Big port 4age popping through carbs at idle

[Teamsdmf]

Alright so over the weekend my car just stopped running I thought it was my hei module I had rigged up to act as my ignitor so I pulled it and installed a msd 6a and some new yamaha r1 carbs I got it all fired back up but now at an idle it backfires through the carbs and doesn't want to stay running but when I give it gas runs fine so I thought maybe coil going out so I replaced it with an msd coil and also got some new plugs and wires and cap and rotor still backfires I went as far as replacing the pickup inside the distributor with a new one I had still backfires I have totally replace the entire ignition system and the fuel system all filters everything but the tank and lines still backfires so only thing I can think is maybe bent valves or valves not seating I also checked the timing and everything was spot on what you guys think? Any help is much appreciated and needed lol if I got to rebuild this thing I needed to know soon

[dr.occa]

Jettings are off, too much advance, fuel pressure is off, idle mixture is set too lean...

[Teamsdmf]

Jetting is the same as gsxr carbs and it ran fine with them well up until it just stopped running that is timing is as 32 degrees fuel pressure is as 1.5 psi which is about perfect for bike carbs I got one more thing I want to try and if that dont work the heads coming off

[Teamsdmf]

i figured it out thanks to the DOCTOR. it ended up being the pilot fuel jet was smaller then what i was told in the carbs i replaced them with the ones out of the gsxr carbs (they were bigger) i was running and popping went away!!!
thanks dr.occa you were right about the lean idle mixture thank god i decided to double check the carbs instead of pulling the head lol runs way better, now i just have to get a longer throttle cable or rig something up since the r1 carbs have the throttle linkage in different location

[dr.occa]

Good deal. Glad it was something easy and inexpensive.

What are your jets for the R1 carbs and the specs on the motor?

[Teamsdmf]

The main fuel jets were drilled out to 1/16" and the pilot fuel jet are 12.5 thats just what it says on the sides of them lol the the air jets are stock untouched from the r1 for ignition it was setup with an hei module to fire the coil and it ran great but I recently changed over to a msd 6a and timing has always been static at 32° other then that and an obx header and 2" home made exhaust straight into a $30 ebay muffler its stock with the exception of the intake of course...... when I bought the motor it had been sitting for two years I got it put new plugs, oil, oil filter, cap and rotor hooked the carbs up didnt even touch the dizzy location, primed the carbs and she fired on the first try no problem and ran quite smoothly I was surprised lol reset the timing and took her for a spin other then a few oil leaks from sitting everything went smooth and had a whole hell of alot more power then the old 4ac lol mainly in higher rpm range

[dr.occa]

Interesting - 1/16 (1.58mm) is equivalent to a 155 (dcoe/dellorto or solex/mikuni) drilled out to just under a 160. 160 mains is really rich for any stock 4AG 16v at any altitude. I'm curious as to what a sniffer would tell you on your setup. What size air correctors are you running?

What size pilot jets WERE in when you were getting the popcorn? 12.5 is even on the lean side for GXRs.

[Teamsdmf]

the carbs arent like a dcoe or solex there are four individual ones one for each cylinder you also have to remember these dont have power valves or anything of that sort like the dcoe have. Im also lucky i dont have any emissions stuff i have to deal with where i live and as far as the air jets/correctors they are stock i cant tell ya right now as i am at school but ill check when i get home tonight..... the pilot jets that were in there said 15 on them but they didnt flow as much as the 12.5 (the 12.5 had a bigger hole for more fuel) the carbs i got are the ones in the picture

[Teamsdmf]

the air jets are 120