3000 RPM Cough

[rickmc2000]

I have a 1978 XS1100E that I am restoring. I have replaced both coils, the TCI box, de-rusted the tank, rebuilt the petcocks and carbs, fixed a broken pick-up coil wire, cleaned the connectors, replaced the sparkplugs, balanced the carbs, new battery, replaced the rectifier/regulator, and she starts good, idles good, and runs like a bat out of hell, above 3000 rpm. At 3000 rpm give or take a hundred, it coughs, sputters, chokes, and acts like it's gonna die. Open it past 3000 and you better hang on. Compression is good, but plugs are very black. Needle valves are at 2 turns out. They drop RPM slightly going in but have little or no effect when backed out. AIr filter is a K&N, everything else on the bike is original. ADded in line fuel filters. So what am I overlooking? I did not change the jet needles cause I didn't have a set of snap ring pliers to reach the snap ring. The needles do have a worn spot about half way up, like they have been rubbing on the side of the jet tube. That's all I can think of. Any help would be greatly appreciated.
Rick

[andreashweiss]

I have tried to help rick on the phone, carbs are not my best topic. I told him to ask th guru's on the list who really understand carbs, come on guys help him out please. He wants to ride not wrench. andreas

[prometheus578]

"HHmmmm...."

I've never experienced it, but that 3,000 RPM stumble sounds like there may be another break in the pickup coil wires.
Sounds carb related, though.
What kind o' exhaust system does it have Stock... aftermarket?
What size main jets are you runnin'?
Need to bring it to the Rally at Denny Z's in two weeks so we can have a look-see.

[randy]

rickmc2000

You indicated that you re-built the carbs. What exactly did you do?

What is your float setting?

Did you remove the pilot jets and clean out the orifices and carb body passages?

Sounds to me like it's starving during pilot-to-part mains transition which may indicate clogged pilots.

Could also have a vacuum leak at a manifold. Are vacuum hoses correctly connected, no breaks?

Plugs are very black how? dry like over-rich fuel mixture or oily like you're burning oil?

[Cyrock]

When I put on my K&N filters I had to adjust the jet needles. Move the clip one notch richer (clip moves down to lift the needle higher) or on the 78 carbs add a washer. You shouldn't need snap ring pliers to do this.

[mro]

I'd re-check float height and see how it runs with pilot screws closer to 1 1/4 to 1 1/2 turns out.
_______
Only one pick up coil wire was broken?


mro

[rickmc2000]

Originally posted by mro
I'd re-check float height and see how it runs with pilot screws closer to 1 1/4 to 1 1/2 turns out.
_______
Only one pick up coil wire was broken?


mro

Thanks for the reply. The front coil had previously been repaired. I fixed the back coil. Both checked good with ohm meter, even when pulling on the wires.

[rickmc2000]

Originally posted by randy
rickmc2000

You indicated that you re-built the carbs. What exactly did you do? replaced all jets, pilot valve and needle in bowl, and needle valves. Cleaned a lot of junk out, even steam cleaned. Cleaned all passages, etc.

What is your float setting? One Inch measured, level just below top of bowl.

Did you remove the pilot jets and clean out the orifices and carb body passages? Yes

Sounds to me like it's starving during pilot-to-part mains transition which may indicate clogged pilots.

Could also have a vacuum leak at a manifold. Are vacuum hoses correctly connected, no breaks? Carb Mounts are new with gaskets. Torqued to 7 foot pounds.

Plugs are very black how? dry like over-rich fuel mixture or oily like you're burning oil? Dry black.

[rickmc2000]

Re: "HHmmmm...."

Originally posted by prometheus578
I've never experienced it, but that 3,000 RPM stumble sounds like there may be another break in the pickup coil wires.
Sounds carb related, though.
What kind o' exhaust system does it have Stock... aftermarket?
What size main jets are you runnin'?
Need to bring it to the Rally at Denny Z's in two weeks so we can have a look-see.

Exhaust is four to two, stock I think. Main jet is 137.5. Where is Denny Z's?

[Ken Talbot]

Deny is near Olympia. Check out the thread in the rallies section about a PNW meet/rally there in August. PNW rallies have a bit of a reputation for having a 'tech' component.

[petejw]

does the splatter happen
both when cold and warmed up
or one or the other, i had a stumble
at around 2500 but only when warmed up
but not when it was cold, it was running to rich.
i leaned out mixture screws problem went away.

tho at 3000 is usually the crossover point from
idle jet to needle jet. if ur needles are worn
u could try leaning them out a bit if u didnt want
2 replace them.

[rickmc2000]

3000 RPM Blues

Originally posted by petejw
does the splatter happen
both when cold and warmed up
or one or the other, i had a stumble
at around 2500 but only when warmed up
but not when it was cold, it was running to rich.
i leaned out mixture screws problem went away.

tho at 3000 is usually the crossover point from
idle jet to needle jet. if ur needles are worn
u could try leaning them out a bit if u didnt want
2 replace them.

Thanks for the reply. The problem does get much worse when the engine is warmed up. I changed the needle jet pins yesterday. The old pins were worn and the clip was set two notches from the bottom, (one notch rich). A little better now but not much. I did notice that the resistance on the pick up coils increases to about 800 ohms when warm. Gonna check the clearance on the pick-up coils too. Guess if the spark is weak it will act like it's rich and smoke up the plugs also. I found a section in the manual abour cam chain adjustment, so I'm gonna set that today.

[petejw]

It still sounds like shes running rich,
try lowering the needle, by raising the
clip up 1 notch from the middle,
have u checked the plugs?
are they black and sooty?
r u running the original air box or pods?
wat fuel levels r u running?
try and get ur carbs right first b4 mucking around
with other stuff, itll make life a lot easier for you in the long run.

[rickmc2000]

Originally posted by petejw
It still sounds like shes running rich,
try lowering the needle, by raising the
clip up 1 notch from the middle,
have u checked the plugs?
are they black and sooty?
r u running the original air box or pods?
wat fuel levels r u running?
try and get ur carbs right first b4 mucking around
with other stuff, itll make life a lot easier for you in the long run.

Thanks, I'll moving the clip up. Plugs are black and sooty. Yes, running origibal air box with a K&N filter. Fuel levels are at gasket level.

[rickmc2000]

Originally posted by rickmc2000


Thanks, I'll moving the clip up. Plugs are black and sooty. Yes, running origibal air box with a K&N filter. Fuel levels are at gasket level.

I think it worked. I moved the needle clips up another notch, (two higher from where I found them). Started the bike, balanced the carbs, and she purrs like a kitten, no a lion, quiet idle, but roars down the road without a cough. OK, I'm excited. I was getting frustrated and about ready to give up. Thanks very much for the great advice. Rick