Carb Needle Shim

[98Redlne]

So I finally located the Radio Shack washers for the carb needle shim

The washers I found had really crappy thickness tolerance (yes I know they are not supposed to be precision shims). Every one I found was at least .025 thick. That would give me .050 shim at the minimum. I figure that this was too much over the .040. Attempting to thin them down did not go as well as I had hoped. I couldn't get them perfectly flat which ended up causing the needle to drag so I went looking for actual shims.

I was able to find a couple of places that had shims that will fit our carbs.

http://www.hiperf.com/acatalog/Snowmobile_Catalog_Jets___Mikuni___Keihin_82.html
http://www.exhaustgas.com/ProductDetail.asp?ProductID=175&DepartmentID=10&CategoryID=61&RepID=&BasketID=


Both kits were significantly less expensive than the custom VMax shims on this site :http://home.comcast.net/~onlyone12/carbs1.htm

Hopefully I will have them in 3-4 days and will be able to continue putting things together.

 

[Icepick]

what, why, is this shim and where do you put it?

 

[eatatjoz]

Simplified, a shim just raises the needle to enrichen the mixture for mid-range.

 

[dannymax]

So I finally located the Radio Shack washers for the carb needle shim

The washers I found had really crappy thickness tolerance (yes I know they are not supposed to be precision shims). Every one I found was at least .025 thick. That would give me .050 shim at the minimum. I figure that this was too much over the .040. Attempting to thin them down did not go as well as I had hoped. I couldn't get them perfectly flat which ended up causing the needle to drag so I went looking for actual shims.

I was able to find a couple of places that had shims that will fit our carbs.

http://www.hiperf.com/acatalog/Snowmobile_Catalog_Jets___Mikuni___Keihin_82.html
http://www.exhaustgas.com/ProductDe...epartmentID=10&CategoryID=61&RepID=&BasketID=


Both kits were significantly less expensive than the custom VMax shims on this site :http://home.comcast.net/~onlyone12/carbs1.htm

Hopefully I will have them in 3-4 days and will be able to continue putting things together.

I found several .018" & .020" washers in the bag I got from R/S...enough to do 2 bikes. Maybe they increased the thickness? :confused2:

Just a thought....did you calibrate your mic?

 

[98Redlne]

Danny...my mic is good, I have a couple of items of known thickness and it is dead on the money for all of them. Not NIST traceable but more than close enough.

I think the stock material they use is what is to blame. Being they are just washers and not shims, the tolerance on thickness I would think is fairly wide.

To tag on to eatatjoz comment, the shims are normally required only if you are changing out your exhaust with new headers and mufflers. Slip ons don't count as they retain the stock header pipes.

In short, there is no reason to mess with the shims unless you have modified either the intake or exhaust significantly.

 

[dannymax]

Danny...my mic is good, I have a couple of items of known thickness and it is dead on the money for all of them. Not NIST traceable but more than close enough.

I think the stock material they use is what is to blame. Being they are just washers and not shims, the tolerance on thickness I would think is fairly wide.

To tag on to eatatjoz comment, the shims are normally required only if you are changing out your exhaust with new headers and mufflers. Slip ons don't count as they retain the stock header pipes.

In short, there is no reason to mess with the shims unless you have modified either the intake or exhaust significantly.

Gotcha...maybe R/S is getting them from a dif supplier now....mine ran within .001" variance. :confused2:

 

[gamorg02]

Gotcha...maybe R/S is getting them from a dif supplier now....mine ran within .001" variance. :confused2:

i just had calipers but then were all identical.

 

[98Redlne]

In the electrical industry RS parts are known as "sweep ups".

All of the components from the manufacturer that don't meet spec get swept off of the floor at the end of the day and sent to RS for packaging and sale.