First of all, I'm a decent mechanic, but rather inexperienced on carbs. Bought this bike used, after having been stored and unridden for a couple years. This is my first street bike.

Initial issue - pops, spits, hesitates, cuts out. Couldn't get the bike above 55mph, wouldn't rev that high, would just keep popping and sputtering if you left the throttle wide open. Plugs seemed rich - black, not tan. Replaced plugs, no change. Bike has straight pipes.

Pulled the carb and cleaned it, replaced the intake seals. They weren't split or anything, didn't find anything wrong or plugged that could see. Carb had been apart in the past - brass inlet elbow, air screw was accessible (cover removed), Phillips screws had marks, didn't appear to be recent though.

Set the Air Screw at 2-3/4 turns out (didn't try to adjust yet - engine too hot!) main jet = 170 second jet had a 33 on it - real tiny hole, had to hold it just right to see light through it. Diaphragm looked good. I did move the float quite a bit - from around .740 to about .770 This float is 2 round cylinders, not boxey. I'm questioning if i got the little seat for the main jet needle in correct, but it only seemed to go together flipped the way i installed it...didn't force anything.

This is a 1988, the one year without an accelerator pump.

Presently, the only way it will run, is with the enrichment **** out at least 1/2 way. Revving it up and playing with the throttle, i got it to really Rev up - probably the only time since i've had it running that the vacuum piston has ever opened up. Spring looked to be intact, never cut. I let it run long enough to warm up, but it isn't rideable as it is, it would stall immediately. Its worse than it was before.

I cannot find good info on the float setting for the 1988 cv carb - an internet page had .760 to .770 The old Clymer manual that came with the bike says .725-.730 Whats correct?

I saw some used take off carbs on ebay for 125-150, and a "tuned" performance carb for around 200. Should i just toss this carb and try another?

I want to RIDE!

 

Yes, get a later model carb with the acc. pump. You will be much happier and you can go with the recommendations posted everywhere for jetting and idle mix screw settings for a starting point.

It will be well worth the money spent and should be a real easy swap out for you. Not sure if the 1988 CV is set up differently (other than no accel pump) but the slow jet number and the float height number sound off from the later CV40 carbs. ?? YD

 

Did a bunch of web surfing last night.

1) I had the needle jet in upside down.

2) Float - reset to .725".

3) Air screw - washer was missing, and I didn't install the packing o-ring initially. I'm sure the washer was not there when I tore it down...I was ultra careful with my parts

Fixed 1 and 2. I put the o ring in without the packing washer, and set it to 3-3/4 turns. then fired it up. Runs much better...warmed it up and took it for a ride. Better...but not great....gaining on it. Wide open, it accelerates great, no skips, good power....never did that before!

Cruising is where my issue is at the moment - at 35 mph, steady cruise, second gear, throttle just cracked, it wants to surge, pop and miss. Going to track down a washer for the air screw and see if it helps this issue.

 

I want a 40mm carb, correct?

 

Yes, CV 40 for any sportster or big twin. Other than jetting they are the same. BTW, you can get your packing washer and almost any other part for your carb here:

http://www.cv-performance.com/

YD

 

Gave up on the 1988 carb (for now)

Bought a used carb off a 1995 883 Sportster on ebay, pulled the bowl, checked the float, cleaned it out - it was pretty clean inside. Had a 170 jet, I installed a 175. Low speed jet was a 45, left that one alone. Installed the CV brass air screw with the ****.

Cranked it up, definite difference - idle was racing with the enrichment **** out, so adjusted the idle down (too far), and took it for a ride - much better so far- -it runs on both cylinders almost all the time now. Also takes off with little to no hesitation when I twist the throttle...close but getting an occasional poop at some throttle positions.

I still need to work on adjusting the air screw and idle screws, as it would not idle for me (stalls), but ran out of daylight today. Still getting and occasional pop in the air cleaner, and a periodic miss at some of the lower throttle positions.

I drove it out on the same 5 mile ride I've been using to test, and when I got back today, the oil tank temp was 175, rather than the 200 it was before, so the richer jetting seems to have helped that out. Checked the exhaust pipe temp with a Temperature gun, and they are within a couple degrees of each other.

Didn't get a chance to look at the plugs since making these changes.

I'm about 90-95% satisfied with it at the moment, its at least ride-able. Hopefully I can tweek the air screw adjustment, and get it a lot better without replacing any jets. Not sure I'm not having some ignition issues either, so I'm going to go over that next.