Hey guys, I´m kinda new at this forums (not really... posted a few years ago but lost the account).
I´ve been battling with an issue on my 1995 Evo Fatboy. I'll try to make the story short but provide sufficient details to see if you guys can help me out.
Some time ago, the bike starting sputtering and having a mild backfire but driveable and it only happened sporadically. Took the carb apart and noticed the brass jets were corroded and the needle had cavitation. Went and changed everything to the original jets and changed gas station. All was good for about a month and then it started again with the same problem. I decided I would just go ahead and changed spark plugs, rebuild the carb and change gaskets altogether. Upon taking the manifold out, I noticed the gaskets were toast, so hey, seems like a good idea. The gaskets were Blue James lipped intake gaskets, I replaced them with OEM style gaskets. The problem was still there, so consulting the forums I saw it could also be an exhaust leak. I changed the exhaust gasket and retightened the intake manifold. Problem was solved!! or so I thought...
Bike ran good for a month, I rode it almost everyday to work without problems. Then, all of a sudden after a gas fill-up I travelled 50m and the bike started sputtering and dying. Had to head back home with the bike running in that state.... much worse than before...
Took it apart, needle and jets were ok, gaskets seem ok, retightened everything again and fired it up. Backfire and sputtering again. Took it to the ignition module (Old module installed) and circuit and got reading I thought were weird so I decided to change it altogether. Bought an Ultima ignition kit (complete with module, timing pickup and ignition coil). Got properly timed and fired it up again. problem was not solved (see attached video).
Took the whole carb off again, cleaned it, put gasket sealer on the intake gaskets, retightened everything let it sit overnight and fired it back up again. Problem is still there, if at all worsens every time. Took a massive backfire out the carb that blew the carb off the manifold (carb is not held down right now) and I could see white smoke coming from the front cylinder through the intake manifold (see picture).
Any other ideas to what it could be?
Thanks.
Last edited by Carlos Argueta; 11-15-2018 at 08:52 AM.
It would seem that you've looked at several items: intake leak, carb, exhaust leak, and ignition. You have to adjust/correct one item at a time to really narrow which it is. You shouldn't have to put gasket sealer on your intake manifold. I think your latest backfire may be caused by improper timing.
Problem: backfire through exhaust or carb?
Here are some suggestions: 1) Look at your carb jet cavities to ensure the carb body is not cracked 2) Ensure there are no holes in your carb rubber diaphragm. 3) Make sure your manifold is not worn where the carb mounts. If this is worn (carb will move up and down easy), it will give backfire through carb and have you searching like crazy thinking it's the carb 4) Re-time your ignition
Just do one thing, and start eliminating rather than a couple of a time.
It would seem that you've looked at several items: intake leak, carb, exhaust leak, and ignition. You have to adjust/correct one item at a time to really narrow which it is. You shouldn't have to put gasket sealer on your intake manifold. I think your latest backfire may be caused by improper timing.
Problem: backfire through exhaust or carb?
Here are some suggestions: 1) Look at your carb jet cavities to ensure the carb body is not cracked 2) Ensure there are no holes in your carb rubber diaphragm. 3) Make sure your manifold is not worn where the carb mounts. If this is worn (carb will move up and down easy), it will give backfire through carb and have you searching like crazy thinking it's the carb 4) Re-time your ignition
Just do one thing, and start eliminating rather than a couple of a time.
It would seem that you've looked at several items: intake leak, carb, exhaust leak, and ignition. You have to adjust/correct one item at a time to really narrow which it is. You shouldn't have to put gasket sealer on your intake manifold. I think your latest backfire may be caused by improper timing.
Problem: backfire through exhaust or carb?
Here are some suggestions: 1) Look at your carb jet cavities to ensure the carb body is not cracked 2) Ensure there are no holes in your carb rubber diaphragm. 3) Make sure your manifold is not worn where the carb mounts. If this is worn (carb will move up and down easy), it will give backfire through carb and have you searching like crazy thinking it's the carb 4) Re-time your ignition
Just do one thing, and start eliminating rather than a couple of a time.[/QUOTE]
Thanks for the answer. This is what I got so far:
1) Jet cavities seem fine, carb is not cracked.
2) the diaphragm is the only thing I didn´t change during the carb rebuid. but doesn´t seem to have any holes.
3) where the carb mounts? The rubber seal?
4) Re-time the ignition as in, internals or throught the timing pickup sensor?
If you could see the video, there is a rear cylinder backfire. The one I had yesterday was a front cylinder one, going through the carb.
3) Flange mount: There should be a rubber gasket on that orifice that your carb mounts to, but once mounted, if you can easily move your carb up and down, that hole is warped.
4) You should be able to static time your Ultima ignition. I don't have one, but I imagine if you have on that has the ignition module in the nose cone, they are timed pretty much like others. Put front cylinder on TDC, then turn timing plate clockwise all the way, and then back counter clockwise until the LED light goes out. That is the basic, but please read your specific instruction.
I like to see what your ignition timing plate looked like. The one you replaced? I really think you had an ignition issue, rather than carb in the first place.
11-15-2018, 08:46 AM
Some sort of intake leak?
