Problem with a Royal Enfield? It's simple

 Online motorcycle forums are great places to learn about vintage motorcycles, and get advice curing them of occasional ills. 

The owner of a 1970 Royal Enfield Series 2 Interceptor issued once such challenge recently to members on the REInterceptor forum. 

"I took it for a ride today and all is good... until I get to high RPMs. That's when it starts cutting out. The tank is clean and petcock filters are clear. Filters on the bottom of the carbs are clear. I have new plugs and coils. I have never replaced the coil to plug wires. Any other ideas?" Jim wrote. 

I was amused that almost the first response offered was the time honored suggestion for curing all Royal Enfield ills: 

"Check that the fuel tank cap vent is not plugged." 

If only life were so easy. It's worth checking, but I am pretty confident this is never the cause of problems. How would the vent have gotten plugged? 

More complex advice started coming fast.

Cutting out misfire. Typically a sign of lean mixture; what main jets are you running? What plugs are you running? What is high rpm?

"There are fake spark plugs that will not give a good spark at high rpm, so first thing, put your old plugs back in."

Has fuel changed to E10 in your neck of the woods? Is the fuel more than two months old?

Gas starvation? Did you fit new petcocks/gas taps? Are you turning on both taps?

Could you have counterfeit spark plugs?

The owner dutifully checked all these things. He replaced the gas, double checked the plugs, double checked the points, opened both taps, checking wiring, and on and on and on.

Then he found the real problem.

"The problem was the choke lever. Oh My God. The lever was wandering back to a point where it was semi choking the engine. So I tightened the screw and went for a ride today. And all is good. The (bike) goes like a scalded ape!"

Did the forum members feel cheated? Did they resent being bothered with a simple problem?

Not a bit of it.

"That's great news," one member responded. "Some things can drive you crazy."

Problems with your vintage motorcycle? Try the forums. You have friends out there.