RMK 700 carb question

[yz400ex]

Finally got my brother in laws sled out and running last night.. Idles great and overall runs very good, but right off idle it has a back hiccup.. It will backfire real bad and then take off.. This seems to be just off idle or if you are just going pretty slow and hit the gas hard.. Havent done a plug read on them yet.. Just wondering what anyone thinks this may be caused by and how to correct it..

 

[skis_n_skid]

Have you pulled the pilot jets to check/clean them? I had similar symptoms and cleaning the pilot jets solved the problem.

 

[yz400ex]

No, I changed the mains, but didnt change anything else or check them since the sled was running fine for the most part..

 

[skis_n_skid]

What year is it? Does it have round slides or flat slides? If if has flat slide carbs with fuel screws then you might just need to back out fuel screws a little bit. If it has round slide carbs, clogged pilot jets are a common ailment.

When you changed the mains, did you re-jet to larger/smaller mains?

 

[yz400ex]

The sled itself is a 99, but the carbs are from an 02 so they are better carbs and are the rack style with flat slides.. When I changed the jets, I went bigger with the mains, due to the addition of twin pipes.. They are PSI.. PSI said to leave the needles and pilots alone so only the mains were changed..