Keihin CVK Main Jets Harley Evo Discuss Keihin CVK Main Jets in the Motorcycles forums; I live at roughly 6K above sea level in CO. Does ANYone have any idea what size main jet I should be looking at for my 95 FLHTC? It IS ...

[kempomark]

I live at roughly 6K above sea level in CO. Does ANYone have any idea what size main jet I should be looking at for my 95 FLHTC? It IS running rich from Texas so I need to lean ur out but I can't see buying 14 different jets to get it right! Float got stuck so I had to take the bowl off anyway. So while I am in there.... Oh, it is got a Ness/K&N filter with pretty unrestricted same side duels. Thanks brothers and sisters!

Kempo

[frisco-rigid]

Hi Kempo

If you are going to continue to live at 6K ft+- then you might consider re-jetting the entire fuel system Not just the Main Jet..

The Main jet doesn't even get "come on" until the Rpm's are quite high with Large throttle opening,, so just leaning it out will not do any good for the lower Rpm A/F and running..

You might consider re-adjusting the Idle A/F mix & changing the slow-spd jet,
and adjusting or changing the needle first..
Then reading and changing the Main..

In case you're Not familiar with the procedure it's easier for you to read it from someone very fam with it rather than me taking the time to type it all out at you..

CV Carburetor Modifications

[kempomark]

That is great information to have. I have contacted a local harley dealer (Roadies in Arvada, CO) about getting a dyno run to see what the bike actually needs. They said it would be around 225.00 to run it and change out the jets if needed. I guess that is money well spent to have someone else with better better equipment and more experience than I have with Harleys. (Which is about a week) Can't say I like the idea of someone doing work for me. I've been turning wrenches my whole life. It's hard to admit that someone is more qualified to work on MY bike. But it's more important to have it running great as opposed to guarding my ego.

Thanks Frisco.

HUmble bow

Kempo

[evoKENevo]

Hi, Kempo
Sounds to me like your "stealer" is more determined to SELL you Dyno time etc (pretty extreme measure) than to simply GIVE you recommendations on rejetting and adjusting based on what he's must have done to numerous similar bikes in your area...not satisfied with just selling you the relatively cheap parts and FACTORY shop manual for YOUR model/year required to do it yourself...which ain't exactly "rocket-surgery"

If someone here on the forum living in your area does'nt chime in with their recommendations on rejetting etc...I'd recommend contacting a few "seasoned" independent Harley wenches in your area for 2'nd and 3'rd opinions on the matter...and that you give it a shot after getting a FACTORY shop manual that'd be useful to you as long as you own the bike

In "mymind" it would be a shame to under estimate the value of your previous experiences...noting that IF you were to botch it (somehow) there's always the "stealer" to fall back on...and there's plenty of the BEST experienced guys here to help get you back on track before that happens.

Your bike...your money...your choice...of course.

[frisco-rigid]

Ahhh Grasshopper

As Master Po once said-----

"Admitting that another pocesses more knowledge of the Jasmine Flower
prepares one to part with coins to mearly pluck same.."

In-other-words,, Kens sugg is very good and since you DO know which end of a wrench to hold I bet a dime to a doughnut you will succeed..

At least try this since you're in the bowl..
Remove the Slow-jet to see the size..
If it's a 45 for instance, go get a 42 or 40, etc etc..
Remove the needle and see how many washers are under it..
The more washers the richer,, maybe remove some or all..

Here's a parts list from that same site, heck you might even want to get a leaner needle..
Keihin CV Carburetor Part Numbers

Before doing anything you might consider running a plug color test and again just after making a change.. Do you know how,, I'll describe if not, very simple..
Hey, just something to consider..

[kempomark]

Thank you for your input. Just one clarification please. Are you saying to take washers out AND change out the low speed jet? I just got it put all back together last night and ran it. It is rich, rich, rich! But I guess my inlet valve problems are over. It's not leaking a drop. I am going to try and see what the idle mixture is set and and see if that is set a little rich. But as we speak, I am giving less and less to the stealership.

Thanks! Getting ready to start collecting parts for the Winter upgrades and repairs.

Kempo

[frisco-rigid]

Hi Kempo

Not exactly..

If it was my sickle I'd remove the Slow-spd jet and the needle to see what sizes they are and also see how many,, if any,, washers are on the needle..

I would then refer to any lit available, like that link I supplied or a manual, to see what the next leaner sizes are and would start the job..
This is all the dealer will do except they'll do it on a Dyno which is NOT like real-time riding----accell & de-cell up & down hills, lights, signs, running from the police, traffic, etc etc..

Try this..
Since you recently rode it and prob idled back into your garage,, pull the plugs and look at the color & condition of the Porcelain and electrodes..
They will show approx. what the A/F mix is at & around idle..

If they are VERY dark start there.. You see, if it was adjusted correctly for your previous Lower altitude then ALL the fuel circuits, slow-jet, needle, and main will need to be re-adjusted..
First, get access to the Idle Mix screw as described in that site..
Then get a size, or 2, lower Slow-jets and install one and re-adjust idle mix and speed then Ride easy style around the neigborhood, motor up to full op temp.. Idle in and look at plugs, they should be lighter color..
Now you're getting close..
Remove all washers and also see if maybe you should get a leaner needle..
Run again, feel by the seat-of-your-pants..
The needle controls the Mid-range Rpm running so you will need to check plugs after a Low-spd shut-down.. I'll explain if you don't know how..
Then do it again until you're satisfied..
Main jet last..

I am unable to make it sound any easier but really man,, tuning your carb is soooo easy & is a very personal thing cuz only You can be the judge of how well it runs and if it needs a wee more tweeking..
YOU are your sickles best friend and Mechanic..

[jimkelley]

Hey Kempo. You might check into a Dynajet kit for your particular model scooter. Back in '03 I put a kit in my EG twin cam. It included a new needle for the main (different profile of the needle taper) and a variety of main jets. I got mine from Dennis Kirk. I also ordered several different low speed and high speed jets. At the time I was in Jackson Hole Wyoming at 6300'. I now live at 7000' in southwest Colorado. I was running a 185 jet until last year. I put on the Screaming Eagle air cleaner kit and had to go to a 190. My exhaust was stock headers with V&H oval slip ons. To the best of my memory my low speed jet was a 45. The high speed jet only functions during the last 1/7th or so of the throttle travel (high rpm). I recall mine was a 50. The rest of the motor was stock. I never had any issues with fouling plugs and plug readings always showed a light tan color. I looked for a little more power and tried a 195 main for a couple of tanks of fuel and the plugs started fouling right away. Went back to a 190. Just be careful to not go to lean. From your mechanical background as you described you will make out ok.

[frisco-rigid]

Holy Cow Kempo

Jim lives waay high too in your area,, you can't get better than that..!!

He'll prob get you real close to correct..

Take it away Jim..

[jimkelley]

Hey guys I had another brain fart. I checked my library of saved handbooks and old magazines and found something that may also help. Back in September of '06 American Iron put out a special issue called American Iron Tuner. It had all kinds of really good hop-up how-to's including carb rejetting (kudo's to Chris and the rest of the gang). Also the Dynajet kit that I used had very explicit instructions ad trouble shooting info. When I did mine I used the kit instructions and the seat of my pants to judge performance changes. I was able to achieve real performance boosts without having to get into the motor or pay someone for dyno time. If you are a real stickler for accuracy then maybe dyno time would be worth it, but I don't think it is needed for street performance improvements. AIM has a site, GREASERAG.COM where I believe you can order reprints and old issues of the magazine. Maybe you can get your hands on a copy of the Tuner issue. Also in recent issues of American Iron, Donnie Peterson has been addressing carb and exhaust issues and the man is a fountain of knowledge. Almost none of the above mentioned references really address altitude specific information but they do provide a solid base for a starting point. Remember the basic rule when re-jetting is to make small changes in jet size. As you do this you will notice improvements in performance. You can increase or decrease the jet size until you notice performance start to decline then back down or go back up one size. Also concentrate on only one jet at a time. A good starting point is the idle mixture screw. Once you have that set then move on to the main jet as that's where most of your driving range is. Then you can make changes to the slow speed and high speed jets, again only going up or down one size at a time. The whole process is a little time consuming but "ye shall be rewarded" in the end. The finished project should even yield a couple of extra horsepower but will definitely improve the way she runs. No more stumbles or hesitation when accelerating, no backfires, etc. Have fun with it!