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Message started by Lunar on 09/06/13 at 03:24:25

Title: Flames out the exhaust
Post by Lunar on 09/06/13 at 03:24:25

I've got a 86 savage with about 25k miles on it, a k&n cone filter, a sportster exhaust, still has the original carb set up, mix screw out 3.5 turns and I added a tab to the timing chain tensioner. Im at sea level. The bike ran more or less fine for about a year but then it started running a little rough and I let it sit for a few months; but now I'm trying to get it back on the road. It starts fine but when I accelerate it bangs and flames come out the tail pipe. During idle and very gradual slight acceleration I also get some puffing coming out from the carb. I've put in fresh gas and cleaned the carb...a couple of times. I've also checked the valve clearance, tighter than specs, but the problem persisted after I adjusted them. I know it was running rich and wonder if it built up enough on the valves to now prevent them from closing properly when the engine speed increases. I have a 2000 that I can swap the carb from, or maybe the whole engine but that carb sat for years...that's another post. Thoughts?

Title: Re: Flames out the exhaust
Post by Dave on 09/06/13 at 04:27:44

The symptoms you are describing are the engine running lean just off idle. It could be an intake air leak somewhere, or a dirty pilot jet or idle circuit, or you may need the white spacer mod to raise your slide needle.

How does the bike run when you open up the throttle a bunch and accelerate hard?

Title: Re: Flames out the exhaust
Post by Lunar on 09/06/13 at 20:33:53

I can't really get it to open up or accelerate hard. To clarify when I said accelerate it is only engine acceleration no actuall moving. These symptom are in the drive way. I took a video of it with my iPad but it won't load to this thread.

Title: Re: Flames out the exhaust
Post by Steve H on 09/06/13 at 20:48:59

I'm with Dave. It sounds like you're lean just off idle. Any chance something's clogging the main jet? Vacuum operated slide moving up and and down freely? Possibility of torn or punctured diaphram at the top?

Title: Re: Flames out the exhaust
Post by justin_o_guy2 on 09/06/13 at 20:51:32

The bike ran more or less fine for about a year but then it started running a little rough and I let it sit for a few months;

The gas in the bowl evaporated, leaving crap. Drain the bowl into glass, see how it looks, maybe drain it again,,

May need to dropthe bowl, check the jets, clean up..

Title: Re: Flames out the exhaust
Post by justin_o_guy2 on 09/06/13 at 20:52:31

OHH yea,drain the tank,, put fresh gas in.. I was having some Rough Run issues,, I did that & Vroom!

Title: Re: Flames out the exhaust
Post by Lunar on 09/07/13 at 02:15:23

I have removed every removable component of the carb and cleaned them. Anything that should have air and/or fuel flowing through it is cleaned. I drained the fuel tank, it has fresh fuel. The diaphragm is good and the slide slides.

Title: Re: Flames out the exhaust
Post by Steve H on 09/07/13 at 08:29:40

When you put the needle back in the slide, did you put the clip on top of or under the spring? The clip should be on top of the spring.

When I got mine, it was under the spring and it had the same symptoms. Would idle great soon as you cracked the throttle lots of popping sputtering and tremendous backfires. Not saying that's what's happening with yours but it could be an easy thing to get wrong when reassembling.

Title: Re: Flames out the exhaust
Post by Lunar on 09/07/13 at 16:15:11

Mine is assembled in this order:
(From l to r in pic or top to bottom as they sit in the carb)
Needle jet plate, white spacer, e-clip, washer, spring and slide body.
That matches the assembly diagrams, they way both of my carbs came apart and what you described.

Any chance I'm running way too rich and when I accelerate excess fuel passes through the chamber and ignites in the header?
Given that I have the stock jets but mix was turned out 3.5 turns?
What would be a good number of turns for the mix screw and white washer thickness with a k&n cone filter, HD exhaust, at sea level if I use the stock jets for the time being?

Title: Re: Flames out the exhaust
Post by Steve H on 09/07/13 at 18:16:12

That looks perfect. Just the way it should be.

A vacuum leak? If you don't have the stock petcock, is the vacuum tap plugged well?

Title: Re: Flames out the exhaust
Post by Lunar on 09/07/13 at 18:53:06

I have the stock petcock. This is also a California model so it has the vent tube on the underside of the tank near the speedo.
Please correct me if I'm wrong but I believe that vent tube should connect to the verticle tube on the right side of the carb under the carb vent tube.
If I swap to a non California carb that I have should I plug the tube on the tank? The emissions stuff is removed.

Title: Re: Flames out the exhaust
Post by verslagen1 on 09/07/13 at 19:19:07

while that is the connection to the carbon canister, I don't think you should hook it up the tank.

plug the carb, leave the vent on the tank open.

Title: Re: Flames out the exhaust
Post by sesamestreet on 09/08/13 at 20:08:00

I get ocassional tiny flames on SOME backfires, is that what you're describing?

Title: Re: Flames out the exhaust
Post by Lunar on 09/10/13 at 00:33:56

You know how a lot of savages have that bang after you shut down.... not that. This is much louder and sharper. The flame varies, at night I can see it extend out the pipe a good foot.
Tonight I installed the newly cleaned carb with a white spacer modified to half original thickness and 2.5 turns on the mix screw from the 2000 savage I have and the problem continues. However, I noticed that the throat of the carb is wet with fuel. So I'm thinking the float is set to high and fuel is getting sucked in at much less throttle than it should.

Title: Re: Flames out the exhaust
Post by Dave on 09/10/13 at 05:31:57

5A63787764160 wrote:

However, I noticed that the throat of the carb is wet with fuel. So I'm thinking the float is set to high and fuel is getting sucked in at much less throttle than it should.

Too much fuel causes black smoke and rich running...it does not make the engine backfire. The backfire while running is caused by a lean mixture that results when you close the throttle.....and the fuel circuits are closed off while the engine has high vacuum and continues to pull in air....the mixture goes so lean that it will not ignite in the cylinder by the spark plug - but can be ignited by the hot exhaust system (or the exhaust flame from the next time the spark plut does ignite the fuel in the cylinder). When the throttle is closed the only fuel that flows is the idle circuit....and it cannot supply enough fuel to the cylinder when the engine is running above idle speed.

The source of the pop/bang when you shut the engine off is that the ignition is switched off....however the engine continues to turn and pump fuel and air throug the engine and into the hot exhaust system....where it can be ignited.

There is nothing wrong with checking your float level - but it will not do much to change the backfire unless the level is too low.

Title: Re: Flames out the exhaust
Post by verslagen1 on 09/10/13 at 07:19:10

what does sparky look like?

Title: Re: Flames out the exhaust
Post by Lunar on 09/11/13 at 00:58:23

First: I have no excuse for not having pulled the spark plug earlier and provided its condition as part of my initial post.
Second: I don't think I'm running lean. I have soot on my rear brake lever arm behind the exhaust pipe and a very sooty spark plug.
Third: The backfire (after fire) sound was provided as a data point for the sound. The banging/flames I'm getting is NOT during deceleration or shut down. I get it when trying to give it more throttle than a little more than idle.
Finally: Yes my cylinder head cover is leaking, thus the oil on the spark plug, and down the front of the engine.

Title: Re: Flames out the exhaust
Post by Lunar on 09/18/13 at 02:08:35

I understand that I should be running lean with the stock carb and that some have commented that the bang during acceleration sounds like I'm running lean. What I don't understand is how I am getting this much soot and fuel pooling at the mouth of the carb and be lean. I took out the white spacer on the 86 carb and reinstalled it and while it runs better than the 2000 carb with half thickness white spacer the banging is still there. And I still have the question of why did it run ok for a year with its present configuration (save for the spacer)?

Title: Re: Flames out the exhaust
Post by Steve H on 09/18/13 at 15:12:46

Guys, why should there be fuel pooling at the mouth of the carb? That sounds like high fuel level / float needle not sealing completely.

I haven't had any carb issues on my bike so I haven't paid that much attention to it. But, on previous bikes, whenever I saw something like this I looked for a float or float valve problem.

Title: Re: Flames out the exhaust
Post by troyrr on 03/22/18 at 10:02:38

Did you ever find a resolution for this issue, because I am having the exact same problem - 10 inch flames shooting out the exhaust on acceleration.

Same troubleshooting: Adjusted the Valves, tried different jets, checked for exhaust leaks. Diaphragm is not punctured or torn.

Performance is terrible. The bike does not exceed 40 MPH. On hard acceleration I get flames out of the tailpipe.

Title: Re: Flames out the exhaust
Post by batman on 03/22/18 at 10:53:33

You may want to check the main jet, there is a washer installed between it and the needle jet , if it's missing it allows the needle jet to move down away from the jet needle and would cause you to start running very rich when you first come of idle. it would explain the soot on the plug, and the gas flowing out the carb(reversion) ,and flames out the exhaust ( fuel ratio to high that there isn't enough air to burn all the excess fuel until it is ignited by the hot pipe ) as you should not be running rich with a full spacer and stock jets at sea level ,you should be running dangerously lean, even more so with a Dyna ,and your air cleaner.

Title: Re: Flames out the exhaust
Post by troyrr on 03/23/18 at 09:36:51

Hey Batman, I'm not the guy living at sealevel. I just found this thread yesterday and wanted to know if there was a resolution.

So, if I understand you correctly, this is strictly a carburetor problem?

I'm using the half spacer on the needle. Main Jet has the washer. The only thing I don't have is a washer under the clip on the needle. At this point I don't remember what jets I have because I have swapped them out several times.

Title: Re: Flames out the exhaust
Post by batman on 03/23/18 at 12:18:53

Troyrr, My answer above was addressing Lunar's problem.(he is at sea level and he is running stock jets ). I would order/find/ replace, the washer that is missing on the needle for starters ( not having the washer in place will effect your needle position). Then jet your carb to your, elevation /air cleaner / exhaust, which details you have not stated . Do I think your problem is the same as Lunar's ? the answer is no , there both fuel related, but flames shooting out the exhaust can be from running to rich Lunar's problem ,or to lean ,your problem .The missing washer allows the clip and therefore the needle to move down inside the spring, dropping your needle rather than holding it up against the spacer, the side moves up sending more air ,but the needle isn't moving away from the main jet ,your fuel mix is so lean it doesn't fire and gets pushed in to the exhaust where the hot pipe makes it explode , sending flames out your muffler, and that's also why changing jets (no matter what size)has had no effect.