Carb needle half step

[JPark]

After finally figuring out why my jet needle ended up in the #2 groove instead of the #4 - the slide was from a different VM20 - I still wasn't satisfied with the performance. The #3 slot was blubbery rich and the #2 seemed just on the edge of too lean. When cold it would run poorly and seemed somewhat torqueless when warm.

I didn't have a shim washer, but made one .5mm thick. This puts the needle as if the clip was on the ridge between the notches. Now it just runs; no adverbs needed. It strikes me that when you have such a small carb, the grooves should have been a finer pitch, but that wouldn't be practical.

Half notch shim washers are stock on some CV Mikunis which have two plastic washers of different thickness that you can juggle to get .5mm increments. I have to wonder how many bikes out there would run a lot better if the needle could be moved a half step instead of choosing the best tradeoff.

[Dale]

I have installed shims on a number of occasions. Sometimes the conditions just require that as a change of a complete notch is just too much. I think altitude, temperature and humidity are big factors but also some degree of wear on the carburetor components as well.

[Joe Ormonde]

Carbs can drive a guy nuttier! I have 3 VM20 carbs that I went through. I have a 1970 100B that runs PERFECT. So, while it`s running tip top I tested the 3 carbs on that Bike. Same deal with My 93 Super Rat Carbs. I test those on my Super Rat. I also have several Stator Plate Assemblies that have been tested. My point is this: If you only have one Hodaka it can be MISERABLE to dial it in. Condensers and Points and Coils OH MY!! In my case I can eliminate a Carb problem because I have spares that have been tested. As for a 1/2 step the stock Needle should be just fine. Quite often the Carb is suspect when it`s something in the Ignition system. Back in the day, Carb Kits came with a Needle with NO marks on it. They probably used that same needle in everything they sold. Keep after it and you will find your problem. Joe.

[Dale]

I agree with Joe's points (no pun intended).
Every 50 year old carburetor, that has been used and abused, has developed its own personality. As has the stator and ignition coil. How is the top end compression? So many factors. It is always a plus to have known working parts to swap in when needed.

[viclioce]

So where can one acquire these half step shims? Victor

[JPark]

Jetsrus lists a 2.7mm hole 6mm diameter shim washer in a pack of 10 or whatever, but the thickness isn't mentioned. I'd suspect they are .5mm as that makes sense. I'm not sure if the recess that they sit in on the old VM20 is 6mm but I think so.....anyone?

I made mine from a scrap camera part which had the right hole and was .5mm [.020]thick. Someone says they found something workable in a dollar store 'thingy'. A piece of plastic .020 sheet would be easy to make them out of; .020 copper or brass would be classy. Unfortunately, the 3/32" bit is 2.4mm , just shy of the 2.5 you need. Just massage the hole with the bit until the needle goes through and then cut or grind around it.