Saito 82 fix-up

Gas and Glow Engine discussion

Saito 82 fix-up

PostPosted: Thu Mar 07, 2013 2:28 pm

Just bought a used Saito 82 locally for my new LamYak 40 (I like 4 strokes, what can I say?)

It was DRY inside...I replaced the bearings, unstuck a valve, oiled everything up...but the compression seems a bit low. It doesn't look like it had a lot of hours on it. The cam gear showed very little wear, the piston and cylinder were shiny and showed very little wear...

I'm wondering if my valves are not seating because some crud is in between the seat and the valve face. I'm thinking I'll just run it, see how it performs after a couple of heat cycles, and dig into further after that.

Hope I didn't get screwed on this deal...it was a nice looking engine...no varnish or other evidence of age...but it's my second 4 stroke and I was in a hurry and didn't think about the lack of compression at the time (the indicator of a stuck exhaust valve). If I got screwed it's my own damn hurried-ass fault.
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Re: Saito 82 fix-up

PostPosted: Thu Mar 07, 2013 2:53 pm

If you have your vavle timing tool check the lash....I bet that one of the valves is not seating all the way. Sometimes this can be heard by a hiss sound. I had this happen to one of my 1.00's. I used to love .82's and 1.00s.....not anymore!
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Re: Saito 82 fix-up

PostPosted: Thu Mar 07, 2013 3:16 pm

I had this with my my 82 after not using it for a long time, very low compression, i started with a electric starter and let it warm up and cool down again and it was back to normal, I think it was just a stuck valve, the tiniest bit of crud under the seat will stop it making good compression,

Just run it and see :-)

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Re: Saito 82 fix-up

PostPosted: Thu Mar 07, 2013 3:20 pm

this won't necessarily fix yer problem but a useful leak detection tool can be made by drilling out the center of an old glow plug and epoxying a short piece of brass fuel tube in the hole you drilled (1/8" i think). Add a length of flexible tubing to it, install the plug in yer suspect engine, submerge it in water and blow into the tube, if there are bubbles they will at least tell you where the leak is coming from, ie exhaust, intake or cylinder...can be used on any glow engine then....obviously you'll wanna dry the engine thoroughly after this.

btw, don't be ashamed of liking four strokes!
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Re: Saito 82 fix-up

PostPosted: Thu Mar 07, 2013 4:12 pm

You can usually hear where the leak is coming through the valve.
Stick a port up to your ear and turn it over compression. If your valves are leaking you will hear the hiss in a particular port. More often than not, it's the exhaust as that's the one that runs hotter and gets built up burnt stuff on it.
Sometimes you can run it and get it going, but it is a sign that things need cleaned out inside.
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 7:54 am

Awesome. Thanks for all the recommendations. I'll pull it back apart and see if I can clean the valves. Not sure how to get them off, I don't have a spring compressor that small...
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 8:07 am

I believe that the fuel helps give it compression also.may want to try it by flying it first. Just my two cents worth
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 9:24 am

chopper wrote:I believe that the fuel helps give it compression also.may want to try it by flying it first. Just my two cents worth

I would run it first.

No spring compressor needed. Fingers can do it fairly easily. One finger up the cylinder to hold the valve in place while the other hand pushes the spring and retainer down, and the clip is slid off. Just the opposite for back together.
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 10:15 am

ThumbSkull wrote:
chopper wrote:I believe that the fuel helps give it compression also.may want to try it by flying it first. Just my two cents worth

I would run it first.

No spring compressor needed. Fingers can do it fairly easily. One finger up the cylinder to hold the valve in place while the other hand pushes the spring and retainer down, and the clip is slid off. Just the opposite for back together.


+1 on what these guys are saying. Many times when you take a Saito apart, or haven't run it for a while, it won't seem to have much compression. But, once you run it, everything is fine. Let us know what you find out.
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 1:18 pm

You guys are great. I've got my new build board set up and first on the docket is the 40 size LamYak...I'll update once it's running.
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Re: Saito 82 fix-up

PostPosted: Fri Mar 08, 2013 7:29 pm

Today I was dinking around with the motor (spinning the prop, making engine noises...etc)...and dropped some after run oil into the cylinder and intake.

Compression is much better...and seems to be holding after multiple spins of the prop. This gives me hope it'll be just fine...but we'll see.
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Re: Saito 82 fix-up

PostPosted: Sat Sep 05, 2020 8:07 am

Just bolted a saito 82 on the front of my mojo40. What prop should I be running? Has 13x4 sport on the os55ax. Couldn't keep it running long enough to tell if I liked it or not. Will be pulling the entire setup off and putting on a primo40 after I get all the bugs worked out. The mojo is just my test mule.
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Re: Saito 82 fix-up

PostPosted: Sat Sep 05, 2020 9:02 am

13x7, 14x6, 15x4 - these are the 30% nitro best props. If you are on 10-15% then 14x4, 13x6
I usually run a 14x6 Xoar wood or MAS S2 on 30% for an 82.
If you want it to feel more like a 2-stroke, go with the 13x7. If you want to exaggerate the 4-stroke feel then go with the 15x4.
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