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Message started by NCSUindy09 on 10/22/14 at 13:23:47

Title: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/22/14 at 13:23:47

Hello. I'm having a little trouble finding the source of my problems. I keep getting massive backfire and loss of power. Sometimes it's only above 1/4 throttle, usually idle is fine. The problem is intermittent, some days it works fine.

I've cleaned the carb a few times within the last couple weeks, each time with minimal results. I've also cleaned out the gas tank and added an in-line fuel filter.

I last tuned the carb when it was around 80F outside. Now it's a regular 60-70F. I was at 2.5 turns out, now I'm maxed out at 3.5ish. The effect was minimal if any. The jets are stock for an 86. I have an aftermarket cone style air filter and the stock muffler.

I've replaced the spark plug. The old one was fine upon inspection but I did this just because I had no idea how old it was.

As for intake/exhaust leaks, I'm fairly confidant my intake is not leaking. Earlier this week (problem had already started) I wrapped my exhaust just for looks. I found that the exhaust header bolts were't torqued very tightly. I also did not replace the gasket when re-installing. I didn't think this could be my problem since sometimes the bike runs totally fine. Also, it ran fine for months since the last time I messed with the exhaust.

One last scary issue - A couple times I've tried to start the bike recently the starter didn't spin and I could hear something arc over. That's a recent development but it only happens rarely and when it happens it doesn't seems to have trouble idling after starting.

THANKS!

Title: Re: Diagnosing backfire/loss of power
Post by verslagen1 on 10/22/14 at 13:38:08

1518080E32353F226B625B0 wrote:

Is that loss of power then backfire and return of power?

I think you're problem is electrical.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/22/14 at 13:59:05

Yeah. It loses power then I'll get a few good pows and then get my power back.

Title: Re: Diagnosing backfire/loss of power
Post by verslagen1 on 10/22/14 at 14:12:45

I think your problem is electrical.

there are a few things to check...
does your heel ever hit the kick stand?
hit your highbeam and see if the blue light comes on. (general power check)
Or turn the signals on since you might be headed to the curb anyway.
check your ground by the oil level check window.
check the battery terms.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/22/14 at 14:37:40

I think you're right. I had a sketchy mess of wires between my signal generator and my battery terminal. I checked them and the connections were good but they were extremely nasty. I cleaned them up and took a quick test ride. I didn't get any backfire. I'll keep an eye on it over the next few days.

Thanks!

Title: Re: Diagnosing backfire/loss of power
Post by Spamy on 10/22/14 at 15:28:49

The search engine on this site just doesnt seem to work for me at all anymore. Seems to search back like 2 days and thats it.

Anyways, I had some issues like that a few months back and found that by wrapping my exhaust the trapped heat caused the inner exhaust pipe on the header to crack loose and was messing with the exhaust flow and the way it was running.

I had pictures and everything, but Ill be darned if I can bring up that post from a few months ago.

An external sign may be if the wrap is getting hot enough at the header bolts to melt the inside of the wrap to glass.

When you said you had wrapped the exhaust I thought Id throw that in there.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/22/14 at 15:39:19

Thanks. I had the problem before I wrapped it though. There was no significant change before/after. I can't rule it out yet though

After going on a longer ride I had troubles again. It seemed to only happen after the bike had warmed up significantly. Before I started getting bad backfire I noticed a little popping and crackling. I think I may be on the lean side of things.

After I got it to happen more consistently I sat there and watched my neutral and turn signal lights. They would dim while it backfired but didn't ever turn all the way off. Is that normal? Lower RPM or even a change in RPM changing voltage on the lights by a small amount.

Title: Re: Diagnosing backfire/loss of power
Post by Yoshi on 10/22/14 at 15:53:49

check your battery voltage with the bike running and without

and hopefully at 14k miles you have had the am chain tensioner checked

Title: Re: Diagnosing backfire/loss of power
Post by verslagen1 on 10/22/14 at 15:54:22

7F726264585F55480108310 wrote:

After I got it to happen more consistently I sat there and watched my neutral and turn signal lights. They would dim while it backfired but didn't ever turn all the way off. Is that normal? Lower RPM or even a change in RPM changing voltage on the lights by a small amount.

If the lights are dimming that either you gotta short, bad connection or the battery is near death. Take your pick.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/22/14 at 16:34:07

Ok thanks. I'll check that out over the weekend.

And yeah I made myself a "verslavy" to deal with the cam chain. I didn't ask his permission so dont tell verslagen :P

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/28/14 at 12:32:20

Hey, resurrecting my old thread. I cleaned all the connectors I could get to with some electronics cleaner. I went to the auto parts store to have the battery tested. They hooked it up to the positive terminal and the brake lever. I actually told them to just use the brake lever because thats where I hook it up if I ever have to jump it. Pretty soon after I got some smoke coming from the decomp. controller area. We unhooked the battery tester and everything seemed to work just as it had before.

Still no results on the battery.

I also changed the oil and found out I only had ~450mL. I'm still getting the loss of power and backfire.

Title: Re: Diagnosing backfire/loss of power
Post by verslagen1 on 10/28/14 at 12:54:16

060B1B1D21262C317871480 wrote:

They hooked it up to the positive terminal and the brake lever. I actually told them to just use the brake lever because thats where I hook it up if I ever have to jump it.

Aluminum is either painted or plated, both don't conduct electricity well.
Then you're going thru 2 flex joints, not known for positive contact.
better to connect to any bolt on the frame. I use the 2 that bolt the starter on. That way if you burn them they're easily replaced.

Quote:

Pretty soon after I got some smoke coming from the decomp. controller area.

Smoke is not good. you've let some out, now you got to replace it. ;)

Title: Re: Diagnosing backfire/loss of power
Post by Serowbot on 10/28/14 at 15:40:57

450ml is half a quart... you have an engine for long if do that...

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/28/14 at 15:59:18

Yeah I must be burning it because there's no way I'm leaking that much that fast. It hasn't been long since I changed the oil.

On another note: What's this? It's the decompression solenoid controller right? How important is it? How can I test it? And is it bad that there's a hole in it and a crack going along the top? ;D

Title: Re: Diagnosing backfire/loss of power
Post by verslagen1 on 10/28/14 at 16:06:43

6568787E42454F521B122B0 wrote:

On another note: What's this? It's the decompression solenoid controller right? How important is it? How can I test it? And is it bad that there's a hole in it and a crack going along the top?

Decomp control... correct.
It actuates the decomp, spins the starter, and releases the decomp.
I believe it also checks the safeties.
Not actually waterproof, several on here have filled with water and failed.
some spin the starter (starting in the middle of the night ain't good) and some just don't work.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 10/28/14 at 16:13:10

My bike starts up normally. I'm pretty sure I hear the click of the decomp when it starts. Can I safely rule this out as the cause of my backfire problems?

Title: Re: Diagnosing backfire/loss of power
Post by old_rider on 10/29/14 at 09:01:57

It truly does sound like you need to do a complete harness look over, meticulously.... starting from the headlight innards all the way back....and down.
If your lights are dimming even in the least.... there is a short somewhere, or the ground wire is broken in half somewhere.

But is does sound like a short in the fire circuit, if it is cutting off for a second and taking your fire, then coming back and firing non-spent fuel, in your exhaust (ever see your exhaust pipe in the dark from the back? its cherry red in there) and making it backfire.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 11/04/14 at 07:02:12

Hey, I'm back to resurrect my thread :)

I've looked over the wiring harness closely but not with a multimeter. I didn't see anything that was obviously broken. I cleaned all the connections.

I think it may just be a carburetion issue. I went for a ride this morning while it was chilly outside (50F). I rode normally first and had quite a bit of power loss but not really the same kind where it wouldn't fire for whole seconds at a time. It was more like just weakness and a little popping/crackling and some hesitation.

After that I shoved a sock around my cone air filter to reduce the air flow. The weakness went away almost entirely and the crackling was reduced.

Since putting new jets in is way easier than testing the entire wiring harness with a multimeter I think I'll try that first.

Right now I've got stock muffler and a cone filter. Everything inside my carb is stock for an 86 and I've already got my mix screw out 3 to 4 turns. Which jets should I replace and for what size?

Thanks!!!

Also: I got very little oil out when I changed it last. How do I know what state my piston rings are in and should I even be driving it at all? I know I was pretty rough on the engine when it was running.

Title: Re: Diagnosing backfire/loss of power
Post by old_rider on 11/04/14 at 17:08:36

you really need to do the cone filter AND put bigger jets on at the SAME time.
If you suck in more air you are going to need more fuel.
If you put on an external air filter, a larger exhaust and don't ad bigger jets, your fuel to air ratio is going to make your bike run like crap.

Title: Re: Diagnosing backfire/loss of power
Post by NCSUindy09 on 11/10/14 at 14:43:19

Hey just posting once more to let you guys know that I got everything figured out. I found about 3 places with exposed wire and covered them up. I also put in a bigger pilot jet. Everything is running smoothly now.

Thanks :)