1981 jet problem

[Gone]

first of all thanks ironmick and max throttle for the generator problem advice. polarizing the gen fixed the problem. my new problem i have been told is possible wrong jets. the bike runs o.k. if i accelerate up to speed slowly, however if i jump on the throttle hard, it bogs down. when i got the bike, it already had after market pipes with the baffles taken out. it also has a kuryakin hypercharger on it. the jets were probably never changed. the main jet is 165. the slow jet is78. my question is how do i find out which number to get. i can order them easy enough. thanks for any advice, i need it!

[IronMick]

Originally Posted by irondripper

... my new problem i have been told is possible wrong jets. the bike runs o.k. if i accelerate up to speed slowly, however if i jump on the throttle hard, it bogs down. when i got the bike, it already had after market pipes with the baffles taken out. it also has a kuryakin hypercharger on it. the jets were probably never changed. the main jet is 165. the slow jet is78 ...

The stock jets for 1981 are 160 main and 68 slow. I would stay with the 165 main as that is what i and at least one other FeHead guy i know use with a similar setup. The 78 may be too big. I get by quite well with the 68.

Is it the original Keihin Carb?

Two other possibilities that yield exactly the same symptom: [1] The fuel filter may be clogged [2] The fuel level in the float bowl may be too low.

[Gone]

thanks ironmick. i will try a 78 slow jet. the carb appears to be a stock keihin with harley davidson stamped on it. i will let you know how it goes.

[IronMick]

Originally Posted by irondripper

thanks ironmick. i will try a 78 slow jet. the carb appears to be a stock keihin with harley davidson stamped on it. i will let you know how it goes.

Did you mistype 78 there? You have a 78 according to your original post; stock was a 68.

Apparently at some point HD bought the design of the carb from Keihin and made some mods; then it would have the HD name on it.

[Max Throttle]

i agree with mick on the jetting and it looks like your in new jersey and not at high altitude that can effect jetting

one thing i noticed on my 1980 sporty i used to have was when i put on a forced air style filter assembly the bike ran like sheot, i ended up with a closed style filter assy and it made a difference immediately for the good

i had alot of problems keeping the intake seals from leaking and i finally ordered the brace for the carb, a leaky intake can cause a multitude of problems with throttle response also, so be sure to go through the seals and get that taken care of, sometimes simply doing leak checks isnt enough and can be undetected and drive you nuts

MT

EDIT:

i found some old info i had written in a post and thought it may help??? so i copied and pasted it below.........................





"My trials and tribulations contribution to this post"

in keeping my ironhead running over the years i have found that some things that happen can cause me to look in the wrong places and the info below is just my encounters with my 1980 ironhead...

1) the "intake seals" i have had to replace numerous times and can cause ya to think it's timing or an electrical deal or even the carb bogging and popping when it's just an air leak at the seals, i check for loosness of these constantly, one thing that helped eliminate alot of seal replacement was a carb bracket to help stop that baby from hanging out there shaking, the bogginess you describe reminds me of old intake seal troubles i had MULTIPLE TIMES and i could go nuts trying to find a leak and never could with conventional methods, ended up just replacing the seals if this would happen, and each time i would just go in and replace the seals i was good to go, problem ended

the sealing area and design for the intake seals on the ironhead is very slack in my opinion (not much sealing area) and i was going through aftermarket seals every other month they got soft and or would crack, so... i went to napa with my intake in hand, the guy looked at it as i came up to the counter and asked what it was (if ya say motorcycle the parts counter guy will send ya to a bike shop) i said never mind that, just take this back to your "gas tank rubber filler neck" stock and find one that fits tight on this seal area, he did and brought me back a rubber hose a foot and a half long and have been making my own seals ever since and not had to do it as often any more, the clamps, well i use 4 instead of 2, one on each head, one on each side of the intake

2) if and when she starts to pop out the exhaust "backfire/sputter/pop" it normally (for my bike) boils down to "2 things", it has done it to me alot over the years and recently it did it again and i had forgotten one of the main things it says causes this in the factory manual...loose battery connections... why in the world a loose connection at the battery would cause this i dunno but it DOES i just lived that scenerio again last week with my negative cable at the battery, man that baby was backfiring/sputting!! shot some impressive flames out the pipes to!! tightened the battery connections and it stopped doing it immediately

the other is sparkplugs, the bike will just out of the blue start the pop and fart deal but no where near as severe as the battery connection deal, i keep a spare set in the tool bag, i have had them go bad in the middle of a ride and when ya clean them it's just a waste of time, my bike for some reason even though i have gone trough the timing on mine it will have a cleaner front plug all the time, i have no explanation for it, i have noticed that when i stop and if any gas passes by the carb into the intake while on the kick stand the rear cylinder's angle is lower and gravity will take the fuel to the rear cylinder but the back plug is always more "black" than the front

maybe a member here can clarify this but "i heard"... that if it's advanced the front plug will burn hotter and if it's retarded the rear will burn hotter, dunno if it's true but has never proved itself to me on my bikes plugs

these are the things i have gone through over the years of having my ironhead, (intake seals, fresh plugs and tight battery connections) figured i would post in hopes it may help someone rip less hair outa their head than i did

My ole ironhead is a kantankerous moody sum beoch but when she gets to feeling ill i fix her up and we ride

[Gone]

thanks ironmick and max throttle again for the advice. i did mistype a 78 jet. i will use the stock 68. first i will try the intake seals. when i had the carb off, i did notice a tear, but didn't know at the time it could be the problem. i do enjoy fixing my own problems as the pop up, and this forum is exactly what someone like me needs. i love that old ironhead, and plan to have it around for a long time. thanks again

[garbiker]

A little tip You can use a small soldering torch not lit and hold it around the manafold and if any leak will make it rev up and no mess like the wd 40 thats hard to get where you need it. and a lots cleaner. and not messy. works even with a small leak. and can check the throttle shafes also that way. lots of problems are from a small leak. . just a old tip cu gar

[Max Throttle]

i was out on a ride one day and a new guy had joined us for the day with a 72 ironhead sporty

the other guys all had 5 speed bikes and were booking down the road and the older bike was back in the rear so i slowed my pace and hung with him, i also had a 1980 ironhead 4 speed so we took up the rear

i noticed as we rode that when he would twist the grip to bump up his speed it would "hesitate" "die off" "sputter" for a second and then go

we got to a stopping point for a drink and a smoke and i walked over to him and asked if he had changed the intake seals, he said no it was the plugs and he was confused because he had just put new ones in but swore it was the plugs, i showed him the seal area and what i had done with mine and he still swore it was the spark plugs so i shut up, a few days later he called and said it had gotten worse and asked if i could rebuild his carb, i told him he had bad intake seals again and if HE WOULD JUST DO THAT instead of argueing he would have his ride back, i had already been that route and thought the same things when mine had done it

a few days later he called and thanked me for the info, he had changed the intake seals and it ran great, he has since brought it to the shop a few times for other stuff and we ride together when we can

moral of the story, those seals can make ya think it's all kinds of stuff causing the problems and even a small leak can make the bike do things that "sound" like something else, the intake seals should be one of the first things done on the old ironheads and checked often, i think it was a poor design myself

the gas line i had bought to make the intake seals out of that i wrote about above was the best seal i had found for the old ironhead, they are thicker and tougher than the store bought seals

anyway, didnt mean to sound like a rant, sorry 'bout that just wanted to tell the story

lets see some pics of this sporty