yup...small stumble.

Alright, condensers on. Huge improvement in starting. It was a horrible machine to start when i first got it. Of course it has the starter issue, so you have to kick. As i slowly got it back to stock airbox etc it got way better, but still a bit of a hoor when cold. Now i can 4 kick it from cold, 8*c in garage. Huge difference in idle, it will idle way down and run smoother now. Throttle response from isle feels alot better now too. Havent taken it for a ride yet, but here hoping. Points are on the way, mine are pitted a bit so i used my points file and some contact cleaner. No more sparky for now.

Ill update again once its warm enough to rip er.

While you're in there,make sure the advancer is working properly.It should twist and snap back cleanly.If not,take it appart and clean and lube it.Remember,the advancer springs are 35 years old. A TON of 750's have this stumble between 3250-4000 rpm.Mine included.I've come to the conclusion that the advancer springs have just gotten weak,and are advancing the timing to soon.After 4250,no problem.If somebody could replicate the advancer springs,they would make a BUNCH of money!!!!

Thats was the first thing i did when i got it was check and lube advancer. All works. Timing does what it should with the timing light. My TX650 has the same predicament involving the Advancer and springs. I did buy an electronic ignintion for it but it requires the mechanical advance. So a combo of a new a little to stiff spring and an older not as stiff one and voila. smooth advance. Although the guy who makes the PAMCO ignition came out with a digital advance this year so i may ditch the mechanical advancer.

Took it for a ride, idles a lot better. seems to really like 1400rpm so thats generally where i leave it. Starts easier. Still a bit of stumble, but it seems alot better than it was. Seems like they dont like agressive throttle where im feeling that stumble. I can roll through it. But its running great and as far as im concerned as good as it's probably gonna get till i can put a Boyer or Dyna in it. Been through the carbies a million times and did the WG coil mod. All new manifolds and box boots. Plus new coils/caps/condensers. Points are coming.

Next winter it gets some new paint and a from scratch wiring harness. Probably check my lash too while its apart.

Well, back again. Stumble is still there, idle is improved cause of condensers. Plugs are tan except plug one. fouled. Found and ultra clean set of vm26 on egay for 70 bones, 8 hours from me not even gummed. Factory paint still on sync screws. Even the air screw only 26's like I have. So, gonna rebuild the the minty rack right from ground up. then have a spare set for plungers etc. Plus...now I might as well double check the ole LASH while im busy..

When going through your carbs, are you setting the Fuel Level with the Clear Tube Test? Fuel level is very important to proper function of all the carb circuits.
I'm sure you checked the needle clip position on the jet needles as well?
Air jets in the Air Horn/ bellmouth clean UN-obstructed?
vacuum sync performed?
Then of course there is always the mechanical, hows the compression balance?

Sync is good. All very close together on the guage. 1/8 difference at most. Floats set with clear tube method. The first two times i had the carb off last year i did use cleaner and air. cleaner flowed through all passages. Im figuring choke pad on that carb. Needes are all in same position. Positive i checked the bell mouth. I always spray and air and poke every freaking hole in carbs when i do them...emulsion tubes are clear too. Even did new pilots.

Did it have the stumble before you installed the new pilots? Ed

Yup. Did it since i got it. im really.thinkin choke plunger on that cyl.

I have this same problem...I read that one guy had a bad spark plug cap and it was fixed by new wires.

New caps. Coils and wires on mine. And second set of plugs. Its still sparking. its just fuel fouled

CDNTX650 wrote: ...Stumble is still there...Plugs are tan except plug one. fouled...might as well double check the ole LASH....

If carb has a side-located pilot air screw, turning the screw on carb #1 should produce a change in idle rpm. But if not, there's usually something still wrong inside the carb (likely an imperfect pilot circuit that's incapable of providing the optimal air/fuel mixture, for whatever reason).

Would also re-examine condition of the pointed end of the adjustment screw.

That's a good idea about re-checking the valve clearances.

Good Fortune!

Thanks for all the great advice. The new set i have looks almost as clean as the set on the bike. So im ready to do another bosy up carb rebuild. I had to do my bs34s on my tx that way including new throttle shaft seals. Patience always prevails.