Bought bike in box. Cct fail. Replaced head with a used one.
Bike fires up great. But as soon as it gets warm it misses and backfires.

What I've done
Empty gas tank new gas (91 octane) tore down tank checked filters all good.
Removed carbs tear down full clean (they looked fine didn't realy need the clean)
New plugs - spark looks great.
Compression 132 front 135 rear (only replaced front head)
Conditioned filter k&n I think. Used foging oil.
New oil. ( old oil was mud. Real bad)
Rad has water in it for now.

Issues I observe
Front cylinder is missing. Backfiring only when warm.
Plug is wet wih gas.
Enough smoke to fill a bingo hall (could be the fogging oil)

Suggestions? My only thought at this point is to swap the front coil and wire?

 

well,first,dont need 91oct in it,it will run better with 87,88, or 89,oct,the most.
after tearing carbs,did you put the needles exactly where they belong,some do look the same,but are not.it all must go in its correct spot,jets,needles,diaphragm etc etc.
after you tore the carbs and put them back together,did you sync them and set the air mixture screws to the proper settings.
K&N filter,well,99% will tell you,go back to oem filter.very,very hard to tune a K&N.
even tho you put new oil,did you put new filter.
is there any gas leaking from any of the exhaust.
will the slides in carbs open and close with some resistance and a air suction sound.
did you plug the tps back in and/or did you do the mod.

over all,we need more info what has been modded on the bike if anything has been,and did the bike have all its parts.
correct harness for parts installed,correct cdi and such.this did come out of a box so this will be a hard start for you.

 

I"m really not sure what more I can tell you.. it came with two brothers racing pipes and block of plates on the valve covers (read valves blocked) pare system plugged.. the work was done by 2 owners back.. the guy I bought it off of knew nothing about bikes so I'm guessing he just rode..

let go into some suggestions I had from a friend..
1.Where does the crank case vent and is it plugged..
2.anyone ever have a fly wheel pin snap and cause the fly wheel to be slightly out of position.. maybe casing bad timing..

 

maybe a video will help

 

that reminds of a bike i worked on that smoked that exact way.
it was a gas leak issue with the petcock.
should check to see if the petcock is leaking and make sure the nipple is in the right place.
the diaphragm could be damaged.

 

doesn't gas burn black and oil/coolant burn white in exhaust?

I would think a gasket leak before petcock issue. Since he is getting gas from the lines the diaphragm should be functioning. It didn't seem like in the video that the bike was starving for gas or sputtering under throttle.

Its possible that the last go of oil was mud because of a oil coolant mix?? just thinking of possibles here

 

thats what i thought when i was working on this other bike.
the only difference between that one and this one is,there was a big amount of gas coming out of the rear exhaust pipe,but some how,he managed to ride the bike like this for months on end with the vacuum line on the wrong place of the petcock.
it is very possible that it is the old oil needing to burn and clean thru.
I cant see gas being a issue since fresh gas was put in,maybe valves and such are gummed up.
4 oz of seafoam to a full 4 gallons of gas might help.its 1 oz per gallon.

i would definately just go thru the bike one more time too feel at ease and make sure everything is set up where it needs to be.

since the pair system was removed,just make sure the air box is capped off and and see if syncing the carbs levels it a little bit,after you double check everything.

 

very,very possible there is a oil/water mixture.

check water and oil to make sure it is not this.

 

oil looked clean, when it came out.. no water present.. same with rad fluid when I drained it no oil present.. not easy to see in this motor to see if there is any signs of water.
My goto at this point is coil, as the front plug is coming out wet and even though the spark looks great when testing I wonder if it's week and is not sparking 100% when under compression. I will swap front and rear coils, check all wiring of course. see if I get the same results.

Frustrating!

 

+1 that would be my next step. If it's bad you may have to upgrade to stick coils. How sad

 

I sincerely doubt that it's coils or any other electrical issue. It might be the over oiled K&N, but I would recheck the oil for water. Since the last thing done was replace a head, and headgasket, I might start there.

 

Some water in the oil isn't going to cause that.

I'd double check your cam timing. You said you had to replace the head due to CCT failure. Make sure the timing is correct and do a compression test to make sure you've got good compression on both cylinders. It could be the used head you put on it could have had a bent valve or something as well.

 

If that is fuel, you would know it,, that much raw fuel and burned fuel coming out the exhaust will make you choke, eyes water, and kill every flying bug for 10 miles.

If it's coolant, you'll have a sticky sweet smell and taste.

If it's oil, well, it'll smell of burnt oil.

That is a LOT of smoke coming out both pipes.

 

took it to a mechanic.. he's not 100% but he said 95% chance the last guy ran this with out oil and killed the lower rings, based on all that was said from previous owner and what we have found.. it is oil burning.. he thinks it's getting up past the rings.
so if he's right.. I'm looking for a motor.. I'm not sure what the walls are coated with.. dosn't seem to be a quick search.. but if it's a light coating. then its more then likly warren out too. so big job to replace that..

thoughts?

 

some optomisim.. I just can't leave this thing alone.. so I took off the front head and YES THE TIMING WAS OFF!! clearly I screwed up the first time, it only out by one tooth so I'm sure it's ok.. but I found my manual tentioners are not ideal for adjust either so I need to fix that.. a little hope!

not sure it will everything but I'm hopping it is..

 

If it ran low on oil you would have much more severe problems then worn rings.Have you checked/adjusted the valve clearances? You might find this will bring your compression back up and she'll run smoother.Your compression is low from either worn rings or badly seated valves,I would check the valves first and if this fails to cure the problem then it's time to open up the motor and check the ring end gaps and signs of blowby

 

ya check valve clearance it was good.. after my last post.. it fired up and sounded great until it warmed up.. then it started missing back firing and stalling.. plugs were coming out wet.. I was lost.. a day latter I discovered that the neutral switch was intermittent and because the bike was on the stand the computer detected it in gear with the stand down so it would shut it down.. then connect and and run then shut down.. so on /off/on off/ on /off.. bang bang bang.. back fire.. so that is fixed and it's running much much better... I need to take it for a good run to see how it really runs.. I warmed it up to 100°C tonight.. but throttle was uneven and I had to keep playing it to keep it running.. every minute or so it would try to stall if i didn't rev it.. not sure why..