I am needing some help with the tuning of my 1995 80" EVO. This engine is built, I'm running Screaming Eagle ported and polished heads, cylinders and 10.5 pistons, S&S 561 long duration cam, Daytona TwinTec ignition, Kuryakn Hypercharger and V&H Big Shots w/Power Chamber and baffles. I overheated the engine a few months back, after which, I changed oil, checking for metal shavings, also cutting the oil filter open and checking for fine shavings finding nothing abnormal. I had to replace the ignition module due to it failing from the heat. I also carefully, but thoroughly cleaned the K&N air filter. Once everything was back to normal the engine started running lean and coughing thru the carb. I replaced the manifold seals and the carb to manifold seal, checked for air leaks and found none. The carb is still the 40mm CV, which I have now reached a #54 slow speed jet, a 185 main and I'm having to run the idle/air screw 3 turns out. The needle is not numbered, but is red and has multiple steps for raising and lowering it. At this point it is set mid way. At this point, I do not have a larger slow speed jet and the engine is still coughing up to where the main takes over. In order to see if the engine would respond to a richer mixture, I wrapped the air filter with a layer of cotton cloth and the coughing went away, however it went way rich on the main and started backfiring thru the exhaust. I can fix the carb jetting issue now, but I am concerned about what would cause the engine to go from running strong on a modified #42 slow jet (not certain exactly how much it was enlaged, but no more than a #48) and a 165 main using the same needle. The timing is still the same, static and advance curve. No excessive oil use, no blow by or excessive oil from the breather.
Any ideas or info on why the engine would start requiring such a substantial change in jetting? Any help is certainly appreciated.

 

I think your knowledge of carbs is probably way past mine but I'll throw this out there anyway. You said all this started with over heating the engine. Was it possibly running lean before and that is what caused you to over heat? Maybe your just correcting the original problem.

 

With my limited cv time, I would have thought your engine mods would have required a much richer main. At least 200. The slow jet actually seems perhaps more rich than I would have started out with. Perhaps you would consider sending the unit to Dale at Killer carbs along with your build description. Also, my own bike is similar in quite a few mods as yours, including wiseco 10.5 pistons. I always run 93 octane, stay away from ethanol and use octane booster in very hot (i.e.above 98 degrees) additionally.

 

Kinda off the subject and definitely no help to the OP, but how is it that folks overheat their bikes? I'm not kidding either. I have read a lot of threads of overheated bikes. Unless they are running lean, I'm just not getting it. Is it sitting in traffic on a hot day? I mean, I don't live in Phoenix or L.A. but it got darn hot here this summer and I spent plenty of time stuck in traffic (not a huge city, but the traffic planners here are world class dumb asses).
I have owned and operated several drag bikes and even a front engine dragster and never overheated them unless running lean.
So someone enlighten me as to how these bikes are getting overheated.

 

There are air passages within the body of the carb that can get clogged with debris and will cause lean issues during the transition from one fuel circuit to another...Blow some compressed air thru those passages and do a test run!

 

Sounds like the previous poster is about right....leave the body soaking in thinners for a few days and then put it all back together and try again....54 slow jet is way OTT.

I did have this issue on a Sporty once and it took ages to fix but it turned out to be the air cleaner assy was put together wrong and the carby wasn't sitting fully into the rubber.....check to see that it goes all the way until it hits the block that stops it going any further.

Also, if all that fails, borrow a carby from someone else and try to see if it cures anything.

 

When you start talking about a "red needle" and a modified pilot jet, it tells me that the carb has had someone modify it. It probably has a different/modified jet holder that may or may not accept stock jets. So a 54 may work with this holder, needle combination.
That being said it makes it a little more difficult to help with your problem. You've changed a lot of things that could cause the problem you are having. Is the diaphragm in correctly with no leaks?? Is the slide modified?? Is the enrichner fully seated?? Is you ignition timing set right. How far apart did you take the carb apart?? Could you please answer these questions so that we can do a little more diagnosing??
Johh

 

Check for vacuum leaks on the VOES, petcock, and Hypercharger.

 

The VOES is removed and I capped the vacuum port (it was connected to the vacuum diaphram on the hypercharger) in order to make certain there wasn't a vacuum leak. I have completely disassembled the card, soaked in cleaner and then blew all the ports out with comressed air. The slide has not been modified and the diaphram is in good condition and seated properly. The emulsion tube/main jet holder is stock and unmodified. The carb is fully seated in the manifold and I have checked for air leaks at the manifold seals and carb to manifold seal. The jets that I have purchased all came from Harley and Screaming Eagle tuner kits. The only piece that I haven't been able to fully identify is the needle. The enrichener is installed properly, timing is set properly with a mild advance curve. Actually I overheated the engine in the local St Patricks Day Parade, about 4 miles of stop for 5 minutes, move ten feet, stop for 5 minutes, repeat, bad mistake as I am also running a Rivera Brute belt drive and dry clutch, behind a closed, but vented primary cover. I ended up losing the clutch by the end of the parade. The engine has not been dyno tested or tuned, however I am now considering doing it. I've been doing plug chop testing trying to get the carb sorted out, but the dramatic change in the slow jet size is concerning me.

 

Coughing at a steady rpm or when trying to throttle it?

Check pushrod adjustment?

On the DTT, were you running a canned map or custom map before?

More timing at idle to 2000 will get rid of some coughing.