Saracen exhaust running HOT

[peter clemmer]

Well, I tried the tape and IR test. After idling it at about 1500 RPM for several minutes. Hopped out and ran the IR. the temperature was pretty even all along the pipe. The tape didn't show a hot spot either.
Went back and tried to run the engine faster. Can't seem to get it much over 1500 Rpm, just tries to stall. shut the engine off and went outside and both the tires were burning pretty good and the grass below and between the tires was pretty scorched. I had a garden hose handy and put it out. There must be something like a flame thrower effect going on. I didn't run the motor for much more than 4 or 5 minutes.
Got any ideas on this one?
Peter