Author Topic: 1981 FL250 Won't Start When Warm  (Read 531 times)

JiveTurkeyJim

  • Newbie
  • *
  • Posts: 3
  • Karma: 0
    • View Profile
1981 FL250 Won't Start When Warm
« on: January 14, 2021, 04:02:25 PM »
I'm not super familiar with the Odysseys and Pilots, so forgive me. I have a 1981 Honda FL250 in my shop and I have it to the point where it starts and runs great if it's been sitting for a while. But if I take it out and ride it then shut it off, it refuses to start. Seems to only happen after it has been running for a bit. It's acting like it's getting too much fuel. Choking it does not help. I'd appreciate any advice. Thanks.

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1038
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: 1981 FL250 Won't Start When Warm
« Reply #1 on: January 15, 2021, 06:25:19 AM »
If it is acting like too much fuel, I would check the fuel system. I am not as familiar with the FL250 as the 350 and Pilot, but I assume it also uses a pulse fuel pump. If there is a tear in the diaphragm they leak fuel into the crank case. If the leak were small, the engine might burn it off as it runs. It might pool right after being shut off. I am not proposing that is the problem, just as an example of how it might only occur on a restart.

I would also check the compression with a gauge. If just on the verge of getting too low, gaps open up when warm.

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: 1981 FL250 Won't Start When Warm
« Reply #2 on: January 31, 2021, 01:23:53 PM »
Hi JiveTurkeyJim, I would start by pulling the spark plug after you've been riding. It shouldn't be wet since it's just been running. Next ground the spark plug to the fins to make sure you're getting spark. I wouldn't have thought about fuel leaking back in through the impulse line. To test this I would shut off the fuel from the gas tank. Then pull the line going to the carb and fill with 32:1 to make sure you're carb fuel bowl is full. At this point you should have a warmed up motor with clean spark plug, fuel only coming from carburetor bowl and as long as the carb is allowing air to pulled in (should since it ran perfectly before you shut it down) it should start.

JiveTurkeyJim

  • Newbie
  • *
  • Posts: 3
  • Karma: 0
    • View Profile
Re: 1981 FL250 Won't Start When Warm
« Reply #3 on: February 02, 2021, 12:01:10 PM »
Thanks for the replies, guys. LiveWire, I replaced the fuel pump, so I don't think that should be an issue. As far as the compression goes, I tested it both warm and cold. When it was cold, I had about 125 PSI. When it was warm I had about 119 PSI, and it held the compression fine. Is that enough of a drop to make a difference?

Marty, it has good spark when warmed up and cold. The plug was dry when I pulled it out after running. I tried your trick to make sure the carb bowl was full and still nothing.

I forgot to mention that when I initially try to start it after shutting it down, it fires for just a second. Then it just dies and won't fire at all until it cools down. I have also noticed that it will start fine once I drain the carburetor and pull it again. But that may be just because it has enough time to cool down while I drain it.

I'm starting to lean towards the compression being just low enough when it gets hot. I wouldn't think 6 PSI would make that much of a difference, though.

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1038
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: 1981 FL250 Won't Start When Warm
« Reply #4 on: February 02, 2021, 04:15:30 PM »
It is not just the 6 psi. I don't know what a 250 is supposed to have, but a 350 is 138. 125 would be low enough on a 350 to cause problems. The 6psi is more the straw that broke the camels back.

If it seems like it has too much fuel, that may just be because it is not igniting it.

JiveTurkeyJim

  • Newbie
  • *
  • Posts: 3
  • Karma: 0
    • View Profile
Re: 1981 FL250 Won't Start When Warm
« Reply #5 on: February 04, 2021, 12:41:46 PM »
The manual says spec compression is 129. I see what you're saying though. Maybe 125 PSI is still enough to make it start, but 119 isn't enough. I just wouldn't think that would be enough to make a difference.

If it is getting too much fuel, any ideas why it would only do that when warm?

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: 1981 FL250 Won't Start When Warm
« Reply #6 on: February 04, 2021, 06:16:42 PM »
No, It should still start at 119. I've seen them running between 150 - 100 psi. (100 being pretty low).  You can always put a little 2 stroke oil in the plug hole before screwing on your compression tester. If you see an increase in psi readings it's because the oil is helping to seal the rings.
On to your warmed up starting problem....... This one's tough cause they usually start easiest when their warm? If you hadn't said you are getting spark when hot I would look towards the electrical/plug side. One thing you could try is to get a new 2 dollar spark plug, gap it and swap in the new plug after it's warmed up. This would rule out a slightly fouled spark plug since you said it's getting too much fuel (running rich) and it's cheap to try.  If it is getting too much fuel only after the engine is heated up, I can't figure out why the carburetor is supplying more fuel only after being run? I would think if your floats are improperly set or your valve seat is not working you'd have these issues cold as well. When it is running do you have any fuel coming out of your carb overflow hoses? There is very little fuel pressure being built up just by spinning the motor with the recoil starter so why flooding then? Just to be sure this is a stock fl250 gas tank/pump and not gravity fed - correct?