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Jan 05, 2019, 08:56 PM
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OS Surpass 120 Exhaust Valve Not Moving


I have an older OS Surpass 120 4 Stroke engine, been setting for several years. Took it out of the box to lube it up for use in a 1/4 scale Cub. Got it all turning free with help of the heat gun and transmission fluid and Marvel Mystery Oil. Intake valve operates as it should. Exhaust valve is not stuck but the pushrod doesn't move. I removed the rocker arm assembly and pushrods, (neither of them are bent), filled the tubes with mystery oil and let it set, also applied a little heat. Reassembled everything. Intake valve operates really good and smooth, still no movement on the exhaust valve. Question is, how is the cam gear set up under the cap with the 2 screws on the right hand side of the engine at the bottom of the pushrod tubes? I took the screws out and tried to remove the plate but it would only come out about a 1/16" or so, it would rotate fine but I couldn't get it to come off and I didn't want to pry it off and break or screw up something, if I haven't already. Anyone have any ideas or suggestions for me. Thanks
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Jan 05, 2019, 09:51 PM
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Heat it up with your heat gun, pull the cam-cover off by working it with a gloved hand. I have had rusted cams come out with the bearing frozen on the shaft, all one piece. If you do any prying on the cam cover, be careful it gets damaged real easy. Use plenty of heat.
Jan 05, 2019, 10:34 PM
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Thread OP
I will do the heat again tomorrow a little bit hotter and see what happens. No, I wasn't going to do any prying, the screw hole ears look to be too easy to break off with too much force applied. I'll just keep working it.
Jan 05, 2019, 11:23 PM
Registered User
Is the valve stock in the open position? If so, remove glow plug, rotate piston to BDC.
Feed some string or small cord into the plug hole. get as much as you canin there.
Heat the head with you heatgun, slowly rotate the crank towards TDC. Watch to see if the valve closes.
If not, try again with more heat. If it does, remove string and rotate crank. move crank threw a few cycles
If the valve stick again, repete.


RCButch
Jan 06, 2019, 07:55 AM
Registered User
A tried and true rust and gunk desolver is a 50/50 blend of ATF (auto trans fluid) and Acetone. It’s very thin and penetrates well. Just mix the minimum you plan to use as the acetone evaporates quickly when just standing.

Disclaimer: I’ve never used it on glow engines but use it on old boat engines and it’s cheap and work very well.
Jan 06, 2019, 08:03 AM
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SRQFlyer's Avatar

Pushrod not moving


If the valve is not stuck and the pushrod is not moving, then the lifter is what is stuck. Concentrate on oiling/degumming the lifter by introducing acetone (or acetone/ATF) down the pushrod tube and then applying heat to the area just above the cam - where the lifters are. Once it starts to free up, you should be able to push it down by manipulating the rocker arm with your finger (downward).
Good luck,
Jim
Jan 06, 2019, 08:43 AM
Closed Account
Just my 2 cents: I think SRQ got it right 100% including the fix, as most likely, dried up castor is the cause....

Although I would use a separate tool (anything that allows you to push down on that lifter, like an old discarded screwdriver with the blade cut off) so you can apply a bit more force without fear of damaging the pushrod or rocker. These lifters can be pretty stubborn at times.
Jan 06, 2019, 09:30 AM
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I'm going to try just what Brutus suggested, acetone and ATF. After watching a Youtube video of what's inside the engine I'm sure the only problem is a stuck lifter/cam follower. That's my project for this afternoon.
Jan 06, 2019, 10:42 AM
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Waaahhhh….. the credit all goes to SRQ....
Jan 06, 2019, 11:07 AM
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I understand, I realized that after I hit the submit. But I will say you both have been extremely helpful.
Jan 06, 2019, 11:08 AM
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SRQFlyer's Avatar

Thanks, but ...


Quote:
Originally Posted by Brutus1967 View Post
Waaahhhh….. the credit all goes to SRQ....
A great deal of my knowledge has come from you!
Jan 06, 2019, 11:11 AM
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Thanks…. but still, credit where credit is due
Jan 06, 2019, 07:21 PM
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Thread OP
Yep, ATF, acetone and lots of heat from the heat gun did the trick. Got it freed up and turning over smooth and whole top end is working as it should. thanks guys for all the help. Now one of these days I'll se if it will run.
Jan 06, 2019, 08:42 PM
Master re-kitter
SRQFlyer's Avatar

Thanks for letting us know!


Always good when the OP returns and advises how things came out (or not).
Jan 06, 2019, 09:01 PM
Closed Account
Yup... +1! thanks for the feedback!


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