popping from carbs

ive been trying to figure out this popping i have from the carbs, 4cy 80 kz750, havent had bike very long, has pods and short exhaust. seems to run shitty at very light throttle and has this poppy, cough, backfire like through the carbs at a very light throttle.

i have cleaned the carbs and went over the ignition, both look good.

what i notice is that when i have the choke on, it goes away. would this tell me that its lean thus be the cause of the popping??? i have not removed the pulgs to the a/f mix screws.

pops with stock jetting and 70 140

Yes, it will run like crap. This should not come as a surprise. You have a bike on which someone without a clue cut off the exhaust system and installed pods, plus the bike has CV carbs. It will always run poorly (if indeed it runs at all) with that combination and stock jetting. Your choices are clear to me. Either put the correct air box, air filter, and exhaust system back on the bike OR prepare to become intimately familiar with those carbs. You may want to do a search on this site using the word "pods" and the search option "Any Date." You will find there has been an enormous number of discussions (see below - 8,730 postings!) on the subject. See if you can find one of them that shows what jetting combination works on your model bike. Ed

when i have the choke on, it goes away. would this tell me that its lean thus be the cause of the popping???

thats what i really want to know.

i do believe that it can run well with tuning

objec123 wrote: when i have the choke on, it goes away. would this tell me that its lean thus be the cause of the popping???

thats what i really want to know.

i do believe that it can run well with tuning

If you don't take 650ed's advise , & believe it can run well with just tuning
all I can say, is good luck, :laugh: :laugh: :laugh:
Pete

My 1980 kz750 E1 has run very well with K&N pods, a MAC 4 into 1 exhaust and the same jetting - 70 primary and 140 secondayry mains and with the air mix screw either 2 or 3 turns out - cant remember exactly - so yes its possible.

I would suspect that the short exhaust is for the most part the cause of the shitty running.
Some things to watch out for -
when cleaning the carb be sure to poke every oriface with a bristle or wire and blow out with compressed air. be very thorough. Pay special attention to the pilot circuit - there is a grea diagram in the factory manual mbsween.bike-night.com/kz750l3/manual.html
Check carb diaphragms for holes.
Some pods will obstruct the air jets ont the air side of the carbs. Compare inside of pod to carb
When I have had spitback through the carbs at low speeds and idle this was caused by poor sealing of the rubber carb boots to the engine . They should go on dry but I found I needed to use threebond 1194 to get a proper seal. Although I had spitting I didnt have "shitty running" .
Good luck

thanks.

i think i narrowed it down to just the far left cylinder. is that 4? the spark plug is dry an black, other plugs look same and normal.

ill check that intake boot also

As you are sitting on the bike and looking down at the engine the cylinders are numbered 1 - 4 from left to right. Ed

i removed and checked the intake boot, looks good. resealed it to head. cleaned carb again and blew air through ports, all clear.

i may try a compression test tomorrow, starting to think its inside motor. wtf

Get a manual, adjust the valves and other maintenance items.
Steve

Just replaced my holders. New ones cost less than $100.
Steve

swest wrote: Just replaced my holders. New ones cost less than $100.
Steve


To abuse a phrase..."what difference did it make?" :ohmy:
Dave

objec123 wrote: pops with stock jetting and 70 140

If that's pods with stock jetting, I'm surprised you can even ride it. Will run terribly lean.