I took my recently purchased 1999 Fatboy in to my local dealer for a 20,000 mile service and a basic tuning job since it went from sea level to 5000 ft. The dealer talked me into a high flow air kit and Dyno jet kit to match the V&H pipes that came on the bike. Ever since the initial service this bike just won't run. I have taken it back twice and each time I get it back it stumbles and pops at low throttle cruise (like when following slow traffic on surface streets) and has no top end power.

I suspected that it was running very lean and a quick check of the spark plug showed that it was bone white. The deler told me I needed baffles in my pipes to solve the problem, so I bought a set and there has been no change in performance. They have basically told me they don't want to look at it again, which is a story for a different time. This bike has gone from a pretty reliable performer to one that can barely maintain 70 MPH on the freeway and falls on its face when pulling up mountain grades.

I need some advice from some of you who have more knowledge than me when it comes to tuning one of these carbs (stock Harley CV). I dismantled it last night to make sure that the dealer had not mistakenly installe too small a slow jet, which I suspected to be the problem during the low throttle cruise. They installed the #45 jet that came with the kit. I then checked the main and it was a 170. I changed out to a 180 and took it for a hard run up a local mountain pass. The performance was better but it will still only haul me at 70 MPH up a 6% grade on the freeway. I only weigh 165 pounds so I think this bike should be able to move me a lot faster than that. The bike has a stock 88. The plug looked beter but it's still pretty white. I looked for intake leaks and couldn't find any.

Sorry for the long post but I though I should put as much information out there as I could. Here are my questions:

1. Does anybody have a good feel for which jets and what metering rod should be in this carb with a high flow air kit and V&H Straightshot pipes?
2. Is there a common point for intake leaks on these bikes? I was a little surprised at how loosely the carb fits into the rubber boot where it connects to the manifold. Is this a common problem area?

Thanks in advance

 

Its been a while since I had my 97 fatboy but I think I had a #190 or #195main jet installed. At cruising speed try pulling out on your choke **** at little at a timeto see if the stumbling / poping gets any better. If it does you are definately running lean. The rubber compliance fittings sometimes leak. Try spraying carb cleaner on the fittings at idle. If theRPM changes you got a leak. When you check your spark plugs, you need to do it at speed. In other words, If you are cruising, hit the kill button, pull in the clutch and coast to a stop. Remove the plugs and take a reading. This is the only way to get an accurate reading....................BG

 

Past miner sorry to hear how you got burned by yet another Dealer that knows nothing except how to collect money. Did they tune your bike on the dyno...if so did you get your graph? The Dyno Jet kit is a good kit BUT it is a tunable kit which means it needs to be tuned....it won't tune itself. Knowing your at 5000ft the jetting is going to be smaller than it would be if you where at sea level, evenat that a 170 main seems EXTREEEEELY small for a twin cam. The 45 pilot is stock for your bike and believe me when Isay that the Dyno Jet kit does not come with apilot jet. If your bike is sputtering down low like you said I'd say the pilot needs to be one size larger but in your case I think they really malfuctioned you carb. They had to screw something up when installing the kitlike apinched the diaphram (small hole in it)not letting the slide operatewhich would account for the lack of power.I'd start with a 185 main jet, needle on the forth groove down. I don't liketelling people what jet sizes to use because each engine is its own air pump and those things vary alot, it needs to be jetted on the dyno to be correctly done.

 

Doc1,
No, they did not run it on the dyno. I went backtoday and raised cain with them and they have grudgingly agreed to run it on the dyno on Saturday. I am aware that the dyno kit lacks a slow jet. However, they put a new one in it and it's definately the same size as the old one. Both clearly say 45 on them.I did not pull the top cover and look at the diaphragm or needle last night, but I will tonight. I appreciate the help, and I understand about being hesitant when giving jetting advice. I have been working on small block Fords for long enough to know that every single one is a different animal. I will also take it down to them and have them run it on the dyno, since they have offered and I personally think it should have been a part of the original install anyway. The price on the install was certainly high enough to justify a dyno run......

BG,

Pulling the choke will eliminate the low throttle cruise problems in almost every instance. Thats was my first suspicion that it was just too lean in the idle circuit. Then I pulled a plug and checked. I didn't really kill it after a hard run but it was almost that fast. The plug I pulled after the change last night was after I let it idle. It was still fairly white though. I will just carry the wrench with me tonight and pull it wherever I stop. Thanks for the help.

 

Credit card dispute?
Doc1 is right.Jetting a carb can be labor intensive to get it dialed in.

 

First question is Have you adjusted the Idle screw?
Also at 5000 ft. you will probably be running smaller jets than us flatlanders.
If you come down the hill, you might be better off running a little rich at home.

When you get it right, this will be a minor memory.
Good Luck!

 

You need an experienced MASTER tech. I am a tech in a dealership. Yes I have heard it (almost) all. Your money is hard earned. Don't let a dealership say " We don't know....now give a $100." Every motor can be tuned, yes a tricker motor can take a little time and some more money. So just because your buddy got his tuned in a single trip to the dealer doesn't mean yours will...hope I can help.

 

opps

 

Oh yes. I spent a whole day changing jets and readjusting the idle screw and adjusting the height of the metering rod. I'm not uncomfortable around a carb by any means, I just haven't ever worked on a Harley before. I know I'mnot imppressed with the Dyno Jet kit. It definately ran better before the conversion. There seems to be a flat spot in the throttle no matter what I do. The biggest problem is that that flat spot is always a backfire-sputter kind of spot, not just a low power spot.

After about 6 changes and road tests I got a combination that works okay, but not well. a 45 slow jet and a 180 main with the clip on the 4th groove of the rod with only 2 washers above the clip seems to work the best. Even at that I have to run the idle mixture screw out at least 3 1/2 turns to keep it from backfiring and sputtering at low power cruise. Even when it's really hot that problem still exists. Pulling the enricher always stops the problem when I'm moving down the street. However, it's the first time since the initial service that the bike would get up and run on the highway. It's just too lean with that high-flow air kit.

The 48 slow jet was just too rich at idle. It would belch black smoke every time you revved it at a stop light. I know that was just too much, but it ran better at cruise. A 190 main was also a bit sluggish at top end.

 

After they told me to put baffles in the pipes "to solve my prblem" and it didn't work I went back and talked to them. The service manager agreed to put it on the dyno and check it. They did tell me that the jet combination they installed "always works" for this altitude. That just tells me that they didn't do any tuning at all.

They called me and said the starter wouldn't engage on Saturday. I have always been able to get it to start but they can't for some reason so I'm sure I will get another $500 bill for that repair. However, the dyno run will answer if it's mixing correctly across the whole range or not. At this point I just want them to fix what they have messed up and get it so it will run well enough that I can get on the road with it. If they can't I am just going to ask for a stock carb and put it all back like it was so I can ride it. At least it ran without any problems before the jet kit install and it will again.