In one of Dick’s posts there was a little write-up about ways of dipensing small amounts of epoxy. Besides the circles and using scales it also mentioned spacers to put over the shafts of the pumps to reduce the volume of each stroke. Does anyone know the length of the spacers to acheive a half dose with the yellow headed pumps? I could figure it out but my pumps are already full of epoxy and I would rather not have to clean them out in order to calibrate them. I was thinking it would be handy if you found that you needed just a “little more” to finish a job and didn’t want to spend the time filling the circles. I’ve used the pumps 3 or 4 times and they’ve made me lazy already.
Thanks
Don
Don -
my pumps are the older (all white) version - so not positive if same as the new yellow ones - but they should be. I watched where pump bottomed out with a full stroke, and then marked half way line on pump shaft.
It “LOOKS” to be about 120mm for resin pump and about 85mm for hardener - to produce 1/2 stroke (hard to measure at the moment).
Next time when you need a full pump amount, mark pump shaft when ready to pump and dispense a full stroke and see where it bottoms out. Mark that point and then measure between the marks. Might be the larger part of the pump head/handle.
Once you know where pump bottoms out, you can measure total stroke and build spacers accordingly. Since I use the “circle” method, I’ve never made spacers, but the ones I have seen are simply a rectangular wood block of appropriate thickness, and a slot cut to all them to slid on the pump shaft, under the pump handle. If you make 1/4 - 1/2 - 3/4 stroke spacers - be sure to label whether resin or hardener and also how much of a stroke… example: “Yellow painted one is Resin and 1/4 stroke” - so match up to the “Green painted one for Hardener for 1/4 stroke”.
If you want to be totally accurate, send en email to Gougeon’s (WEST System) and the tech guys should know what the stroke length is for each pump. Be sure to tell them it’s for the quart/pint size so they don’t give you the gallon sized pump dimensions in error.
Good luck - Dick
Jeez, I don’t know where my brain was. I had experimented with the 3rd(3-1) pump that cams with the new mini pump kit and for some reason cutting the stroke in half didn’t seem to work(Which didn’t make sense at the time) so I just cut and tried until it worked. Anyway, after your suggestion I measured again and it all works out. I think that the upper part of the pump nesting in the lower part was messing with my head. Thanks Dick, for setting me back on the path of reason.
Don
The pumps can go bad , still pump epoxy , but the ratios change.
I dont trust them anymore.
You can buy cheap accurate digital scales now.
I have had problems with the pumps pumping air and going out of adjustment and have read of others having the same problems.
Some people have used them for years though, and not had a problem, but I would not use them without checking them with a scale every so often.
I’ve still using my original pumps that I bought in 1983-84 ! 
I do admit to cleaning them every once in a while which is a messy, sticky job - but it does prolong the life and frees up the internal ball check valving that will sometimes stick.
Where many folks run into problems, is in one of two dispensing areas - 1) they are trying to squeeze the last bit of resin or hardener out of an empty can and pick up air or less than full feed tube, … or … 2) they are in a hurry and push the pump too fast not allowing it to refill properly.
For #1, drain the left-over resin or hardener into the new can - there is usually enough room for what is left over. Will take a good day to assure as much as possible has been drained.
For #2, a slow push to dispense and allow pump to come up to top of stroke on it’s own. Normally, when dispensing material, as you push down the resin ( for example) that has filled the pump feed tube is expelled. When the pump is released and raises, it opens the steel ball bearing at bottom of feed tube to allow resin to be sucked up into the tube. Once pump reaches the top of it’s stroke, the ball bearing “should” close off the bottom of the tube and hold the resin until the next pump. Keeping this ball bearing clean helps it seal and open easily. Last time I looked, replacement pumps were $11 and considering the cost of resin and hardener - is inexpensive by comparison.
All of the above is based on the quart/pint cans and pumps.
Thanks Dick
If anyone has this type of hardner pump ,check it.
www.oneoceankayaks.com/Epoxresl.htm#review
I used pumps for years until I had problems with three different sets, I switched to a scale and I like it much better.
I can mix any size/very small batches if I like, I dont have to worry about priming and I know the ratios are correct.
Very nice article Robert - thank you for the link and post. I learned something new as well. :zbeer: