I have a '98 Heritage Springer with an EVO carbed engine that I bought new.
Low mileage (under 10,000) and it has been pampered from Day 1.

This bike sits a lot (as you can see by the mileage) and I've had to remove the carb and and clean it out a few times and I always make sure it has fresh fuel in the tank before putting it away for the cooler months.
I've never found anything in the carb when I've disassembled it for a thorough cleaning so I'm assuming () that it was just "gummed up" being that all of our gasoline here has 10% ethanol.

I got the bike out this year and it starts great and pulls great but at a constant speed/RPM it has a "flutter" in the engine with a noticeable small surge when it's going down the road.

A couple of years I ago when I had the carb off for cleaning I installed new intake seals and there and the old seals had no visible faults.

I've just put about 75 miles on the bike so far this year and I just filled the tank with fresh fuel and added a few ounces of carb cleaner to each tank to see if that helps with the surging. I'll put a few more miles on the bike before I clean it and out it away for the winter. If not, I think I'll pull the carb next year and take it to the shop and let them see if I've missed something.

 

i would guess it is in the transfer circuit. these are very small holes and can easily get screwed up. if they become corroded and change, the thing is a paper weight.

 

The first photo is of the ports where the low jet feeds. Each tiny hole (4 of them) will flow as much as a big size slow jet. However, if any one of those are plugged, it won't act right.

It takes a tiny piece of wire to get in them and they are very shallow. Difficult to get anything in there to blow backwards. If you have an air blow gun with a removable tip (1/8 npt) you can get a "street L" at any hardware store that is a short enough to do it. Best to prop open the butterfly with something soft. A wooden clothes pin works good.

In the end - with the butterfly open, low jet removed and holding a finger over the bore for the low jet, spraying fluid into the low air port in 2nd pic, you should see a strong stream blowing out each of those 4 holes. The idle mix screw should be seated while doing this. If it still has the factory tamper plug, you can still do it but also look for fluid out the 5th hole closest to manifold. Flow there will be minimal.






Only other thing that will cause one to "hunt" or surge at even throttle is a pinhole in the slide diaphragm. This is assuming the carb is stock and the slide spring has not been changed or modified and the slide vacuum port has not been drilled out.

 

Thanks guys for the suggestions.
I think I'll order a rebuild kit and the next time I remove and disassemble the carb I'll do it right and have the carb dunked in a cleaner before reassembly.

 

I ordered an after market rebuilt carb to get me through this season and I plan to rebuild my stock carb before next year.

Got a late start today but I got the new carb on the bike but I have to tinker on the cables (throttle and choke) before I take it out for a test ride.
The throttle cables seem a little "sticky" and the choke will not stay on unless I hold the ****.
I tightened the nut on the choke cable as much as I can without breaking so I'll have to see what's going on there.

 

I discovered that the new enricher (choke) cable for the rebuilt carb was the problem with it allowing the choke to open unless I held it closed.

I put my old cable back on the rebuilt and re-adjusted the accelerator and took it out for a test ride.
It starts great, idles great and pulls great but I still have a little too much "flutter" at constant speed.

Perhaps I'm expecting too much.
I took my wife's '08 Heritage (T/C 96 EFI bike) and it seems to also have the same "flutter" at a constant speed!

I've put fresh fuel in both bikes, along with some carb/injector cleaner and I'm just gonna run them and see if anything changes with time or mileage.

Still planning to rebuild my OEM carb and increase the jetting (slightly) along with the diaphragm and needle to have it run a bit richer than it did from the factory.