Anone know if/where there is a DIY link in the forum or elsewhere for needle shimming? Looking for info relating to how much to shim based on setups, how-to's, etc... Where do you find shims that are the right thickness? Imagine anything I might find in the bins at Lowe's won't have tolerances to be accurate thickness.

And last questions....How much of a difference can shimming make? I did the jets alone and that has made a big difference in itself. Will I feel a change with shimming too?

 

Found them...

Rejet Suggestions

and

Sportster carb rejetting

From the latter... " Blindly shimming the needle up or replacing it is not recommended. Late model needles are richer, sometimes more so than aftermarket. The only time this is required is when dyno tuning. In the process of dynoing, starting with a small main jet and doing runs with progressively larger main jets, if going up one main jet size causes high rpm horsepower to fall off (i.e. if you've just gone past the optimum main jet size) but low rpm power improved, go back to the previous main jet size, and shim the needle up .030" or so with a small washers. This is not common, and seldom required. "

So answering my own question, shimming is not required unless I'm uber tweaking every ounce of HP and my optimal setup falls between a couple jet sizes; which the butt dyno says it does not.

Thanks for listening.

 

Great info! Thanks, Tim

 

Actually the shimming brings on the fuel curve a bit sooner to eliminate coughs and lean areas in the fuel curve. It will allow more fuel at a lower RPM and give you more tunability in transition points of the different circuits of the carb. You should notice a difference shimming verses not shimming.

 

Ok, in that case, is there some data somewhere I can reference to determine a starting point/specs (size of shim) based on my setup? Can you notice shimming performance changes without a Dyno?

I don't have any perceptible problems with coughing or spitting (sans cold weather while the bike comes up to temp). I'm just looking to FINE tune for street riding - no racing.

 

Not sure what you refer to as a starting point, I would think that would be a stock carb and go by the link posted above by you .

The shim should be a brass washer approx. .050" or 1/16" thick each X2 to raise the needle a pre determined amount along with the other mods that are in that post. As far as if you can feel the difference, there are many people that can't tell if the engine is running properly so that is hard to say. I can notice the difference but that's me,I've worked on bikes all my life and aircraft before that.

 

Check this out also...
Shimming the Needle

 

I just replace the needle with a freeer flowing needle like the SE needle.

 

aka a #4 flat washer, brass - available at most any hardware store...

 

check out theshimshack.com - you can build custom metal shims to your specified size, thicknesss, material type, etc. and they will ship out within 24-48 hours if the material is in stock (upon request).