Spark partial failure at mid to high.. Ive tried it all!!

[McQuade]

DIdn't you mean to say Mustang?

Unsure how that was relevant, but anyways. Tried both lines, tried the timing chain one tooth either way, and every combination associated with this. It is timed as it should be. I tore the advamce apart and lubed it again. Checked every gap. Flawless. Valve lash a ok.

[barnett468]

So you checked the timing using the method I suggested and the f is lined up at idle and you gasve it gas and the timing advanced?

[McQuade]

Yes, though on a seperate thread, someone said the exact opposite of what you did. I tried both ways. I advanced it while running with my hand too, and either way where it's at is where it works "best"

[barnett468]

Yes, though on a seperate thread, someone said the exact opposite of what you did. I tried both ways. I advanced it while running with my hand too, and either way where it's at is where it works "best"

What do you mean they said the exact opposite of what I did? . . I said several things

Have you tried different jetting yet?

Did you look at the timing lite to see it the lite was breaking up? . . if it was then your prob is electrical.

[danbur55]

Have you put an air filter on it as this will alter air flow that might be affecting fuel delivery. Was new carb a Chinese model as many have stated the jets were not correct size beyond this I am of little help to you

[McQuade]

I just finished reading one of the threads you and "kd only" or so thing like that helped with in 2013. Perhaps you'll remember this one. About two hundred posts, every hundred you get free steak knives. In any case, I read that and the follow up. I'm not sure how I read his discription about the noise his bike was making, the difference between misfire bogging ect. Forgive my analysis of you, but after reading that I think I'll be able to help you help me.
This post will be long an I'm sorry but I'll give you a background and the steps I followed. (I'm a licensed diesel tech though this is irrelevant other then electrical theory)

I bought two bikes, an 84 and this 85. The other was a runner but the frame was bent and had no plastic. It was more work then it was worth. THIS bike never ran. It was missing a carb. So I swapped the carb. This exact symptom happened. Hollow knocking at mid to high, speed not load specific. Thinking I bought a blown bike I swapped the engine (it's current state) changing the RUNNING engine into this trike made no difference. Not having a manual I began to individually chamge over the parts still on the previously running bike. Coil regulator, cdi. Finally complete component transfer. This is now the running bike minus the frame. I noticed the head gasket was leaking, so I pulled the engine, and freshened up the top end.
After getting more compression it ran stronger at idle and had more low end, but still this hollow knocking almost like a rod knock. But I checked the bearings so that isn't it. After acquiring a manual I purchased a new carb (same as your 2013 guy, it was too large) it made no difference. I then tried all ignition components and chasing a ghost I ended up replacing it all.

Today I checked the stator, 275.3 ohms in exciter coil. It's on the upper of the gtg (1-400 ohm)

This was when I read that post, about the exhaust being the culprit. So that's where I am currently.

[McQuade]

And by opposite" I meant on another thread, actually quite a few, most say to static time the pulse with the "f". But I tried both, and either one appeared to make any difference on performance.

[barnett468]

Lol OK free steak knives yup . . there were two such threads . . one was the Honda that ended up being squirrel nuts in the muffler . . I think KB only suggested he look there . . the other was a cdi next to an exhaust pipe that got hot from the pipe after a few minutes and would qstart missing after that and would not run properly until the cdi cooled which took around 45 minutes . . i told him to put it in the freezer for 10 minutes right after the prob occured then try it . . if it worked then it was the cdi

Anyway so you know a bit about me then lol . . there are several knowledgeable people here but far fewer are posting these days . . i have no idea what happened to kb only.

I will be glad to help the best i csn as will others that post but i took a look and it looked like you have posted 1or 2 other threads regarding this and still have the problem.

The f should be in the window with the lite when the engine is idling unless the service manual says no otherwise . . if it is lined up when the bike is off but not when it is running, the springs are too loose on the mechanical advance and are allowing it yo advance sooner than it should . . if it advances way too soon, it certainly cause eratic running at the very lesst . . if your sound is not mechanical like a loose rod or piston etc, it could be detonation from too much advance . . i have had this prob before but it would be rare and unlikely but keep in mind, it tyook 200 posts to figure out one guy had acorns in his muffler and ther other guy had his cdi laying on the friggen ex pipe.

In yor case, i would do the timing test and remove the exhaust and make sure the head pipe is clear even if you used different exhaust . . leave the muffler off if possible to eliminate that as a possible prob. . . this will make the bike run leaner than it currently is so you may or may not need to address that

Post a close up photo of the end of yhe spark plug and tell us how long it has been in there.

Try all suggestions from everyone like the one danbur posted . .

Check the timing lite yo see if it misses as i suggested.

Check valve clearance.

Could be week valve springs . . yes I know both engines did the same thing.

If the cdi is Chinese instead of a Honda one it could be the cdi unless you sealed in a good Honda one.

If none of these tests yield results then its just guessing after that. Which is not good.

[barnett468]

Please excuse the typos . . I can't erase on my phone and don't have an edit button . . since you know diesel engines this stuff should be simple for you.

[McQuade]

I'm referring to squirrel nuts guy. Essentially same sort of issue, minus the distinctive (I'm going to guess) spark knock. I do recall early on in my tinkering trying open header, but it was too noisy to hear a knock lol. I will try the timing light thing to reinterate my claim of proper timing. I do have some concerns regarding the advance. One; my pin is on my cam. I slide said advance on it.. I have a bit of play in the "key way" between the pin and it. I also have a bit of play before the weights actually start to move it. It's been twenty years since I've seen my old big red and don't recall how tight this stuff is.. I'll guess this is something to address. Also, plug check: mildly sooty, not good, not really fluffy either. Just black.
I think my main problem is trying to establish if this is fuel causing the fire or the fire causing the fuel issue lol. I'll report back in when I aquire my fathers test light, mine isn't the greatest if shape. I whacked it off the fan on my camaro checking the time. What a racket haha

[barnett468]

OK I clearly understand everything you are saying . . look at the light or point it toward the front when you rev it . . do this in a dark place so you can easily see it . . if the light skips when the engine starts missing, it is most likely the ignition unless it is so rich the gas is nkilling the spark .

You must clean the plug thoroughly . . if there is a lot of carbon, it will do exactly what it is doing . . if it does it with a clean good plug it is obviously not the plug.

Set the plug gap .004" narrower then the spec . . this will help a weak ignition.

Tell us what color the spark is.

Go into the dear b engine o. The site . . put my name in . . search for gas level or float level within the last 4 weeks . . look for a post with two carburetor photos . . set your gas level so it is just below the bottom edge of the upper carb body because it might be too high even though it is a different carb.

Clean the spark plug fist.

[barnett468]

Correction

"Go into the search engine"

[barnett468]

Your advance unit should not have any free play . . it should have tension on the springs . . this explains why the F does not line up at idle . . this may be part of your problem.

If you have safety vwire, you can try to wire the advance closed and try it right after you clean the spsrk plug lol

You may be able to bend the end of the springs on the advance to fix it. . . it should have a fair amount of tension on it

[McQuade]

Ok free play I will try to address. The cam pin to advance mech. Not sure how to repair this. The plug has less then I'll say, 35 mins total of running on it.i have a slew of them. No difference. I also did try tightening the gap. I'm ised to vacuum advances. Sooo easy. It works or it doesn't. Lol. Should it run better without the advance operating? And I'll check my float(s) the origional mikuni was in haggard shape. No rebuild kit could fix that trainwreck

[barnett468]

OK

If the gas is yellow, it is bad . . if the tank had dried up too from old gas and you put new gas in it the too will mix with the gas . . old gas will cause this exact problem in every way.

Don't worry about the loose can pin now . . it is not a problem because the inner shaft on the advance is locked into place on the can by the bolt . . the pin is just too generally line the advance up . . no big deal.


If the advance is your problem then locking it with wire will eliminate the miss but it might not rev to the max.

You can do these other things without a timing lite and you may get positive results.

I will be around for a few hours.