Author Topic: Tuning up a new FL250 Ody rebuild  (Read 735 times)

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Tuning up a new FL250 Ody rebuild
« on: November 21, 2020, 04:42:05 PM »
Throwing out a bunch of new rebuild stuff.....   I have two odyssey's a 1983 and a 1979 both kept pretty original. Both engines have been bored up to .25 oversize. I have noticed both seem to drip a lot more oil around the exhaust then they originally did. Has anyone else done a rebuild bored up a size and experienced this? My uneducated guess is that with a larger bore it is able to pull more fuel/oil into the carb. I'm mixing at 32:1 with Amsoil dominator 2 stroke oil (it has a pretty low flash point). Open to any oil suggestions.
     Another thing I noticed the exhaust schematic show a circular cardboard gasket. Tried this but found it would not fit on the stock exhaust. A quick measurement showed why. The exhaust connector off the engine is about an 1 1/4" and the pipe that connects to it slides in about an 1 1/4" so there's really no room for it to fit. Curious what others are doing.
     The 1979 rebuild I was testing out today starts right up but hangs a while before dropping back to idle. Since this was vacuum/pressure tested and passed,  I tried spraying starter fluid around gasket, seals, carburetor but didn't notice any rpm increase. So took it out for a quick spin. This one is faster than the 83"!  Next problem is runs right until you try to go to wide open throttle - then immediately bogs. The 1983, same build, runs at all speeds. Both are run with non ethanol gas and carburetors have been rebuilt. I'm guessing I'll need to recheck the carb, maybe jets? Anyway if anyone can point me in the right direction I'd appreciate it. Sorry for the long post, Marty.

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1035
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: Tuning up a new FL250 Ody rebuild
« Reply #1 on: November 24, 2020, 11:21:35 AM »
It is probably more due to being freshened up than the bore size. The oil leaking is coming from the mixed fuel after the fuel is burned. I would say you might be able to jet the pilot jet size down from where it is, but that would make the dropping back to idle problem worse. That is a sign of being lean at idle. Turn the air bleed in and see if that helps. I would check your main jet by looking at the plug color after shutting down right after the bog and check plug color. If wet/black, drop the main jet size. Compare the pilot and main jet sizes in both machines and the clip position on the needles.

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #2 on: November 24, 2020, 03:12:04 PM »
Wow that's interesting. I wouldn't of guessed the hanging at idle could be a lean issue! I pulled the spark plug and brought the piston up to top dead center and took a look. The piston confirms it is running rich. Also the bog sound going wide open sounds like whaaaaa which sounds lean as well. The clip, pilot and main jets are identical on both carbs. Two things I'm going to try are to bypass the check valve tee in case the carb is being over pressurized (tank fuel return is working but worth a shot). Install the other carburetor to see if there are improvements and double check the rebuilt problem one. Only I could end up with a black/oily spark plug and exhaust while running into a lean condition. :o  Oh well, I'll keep at it. Thanks for your reply, Marty.

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1035
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: Tuning up a new FL250 Ody rebuild
« Reply #3 on: November 25, 2020, 06:57:11 AM »
You could be lean at idle, but rich at WOT. The pilot jet and air bleed screw is idle to 1/4 throttle. The main primarily affects 3/4 to WOT. The needle is in between those. Something really common with the FL350s is since the stock pilot jet is too big, it loads up. People will drop the main and find the machine runs better. That is because it burns off the excess fuel faster. Then one day they hold WOT for a mile and burn it up.

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #4 on: January 02, 2021, 01:26:29 PM »
OK, Haven't given up yet. Fired up on choke a few days ago - still having the bog/stall at Wide Open throttle. Installed a temporary gravity fed tank and then it refused to start. Previously had installed and set new points but the tester showed they were off a tiny bit? Reset points and it fired right up. Today with lousy weather, I jacked up the back end and removed the tires for safety. Installed and gapped a new BR7ES spark plug and it fired right up. After warmed up I ran it at all speed settings with no bog. Clear fuel line seems to show fuel filter is doing its job. Still no load so could be the difference. Ran for about 40 minutes and then died on me. Went back in to the points to check timing and light dimmed right at the mark (|F) to the left of the"F". So good. Tested new spark plug and no spark. Held spark plug in my hand and no spark:(. Rested my hand against the head while holding spark plug and mild jolt but no spark. Tested 4 other old BR7ES spark plugs against engine fins and all no spark. Tried both a BR8ES and a BR9ES plugs I had and both show spark. Both these fire right up but seem to smoke a lot so maybe cooler plugs not burning all fuel/oil? I know both the NGK cap and all spark plugs are resistor types. I've tested other fl250'S so this seems to be normal. Happy to listen to any advice:)  All grounds are great so maybe should replace coil/condensor unit (still running original 1979). Any spark plug advice?  Thanks for reading, Marty

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #5 on: January 02, 2021, 02:39:19 PM »
Just to make things interested I decided to multi test my sparkplugs. The (2) BR7ES spark plugs tested out at 4.55 & 4.10 stem to electrode, stem to ground was open and ground to ground stem was closed or 0.00. (1) BR8ES spark plugs tested out at 4.34 stem to electrode, stem to ground was open and ground to ground stem was closed or 0.00. (1) BR9ES spark plugs tested out at 4.06 stem to electrode, stem to ground was open and ground to ground stem was closed or 0.00. The only different readings I got were on the non-resistor versions (2) B7ES spark plugs tested out at 0.00 or closed stem to electrode which makes sense since there are no resistors in them, stem to ground was open and ground to ground stem was closed or 0.00.  Are the B7ES plugs ok to use since the resistor version is called for in the manual? Well since none of these spark plugs failed and the resistance readings between the 7, 8 and 9 series were closer than expected now I'm wondering why no spark on the 7 series at least towards the end of my testing! Well either way I learned a lot about testing spark plugs!!!

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1035
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: Tuning up a new FL250 Ody rebuild
« Reply #6 on: January 02, 2021, 02:53:40 PM »
A 350 uses BR9ES stock. The hotter/colder description sometimes makes people think hotter = better. A colder plug means it sheds heat from the electrode to the head faster. So an FL350 that runs hot, needs a colder plug. I run a BR8ES in a water cooled head. There should be a wet line about half way up the strap. If all dry, plug is too hot. If all wet, plug is too cold. I doubt it makes much difference at start up.

You can burn things out if you run non-resistor plugs when required. Plus, the voltage drop across the resistor will produce heat. That might help with starting.

Points annoy me. I don't have FL250s, but I have a garden tractor modified  for pulling that has them. I plan to convert that to a GM LS2 coil pack and a custom controller with adjustable advance curve I am building. The spark from those packs is so powerful, it looks like a barrel. It gets wider in the middle.

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #7 on: January 02, 2021, 05:45:44 PM »
Might have to look into one of those GM LS2 coil packs for the FL250 ;D  Yeah, I rebuilt two windsor 351's on a cruiser. Might change over from points but knock on wood so far so good. Have two FL250's and both run wet so come Spring time may see me jetting/plug chop etc. Other one is CDI, so just need to get this one running well enough to perform testing. Probably try another BR7ES even though I don't think that's the problem. The other thing is the FL250 coils have a built in condensor which is riveted and soldered in. Hate to throw more parts at it but if I can figure out what size condensor this used I can drill out the rivets and replace. If not, might have to replace as a unit. I'll update as I go. Thanks :-\

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #8 on: January 31, 2021, 12:59:52 PM »
Ok so....  Rechecked points/timing etc. and all looked good. Went down and picked up yet another BR7es spark plug and what do you know I got spark! With the back end jacked up I ran this at all rpm's for about 2 weeks. Two pulls to start with choke on and one once warmed up. Also, after LiveWire mentioned the lean bog I was having at WOT I went back through the fuel system. Blew air through the fuel tank lines to make sure they were clear. Retested the fuel output on fuel pump. And finally disconnected the fuel tee to check. This was a brand new OEM Honda fuel Tee removed from an unopened package. Guess what!!! The Tee is completely open??? You can blow on any part of the tee and there is absolutely NO resistance. Sucks! Luckily I'm a bit of a pack rat and after some searching located the original 1979 Tee. This at least has some resistance when blowing in towards the check valve where as the new Tee has zero. Hoping the replaced tee might let me go to full throttle without the bog I warmed it up good for about five minutes and went for a ride. Well it did ok to about 1/2 throttle but quickly seemed like it might stall. I tried unsuccessfully to bring it up to full speed a few times but then it did stall and wouldn't restart. This time I went right to the spark plug - No spark:(   Pulled the spark plug and it really doesn't look that bad. Pretty clean overall, a bit of brown around the white resistor but not terrible. Geez, I once ran a chainsaw which died on me and when I pulled the spark plug it looked like black carbon was growing out of it (blocked muffler screen was the culprit). Anyway, I took a brass brush and parts cleaner to all the non working spark plugs and now all have spark. So I guess I'll have to pull the rebuilt carburetor. Since it's already been rebuilt, float set to manual specs. I'm hoping I can find something obviously wrong with it. Until I can figure out why its fouling out the plugs I can't do any other testing. Oh well, It's 27 degrees and snowing at the moment so looks like it will have to wait for warmer weather. Thanks, Marty

LiveWire

  • Administrator
  • Hero Member
  • *****
  • Posts: 1035
  • Karma: 20
    • View Profile
    • 85 Honda Odyssey FL350 Parts
Re: Tuning up a new FL250 Ody rebuild
« Reply #9 on: February 01, 2021, 11:28:03 AM »
Your problem with the regulator (check tee) has been experienced by many. They are missing the spring and ball. This is why I do not use them at all. I have heard it was just a bad batch and that they were good again after that. Maybe they still pop up though. I use a regular tee and run the return line to the top of the cage and back down. That height sets the fuel pressure.

Marty

  • Newbie
  • *
  • Posts: 32
  • Karma: 1
    • View Profile
Re: Tuning up a new FL250 Ody rebuild
« Reply #10 on: April 28, 2021, 05:54:50 PM »
Hello all :)
Just wanted to let you know I haven't given up. I'm looking forward to getting back into this project. My elderly Father has had quite a bit of health problems and my free time has been quite limited. Don't get me wrong, I love my dad and I am not complaining. I'm currently putting an elderly friendly garden together to hopefully keep him motivated and happy. Just tuff going thru this :'(   Anyway........ Sorry for the rant, will be back soon. Marty