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1980 FL250 popping/backfiring mid range
http://www.pilotodyssey.com/PO/viewtopic.php?f=31&t=16213		 Page 1 of 1
Author:  srohn113 [ Tue Nov 17, 2015 3:06 pm ]
Post subject:  1980 FL250 popping/backfiring mid range
Need some help I am out of ideas. Have a 1980 FL250 that will start and wrap up. Under load about mid rpm it will back fire and cut out, and wont wrap any higher. This only happens above 1/3 throttle, same rpm less than 1/3 throttle runs just fine. Rpm still wont go any higher.
motor (( Internal Combustion Engine ? )) is rebuilt, stator has been rebuilt by Rick Electric, new points, new coil, new condenser. New spark plug several times over. New wire and cap. Has great spark. New kill switch, good Engine to frame ground. Points are adjusted correctly and I have timed the motor (( Internal Combustion Engine ? )) every single way in an attempt to make it run different, to no avail. Timing advance is working and clean. Carb has been rebuilt, cleaned several times. Fuel is good, pump is good, float level is good. No vacuum leaks in any crank seals, intake boot, head or base gasket, or fuel pump vacuum line. Has K&N air filter. stock exhaust with no spark arrestor. Runs great till mid rpm then backfires like crazy. Gets worse as it warms up.
Author:  rmesser [ Tue Nov 17, 2015 4:59 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
loosen the exhaust at the manifold and see if that helps. I wonder if the exhaust could be pugged?
Author:  srohn113 [ Tue Nov 17, 2015 5:20 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
I've pulled it not plugged but I was thinking about knocking out the baffle. I haven't heard of anyone doing that, any thoughts?
Author:  rmesser [ Tue Nov 17, 2015 6:13 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
What method did you use to set the points?

Post a few pictures please.
Author:  srohn113 [ Tue Nov 17, 2015 6:28 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
using the light bulb method, like the service manual says. adjusted the gap with a feeler gauge. But sorry not going to tear it back down to send you photos.
Author:  rmesser [ Tue Nov 17, 2015 6:46 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Not wanting to you tear it back down. How about a few pictures of your Engine and machine just to look at. Photos are liked here. They usually help.

I know you have been over things, but can't assume it is right as it is not running properly.

I wonder if the fuel pump could have a leak in the diaphragm and not pumping the proper volume of fuel?

Are you sure the fuel tee is in properly?

Just because parts are new does not guarantee they are functioning properly.
Author:  canadian oddy [ Wed Nov 18, 2015 3:27 am ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
The way you explain it here I think you have done a good job at trying to hunt it down.
You said it runs fine until you get to 1/3 throttle so that tells me it is an ignition advance issue in my opinion. That's about the time your advance probably kicks in and something is wrong there. You say the advance works but that's what I would be looking at. It's timing. You also said that the stator was redone hummmmm. I am not saying it was done wrong but I feel it is timing the way you explain it here.
Author:  canadian oddy [ Wed Nov 18, 2015 3:31 am ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
By the way welcome new guy.
Author:  srohn113 [ Wed Nov 18, 2015 2:11 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Thanks for the welcome. But I totally agree with you on timing, but the stator does not control when it sparks, it only builds the energy to spark. As far as the timing advance the only thing left to try there is a different rotor I suppose. The advance isn't stuck or broken, so i'm leaning towards the fact that it might be the wrong rotor (wrong timing mark wrong advancement).

rmesser
The fuel tee is a new one, as far as the fuel pump if it didn't have enough fuel pressure or volume it could backfire because it would cause a lean condition but you would see that on the spark plug. You would also see fuel in your pulse line to the crank. I have also ran it on IV gravity fed, no fuel valve, no fuel tee, no pump. Same issue. I'm sorry I did not say that in my original post.
And yes you are correct on not all new parts work, but they are least new Honda factory parts not parts off Ebay or other used outlets. I will continue to look over, and recheck parts.

I'm really considering a new rotor.

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Author:  canadian oddy [ Wed Nov 18, 2015 3:13 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Is it possible that you sheared the key on the flywheel ?? It don't take much. That actually happened to another guy here when I told him to check it, but his wouldn't start anymore after it initially ran.
Author:  srohn113 [ Wed Nov 18, 2015 4:57 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
It actually already did sheer the key way, back when I first got it running. Put a new one, I have checked it several times since. Good idea though!
Author:  rmesser [ Wed Nov 18, 2015 5:03 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Your tee does not appear to be oem. The oem tee is a fuel regulator, it has some guts inside of it, not just an open tee. I would start by replacing that with oem.

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Author:  rmesser [ Wed Nov 18, 2015 5:10 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
what is this? a kill switch?

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Author:  srohn113 [ Wed Nov 18, 2015 5:23 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
No it is not an oem fuel tee but did you read the part about the IV bottle. Yes that is a kill switch, factory one does not work anymore.
Author:  canadian oddy [ Wed Nov 18, 2015 5:39 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
srohn113 wrote:
No it is not an oem fuel tee but did you read the part about the IV bottle. Yes that is a kill switch, factory one does not work anymore.


That fuel tee is no good but I don't think it matters here right now as you ran it gravity feed and the same thing was happening. But I do have a question. When you run it gravity feed was your tank vented. ?.? Still think it's timing.
Author:  srohn113 [ Wed Nov 18, 2015 6:10 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Yes it was vented.
Author:  srohn113 [ Wed Nov 18, 2015 6:23 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
It's definitely not that just ran it with a oem tee in it.
Author:  canadian oddy [ Wed Nov 18, 2015 7:14 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Do you have a spare ignition coil? ?
On one of our race cars we had a bad coil that was shorting out between the high and low voltage side. I wonder if something similar is happening here when the rpm comes up. Coil craps out under heavy load.
Author:  canadian oddy [ Wed Nov 18, 2015 7:17 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
I am not familiar with the fl250. Does it have any electronics on ignition system or just points? ?
Author:  srohn113 [ Wed Nov 18, 2015 8:25 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Stator, rotor, points, coil, condenser, spark plug. But I do have another coil I will try tomorrow.
Author:  canadian oddy [ Wed Nov 18, 2015 9:20 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
If it still don't work tomorrow with the other coil then I feel the advance is not working correctly.
Author:  rmesser [ Wed Nov 18, 2015 9:50 pm ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
It looks like your fuel filter is after the fuel pump. If you move it before the pump you will protect the fuel pump from debris. If debris gets around the check valve and spring it will affect the pump.

Stock design is to have the filter before the pump.
Author:  rmesser [ Tue Dec 01, 2015 10:58 am ]
Post subject:  Re: 1980 FL250 popping/backfiring mid range
Any update?
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