Easy YPVS question.

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Boehly
Posts: 4
Joined: Wed Sep 05, 2018 11:28 pm

Easy YPVS question.

#1 Post by Boehly » Mon Sep 17, 2018 6:50 pm

Hi,
I am in the process of replacing all parts on my 1986 RD350-S and have had conflicts on the positioning of the power valves at rest. I believe with the ignition turned off and the hole from the cable pulley lined up with the cylinder hole that power valves should be fully open. I believe that is how they were when I disassembled the old ones. Could someone put my mind at ease?

Thanks!

evan_calgary
Posts: 1367
Joined: Tue Nov 12, 2013 2:34 am

Re: Easy YPVS question.

#2 Post by evan_calgary » Mon Sep 17, 2018 6:57 pm

Hmmm. I don't think that is correct. Not positive though.

The hole lined up with the pulley is definitely correct when at rest and there is no way for them to be installed incorrectly unless you somehow managed to put them in 180 backwards.

When at rest the exhaust should have a lower roof and therefore more torque due to less exhaust duration. At revs it should open to increase exhaust duration.

Racers would keep them open at all times which would reduce low end and increase the size of the hit.

When looking in the exhaust the face of the PV should be continuous with the port and not dished out (which would indicate in backwards).

RuZty
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Posts: 3584
Joined: Fri Oct 03, 2003 11:11 pm
Location: Southern Ontario, Canada

Re: Easy YPVS question.

#3 Post by RuZty » Tue Sep 18, 2018 12:31 am

...but when you turn the ignition on it does a cleaning cycle and stops with the valves full open for easier kick starting. As soon as it fires they close.

Hooligan
Posts: 1966
Joined: Mon Aug 20, 2012 1:37 am
Location: Calgary, Alberta

Re: Easy YPVS question.

#4 Post by Hooligan » Tue Sep 18, 2018 1:24 am

Is it even possible to put the valves in backwards? I doubt it.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

Darrell
Posts: 179
Joined: Thu Feb 22, 2018 6:21 pm
Location: Crab Orchard, TN

Re: Easy YPVS question.

#5 Post by Darrell » Tue Sep 18, 2018 3:03 pm

Yes, you can get it backwards. I found out when racing my RZ back in the 80's. Went out in a qualifying session and watched every other bike on the track go away in a hurry. It was a quick adjustment and I got it right for the race, but it sure was an eye-opener for a lap.
89 Canadian Spec RD-350
2013 BMW R1200RT
2007 Harley XL1200C Sportster
2008 Ducati 1098R
2015 Gas Gas 300 Trials bike
1972 Turbo-Charged 240Z
Zastava Black Arrow .50 BMG

Boehly
Posts: 4
Joined: Wed Sep 05, 2018 11:28 pm

Re: Easy YPVS question.

#6 Post by Boehly » Tue Sep 18, 2018 4:26 pm

Thanks everyone!
I was pretty sure that the valves are wide open with the pin through the hole in the pulley and into the cylinder block? You can assemble 180 degrees off. Just wanted to be sure before buttoning it up. Unfortunately I had ordered new bushings and o-rings and one of them is oversize. I could reuse the old one for it is in fine shape if I have to. Will she what the e-bay seller says.
Thanks!
Bill

Hooligan
Posts: 1966
Joined: Mon Aug 20, 2012 1:37 am
Location: Calgary, Alberta

Re: Easy YPVS question.

#7 Post by Hooligan » Tue Sep 18, 2018 10:33 pm

If your other choice is 180 deg out then it should be easy. The valves don't rotate nearly that far. They prob only turn 40-50 deg at most.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

evan_calgary
Posts: 1367
Joined: Tue Nov 12, 2013 2:34 am

Re: Easy YPVS question.

#8 Post by evan_calgary » Wed Sep 19, 2018 1:13 pm

They literally complete the circle with the exhaust port. If they make the exhaust port look like a kidney bean they are in incorrectly.

Boehly
Posts: 4
Joined: Wed Sep 05, 2018 11:28 pm

Re: Easy YPVS question.

#9 Post by Boehly » Wed Sep 19, 2018 5:32 pm

Thank you Evan!
You guys are a wealth of knowledge!
I think I know what to do now!
The only other question is what I disassembled the two halves for the two Power valves, on one side they had a small washer on the long Allen bolt that held the two halves together. On the other side there was none. If I do not use the washer the head of the Allen screw is flush with the end of the power valve whe screwed in fully. Should I skip any washers? Is it a good idea to use loktite on that Allen screw? The screw had come loose on the originals and that is what caused all of my problems.

Thanks!!!

tacky1
Posts: 950
Joined: Wed May 13, 2015 1:11 am
Location: Pacifica,,

Re: Easy YPVS question.

#10 Post by tacky1 » Wed Sep 19, 2018 6:27 pm

Fit the washers, They will tighten them together a little more, I use blue loctite on all mine and never had a problem with them loosening,
I also sand down the middle coupler a little so it gets a tighter grip on the valves, Sand down the outer flat edges where they clamp together, Just makes it a lot better fit.
Also, You need to set the valves by eye or feel if you have any porting work done, You need to pop off the left exhaust and cycle the valves and set them by feel to get the back of the valve level with the new port height, Don't want to loose all that 40HP you just gained by porting :P
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

Boehly
Posts: 4
Joined: Wed Sep 05, 2018 11:28 pm

Re: Easy YPVS question.

#11 Post by Boehly » Wed Sep 19, 2018 11:14 pm

Hi Tacky1.
Seems you know a great deal about modifications! I will do what you suggested!
I am unsure on the Historybon this bike except that supposedly it had been set up for racing at one time. They had cut out the side to expose the pinion gear for fast change. I believe that it has oversize pistons for they measure 5 thousandths over normal. Also it might have been ported for there is engraved one each cylinder "DG". Also on the fairing is says "RD400" instead of RD350. If you wnt me to send you pictures of the cylinders and stuff just message me you e-mail address and I will send. Would like to know more of what I have since when I bought it the previous owner did not know.
Thanks!
Bill

tacky1
Posts: 950
Joined: Wed May 13, 2015 1:11 am
Location: Pacifica,,

Re: Easy YPVS question.

#12 Post by tacky1 » Thu Sep 20, 2018 3:02 am

Where are you located bill.
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

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