Author Topic: It has a hard time starting, and when it finally starts it dies (Read 3048 times)

seanbarney41 · « **Reply #25 on:** January 07, 2014, 08:06:29 PM »

I'm guessing you don't have the stock airbox or a proper exhaust to try out?

leesfer · « **Reply #26 on:** January 07, 2014, 08:43:43 PM »

Correct, I have neither, but I've jetted the carbs to compensate for the airflow as best I can according to these forums

leesfer · « **Reply #27 on:** January 07, 2014, 08:51:40 PM »

Checking the timing as close as I can to idle and it looks okay besides the bouncing from the backfires/popping

1975 Honda CB750 pamco ignition timing

seanbarney41 · « **Reply #28 on:** January 07, 2014, 09:11:07 PM »

at least it sounds like 4 cylinders are firing some of the time now??? Are all 4 pipe getting hot? ...sounds better than your earlier video. I would triple check all ignition wiring connections from the battery, through the ignition switch, handle bar switch, to the coils, and to your Pamco. Kinda sounds like a loose connection somewhere?

leesfer · « **Reply #29 on:** January 07, 2014, 09:47:49 PM »

Quote from: seanbarney41 on January 07, 2014, 09:11:07 PM

Are all 4 pipe getting hot?

Forgot to check that, I will tomorrow after work. Maybe I can feel which cylinder the backfiring is coming from with my hand on the pipe...

I will run it in the dark to see if I can spot any arcing from the wires, too

Could valves cause this if not adjusted properly?

leesfer · « **Reply #30 on:** January 08, 2014, 07:33:44 AM »

I'm going to turn the air/fuel screw back in a bit to lean it out and see if it changes the backfiring also

leesfer · « **Reply #31 on:** January 08, 2014, 08:46:24 AM »

One more video from last night when it was running way above idle and backfiring, kinda scared me a little when it happened as you can see haha

http://youtu.be/sm-AfW_paNo

lucky · « **Reply #32 on:** January 08, 2014, 09:04:29 AM »

In the video I see a possible problem.
The fuel line.
From the fuel valve it needs to be 3/8 then devide into two hoses 5/16,each feeding two carbs.

Get it to idle FIRST then move on.
You never did mention the needle position at all.
This is VERY IMPORTANT.

The needle with this set up needs to be one notch lower than stock to raise the slides upward. You CANNOT just get a bigger main jet and larger slow jets.

From 1/4 throttle to 3/4 throttle the carb is working from the slide position.
This is most of all the driving you will be doing.

lucky · « **Reply #33 on:** January 08, 2014, 09:07:08 AM »

Quote from: leesfer on January 07, 2014, 05:37:27 PM

I just connected the tank and let the bowls fill for a sec and checked them right now...

bowl #1 had slightly more than the others, #2 and #3 were identical, and #4 had slightly less than the rest... do they need to be EXACTLY the same amount of fuel? They are all carrying a good amount

No...Forget this.
The reason is, that by the time you remove the float bowl.. fuel was dribbling into the float bowl as you were removing it.

You have set the float height with a measuring instrument.
That is all you need.

leesfer · « **Reply #34 on:** January 08, 2014, 10:24:44 AM »

Quote from: lucky on January 08, 2014, 09:04:29 AM

In the video I see a possible problem.
The fuel line.
From the fuel valve it needs to be 3/8 then devide into two hoses 5/16,each feeding two carbs.

The needle with this set up needs to be one notch lower than stock to raise the slides upward. You CANNOT just get a bigger main jet and larger slow jets.

I had no idea about the needle position, I will pull the carbs tonight and change that. When you say a notch lower, you mean raise the needle up one notch, right?

Does someone have a picture or diagram of the best way to route the fuel lines? When I got the bike it had none so I did what seemed best but I am new to the CBs

leesfer · « **Reply #35 on:** January 08, 2014, 10:28:59 AM »

I have one more detail that I should have mentioned and maybe it is causing an issue.

My tank is from an older bike, I believe, and the petcock is the bowl type where there are two nipples coming down from it. Should I be running a 3/8 line from each nipple to two carbs? Or should I cap one off and split the line?

goldarrow · « **Reply #36 on:** January 08, 2014, 02:47:18 PM »

Changing clip position can be done with the carbs still on the bike. clip down one notch to bring needle up

LesterPiglet · « **Reply #37 on:** January 08, 2014, 03:30:42 PM »

Quote from: leesfer on January 08, 2014, 10:28:59 AM

I have one more detail that I should have mentioned and maybe it is causing an issue.

My tank is from an older bike, I believe, and the petcock is the bowl type where there are two nipples coming down from it. Should I be running a 3/8 line from each nipple to two carbs? Or should I cap one off and split the line?

If you have two outlets and two inlets use both.

leesfer · « **Reply #38 on:** January 08, 2014, 04:38:58 PM »

Just checked the needle and it's currently on the second one from the bottom already

Should I leave it there or still go one down?

cheftuskey121 · « **Reply #39 on:** January 08, 2014, 04:53:50 PM »

I don't have much input but am along for the ride. I had the same situation as you with my K1, I replaced everything on it with the ultimate coils and pamco, new plugs, new wiring harness, new carb internals, etc etc etc. I was fortunate enough to get it going great. I did have stock carb jetting, stock airbox, and stock pipes. thats about the only difference I can see. I wish you luck, it seems like you're going through the right processes to determine it. keep it up, hopefully it will be something silly.

how is your pamco wired into the harness? do you have the two green wires switched? usually it won't even start at all if they are reversed though...hmmm

leesfer · « **Reply #40 on:** January 08, 2014, 04:57:48 PM »

Haha funny you mention that because I went through a debacle with the pamco before so I known its 100% correct now, confirmed by Pete himself

cheftuskey121 · « **Reply #41 on:** January 08, 2014, 04:59:25 PM »

Quote from: leesfer on January 08, 2014, 04:57:48 PM

Haha funny you mention that because I went through a debacle with the pamco before so I known its 100% correct now, confirmed by Pete himself

good to know. I was a little stumped at first, but then I got it. when I put it on the second bike it was much easier. good luck brother.

leesfer · « **Reply #42 on:** January 08, 2014, 06:27:15 PM »

Okay, ran the bike for a little bit and it looks like cyl #3 is not firing, it is the only pipe from the header that stays cool

I checked the wire and it's definitely sparking, I checked the bowl and there is definitely plenty of fuel in it

Any ideas?

I am going to switch the plug between 3 and 4 to see if it changes things

LesterPiglet · « **Reply #43 on:** January 08, 2014, 06:29:05 PM »

Swap a plug from another to three.

pamcopete · « **Reply #44 on:** January 09, 2014, 08:40:26 AM »

leesfer,

I think I had suggested this before, but judging from the blackened condition of your plugs in the pic, I think you should change the plugs. Just because you are seeing a spark with them out of the engine doesn't mean they will work in the engine.

Also, have you had a chance to do a continuity check from plug cap to cap?

leesfer · « **Reply #45 on:** January 09, 2014, 10:23:27 AM »

Quote from: pamcopete on January 09, 2014, 08:40:26 AM

leesfer,

I think I had suggested this before, but judging from the blackened condition of your plugs in the pic, I think you should change the plugs. Just because you are seeing a spark with them out of the engine doesn't mean they will work in the engine.

Also, have you had a chance to do a continuity check from plug cap to cap?

I will change my plugs just to take that out of the equation.

I tested my coils back during my ignition fiasco but I will do a test plug to plug tonight when I get home.

I am just going to pull my tank off and go at the valves too just to confirm they are all adjusted correctly

lucky · « **Reply #46 on:** January 09, 2014, 11:26:39 AM »

Quote from: leesfer on January 08, 2014, 10:24:44 AM

Quote from: lucky on January 08, 2014, 09:04:29 AM
In the video I see a possible problem.
The fuel line.
From the fuel valve it needs to be 3/8 then devide into two hoses 5/16,each feeding two carbs.

The needle with this set up needs to be one notch lower than stock to raise the slides upward. You CANNOT just get a bigger main jet and larger slow jets.

I had no idea about the needle position, I will pull the carbs tonight and change that. When you say a notch lower, you mean raise the needle up one notch, right?

Does someone have a picture or diagram of the best way to route the fuel lines? When I got the bike it had none so I did what seemed best but I am new to the CBs

Yes...You will be raising the needle by lowering the clip one notch from the stock position.

Make the fuel lines direct, downhill to the carbs.

leesfer · « **Reply #47 on:** January 09, 2014, 05:39:24 PM »

We are getting somewhere!

I took it apart and checked the valves which all seem to be okay, maybe not perfect but definitely okay

I changed all the spark plugs and when I put it all back together I switched the #2 and #3 plug caps. I started it up and now #2 isn't firing instead of #3...

So it's obviously something electrical here. I checked the Ohms between #1 and #4, and then between #2 and #3 and they both read ~24.6

Is it possible for a coil to only fire one wire? What should I test or try now?

cheftuskey121 · « **Reply #48 on:** January 09, 2014, 06:27:22 PM »

you're using the "ultimate" coils with pamco right? I wouldnt think the coil could only fire one side...but put in new spark plug wire. if the problem persists, swap the NGK plug to see if the problem follows that plug. or you could do reverse order. in short, test each component for failure

seanbarney41 · « **Reply #49 on:** January 09, 2014, 06:29:49 PM »

+1 Tuskey

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Author Topic: It has a hard time starting, and when it finally starts it dies (Read 3048 times)