My son brought home a pretty nice 04 Low Rider this week. It has the 88ci Evo engine.

My question is that this bike, while riding at highway speeds, occasionally has a hesitation in running. It is more noticeable when the engine is cold, but improves as the engine warms up, but doesn’t completely go away. It sort of feels like a hiccup.

The bike idles fine and runs great when accelerating.

It does have drag pipes and I don’t think any baffles.

Could this issue be caused by a lack of back pressure?

If you have an idea as to a cure for this problem, I would appreciate hearing it.

Hmm, hardly an expert on this, but I have an '04 Electra Glide with a Twin Cam 88 engine, which I believe is what your son's bike has. Is it EFI or carb'd? With the non-stock pipes maybe it needs to be remapped (if EFI), or rejetted (if carb). Just a guess.

No fuel injection on this one. The bike has probably spent a lot of time sitting. The carb could be gummed up a bit. I just don’t know where to start checking.

The 04 would be a Twin Cam 88 motor.

If it were mine I'd make sure all the gas is fresh and at least 93 octane.

They run best with their stock CV carb and factory exhaust. I'd try to find factory exhaust and make sure the carb is clean.

If you're gonna run aftermarket pipes you need a jet kit for the carb; think Harley calls that their Screamin Eagle Stage 1 kit.

On a side note, check the tires. Motorcycle tires can get brittle with age.

If it's been sitting for a while it won't hurt to run some Seafoam through the system to try and clean up the carbs. If that doesn't help I'd go back to the jet thing as a place to start. BTW, an 88 with no baffles in drag pipes must be one loud son-of-a-gun!

Yes sir. You can hear him coming.

Any thing you do over stock requires more fuel to get rid of the bog. They work on back pressure on the factory exhaust for emissions.

I’m not a motorcycle guy and my only professional experience as a mechanic was on forklifts, tractors graders industrial equipment and limited time working on cars and pickups. The first thing I’d do is check the fuel filter or screen or whatever a Harley has. Might also be a good idea to drain the fuel system as the occasional hiccup could indicate a moisture buildup in the fuel tank. If it runs good when cold and idling but hiccups when moving it could be something as simple as a loose spark plug connection or other electrical connection aggravated by road vibrations.

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Dave

First off I don't believe your 88 is an EVO. The EVO was the previous motor. The 2004 H-D 88 should be a "Twin Cam" motor.

In 2004 Harleys were available with both Carb's and fuel injection - so I do not know which you have. When anything is done to the air intake and or the exhaust system, the bike's spec's have been changed and in order for it to run properly it must be tuned. A lack of back pressure can definitely affect the way it runs as changing the pipes and or air cleaner changes the amount of air going into the engine.

Most guys I know do change exhaust pipes and or the air intake systems, however they also use some sort of "tuner" made by Vance and Hines, Harley, etc. to smooth out the performance.

I changed the air intake and the mufflers on my own 2008 Ultra because the Bike was running quite hot due to factory mandatory setting. When I did that I also installed a V&H Tuner and set each individual power band to recommended spec's for the air intake and model mufflers I used in the upgrade. The instruction manual that came with the Tuner has HUNDREDS of "Maps" for all the different possible brand and model component combinations. You can mix and match components but then the Map changes. All runs correctly, smoothly and no popping like some guys get. I have since tweaked the Tuner on certain power bands for slightly better performance in 6th gear.

Like in most machinery, changing OEM parts can be done but it must be done so the original parts still work as designed and in conjunction with the new parts. Kind of like when parts are changed on a Revolver...... sometimes (many times) other parts are also affected.

I suggest you bring it in to a "competent" Mechanic with a good reputation. I would also see if a Tuner has been installed (usually put under the seat) and if it is set correctly. If there is no Tuner, one might be in order - but let a Pro tell you that after determining exactly what the issue is.

Drag pipes without baffles may be good for the drags, where they run wide open. Not so good for low/mid end torque, even if it is tuned. They sell "lollipops" to gain back some low end torque, and don't tone it down so much. IMO any pipes without baffles are just plain obnoxious in town, and just for the "look at me value".

One more thought. The fact that it runs better the hotter it gets tells me the motor is looking for a richer mix of fuel.

Thanks guys! We’re going to try a larger low speed jet and see what happens.

See if you can find some info on the pipes regarding the jet sizes. Also, the air intake may need to be modified too. Open pipes need more air and fuel. Good luck.

I think Harley was using Mikuni carburetors. My Road King is an 04 but I ordered it EFI. New pipes new map and got rid of the chain driven cams and installed S&S gear driven. No more worries of plastic tensioner pieces plugging up oil passages and oil starving the motor avoiding a burned up engine.

If it’s got over 50k on it check your cam chain tensioner. Could need replacing.

New jets in the carb will probably cure the rough running

If they are carburetors .002 larger should fix. Pull a plug after you ride for about 10 miles after cooling down. the color should be about the color of a cardboard box. Too large a jet will hurt the mileage. The main jet jet is the one to change. If it idles good the low speed is good. If it has been sitting for a year you will need to run some fine steel wires through the idle passages and add some cleaning additive to fuel.

You sure? When you twist the throttle, this thing screams. Loading along at 40-50 mph is where I feel the stutter.

Do you know if it ever ran right, if it did something changed. If it’s got a carb it could need cleaning and proper adjustment. I’ve never had problems with Harley’s fuel injection, however if you are using a high flow intake (air filter & housing) along with “straight pipes” you will have to add fuel to the low speed and midrange. Baffles might help but proper fuel mapping will make a big difference, get someone qualified to make the adjustments. I’m using a Powercommander 5 on my 2013 FXS with a Dynojet downloaded map, no dyno tuning but it works very well and the only expense was the PC 5 module.
Again if it’s got a carb, a good cleaning to make sure there’s no fuel restriction also check to see if the accelerator pump is working and slide diaphragm is not torn or leaking, allowing the slide to smoothly move up and down on vaccum demand from the diaphragm. Shimming the needle .030-.040” will richen it up but don’t double up if it’s already done. If not previously done drill the pressed in lead “dead” plug covering the carbs fuel mixture screw, turn it out from gently seated to 2 1/2 to 3 1/2 turns the further out the richer it gets. When drilling the “dead” plug out don’t go too far or the drill bit will grab the adjustment screw and make a mess of things. Look at the spark plugs and air filter too and the proper ratio to the fuel tank of Chemtool b12 will help clean things out.

Could be loading up from too much fuel at that rpm or throttle position (could be clearing out the fuel when you open the throttle and get it screaming on pipe)
Or could be lean hesitation, try barely cracking the choke to see if it’s a bit more fuel it wants

...thus I am not very helpful but check hdforum.com.

There you will find bike specific info that I have found really useful.

Be safe...be well.

I've owned three Harley's over the years, two of which had carbs. Check the color of the spark plugs - if they are cocoa-colored brown then they are OK.

My first bet is a dirty fuel filter (cheap and easy). After that, run some Sea Foam carb cleaner through at least 2 full tanks of gas (3-4 would be better), and if the problem persists then it could be your high speed carb jet is either dirty, adjusted poorly (too lean) or is too small for the engine mods that were done. Jet size choice is based on a lot of factors, including aftermarket cam selection as well as intake and exhaust choices.

Of course, it could also be simple maintenance items on the ignition side - bad plugs or wires are my first bet as I'm sure the ignition is electronic and doesn't really ever wear out. Only after that would I spend any serious $$ looking at the rest of the ignition. Lots of good info online.

On my former '95 Softail I entirely reworked the factory carb after a new cam, intake and exhaust install - lighter slide springs, larger vacuum holes and a fatter high speed jet (and even then it still required several attempts to get the mixture adjustment correct). The only thing I didn't need to change was the idle (low speed) jet.

Good luck!

Attached Images

1995 FXSTC-1.jpg (182.0 KB, 12 views)

Just take it to a certified HD mechanic. Time and parts messing with it is $$$. ymmv

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Sure you did

I would, but my son who bought it is a college student working part time, and about tapped out from buying it. I figure we can maybe save him some money. Should be a good experience for him as well.

My first wife was a surgery nurse and all of her surgery docs referred to motorcycle riders as organ donors. I rode for several years and have a tendency to agree with the docs.

I'd bet its running lean. They were jetted lean from the factory to meet EPA regulations. Straight pipes enhance that condition. Are the pipes heavily "blued"? That's a sign of a lean condition. Also an air cooled motor like the HD will run hotter when lean. "Surging" at steady throttle is a sign. You get good acceleration at heavy throttle because of the accelerator pump used on these carbs. Air cooled motors tend to accelerate best on the lean side, as compared to a little rich, but you pay for it with increased heat and possible engine / valve damage.

Larry

Nothing like digging into it to figure out what makes it tick. I made a ton of mistakes when working on my first bike - a Triumph - but the education was invaluable.

Free flow exhaust usually requires some increase in carb jetting.

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No life story has happy end.

If someone installed a different cam that could be what you are feeling at a low rpm in high gear.

Let me just say this about the mechanics at H-D dealers - they just may be the best out there in knowing your bike inside and out, but they may be tied to "factory-only" or "factory-authorized" rules at the dealer shop that prevent them from doing anything aftermarket unless it's Genuine H-D, Screaming Eagle, and such. Without a doubt, they will be expensive...

If there have been more than a few mods done to the motor but nothing done to the carb then I would recommend a "tuner's kit" for the carb that will have a lot of the pieces and parts you will need to improve air and fuel flow (calibrated drill bits, new springs, new jets, etc.). Another nice thing is that many of the aftermarket parts companies have help lines you can call that will give you solid advice (like which jet to use based on the mods you have, for example).

But unless the mods were very recent, I would do basic maintenance items first because I can't imagine anyone doing all that to a 2004 and not fine-tuning it over the next decade+ just to reduce aggravation if nothing else.

This is about outboards but it translates well over to Harleys. I have an old cajun mechanic that works on my Mercury. HE KNOWS HIS STUFF and works for cash and beer at about half the price the licensed mechanics charge-He does this part time as his main job is maintaining a fleet of about 40 small boats used by the pipeline companies in the marsh. This guy knows ALL the tricks and what he can do to an outboard is pure genius. There are people like this who work on Harley's. Find one! He will in all likelyhood be all tatted up, smell like grease and not have a nice pressed shirt with his name on it. He can only be reached by his cell and you have to be prepared to let him take his time with it as he will do the work on HIS timetable, not yours. If you need it by a certain date tell him and he will either tell you yep. he can do it or nope he can;t. But above all he will NOT screw you and will do a great job. When you come to get your bike, bring hundreds and twenty's and at least a 12 of his brand of beer. The beer will get passed around to those that are in the vicinity, you get a perfectly functioning bike, boat or whatever and everyone is happy. Guard this relationship with your life

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Forum consigliere

But NOT a HD dealership! Find a good indy shop near you.

Op said it had open drag pipes. Sounds to me like it needs more air. What type of air cleaner is on the bike?

I miss the days of just swapping out the AC, mufflers, and rejetting the carb.

I had to pay around $500 for a tuner for my current Harley. It was easy thou, bought the tuner and AC backing plate from Fuel Moto. All I had to do was tell them my exact exhaust set up, and they pre loaded a map on it when they shipped it.

Finding a mechanic like that is harder than finding a doctor you can trust.

You sound like my wife. I want to get the boy's bike running right. I wasn't looking for the fun police.

I think I know a guy.

Hi, Greg!

I was a Factory Certified Harley-Davidson Master of Technology (their highest rating) for over 30 years.

Disassemble and clean all the passages of the carb (Is it still the stock Mikuni?) being extra attentive to the slow speed (idle) jet.

If it idles OK but still surges at 40mph, go up 1 or 2 sizes on the slow jet.

I think you are on the right track.

If you have any problems, I am happy to help.

John

We got it taken apart and can’t find anybody local with the jet we need in stock, so now we wait on the mail. It’s supposed to rain all week anyway.

A #50 jet cured it’s ills! Thanks a lot for the help, guys. Now that f I can convince him to keep the greasy side down, I think he’s in business.

Glad to have been of service.

John

I’m glad you were as well. Can you believe the plug is still on the fuel mixture screw? Whoever had it before simply bolted on the drag pipes and stopped right there.

I know what you mean, Greg.

Most folks don't understand carburetion any better than they understand fuel injection.

They would be surprised to find out that at highway cruise speeds, the throttle is seldom more that about 1/4 to 1/3 open and that the engine is being fed primarily from the idle jet, even though it's their own bike!

Good job at finding the problem and helping your son.

John

Five bucks and about 20 minutes. Dealership mechanics are $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$.

And this is another reason that makes this board so special to so many.

And why are Dealership Mechanics so expensive?

Because, much like divorce lawyers, they are worth it!!

Having been a Motorcycle Dealership Mechanic, Service Manager, and General Manager throughout my occupational history, I tend to bristle at the notion that we are overpriced and overpaid, tattooed neanderthals.

I've never had a tattoo and that stereotypical caricature is most often shared by soft people with soft hands who never do any hard work.

What if I were to say that all lawyers are chubby, balding guys who smoke smelly cigars, wear cheap suits, and chase ambulances?

Except I wouldn't because I know quite a few lawyers as well as hundreds of Motorcycle Mechanics and nearly all of them, lawyers and mechanics alike, are dedicated and hard working individuals who have bailed out a whole bunch of folks from bad situations, mostly of their own making.

Let's not heap derision on the professions and earnings of others lest we all be examined under that same harsh illumination.

John

We serviced his bike a few days ago, and today we replaced frayed throttle cables. Turns out he loves riding the bike, and I’ve enjoyed getting to spend a bit of time with him working on it.

A #50 jet is the high side.

It is the high side of a pilot jet.

John

I also got to dig out my lonely, neglected SAE tools. Most everything else we have is metric it seems.

How does she run right now ?

My husband owns a 88 Twin Cam Low Rider as well. Currently the frame is suspended to the roof skeleton in the garage, engine and gearbox are on the workbench and there are parts everywhere in a room.

Me I ride a lil 883R sportster.

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French Pollywog

Running great! He’ll need a new back tire by the end of the season, but otherwise, I think it’s good to go.