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OS 70 Broken valve spring

Old 11-04-2002, 12:51 AM
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Default OS 70 Broken valve spring

I've got an OS 70 with about 15 hours on it. Saturday it flew just fine for my son. On the second flight when I went to start couldn't get compression. I removed the valve cover and noticed the intake valve spring was broken. I don't have alot of experience with 4 strokes and was curious if this is a common problem? Should the exhaust spring also be replaced? Where can I find the parts? I'm not sure if this is a surpass as bought the plane from someone with no documentation. How can I tell?

Thanks
John
Old 11-04-2002, 05:30 PM
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Default OS 70 Broken valve spring

John,

Any O.S. Max FS-70 is a Surpass engine.

Here's the stock number and retail price of the valve spring:

OSMG9242 45960200 VALVE SPRING FS91SUR $2.99

You can order this part through any hobby retailer who sells O.S. Max engines and accessories.
Old 11-05-2002, 01:36 AM
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Default OS 70 Broken valve spring

Thanks for the info!

John
Old 11-09-2002, 04:45 AM
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Default OS 70 Broken valve spring

I had the same thing happen to my .91 FS, and the parts are pretty easy to change.

I believe it was my fault due to pulling 11.000 rpm on the ground, which surely overreved it in the air. I didn't know any better at the time, oop's!.

Bax,

I've read that you shouldn't exceed 9,500 on the ground with the four strokes. What are your thoughts on this?

Thanks, Brad
Old 11-11-2002, 04:26 PM
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Default OS 70 Broken valve spring

Brad,

The O.S. Max Surpass series of four-stroke engines can turn higher RPM than previous series of engines. All of them can be run in the high-9,000's to low 10's, but the larger ones seem happiest in the mid- to high-9's

the FS-26 Surpass and the new FS-30 Surpass can easily be run into the high 10's with no problems.
Old 01-14-2003, 09:46 PM
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Default OS 70 Broken valve spring

Hello, i have an os surpass 70 head that still has good valves, no cover but the springs are still good its a freebie if you want it...... Email me if you are interrested....
Old 01-22-2003, 07:45 PM
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Default OS 70 Broken valve spring

If you still have that head, I could really use it. Let me know.

Gordy

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