Miss ,crack,pop.....

[RaWarrior]

Since you have an '85, you have the old analog ignition. They're not known for being super reliable, and on their way out they can cause all sorts of wacky problems.

I suspect the heat rising from the engine(since you mentioned it happens while idling) warms up the box(it sits right above the front head) and aggravates the problem. I suspect the pop/miss is from intermittent/weak spark.

Unfortunately, it's not the easiest fix. Even if you got your hands on a good analog box, it's a PITA to change....buried in front of the carbs. Someone here would repair the analog boxes, but I don't remember who or if they still are. It's possible to swap in the '90 and up digital box(which tend to be very reliable), but you'd also need a '90up wiring harness since the connectors are different.

I think your problem is weak spark, which can be caused by bad wires, crappy plugs, and most likely, a corroded connection at the coil. Unscrew the plastic cap and pull the wire out. Cut like 1/4" of wire off to expose fresh conductor and put it back in, or better yet if they're the original wires, replace them.

I highly doubt the fuel pump is the problem, if it was the problem would emerge at WOT or high RPMs, not idle. If it was a tank vent issue, revving it up wouldn't really make a difference since the fuel pump is electric and it's "pump strength" isn't dependent on RPM.

Good luck.

 

[wiretwister]

I am incline to think its a ignition problem, Mainly because I just dont see carbs dropping out , 1st one..then another ..and so on, I mean when this thing acts up...It sounds like its gotta be cross firing...whats funny, when I bought this bike...the guy had a 4-1/2"can with the side blew out of it...he said the bike backfired and did it, if I dont get it fixed...its gonna do that again, I will throw a ignition module at it, and see what happens.
One things for sure, Im pretty much covering everything......now dont tell me it could be the pickup coils..( or could it )???

 

[dannymax]

Just a thought....when it starts acting up can you shut it down and have a look at the plugs? It might tell you something. :confused2:

The firing right back up is sure confusing the issue! unk:

 

[wiretwister]

Yea...firing right back up and running good for a few minutes...........

This weekend I will attack this thing ( provided its not raining) Im gonna go over the fuel side ( pump,filter, vent ) and I will replace the Ignition box as well, yea I bought one.......

Its high time I get this beast right..........not being able to get more then a few miles from home sucks!!!

 

[dannymax]

Venting could cause problems like this but all 4 carbs have seperate vents.....:ummm: Unless all 4 hoses are pinched behind the airbox somehow, or plugged by mud bees??? I'm really reaching here.:confused2:

 

[gamorg02]

i know its a stretch danny but what about the fuel tank vent?

this really seems to me something has enough fuel then some sort of vacuum is reached, then once the engine is shut off all is good.

like a shop vac when it tips over.

 

[wiretwister]

If I had thought ...I could have checked that when it nutted up Sunday.....I was to pissed to do anything except pray I made it home, I rode 70 miles the weekend before without a problem.....I thought it was all good, you see its done this several times...... I thought it was because of low voltage when it went nuts.......not the case.
Like I said.....I bought a Ignition box, and a stock fuel pump.......surely going through both will fix me up......If not Im leaning toward a gernade.

But..before I don anything.....In gonna let it nut up and see if there is a vacuum on the tank, now that would be some shit.

 

[dannymax]

i know its a stretch danny but what about the fuel tank vent?

this really seems to me something has enough fuel then some sort of vacuum is reached, then once the engine is shut off all is good.

like a shop vac when it tips over.

May not be a reach at all Garrett, I didn't go back 'upstream' from the carbs but, sure, that's a common vent....if it turns out to be a vent issue the tank vent is the logical place to start looking!

Will be very interested in finding out what's causing this problem....keep us posted.

 

[tugla]

sounds electrical, runs fine when he shuts it down for a few mins could be the components cooled off and runs ok for a few mins, maybe.

also start with new plugs and wires.
what happens when it starts to pop if you slightly turn on the choke? just to see if it still acts like a normal bike in the sense warm engine and turn on the choke. If it starts to run nice, might lead you to something else.
also guys dont coil cracks cause this issue? especially when they get warm/hot?

 

[wiretwister]

I tried the choke thing Sunday and it didnt help a thing..... Thats kinda why Im leaning toward the Ignition....

Would bad pulse generators cause such a issue ??
How about this question....Do you think a carb issue ( one that the bike runs fine cold "no choke") could/would cause enough problem to backfire hard enough to blow the whole side out of a hindle can ??

 

[RaWarrior]

I can't imagine that happening. Automotive mufflers with series of "walls" inside are much more restrictive and in extreme cases, a sudden blast of pressure can pop one. Bike cans tend to be straight out, with baffling around the edges. Unless for some reason the outlet was blocked, I can't imagine blowing the side out of a can.

I suspect it runs OK after letting it sit for a while is because the ignition box cooled off. The current running through it is producing more heat than it should, well, because it's old and was poorly designed to start with. Eventually it gets too hot in the box and it starts acting up. Shut it down, current stops, it cools off, then fires up again and runs OK.

Was the 70 mile no-problem ride mostly "moving", as in no getting stuck in traffic? The extra heat added from it rising off the motor when stopped might be just enough extra to make it act up.

Trigger coils could be the issue also, it's not unheard of. They should read 110ohms +/- 15% according to the manual, though it's also not unheard of for coils to test fine on the bench but not work under heat and load. The ignition box would "cool off" a lot faster when shut down than the pickup coils would, since they're inside the hot crankcase covered in hot oil.

I'm still thinking it's the ignition box.

 

[wiretwister]

Today I put the Ignition box in......zipped it all up, rolled it out warmed it up....was running great, put my helment on pulled the clutch dropped it in 1st and it quit, Im saying WTF !!!! .....OK what the hell just happened ?? of coarse I tried it several times.....So I assume its the kick stand relay ?? I will start another thead on this problem cause I need the answer fast !!!
NOW.....I let the bike run 20 minutes,fan cycled a couple of times , the bike ran super never missed a lick I think its fixed, will test ride as soon as I find which wire to snip to make it run in gear..

 

[wiretwister]

How in the world did changing ignition boxs make the side stand shutdown act up..........What the ???

 

[wiretwister]

Rode it yesterday..NO more crack and pop..never backfired, Ignition box seemed to be the problem...OH, I cut the blabk wire on the sidestand relay also.

BUT, Now a new problem....I guess i will start a new thread.

 

[Creepshow]

Rode it yesterday..NO more crack and pop..never backfired, Ignition box seemed to be the problem...OH, I cut the blabk wire on the sidestand relay also.

BUT, Now a new problem....I guess i will start a new thread.

Hello, having a similar issue. Did this clear up permanently with the ignition box change?