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Old Sep 01, 2009, 08:22 AM
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Saito 125 Problems

Hi All,

Went out with the Fliton Inspire 90 today, which has a Saito 125 up front.

Took off as normal but immediately seemed to be lacking power in the uplines, so I landed immediately. Suspecting an out of tune engine (thinking maybe i'd knocked the needle) i walked over to the model, engine still running, with the tacho in hand. But when i got to the model I noticed that the engine sounded really odd. A sort of tinging rattle, rather like when an aluminium spinner has come loose.

I cut the throttle, and on inspection, the spinner was nice and tight. Turning the engine over by hand produced the characteristic clicks of the valves operation, but the clicks seemed a lot louder than normal, perhaps as loud as my YS.

Took the cowl off and took the rocker covers off. The engine is mounted inverted in the Inspire. The exhaust rocket chamber was full of oil, as expected, but the inlet rocker chamber was bone dry - and i mean bone dry, the rocker cover itself has no signs of oil on the inside.

I then noticed that the pushrod on the inlet side was not sitting in the recess in the adjuster screw on the rocker itself - the screw has a hole machined in the end of it which the pointed end of the pushrod is supposed to sit in - the end of the pushrod was actually pushing on the outside end of the screw. When i popped the pushrod back into place, and checked the tappet gap, it was spot on perfect, so it doesn't seem like a loose tappet allowed this to happen.

I didn't reassemble the engine after this, i thought i'd take it home and investigate further.

But this leaves questions:- how did the pushrod come out of the recess in the adjuster screw? why is the inlet rocket chamber bone dry (am i correct in thinking that the saito design is for oil to penetrate from the cam area through the pushrod tubes to lubricate the rockers? )

any ideas?
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Old Sep 01, 2009, 08:23 AM
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UPDATE:

This engine has never seen any castor oil at all. It was initially run on 10% Model Technics ProPower (18% synthetic oil) - about 4 gallons went through it. Then more recently i've switch to Optifuel MV 20%.

I've taken the rockers off, removed the pushrods and tubes and removed the cam cover.

I noticed that, once the tubes were removed and you're left with the little brass tubes that come out of the cam cover, which the cam followers are mounted in, one was full of oil and one was quite dry. Furthermore, once i'd removed the cam cover, rotating the cam gear, the oily cam follower rises and falls under gravity, whereas the dryer follower rises and doesn't descend on it's own.

i'm thinking that for whatever reason- manufacturing tolerances or perhaps corrosion, the one follower is a tight fit, preventing a sufficient flow of oil passing along side it, causing a lubrication issue.

any ideas on how i can free it up so that oil can pass? could i rub the follower gently on some 1500+grit wet'n'dry ? or would that kill it?
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Old Sep 01, 2009, 08:37 AM
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I would say that you over revved it a bit. I lube my rockers periodically with power steering fliud. The stuff is tenacious when it comes to staying where you put it. I do this with OS, LASER and Enya fourstrokes as well as the Saitos. You should be running about 3% castor in your fuel. Contrary to popular myth it will not build up on anything except the muffler and if you seal the muffler joints with Teflon Plumbers Tape it will not build up on that.
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