so I am on a different carburetor now, a Demon 525 vac secondary.



when accelerating, the vac secondary seem to open for a split second causing stumble. is this a normal operation for this type of carburetor? i dont think this happend with my holley.



the only way i am getting it some what drivable is to adjust the accelerator pump cam with one that give a big shot a beginning to cover up the secondary opening. am I going it the correct way or is there something else i need to fix on the carb?

Holun,

          If it is a vacuum secondary it will have a diaphragm on the rear of the passenger side of the carb. It will have a removeable top and springs. Stiffer springs will slow the opening. If it's not new, but "Modified" by some expert, go back to the original spring. That will normally solve the problem.

Frank/Rebop

Bristol, In ( by Elkhart) 

I just put a stiffer spring in it yesterday, but its still doing it. I got most of the hesitation out today by playing with the pump cams, i am on the green one with a sharp angle on #1 hole. I am going to order some bigger nozzle and see if that will cure it.

Hello; The company that made your carb wants its customers to be happy. They origionally made that carb to work well out of the box. Someone has 'IMPROVED" it to the point that it is a piece of crap. Call the tech line of the manufacturer and find out how it was when it left the factory. They spent a lot of time and money to make it work and work well. Start with what they started with. Then if it don`t work go from there but don`t wing it. Bad move. Pete

Holun,

        At this point I'd check float levels and make sure the correct metering block and or jets are installed. Carefully inspect the gaskets and make sure there's no air leaks. Make double sure all the unused vacuum ports are closed/capped. You might try blocking off the secondaries with a rag or tape to sure the issue is in the secondaries. I'd check the fuel passages to the secondaries carefully now also. The thing that bothers me about your description is that by the time the secondaries start to open any pump shot you have is long since history. This sounds to me like a primary side lean issue. Low float level, leak in the metering block gasket, Vacuum leak, plugged accel pump passage or shooter.  

Frank/Rebop

Bristol, In ( by Elkhart) 

As Frank mentioned, float level is important on the Demons as the float level dictates the rpm that the fuel is actually picked up in the main fuel well.  With that said, the level being in the middle of the sight glass is a good baseline.  The secondary float level is important also as there is also an idle circuit in the secondary side of the carb.  Whether that particular circuit is 'fixed' or adjustable depends upon which model carb you have.

Don't forget the ignition timing also.  The Demon carbs are partial to more ignition advance at idle due to the leaner fuel circuitry and this is a player when accelerating.  Advancing the idle ignition timing may require shortening up the timing lead in the distributor to keep from having too much total timing at rpm.

Lorena, Texas (South of Waco)

I got the road demon jr, 525, i dont see any screws on the secondary side for idle, float level is at 3/4 full on the sight glass, advance is at 14degree BTDC, i am going to check for vacuum leaks and blocking off the secondaries to see if it is really the seconday's problem this weekend.