FW: OS 160 pump backplate

[Koenig, Tom]

Gents-just passing on Chris's comments ( I tried to get him to sign up)

Tom

Dear Discussion list,

Regarding Eric's comments for the OS160. I have been flying this set-up for around two years now with none of the problems that were mentioned. There are multiple things that will affect mixtures through the rev range. Type of pipe, tuning of pipe( lengths etc), fuel used(oil and nitro content), plug, compression ratio etc.

    All I have done is reduced pump pressure by half a turn, run an OS F plug, an old carbon Mintor pipe, 15% cool power oil 15% nitro and spent a lot of time initially setting the optimum pipe length( don't ask me what it is), as all I have done is kept changing it until I was satisfied. My set-up is very soft, the motor comes on the pipe very early in the rev range ( maybe you are running a peaky set-up?)

 Out of all the engines I have run over the years ( including YS's) I have found it to be the best set-up for me. It is the smoothest in regards to mixture and rpm's. You may not have explored all the tuning options? What works for me hasn't obviously worked for others. By the same token there are many guys who have problems with a YS, OS or whatever they choose to run.

Feel free to contact me at   <mailto:Christopher.Swain at csiro.au> Christopher.Swain at csiro.au

Best regards

Chris Swain
-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Grow Pattern
Sent: Saturday, 1 October 2005 1:37 PM
To: Discussion
Subject: Re: OS 160 pump backplate


Before you all leap out and spend a bunch of money on an OS pump for your OS 1.60 here is what I found out while experimenting with the OS 1.60's.

First of all, you cannot buy the pump separately. It comes installed on the 1.40 back plate.approx $150.

Secondly, the standard OS 1.60 carb did not like the OS pump anywhere near as much as it liked the Cline regulator. (Other 1.60 users swear by the Perry). Either way the OS pump produced too much fuel for the OS 1.60 carb.

I spent a lot of time working on the pump in the backplate with the std carb. Tried twin pug heads etc. Still could not get a good transition. If I leaned the pump for  a good transition then the engine would go lean in the verticals. I finally had enough of this and went to the OS mix carb (the one that is sadly not available).

You, (or at least I, could not) cannot get the std carb to work well with a pipe when the fuel is supplied from an OS 1.40 pump. I did get it to work well with a 1.40 RX carb. This carb is designed for the pump but needs to be drilled and tapped to take 3.5-mm screws to hold it in place.

The Cline will get you much better results for around $40. (Or Perry if you prefer) and you can use your existing.

Regards,

Eric.




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