Engine miss at highway speeds........FIXED!

[elslimdiablo]

I checked the 1500 coils themselves , they both checked in at 14K ohms each. The new wires were under an ohm each and the caps were all just under 5 ohms (4.98). I figure that my meter isnt perfectly accurate, but that gets me into the ball park. When I get back into it, I'll check my pump first as that is the last unknown part of the equation. If that isnt it, I'll see if I can get that ignition resistance down with some new coils.

[ericheath]

I believe that with more than half a tank of fuel, the bike should run fine without a working fuel pump.

[elslimdiablo]

I kinda thought that too. But I think that with the carbs up with the center line of the tank that fuel will reach them but not with enough volume to keep the bowls supplied at speed. (just my thoughts, Im probably wrong)

[Sagebrush]

Does running on reserve make a difference? Maybe a bad petcock. How about the fuel filter, if partially plugged it could cause your symptoms. I've seen a fuel filter on a 1500 cause your exact symptoms.

[elslimdiablo]

It doesnt change when in reserve, I rebuilt the petcock last weekend. Same issue before and after. The fuel filter is a Randakk unit and I've had it apart recently to check for a restriction. When I did the petcock I also renewed all the fuel lines.
It really does seem to be a fuel issue. I wish I had the time this weekend to open up that fuel pump.

[KYpondman]

Check the float valve filters as a really fine sediment can pass through a 40 micron filter and partially block that filter, starving one or more cylinders at speed.
Claude

[82aspy]

lucky me, just a miss in top gear low RPM pulls ..so far

[robin1731]

It doesnt change when in reserve, I rebuilt the petcock last weekend. Same issue before and after. The fuel filter is a Randakk unit and I've had it apart recently to check for a restriction. When I did the petcock I also renewed all the fuel lines.
It really does seem to be a fuel issue. I wish I had the time this weekend to open up that fuel pump.

What about the internal fuel lines and screens in the tank?

.

[elslimdiablo]

The tank was nearly empty when I did the petcock, so I pulled the sender and checked that. I shot some air back through the lines from the petcock mount and did not get anything but gass and bubbles through the screens. Both times when the carbs were out, I stripped the carbs all the way, including the new float valves, seats, and screens. All was good.

[82aspy]

The way you describe this it does not come on immediately and stays until you stop or until you shut down for a bit??

everything fine until operating temps top gear low RPM pulls ..then

This only happens when I get the bike moving at highway speed (rpm from 3500 on up. ) If I am winding around back roads I have full rpm range without a problem. I'm kind of leaning towards a fuel starvation issue at steady middle rpm range, but what throws me off is that once it starts doing it it will continue to do it at lower rpms until I shut it down.

[elslimdiablo]

Finally had a little time to check the fuel pump. Pressure while cranking is nearly half of what it should be and drops off to near 1/2 a pound with running at any rpm. Fuel flow is a little hard to measure as it immediately starts coming out when the petcock is opened up. It is getting what it needs, just no pressure to keep up with demand. I'll pull the pump apart sometime tomorrow and look at the check valves. *Note* there is no fuel leaking out of the weep hole.

[82aspy]

good to find that prob but just in case you don't know, when the tank is full, the engine will run normal without a fuel pump, with forget the amount but guessing a gallon or so

[77Gowing]

This is for what it's worth.
Some capacitors begin to break down when they get hot. I had a Van when I was 19 and it would start just fine and run great until it came up to operating temp, then it would miss. This happened after a tune up and I had put in a new condenser (capacitor). I put the old cap back in and the problem went away.
Later on I had a 68 Caddy with a 472 ci engine. It ran great for many months then one summer after I was driving with engine up to temp she started missing and back firing. My dad came to my aid and told me it was the condenser. I did not believe him, till she backfired and blew the exhaust system off the car. I went to the auto parts store, bought a new condenser for $5, put it in and she ran like a kitten. Then I went back to the parts store and had to buy a new exhaust system.

Not saying this is your problem, just suggesting you check if you are running points.

Good luck!

[elslimdiablo]

I took the fuel pump apart and found the check valve from the pump to the carbs leaking pressure back into the pump during the suction stroke. I pulled the valves and cleaned the seats. This slowed the leak down and brought the pressure up, but not enough. Interesting enough, while pulling the pressure gauge off the shelf, a small box of ignition parts fell off the top shelf and little parts scattered all over the bench. When I looked down I saw a shiney new condenser laying there. I went and looked at the wing, at some point I took that new one back off and put the old one back on. I think it was when I first stated having coil problems when I had the engine running for the first time. I swapped them out, now the bike starts right up and has a pretty immediate good idle. I havent taken it out yet as I want to still replace the pump. I'll let you know how it goes.

[Whiskerfish]

Sometime it is better to be luck than good