Xs650 misfire issues. Piss....

Ok, first off I would like to say hi to everyone.
Long time viewer,new member.

Here's the story.
Bought a great running 75xs.
Chopped it for a tc bros hardtail.
Motor was removed for paint along with all wiring.
Motor was replaced, along with a tc bros wiring harness.
Wired up the condenser,coils and points and tried firing it up with out the chargeback system hooked up just as a test and to satisfy my impatient behavior.
Fired up first kick no problem. Awesome. Sounded a little funny to me and upon further investigation only the left cylinder was firing. Nothing expect air pumping out of the right. Shitballs.
Checked over the wiring diagram and it seems like I have it wired properly.
The right bank only fires very rarely, for a split second only, then back to air.
Yes, I have spark.
No, I'm 100% it's getting fuel.
No, I did not touch the carbs at all before it ran healthy.

Any help would kick ass, I'm really trying to ruin a back tore soon.
Thanks guys

My quick guess would be too little juice to produce a decent spark. If your charging system is stock then it is weak at best. A well-charged battery makes up for the times (like a cold idle) when the charging system just isn't up to the task. As to why you have good spark on the left and poor spark on the right I think it may have to do with the path of least resistance. Perhaps the resistance is higher on the right side's circuit. Anyway, I'd wait until I have a charged battery hooked up before I start pulling out hair. I'm no expert. I'm just going on what little I know. Hope it helps.

Make sure to check for vacuum leaks at the carb manifold too.

Originally Posted by MTW

My quick guess would be too little juice to produce a decent spark. If your charging system is stock then it is weak at best. A well-charged battery makes up for the times (like a cold idle) when the charging system just isn't up to the task. As to why you have good spark on the left and poor spark on the right I think it may have to do with the path of least resistance. Perhaps the resistance is higher on the right side's circuit. Anyway, I'd wait until I have a charged battery hooked up before I start pulling out hair. I'm no expert. I'm just going on what little I know. Hope it helps.

my charging system is not hooked up at the moment, just firing.
the battery is fully charged and brand new.

both points are making contact too.

checked for leaks at the carbs already. all perfect

I think it might be your points, check your gaps, and make sure they are clean to make contact.

Originally Posted by swinewerx

I think it might be your points, check your gaps, and make sure they are clean to make contact.

Point gap is set at 12 thou
Deff making contact I have spark.
Seems like the carb won't feed the cylinder.
I can almost fully open the butterfly with no change.
Carb was just cleaned for the 11th time. It's spotless

Originally Posted by breetime

Point gap is set at 12 thou
Deff making contact I have spark.
Seems like the carb won't feed the cylinder.
I can almost fully open the butterfly with no change.
Carb was just cleaned for the 11th time. It's spotless

So you have spark at they plug to the cylinder?

Give it a compression test and see where you're at.

Believe it or not i just had the same problem with mine.Try switching the spark plugs around.I had a spark at both plugs but it wasnt getting to the fuel in the head.One plug went then the other a day later!I have never had a duff spark plug in 33 years then i get two!!

Compression test x2. Something's going on somewhere else if you have spark. Unless its misfiring while running, shit coil, loose or fucked up cable that's grounding out when it's running and vibrating?

Check the manifold on that side too

If you are running the points maybe something's loose or there's carbon buildup on the tips of that right side point.

Could be a lot of things. If you plan on riding that thing a lot I'd suggest just grabbing a pamco ignition and a super coil. That should clear up all your problems

One other thing that shouldn't make a difference and I don't even know if it applies to xs spark systems but there is polarity to plugs if you yank it and put a pencil between the engine block and plug and kick it over the sparks will either bounce off the pencil tip to the plug or go towards the engine (I think). If they don't go toward the engine switch the plugs and wires to opposite sides. I think this just is an anal performance enhancement but if you are playing with the shit anyway can't hurt to pick up a pencil

Originally Posted by backwithabang

Compression test x2. Something's going on somewhere else if you have spark. Unless its misfiring while running, shit coil, loose or fucked up cable that's grounding out when it's running and vibrating?

Check the manifold on that side too

If you are running the points maybe something's loose or there's carbon buildup on the tips of that right side point.

Could be a lot of things. If you plan on riding that thing a lot I'd suggest just grabbing a pamco ignition and a super coil. That should clear up all your problems

One other thing that shouldn't make a difference and I don't even know if it applies to xs spark systems but there is polarity to plugs if you yank it and put a pencil between the engine block and plug and kick it over the sparks will either bounce off the pencil tip to the plug or go towards the engine (I think). If they don't go toward the engine switch the plugs and wires to opposite sides. I think this just is an anal performance enhancement but if you are playing with the shit anyway can't hurt to pick up a pencil

manifolds are good, points are cleaned and gaps are set. and yes i am going to get a pamco and new coils. this charging/firing system on these bikes suck a bag of dicks.
ill try switching the plug wires and plugs. is that works ill do a fucking backflip

The manifolds can be deceiving....

My understanding is that the band clamp on the old factory manifolds needs to be cinched down good, so that the two ends are touching.

I was getting vacuum leak and located at the manifold using propane. They were tight but still took a few more turns, that seemed to fix the issue.

But your problem sounds compression related. If you have a tester I'd say do that while you swap plugs/wires.

Originally Posted by Blackbetty

The manifolds can be deceiving....

My understanding is that the band clamp on the old factory manifolds needs to be cinched down good, so that the two ends are touching.

I was getting vacuum leak and located at the manifold using propane. They were tight but still took a few more turns, that seemed to fix the issue.

But your problem sounds compression related. If you have a tester I'd say do that while you swap plugs/wires.

was going to try swapping the plugs/wires around tonight. but couldnt get the thing started at all. not even the one cylinder, so i said fuck it and worked on my mid controls.
ill do a leak down test tomrrow.fack

UPDATE:

nothing.
finally got my pamco tci in.
install was a breeze.
used a late model dual output coil off my other 650 along with new plug wires. wired it up just like pamco instructed with my timing in the "ballpark" he recommends.

still only firing on one cylinder. took about 20 kicks to start, but like last time only left side bang firing. right side will pop/cracl very rarely.

carbs are perfect, even tried some late model carbs off my other 650. same shit.

WHAT THE FUCK AM I MISSING?

Compression test x3, I had the same problem, I started it and would only get one cylinder, I did a compression test and had shit on the right cylinder, put some oil in the spark plug hole and had about 20-30psi I think, if thats the case its either bad rings, or a bad valve, mine was a valve, I had to pull the head lap the valves and put in new ones, since thin its been great, just my .02

Originally Posted by christopher26

Compression test x3, I had the same problem, I started it and would only get one cylinder, I did a compression test and had shit on the right cylinder, put some oil in the spark plug hole and had about 20-30psi I think, if thats the case its either bad rings, or a bad valve, mine was a valve, I had to pull the head lap the valves and put in new ones, since thin its been great, just my .02

doing a compression tonight. i hope the numbers are close lol.

hopefully a stuck valve i can just soak the head in brake parts cleaner

compression couldnt be better. 90 on both cyl

timing light indicates spark from both plugs. pouring gas in each cylinder will keep it running for a quick second but then it dies out......starting to think my problem is carbs? even tho ive cleaned then 40 times, even switched carbs from either cly and tried late model carbs, same result for all variations.

im stumped

Plugged carbs? Seems like even if you did a rebuild, your carbs still may be screwed.

are you using the same gas tank for all these carb tests? could it just be a vacuum problem?

also you said that only the left cylinder is (was) firing....could be your choke circuit. look into replacing the plunger, dust seal, and choke body gasket.

and do you have a good baseline setup on your carbs. you cant just clean shit and throw everything back together. if you changed your pipes, and intake then you will need to rejet. also, do you have any kind of airfilter on the carbs.
read the fuck out of this. almost everything you need to know is in here carb wise.
http://www.amckayltd.com/carbguide.pdf



check your oil for gas.