KZ750H Return to stock exhaust? Or rejet carb?

Ok, looking for some advice. I have a 1982 KZ750H LTD 4 cylinder. It was sitting for 4 years and I have been waking it up. Carbs are fully cleaned, all pilots, jets, ports have been cleaned and double checked. All pilots and jets are stock. Engine mechanicals (compression, timing, valve clearances) are all good. Carbs are sync'd. Starts and idles well with the choke on. Revs with the choke on. Turn choke off and it bogs off idle, and when I do get it to rev, it slowly returns to idle. I've played with the idle mixture and have had them turned out as far as 4.5 turns.

It has the stock intake airbox on it, but an after market exhaust. Judging by pictures I can find, I believe its a MAC turnout style 4 into 2. Baffled, but significantly louder than a buddy's GPZ750 with a Kerker exhaust.

We pretty much have it narrowed down to the engine is running way too lean due to the exhaust system. So I have 2 options. Find a factory exhaust system and return it to 100% factory. Or get a DynoJet kit and rejet the carbs. DynoJet would probably be cheaper, but may result in additional putzing when I just want to ride before it gets cold out.

What say the masses? Is this the right direction to head?

Your carbs are still clogged up. Re-clean them and pay extra attention to the little passageways in the carb bodies. Make sure they are clear.

100% certain that carbs are not still plugged up.

Yes they are. Running only on choke is the symptom of clogged passageways. Most people take the float bowls off, take out the jets hose everything down with carb cleaner then put it all back together and call it good. That won't work, I takes me about 4 hours to properly clean a set. And sometimes it takes more than one cleaning to get it done especially on a set that is really nasty.

Everything I've read so far is about how the bike performs at idle. My question is how does it perform on the road? At 1/4 throttle? At 1/2 throttle? At 3/4 throttle?

If you have fuel/air screws, turning them out means more air and less fuel, which is the opposite of what you want at idle. In any case, out 4.5 turns is excessive. Your problem is not your exhaust...it's somewhere else.

Yes, problem is elsewhere, are your carb boots sealing properly, and are the vacuum stubbs all capped, put the air screws back to factory settings after you have sonic cleaned the carbs.

Sorry for the delay in a follow up guys. Ended up pulling the carbs completely back off the bike intending to replace with pilot jets with a set 1 size larger and also install a Dynajet kit. Turns out the pilot jets I ordered were the wrong ones. So instead of spending $100 on a set of the correct jets, I ended up picking up a micro drill kit and started out just planning to drill the pilot jets a size larger. Turns out they were still partially clogged.

Drilled them to the factory size and installed the Dynajet kit. Reinstalled the carbs and put the bike completely back together. Bike fired up on the first try. No choke needed. Idled nicely, and revved nicely. Adjusted the idle needles (still need some more adjusting I think) and have put 72 miles on it since. Longest ride so far was 13 miles. Very happy with how it performs and slowly getting used an engine that likes the RPM's as opposed to the low-rpm, high torque I'm used to. (trucks)

Thanks again to everyone for the assistance. Hoping to get just 28 more miles on before the bike is parked for the winter. Not looking good. Rain forecasted through the weekend, and cold temps after that. Winter is quickly approaching here in Minnesota. But doesn't mean the riding season is over. My father-in-law has successfully rode his Valkyrie at least once around the block every month of the year.

Seth82KZ750HLTD wrote: Sorry for the delay in a follow up guys. Ended up pulling the carbs completely back off the bike intending to replace with pilot jets with a set 1 size larger and also install a Dynajet kit. Turns out the pilot jets I ordered were the wrong ones. So instead of spending $100 on a set of the correct jets, I ended up picking up a micro drill kit and started out just planning to drill the pilot jets a size larger. Turns out they were still partially clogged.

Drilled them to the factory size and installed the Dynajet kit. Reinstalled the carbs and put the bike completely back together. Bike fired up on the first try. No choke needed. Idled nicely, and revved nicely. Adjusted the idle needles (still need some more adjusting I think) and have put 72 miles on it since. Longest ride so far was 13 miles. Very happy with how it performs and slowly getting used an engine that likes the RPM's as opposed to the low-rpm, high torque I'm used to. (trucks)

Thanks again to everyone for the assistance. Hoping to get just 28 more miles on before the bike is parked for the winter. Not looking good. Rain forecasted through the weekend, and cold temps after that. Winter is quickly approaching here in Minnesota. But doesn't mean the riding season is over. My father-in-law has successfully rode his Valkyrie at least once around the block every month of the year.

Congratulation, a good feeling