off-idle & low end dialed in 1st, then let the engine tell you which main it likes the best. Jets are cheap & since you don't have the crossover pipe right under the carb like on my older models, you can drop the float-bowl to make jet changes quicker & without worrying about cooking your hands !!

Thanks for the reply. I'll have a go at the jetting and see what happens.

http://bike-talk.com/forum/attachments/motorcycle-tech-talk/903d1208346402-making-sense-jets.jpg

Seems to be the same question you had in Dec of last year man. 2006 manual hasn't changed on the base jets, 42 slow 175 main.

I have fought the CV on my 05 for a while and finally seem to have it pretty happy. From time to time I still get the Sporty carb fart but not like before.

First question on the over 60 is how big a fella are ya? Me I am on the more to love side LOL and my Sporty seems to be straining over 60 as well. However, you just got to get used to her. These bikes will run with the best of them. Mine will break 100 and keep right on climbing (Me I chickened out at 103 on the street) since my goal was just to break 100 on her.

If you have been suffering too many of the coughs you might want to take the time to wash that SE filter before you start. Mine got all nasty and that caused problems too as it cuts down airflow (thus air fuel mix blah blah blah just clean it). Don't run it with constant (more than 3 or 4) coughs in short period of time. Mine burnt the dang slider diaphram, leading to MORE problems.

Like Art said lose the gimmick crap. I hope no one was foolish enough to drill your slider either, if so replace that too even if not burnt. The CV is a good little street carb if you have the patience to work it out. It isn't over complicated but boy can it be a PITA. Once she is working though, Hold on cause that little 883 will pack some punch.

Good luck. Also I have the Clymer manual in pdf format for the 06 Sportster if you would like it let me know. It isn't a replacement for factory manuals but it is better than nothing.

Yes. Had this issue early on and swapped out all the junk for the right stuff. Still get an occasional cough when down shifting so thought it might be the intake leaking. Guess you're right about getting use to but been giving some serious thought to an 883 to 1200 conversion. Any thoughts on this as a worthwhile upgrade, or a waste of time?

Do more research than just looking at price. I found conversions real reasonable but then after talking to those that know more I found out there is more to it than some would lead you to believe. I can't say it isn't worth while since I am still looking at doing the same myself down the road. One thing I have found time and time again is to change your front cog if you do the conversion and want to keep the front tire on the ground. The 883 has a 27 tooth front and the 1200 has a 29.

Again, thanks for the replies. I'm looking at a conversion of both the jugs and the cylinder heads. I've been told by those who have done the conversion that the cylinder heads make a big difference in the performance of the bike. The front wheel in the air once, and a while probably isn't a bad thing. I guess the big question is who has the best stuff. Should I stick with the Harley Scremin Eagle kit, or something else?

You will get that when you down shift because you have increased the rpm the engine is turning, but backed off the throttle causing a instant lean condition. It will cough!

There are a LOT of ways to do an 883>1200 conversion & the basic one is definitely the "best bang for the buck" of any modification. Depending on how much work you can do yourself, you're looking @ somewhere in the $500 - $750 range. A typical basic conversion will change a "tax paid" 883 (improved intake & exhaust from stock) that makes 49-53 HP into a 1200 that makes 70-74 HP & the torque increase is even more.

Until 2004, the 883 heads were actually better than the 1200 heads. Cleaned up a bit & using "reverse dome" pistons made specifically for an 883>1200 conversion, you get a great combination with stock cams & very little machine work. The '04-up 883 & 1200 heads look the same on the outside, but they're not on the inside. The basic castings are the same as the Buell XB heads (best H-D ever made for street bikes), but while the 1200 heads have the Buell combustion chamber & valve size, the 883 heads retain the '91-'03 combustion chamber & valve size.

You can go 2 ways with the '04-up 883 heads - use "reverse dome" pistons as before, or have a qualified machine shop turn them into Buell heads & use flat-top pistons. Either way, you do not have to buy new heads. What the "reverse dome" (dish-top) conversion pistons do is mirror the shape of the smaller 883 combusion chamber so the size is effectively increased, but without machine work. If you put flat-top 1200 pistons in a conversion with stock 883 heads, the compression ratio will be way too high.

I always say think "system" rather than individual parts & determine what you want the bike to do on the budget you have before you buy anything. A basic 883>1200 conversion will beat a stock 1200 stoplight-to-stoplight, so if you're riding in a city most of the time, that's definitely the "best bang for the buck". If you want more top-end power for interstate riding, you'll want the bigger valves in the 1200 heads.

Cams are the last thing I'd change on a street / road Sportster & I believe the '06 883's came with the same "W" grind cams that all 1200's since '04 came with. Even if I'm wrong, the "D" cams used in 883's previously I happen to like & although you won't get as much top-end HP, they work great from 2000-6000 rpm & the engine's torque band is wider than with any other cam set.

JUst a followup...I added the big bore kit(aluminum dished Wiesco pistons) and Andrew's n4 cams. I left the heads alone for the moment. What a difference from the stock 883. The mid range is great! I'm taking it easy for the moment to break in the rings. Coming away from a light is the best. Sometime in the future, I'd like to add the Buell heads that everyone likes. I'd recommend this conversion. Pretty easy to do. Needed to jet the carb up a bit. Barely need the choke now.

XB 1200 Sportster (Buell) heads are a bolt-on, but you'll have to change to matching flat-top pistons, as the "reverse dome" pistons for the smaller 883 combustion chambers will make the compression ratio too low.

Also, you do not need to buy new heads to make the change, as the basic casting is the same & a qualified machinist can open up the combustion chambers & switch to the larger 1200 sized valves. The valve-stem length is different so you can't just put 1200 valves in 883 heads, but Baisley & others make conversion valves for the application - still have to open up / change the valve seat area, but again, a qualified machinist can do that.

And I'd rather take 883 heads to a machine shop than buy new 1200 heads because you'll end up with better parts. Heads are castings, the port size / shape isn't precise & neither are the combustion chambers. Mass-produced parts are never as good as those worked one-at-a-time in a machine shop.

For example, before the XB heads came out, I got a set of 883 heads turned into Buell Thunderstorm heads by Head Quarters - they flow a lot better than off-the-shelf T-Storm heads & the "squish band" is cut precisely to match up with T-Storm pistons. Adding HQ "Whipperstick" cams to the mix (all calculated beforehand), a ~50 HP 883 turns into a 95 HP 1200 & that's HP measured @ the rear wheel on a chassis dyno, not estimated @ the crank (T-Storm Buell was rated @ 101 HP).

But remember there's always a compromise involved with larger valves, more cam, bigger ports, etc. - to get more top-end HP, you must give away low-end torque. In other words, while the T-Storm setup will pull away from a conversion with stock 883 heads on the top end, your current setup would beat mine stoplight-to-stoplight & have better throttle response around town.

The bike is a 2006 so the heads are in good shape. I was looking at it more from a performance point of view. Probably just gonna leave it alone for a while. As I said, I would recommend this conversion to anyone who wants to "wakeup" their sporty.

Will do. Thanks

HRK's right - you will get more for your money by having a professional shop work the heads you already have than buying new ones. I know HRK likes Bishop's Performance & there are many good shops - I'll mention 4 others - Head Quarters in Canada (I have a set of 883>Buell heads from them), Zippers Performance in Maryland (most of my race engine came from them), NRHS in Colorado (been there, know the owners) & ECS Engineering here in North Carolina (I go there for things I can't do myself).

Heads are castings machined on a production line & a mass-production manufacturer cannot work each head individually, take it to a flow bench, get the front head to flow exactly the same as the rear head, hone valve guides to the 10-thousandth of an inch, etc. If they did take the time to do the extreme detail work, the cost of the bikes they sold would skyrocket.

But independent shops which have the necessary equipment & deal with one customer @ a time can do the detail work & you'll end up with heads (or any other parts) made specifically for the given application. And I know for a fact that '06 883 heads can be machined to be XB 1200 heads that are better than XB's you'd get from a H-D dealer.