700 preignition backfire?

[sagerider]

Hi, posting this for a friend. Though I am somewhat familiar with this sled.

2000 ZR 700 (Green) carbed.

Carbs, super cleaned.
Air box, super cleaned/clear
Fresh gas

Sled fires up, idles okay. With any throttle at all it starts puking back through the carbs. WTF?

Sled used to be mine. I had nothing but trouble with it, and when it did run I would always find a tree to break it on. It started this backfiring business at the first of last season and got put away until buddy bought it and start cleaning on it. Prior to that sled had new top end (less than 200 miles) which, if I remember right, was one new jug and both pistons.

What could this be?

 

[Mr. BB]

Hi, posting this for a friend. Though I am somewhat familiar with this sled.

2000 ZR 700 (Green) carbed.

Carbs, super cleaned.
Air box, super cleaned/clear
Fresh gas

Sled fires up, idles okay. With any throttle at all it starts puking back through the carbs. WTF?

Sled used to be mine. I had nothing but trouble with it, and when it did run I would always find a tree to break it on. It started this backfiring business at the first of last season and got put away until buddy bought it and start cleaning on it. Prior to that sled had new top end (less than 200 miles) which, if I remember right, was one new jug and both pistons.

What could this be?

Best case senario.
Throttle position switch could do this. Cable would need adjusting. I have a 99 ZR700 and this happened 1st trip out when new. I would check this 1st just going by what you said about the "any throttle at all it starts" etc. Could be other things, but this would be a good place to start, should be an easy fix. Can't tell you how to adjust this though. If there isn't any play in throttle lever that would be a tell-tale sign. Hope this helps.