Hi Troy,

Have finally recieved a 170 from YS for Adam to take to Argentina, but having some fun getting it to running properly.
At first would not go over half throttle with out going lean and throwing prop, pulled pump apart and found internals differant from the 160.
Found pump body and pump plate were not machined square so diaphragm was not seating properly and the pump valves were binding on the pump gasket. After repairs were done I received the next day from YS new pump valve springs which were shorter and heavier coils than the old ones which are the same as the 160, and a new pump gasket which was now the same as the old one I just modified.
Tried assembling the new springs but they were too short and the pump valves would not close off properly, so I streched the new springs to suit.

Ran the 170 again tonight and now it will go to full throttle with out throwing the prop, 8200 rpm on 17x13 (is this a smick too big?) with 30%, but it is still on the lean side, richened top end back to 7800 rpm and tried to reset bottom end, best I could get was 2250 rpm with a semi steady idle but could not richen up bottom end, went in 3 turns of the regulator from flush with virtually no differance, I feel I should be able run the bottom end richer than what it is.
I will try swaping over the complete pump assembly with one from a 160, if that does nothing will then try swapping the carby housing assembly and then the black check valve.

Knowing how the pump and regulator works with the front vent tube, I have found that a good DZ will run on about 2 to 4 inchs of vacume at idle (2000 rpm or lower) at the vent tube, but this 170 runs a whopping 8 inchs of vacume at 2250 rpm.
I feel that this high vacume may also be affecting how the diaphragm is behaving, this could be why I can't richen the bottom end.

And this brings me to another question, any idea why YS have drilled the 1mm hole (approxmatly) in the crankshaft disc just below where the crank ring runs, is this to do with pressures/vacume in front and behind the crank ring?
Apart from the pump internals, I can see the benifits of the other changes, but putting a heavier valve spring on the inlet valve only had me thinking for a while.

Will

TEAM XMAN

I can't speak to your questions about the pump. I don't have a production engine. My have been prototype engines. I do have one of the "production pumps" running on a 170 and it is running the same as the 160 pump I had on that engine.

The hole in the rear disc of the crank was my understanding to improve lubrication of the front of the engine. You will also see Small hole in the crank near the cam gear area this allows for better flow of oil to the cam. The connecting rod has some changes in it also at both ends to better lubricate the connections and the crank pin shape is a changes a little to accommodate this better lubrication change on the rod.

As far as I know the only change to the pump was the housing...and the bore, and shape of the piston inside the pump. I have not compared springs and plunger parts from the pumps but I can at some point. I want to get a production engine and compare it side by side with the 160DZ production engine. I only have 1 production 160. The other 2 are test engines that have been updated with some production parts. My 170's all 3 of them I have had are slightly different from each other. The only changes I have not run are the new case. This is because I have basically not needed a new case. The newer style crank, pump and the other 170 changes including various throttle barrel seal changes have been tested on my engines. I don't know if Yamada used the changes to the throttle barrel or not. I have had 3 different engines with 3 different throttle barrel versions. One of them was a 160 carb and barrel because I pulled it off one of my 160's. To my understanding the carb and throttle barrel are basically no changes functionally, just the o-ring was replaced with the oil seal from the 140L. I don't know if this is what is happening on the production engines or not.



Troy Newman
Team YS

Hi Troy

The production engine has the same o ring set up in the carb as the 160.
I now have the 170 running as sweet as honey and it is an improvment over the 160.

Now this may sound odd but what I did initally to get the 170 running good was to put a T/ piece
in the front tube, pump to crankcase line, and then add a one way valve on to the T, allowing the vacuum in the engine to bleed off but hold the pressure in the front housing.

Bingo, what a differant engine it was, soon as it started it sounded right, gave it a quick tune and could not fault it at all, great idle, good top end, and transition, it was beautiful, could not fault it on the test bench. had total of about 3 tanks go through on the bench.

Mounted the 170 in a model and flew last w/end, could not get through a full tank, dead sticked about 2/3 of a tank, had 3 flights with same result, fitted a header tank thinking that may be a problem.
Next day another 2 flights same result.

Sitting there looking at model and thought, wonder what happens if I take the T and check valve off, so I did and motor still ran great but now, no dead sticks.
Have had another 6 flights with out a problem except for the last when the plug blew. Can't fault it now.

Seems as if this engine needed a bit of help to get bedded in, what else could it have been.
Even the gauge readings are now close to what the 160's run

We here in Australia are awaiting 5 more 170 's to come in, in the next week or so, will get my hands on them and see what they do, was it just this engine or do the others need a bit of help as well?

Troy, do you have any contact details on Albert Glenn, the American Team manager,
if so I would like to get in touch with him asap.

Will Crossman
Australian Team Manager