Help! Bike shuts down while riding

Hi everyone, first post. I own a 1978 650d that i have done a mild cafe conversion to. The problem I am having is that after about 100 miles of having it on the road, the bike will begin to have a "pulse" in power and than shut down. This usually occurrs around 10 to 20 miles into the ride. After the bike got back to my garage, I pulled the plugs and they are fouled. I originallythought it was due to weak ignition, because I'm pretty sure with the filter pods I have on the bike it is not running rich.(if anything a little lean without a rejet)

Anyway, replaced the coils with new emgo replicas, bike ran strong..for ten miles and shut down again. Fould plugs. New plugs(b7es) and points and condensor just installed today, and fired up and ran til idle correct without choke. Pulled plugs and all are clean except# 2(small amount of oil).

Is this the culpret? Would bad rings or seals oil fouling out in one jug cause all of them to carbon foul out. Do I just need hotter plugs or will this cause more problems in the other jugs? Any ideas or further steps? I'm just tired of pushing the bike back to my housemore than riding.

When you say fouling plugs, are they all black and powdery, or wet? Wet with gas, or oily?

If its black and powdery/gas wet, your too rich or ignition system is weak. Check to make sure the coils are getting 12 volts.

Is the jetting stock? Do you know what the jets are? What are the fuel levels while checked on the bike?

Cheers.

Oil fouling in one cylinder will not cause the others to foul.

Use the recommended spark plug only. A b7 is hotter. If you use alot of high revs/wot you could have overheating issues/ping.

One fouled plug will not make the bike shut down.
It will run w/ three. It will run rough, and no good power, but it should certainly get you home.
I dont think that the single fouled plug is the culprit.

When you "shut down" Means what? wont fire? electric is gone?

I would look at something heat related.

When you get it home, what do you do to get it restarted?

Battery fully charged? Alternator output been checked? Battery cables all clean and tight? Charging system in good shape?

Check your tank vent.

rsrcafe wrote:

bike ran strong..for ten miles and shut down again. .

I would check the gas cap vent for sure.

If problem persists, would also check valve clearances, which might be too tight and result in loss of compression when engine reaches normal operating temp.

Good Luck!

Are you pod clean no restrictions ? Do you oil them?

Bike will bigin to have rough pulse and as soon as you drop off the throttle, engine shuts down and will not allow you to start.
Do have all electrics and plenty of juice, just can't get it to run other than putting choke on full and even then it shuts right off after about 2 seconds.

Once I get home I pull plugs, all four are fouled and then I clean them again, and then its like groundhog day for the next short ride.
You bring up a good point about heat related though. When the bike would get me back and forth to work(40mile round trip) without any problems, it was 70 or below outside. I thought maybe cooler air it ran better with jetting as is. I pretty much ruled this out though because I did not bump up the jets, and the plugs are not white gray for a lean condition but black when the problem occurs. It is strange that the bike has shut down during days that are around 80 degrees.

Thanks for some of the info guys. I'll give you more info as I continue to trouble shoot on labor day. We'll see !!!

So. You ride, it fails, you push it home. Then it won't start until you clean the plugs?

After you clean the plugs it starts up? That doesn't seem right. They can't be that fouled, i've ridden my bike on the worst fouled plugs in the world. I can tell the diff when i change them out, but it should still run crappily.

Have you left it to cool completely down then tried to start it?

Also, next time it does that, pull a spark plug and turn the engine, see if you are getting a spark, if you are, then the plug fouling probably is a side issue.

I am not sure if the bike has a vaccume petcock, but if it does, check the vaccume line. Is it connected to the right port? Are there an cracks in it?

I pulled the tank yesterday and connected the vent host to the vaccume line, it started and ran very poorly and would die if the choke was closed or the throttle was opened.

After reversing the lines the bike ran beautifully.

KR