86 evo missfire???? Harley Evo Discuss 86 evo missfire???? in the Motorcycles forums; I am new to this forum so hi to you all. I am a brit living in Jervis Bay Australia. My bike is a USA model that was imported to ...

[billski]

I am new to this forum so hi to you all. I am a brit living in Jervis Bay Australia. My bike is a USA model that was imported to the UK in 87 and I brought it with me when I moved to OZ two years ago. It has about 70000 miles on it.
I have a 86 Heritage with a few mods- Headquarters single fire ignition, Headquarters Torque cam, S&S adjustable pushrods, S&S E carb, Jims solid lifters, S&S billet oil pump, Jims cam cover (nosecone), S&S steel breather, Pingel petcock, V&H Longshots the rest of the engine is stock. My problem is a bad missfire anytime I use more than half throttle in any gear with the baffles installed in the longshots. If I take the baffles out or put the stock pipes back on it runs great all the way to the redline. Put the baffles back in and the missfire is back. I ran it in the Uk without baffles for years but it is way to loud to run like that in OZ. I have changed the spark plugs, have new wires and have tried changing main jets both bigger and smaller. I say it is a missfire but what it sounds like is if I have hit a rev limiter when it happens. Anyone have any idea what to try next? It might not be related but recently when starting I get a cloud of gas from around the aircleaner . The cloud is big enough that I worry about the fire hazard if there was to be a spark to ignite it.

[evoKENevo]

Welcome aboard, billski

This is just a "long shot" (excuse the pun) here...but it sounds to me like maybe your V&H baffles might have seen better days. Years ago I had a car do what your describing..and it turned out that the insides of the muffler had rusted away and the baffle plate(s) had fallen out of place and were blocking it up...running OK until higher speeds

Of course I could be all wrong here...but you say when you take the baffles out (unrestricted) you're fine..and when you use the stock mufflers (supposedly more restrictive) you're fine...might even have something to do with that"cloud of gas" (no where else to go) coming out of your carb on start up...or not !?!? Does that happen only when you have the V&H baffles in..or, just anytime.?? You mentioned you ran the pipes w/o baffles for years. Where were the baflles stored in the meantime ? Could a mouse or bird (examples) have built a nest in them ?

Just "mymind' doing whatever it does up there.

[wideglidebill]

I would very carefully check those baffles for any blockage. can you see through
them? maybe try to blow air from compressor through to see if air passes???

[billski]

evoKenevo,
I bought the Longshots second hand on eBay and had the same problem with the baffles when I first installed the pipes which is why I ran without them. I think I had the loudest bike in England as it would set off car alarms when riding through narrow village streets. The baffles that came with the pipes seemed very long to me, they are at least 10" long. Does that sound like the right length for the original baffles? Would there be any benefit in making them shorter? The baffles were not installed in the pipes when they arrived and were very sooty, I assume the previous owner was running rich. I did bang em against the bench a few times to knock the soot out and I think I was able to look through the centre of them. They were also an extremely tight fit.
I do like your idea about them being blocked so I will pull them out and check.
I have also thought of having a go at making a disc baffle I saw online somewhere. It's basically a 3/4" or 1" flat washer welded to a short length of threaded bar. You can cut a slot with a hacksaw on the end of the threaded bar that sticks out of the pipe so you can see the angle that the baffle is at. You bolt it up through one of the original baffle fixing holes. You can supposedly tune the baffle or vary the amount of back pressure by turning the washer so it is in line or more of a right angle to the flow through the pipe. Do you know of anyone trying this?

[wideglidebill]

do you have a friend with the like pipes??? try switching them out and see if you still have the same problem.


I am just jumping in with suggestions, I have a 1996 fxdwg with some type of pipe that is not marked, but not stock. I presume that they are a harley performance pipe of sometype. I have no problem with them at all.
This is my first harley. I just got it after waiting 20 years for kids to get gone and have the money to buy. it had 11,000 miles on it, and looks like new, and previous owner spent lots of money on harley chrome. Anyhow, now that i am being long winded...... I would take the baffles and clean them real well with maybe oven cleaner and let them soak over night and try them again.

[frisco-rigid]

Hi Bill

Good, you answered one of my questions ------has the problem always been there since the first time you used the baffles in these longshots, you say yes.. Soo, based on your info------
Perhaps this system will never work well in the manner your motor is set up.. In-other-words, primarily motor size and cam and carb..

The first thing I always suggest is to be absolutely sure the timing is correct before trying to correct any intake or exhaust probs.. Also be sure there are NO other contributing probs like intake leaks..

If the timing is confirmed then the next first thing I would look at is the size of the Longshots.. It says in the book that they are 1 3/4" head pipes but at what point do they become 2 1/4".? If the pipes have too much diameter for too much of their length, it will affect exhaust flow and perhaps be very in-efficient.. Also the over-all length of the pipes is important.. Too long is just as bad as too short..

The fuel misting out the carb is generally called "stand-off" it is often caused by reversion at certain RPM's where the exhaust reversion pulse comes back up the pipe and because the cam over-lap is still holding the exhaust valve open it is shooting alot of your intake charge out and is wasted.. That is amplified by being too rich also..
OK,, changing the main jet may have no affect at all unless, when this prob occurs, you are at or above the point at which the Main jet comes in which is anywhere from 2500 to over 3000 RPM's.. Trying to properly jet a large carb like that with those pipes could cause insanity..

Now I want your best "seat of the pants" opinion-- do you feel you get more or less perfomance from these Longshots compared to your stock exhaust.?

You have basically a stock 80" motor and they are generally not tolerant of too much carb or cam or an in-efficient exhaust system.. I would consider installing your stock headers back on with some good flowing muffs like the KromeWerks A-100's or CycleShacks etc..

As for the "bolt and Washer" trick you refer to, go to "Exhaust" section and look about 7 threads down.. You will see a thread called "Muffler Inserts"..
I posted a couple photos that might assist you.. It is only a band-aid..
The trick works if you have a very in-efficient system.. It will never work as well as a properly set-up exhaust system..

[billski]

frisco-rigid,
Thanks for the reply.
I have checked the timing and looked for intake and exhaust leaks but that was a while ago so will do them again. I will also measure the pipes and get back to you on that.
This bike on stock pipes has lots of low down torque and the power gradually fades at the top end. It is the opposite with the longshots without baffles- pretty average low down but good power from mid throttle all the way to the red line. This bike is noticably quicker with the longshots but you have to work hard to get there.
I am new here but had a look around where is the "Exhaust" section???
I do not understand how reversion works when you are starting the bike I thought the bike had to be running for that to be an issue. I guess I didn't think the motor was turning fast enough to develop the pulse.
I will try to measure the pipes tonight.

[evoKENevo]

billski:
Like I said when I started my original repy here..I was taking a "long shot" at the problem you described...starting with the "quirkiest" idea that came to "mymind". I've gotten into the habit of that. Because of the countless times something "dumb" has been at the root of an issue...and, the easiest to find...which I always try to at least "rule-out" (or not) first.

Frisco hit on the crux of things..and, that's who I'd think of first here (among a few others) for exhaust questions,in particular,(not limited to) when I have them. Yeah,and,now that you've got his attention, I'm just going to kind of "butt-out" and "listen-in",here, for the most part...noting that like he said (in other words) you'd come out further ahead (perf-wise) to lose the V&H long shots (essentially straight pipes) and retune your bike to a known performance set-up,that suits your needs.

Meanwhile though, in regard to navigating your way around the forum..
Once you log-in, the main forum page appears...as you scroll down you'll come the various topics,like the "Harley Evos" you started this thead under...keep scrolling down from there aways until you come to "Exhaust"...click on that...and,like frisco said you'll find the "muffler inserts" thread he mentioned to be the 7th one down from the top (currently) and a good read from start to finish, as far as "baffles" etc. go.

[milindh]

I'd also check the compression. Leaky exhaust valves can sometimes cause your start up back misting symptom as could timing as Frisco said.

Also your description of the misfiring is pretty good but it's hard to pinpoint what's really going on. One guy's "misfire" might be a "bad burble" to another. To either verify or eliminate the the carb as a possible cause you should do a "plug check" of your spark plugs. The Mikuni website has a detailed step by step system for this procedure. It's for tuning their carbs but works with any carb. Learn this system and you'll be able to diagnose and fix any carb problem.

The pipes do seem to be the most likely culprits but, like any good mystery, careful investigation of the basics is the key here. Lots of good advice given here already.

Good Luck

[frisco-rigid]

Yes, a Mis-fire to one could be a burble to another..

We are all aware how diff it can be sometimes to try to assist a guy with a prob when you cannot hear it touch it see it and ya gotta wait for replies that might give you more needed info,,,, but still,, we do our best..
Kens ideas were certainly feasible, nothing can be over-looked..

Even though Mik's are my fav carb, I haven't been to the Mikuni site to read their plug test procedure, but for the S&S the old-style plug test is very straight forward and more in line with the way S&S carbs work..
Remember, Mik's jet by throttle position while S&S and most other Butterfly carbs jet by RPM's.. If you're interested I'll explain the old-style plug test,, when you're ready..

Mil is certainly on the ball to suggest a good jetting test because I'm pretty sure your prob is affected by both carburation and mostly exhaust..
BUT once the exhaust is straightened out the carb will prob need a final adjustment..
Bill, I'm going to venture a guess here about the diff you feel between your stock system and the Shots.. You see, it's very much like running a carb that is too big for a motor.. It will feed the motor kinda OK in the lower RPM's but really make it come alive at much higher RPM's.. I think that's kinda what's going on with your motor and the shots.. If you're like most of us, you mostly live in the low to mid RPM's..

I will predict,, (Darn I hate when I do this), that you will get low-end and more of the top end you like with the shots, once you get a good efficient exhaust system that is more matched to your motor along with proper jetting of the E or even another carb..
I'm not saying that good results here are dependant on another carb, I am saying however that there are better carbs for your mostly stock motor..
The 39.6mm venturi of the E is pretty big for a stocker.. I think you'd be better off with a 38mm.. That's my experience anyway..