Timing issues?

Hey guys,

Went to work on my bike this week and installed N4 cams. Went to fire it up and ajust idle. Ran great. Went to take it a spin and noticed around 1800 to 2600 rpm that bike would stumble. If I ran it wide open it ran great except for some backfiring. I advanced the timing and it did improve but still not a fix. Carb has been rejetted so I don't think that is an issue. I would greatly appreciate any help. 1200 sport:witsend:

Thanks

Check for intake and exhaust leaks...the stumble could be the needle jet or running unbaffled straight pipes. Is it backfiring through the carb or exhaust when wide open?? What jets you using??

Thanks for the help, Lucifer. There is no intake or exhaust leak. The exhaust is Vance & Hines straight shots, they do have the baffles. I can't really say, but it sounds like it's backfiring through the carb. Jets I'm using are 42, 170, and I have the spike ac. As far as the needle jet goes, what should I do...raise it one notch? The reason I ask is because it smells like it's already running rich. I guess I should take the plugs out and look and see. But I haven't messed with the carb because I thought that since everything was running fine before, that it must be the timing. What do you think?

Thanks hotroadking for the reply.

That is exactly how it is responding. I ran the throttle at less than a quarter turn and it was running good. It was when I would turn it past the quarter throttle that it would start the stumbling and then it would work itself out.
I have a Mukuni carb. Should I go ahead and put it on? What do you think?

Sounds like excellent advice to me.
Thanks

On Evo Sportsters thru 2003, the needle in the CV carb is the cause of the "carb farts" & the easiest fix is to replace it with the infamous N65C, H-D part no. 27094-88. You can see the problem on a dyno with an air/fuel ratio "sniffer" attachment - during the transition phase when fuel is just starting to come up/out the main jet, the carb spikes way lean - the A/F ratio jumps to 16:1 or even higher. The N65C needle came in 1988 model XL1200's & that carb had no accelerator pump, so the needle had to make the transition from slow to main happen sooner & faster - it does & it smooths the troublesome transition range right out. You'll never get a flat line on the A/F ratio charts, but you can get pretty darn close with that needle.

The N65C works great in later model Sportster CV carbs with the stock 42 slow jet & baseline for a 1200 (thru 2003) is a 175 main. But with the N4 cams you may need a 180 main - leave the slow jet alone though. And since you mentioned raising or lowering the needle, I'm going to assume the carb's got a "DynoJet" kit in it - if so, get rid of it & go back with factory parts. The DynoJet kit is an attempt to make a "one size fits all" adjustable setup which doesn't work very well & the N65C needle meters fuel far more accurately. Also, baseline on the idle mixture screw is 2.5 turns out & you shouldn't have to go more than 1/4 turn either way to hit the "sweet spot", 1/2 way between too rich & too lean.

The CV carb is a "set it & forget it" deal & while Mikuni carbs are great, I prefer the CV for a street/road Sportster. Throttle response with a properly adjusted CV is just as good as the Mikuni & the CV does a good job of adjusting itself to weather & altitude changes. The Mikuni will give you a couple more ponies on the top end, but unless you're racing for that last 10th of a mph, the switch isn't worth it.

Thanks ART_NJR
I have worked on the cv and have had great experiences with it. I am pretty new at working on bikes so I am learning. I have had so many people tell me just how great the mik is but I know that after I put the dyno kit in and got it adjusted right I just could not understand how another carb could make that much of a differance. But I figured they knew better than I so I bought one for the cams. I am first going to try and fix the cv the way you and Hotroadking said to but just for fun I am going to try the mik afterwards just to see what all the hype is about. Thank you guys again for your help.

I remember when I was first getting my bike done, the guy that originally did the engine work was pushing really hard to get rid of the CV. I almost did, but I am glad that I stayed with it.

Informme, if you still have issues, shim the needle and bump your pilot up to about a 45.

Some folks have shimmed the (N65C) needle .020" - .040", but just for fine-tuning after everything else is right. It makes the low end a little bit richer & going up to a 45 slow (pilot) jet makes it way too rich - that's just a Band-Aid for a problem the proper needle will fix.

LOL !!! Nope, the doctors did - had to have emergency abdominal surgery last October & was hospitalized twice after that due to complications. But the worst is over & I'm doing a lot better now.

Good to hear you're doing better Art...hope you have a speedy and complete recovery

sorry to hear about your surgery but am glad to know you are on the up swing now.
As far as the needle goes can I order it here or should I get it from dealership?

Thanks JB for you reply. I think I am going to stick with cv as well.

I am sure that you could buy the needle through Ken, if you want to just shim it, I do not know if he offers a kit for that or not, if not, Keine makes them.