Power Valve Talk-Yamaha Based Engines

Sanoman

thecolorpurple
Site Supporter
Location
NE Tenn
l recently have been working on and wanted to change my PV’s to come on a little bit later in the powerband.

First was to find where l had a leak coming from on the rear valve.Pulled both of the pv’s,broke them down and cleaned throughly.Examined for any holes or tears.As a side note,using good 2 stroke oil (maxima K2 is what l have used for years) have kept the inside of these oily but no build up.They were do a good cleaning and should be done on a periodic basis (thanks @Jr.).

Next was to figure out what spring l should go too.
These pv’s were on early versions of Xscream engines.l have a stock stroke 735pv built by @SUPERTUNE a number of years ago..Duel 46 mikuni’s,and added this year,a zeeltronics ignition.
The picture below shows a 951 Rave valve and here is what mine look like.Chucky made some changes to be able to fit under a bpipe

The original springs were as follows:
37.71mm in total length
5.06mm between coils
1.05mm in thickness (of the wire)

l installed these new springs:
38.60mm total length
5.56mm between coils
1.21mm in thickness

Results were the valves opened up a bit (small amount) later,in doing so,it made them open up closer to mid range which is close to what l wanted.l have another couple sets of springs that are heavier to try.But for now l want to ride the next couple weeks and feel these new springs out.l could not have done this without help from @Jr. and @ScottS,thank you.

Has any other riders messed around with their power valves,please chime in!1593344421397.jpegFE400068-8B17-4992-9BD4-9D605A204921.jpeg7ED64F3A-7B1A-46A9-8F94-79B6707F99B0.jpegD38C5BE2-A531-4A7F-AD5C-ECCD44B3ABE6.jpeg










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