slant runs crappy when cold...

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73goldduster

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santa cruz, ca
i have been riding my bike alot lately, and letting the duster sit. problem is, after a few days off, it runs awful for the first few minutes. sounds like it's missing cylinders and runs super choppy, coughing and jumping, etc... bogs down and tries to stall if i floor the gas.
after about 3-5 minutes of driving, its fine. runs like a champ.
i figured the choke was stuck open, checked out fine though.
carb was recently rebuilt and looks good, no leaks.
pulled the plugs, they looked a little pale, but nothing serious.
pulled the fuel filter and blew some junk out the inlet side, which seemed to help a little.
any ideas? new fuel filter, plugs? maybe intake leak?
 
try adjusting both the choke and the idle, my slant used to do this same thing and thats all it was, start with the choke then move to the idle. changing weather and all that ya know.
 
Tune-up parts and technique suggestions in this thread. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. See here for choke system adjustment, and if your choke thermostat is old and decrepit, you may want to put in one of the electric choke kits.
 
Santa Cruz -- Go Banana Slugs! They love the moist woods near the coast.

Perhaps condensation in the cap. WD40 might be your new friend.
 
wish i could say that i did something to clear up the problem, but it seems to have cleared up on its own! if it comes back, i'll try adjusting the choke or cleaning/drying the dist. cap. thanks for the suggestions!
 
I have the same exact problem on my 63 Valiant /6. Went so far as to buy new carb, change the plugs, points, condenser, new distributor and wires and new timing chain, new fuel pump and filter. Still does the same thing! Usually in the colder weather. On the open highway when it is warmed up, it goes like a 'bat out of hell!' Can't figure it out.
 
FlatheadGeo said:
I have the same exact problem on my 63 Valiant /6. Went so far as to buy new carb, change the plugs, points, condenser, new distributor and wires and new timing chain, new fuel pump and filter. Still does the same thing! Usually in the colder weather. On the open highway when it is warmed up, it goes like a 'bat out of hell!' Can't figure it out.
Click to expand...

Could also be fuel supply. I think there are 6 formulations now depending on the season. The gas sitting in the carb will have the more volatile fractions boil off from the engine heat. In cold weather those are exactly what you need to keep things moving until manifold heat kicks in.
 
Also the heat riser valve is in the mix as well as the unloader-If the choke unloader is to fast (opens to soon or to much) it will cause drivability problems.
 
These stock carb setups are pretty simple, but you can mess 'em up, or they can get out of whack. Not many shops know what they are doing on the old stuff. The choke unloader needs to be adjusted correctly, along with the choke linkage/gap. If you have an old choke, consider tracking down a new one (chokes for later models can be adapted to fit easily). They are not going to be available forever. An old choke spring can appear to be working, but weak, and the vacuum on a cold engine and pull it open. Find the full instructions on adjusting the choke and unloader and patiently go through the steps.

Also, old carbs and a lot of rebuilds are sloppy, meaning the throttle and choke axles are sloppy where they fit in the carb body, and they let air in, so you'll need to compensate by cheating a bit on the air gap setting on the choke at full-choke (closing a few thousandths more than the instructions for a new carb). Warmed up, when you adjust the idle you'll never know the difference, but cold, if the choke spring is weak, or the setup is not tuned in, you'll continue to get balk.

If you just don't have the patience to mess with adjusting the auto choke, consider a manual choke conversion, if you are up for it. A last resort, but did that on a couple of my old pickups, and as long as you are used to a manual choke and don't forget and leave it on all the time [:) it cures choke issues.
 
Could be as simple as a sticking pcv valve. Good luck
 
I was having an issue with my slant a little while ago. I replaced the vacuum choke pot on the carb and it warms up and runs great now. It was a $16.00 fix.
 
Probably something in gas. I have a 72 Dart with a 225. I had charcoal canister losing vacuum so bad it would bog down when pushing gas pedal. For now I unplugged the line and capped it. It runs great now.
 
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