Ironhead runs like chit

[craneman]

Hi i,m new here and having problems with my newly aquired 81 xlh sporster ironhead
almost everytime i give it gas it backfires though the carb and then picks up revs.
and it doesn't seem to pull much under driving
any ideas where to start?
by the way it starts perfecty on choke ,, two gas shots and choke and it hardly has to turn over and brooum !!
turn choke of and it runs but seems rear cylinder only fires once it a while on idle ,,
any ideas?
Peter

[craneman]

i guess tuning for dummies would be for me !
maybe someone has a good link to manual for my bike.
would probably be a good start to set timing and point for my ironhead 81

[Jafa39]

Sounds like either an intake leak or your low speed jet is too small.....Maybe accelerator pump needs work too

[wilbur]

Originally Posted by craneman

Hi i,m new here and having problems with my newly aquired 81 xlh sporster ironhead
almost everytime i give it gas it backfires though the carb and then picks up revs.
and it doesn't seem to pull much under driving
any ideas where to start?
by the way it starts perfecty on choke ,, two gas shots and choke and it hardly has to turn over and brooum !!
turn choke of and it runs but seems rear cylinder only fires once it a while on idle ,,
any ideas?
Peter

Seal up intake and exhaust leaks. Flush carb and take note of jet sizes. Clean gas tank and post a picture of the plugs. Or at least describe what the plugs look like.

[GA_Ironhead]

Originally Posted by craneman

...
maybe someone has a good link to manual for my bike.
would probably be a good start to set timing and point for my ironhead 81

Some libraries subscribe to Ebsco Host. They publish on-line small engine manuals. One of them is for the IH Sportster - Clymer I believe. Check with your local library.

www.sunnymeadcycles.com has the FSM in pdf format, as do others. Ebay as well...

You need a manual (or 2).

And if you haven't checked out the stickies, (orange links at the top of the IH Forum page) start there: http://xlforum.net/forums/s...d.php?t=465866

[IronMick]

1. adjust pushrods - See Sticky post

2. return carb to stock jets; go one size larger on both jets if running open pipes and A/C; set pilot screw to 1 turn out from gently seated - Sticky on cleaning a carb

3. set ignition timing to stock [40` BTDC] - Sticky

4. check for and fix intake and exhaust leaks - Sticky

5. set slow jet and pilot screw to optimal setting - Sticky on carb tuning

6. set main jet to optimal setting - Sticky on carb tuning

[nativebroncofan]

Just curious, hasn't been stated but which carb are you running?

[83XLX]

Originally Posted by Jafa39

Sounds like either an intake leak or your low speed jet is too small.....Maybe accelerator pump needs work too

My thoughts, too. A lean condition and/or accelerator pump not working.

[1976 XL]

My money is on an intake leak, but if you don't have a manual, get one! Until you do, the stickies will get you started, just like the guys said. Intake\Exhaust sealing is crucial for tuning. Pushrod\Valve adjustment is also very important, you could burn valves or worse if not done correctly. Carb. support is also vital. The weight of the carb(if not supported well,with a bracket) will cause intake sealing issues. Get a manual(or two) soon. Good Luck and welcome to the forum.

[craneman]

where do i start! carb is kehin stock ,, i cleaned it out good ,,was not real dirty to start with.
next i sealed up intake ,disassembled carb and intake ,, resealed it good with a light coat of high temp gasket orange,rubber rings looked a little worn so i put a little sealant, along with the carb flange .
not much change yet
adjusted carb mix ,, not much change ,,
drove it again ,, swore at it again but in a harley ironhead manner! lol
anyway keeps getin worse ,, now its back firin through rear pipe !
ok ok ,, start again,, check compression , (which i should have done when i bought the old horse) 90 in rear 110 in front , don,t know what it should be (if all else fails read the manual) dosn,t look good to me but it should still run i,m thinking.
lets check fire ,,plugs are black ,,rich i guess but should still run ,, rear cyl not running good , ok play with points, change wires to plugs ,, still no diff.
noticed coil was bleeding ,, ok i guess i need a new coil,, but still has nice blue flame on both plugs?
this might be another problem that is arising
for me at this point it seems that my rear cylinder is going to the hounds either pushrods or rockers or valves and maybe even rings but seems to be exhaust valve i think?
any way to make a long story long ,har har i think i bought i winter project!
what is compression test pressure supposed to be ?
now i know why everybody has more that one bike !! lol