Author Topic: Tuning up a new FL250 Ody rebuild  (Read 59 times)

Marty

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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

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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

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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

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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.