buzzard bait

I have a very old Saito 45 I got with a Flair Taube that I picked up from another club member.

It had no compression, but it started and ran fine, except that max power was 8700 on a 12x4 Zinger, which of course is very poor. So I adjusted the valves using feeler gauges from my OS 70, which I understand to be correct for Saitos as well. That brought back the compression, which actually felt pretty good.

The LS needle was out 6 turns, so after a quick adjustment of the HS needle, I worked on the LS needle. It wound up at 4 1/2, which surprised me; it's still a bit rich by the pinch test, but I left it there because it idles at 2400 and picks back up again just fine.

Now here's the part I don't get: When I open the throttle, it will get to about 8900 rpm at about 3/4 throttle, but then as I advance the throttle further, the rpms DROP. It also gets a little rough. I can't cure it by leaning out the HS needle. Note that the power is hardly any better than it was when it had almost no compression, but I can't actually open it up all the way because of the weird throttle reversal.

Anyone have any ideas?

Thanks,
Jim

p.s., the 80 inch, 6 pound Taube took off and flew with the engine turning 8700, and since full scale Taubes were also very low-powered, I don't actually need any more power than I'm getting. I'd just like to solve the mystery of the throttle "reversal" if possible.

w8ye

My Feedback: (16)

The low speed needle is too lean

buzzard bait

Even at 4 1/2 turns open? It seemed still a bit rich by the pinch test, but if you think this could be it I'll give it a try.

Thanks

w8ye

My Feedback: (16)

The low speed will effect a considerable amount of the high speed. As you get the low speed closed down too much, the high speed will become completely ineffective to where you can open it until it falls out and the engine will still be too lean.

buzzard bait

I've experienced that kind of issue before, but I don't think that's what is going on here. I did go back out and try richening up the LS needle some more, and that did allow full use of the throttle, but top end was still 8900, and worse, the engine would die instantly when I tried to throttle down. More messing with different needle settings, HS and LS, just altered the problem a little. In the end, I cannot find settings that allow the engine to run and transition at all speeds.

What is odd is that the engine ran fine when the exhaust valve had practically no clearance at all and was not closing. Could there be a problem with the valves? I adjusted them so the 0.1 gauge just fit.

Jim

w8ye

My Feedback: (16)

If you have a 45 MK II style engine I would venture to say that 8900 is pushing it in the rpm department

The recomended valve clearance is more in the order of .002" - .004"

It will idle better with the wider clearance.

Hobbsy

My Feedback: (102)

Jim, I been cypherin on this a while and if I understand correctly he is running the HS needle at 4 turns out, that's a lot. T I think the clue is that when reaching 3/4 throttle the engine gets rough and slows telling me the HS needle is too rich. If it were lean it would just quit instantly. I could run my .45 MKII tomorrow and see where the HS needle ends up.

BB, what fuel are you running and I'll come as close to it as I can. I have 5, 10 and 15% WildCat.

buzzard bait

Thanks Hobbsy and Bruce. The HS needle is about 2 turns out. It's the LS needle that is very far out...it was 6 turns out when I got it and I've adjusted it as low as 4 and about everything in between. The LS needle is a nice brass piece with fine threads.

I'm using Cooper Fuel with 10% nitro; it has a good synthetic oil and a very small amount of castor.

I'd be interested in hearing what your settings are, Hobbsy, even though I know those can vary quite a bit. I'm especially interested in whether the LS needle is normally 4 or more turns out.

I re-read this piece, http://saito-engines.info/maintenance.html, and I do wonder if the exhaust valve gap is a bit wide, since mine allows a 0.1mm (.04 in.) gauge to slide through now, after adjustment. It was valve adjustment that started all the problems.

Yes, it is an old Mk.II, I believe...no powerhouse, I know, but it should do better than this. I have a .40 of the the same vintage (identical case externally) and it is much stronger.

Anyway, I appreciate you guys considering this and coming up with some ideas. Thank you,

Jim

w8ye

My Feedback: (16)

The timing could be advanced a tooth?

buzzard bait

OK, but can that happen without dismantling something? All I took off was the valve covers.

Here's another question: Suppose the exhaust valve adjustment was too loose, meaning that the valve was not opening quite as much as it should. Could that cause a problem at higher rpm, but not at lower rpm? Because the first time I tried to adjust the valves the engine would only run at about 1/2 throttle and it was very rough. Turned out the exhaust valve screw had loosened and I had a big gap. When I got the gap down to 0.1 mm, it improved, but only to a point (8900 rpm) and if I opened the throttle more, it ran rough and slowed down. Very similar to the symptoms when the gap was way too much, but less extreme. So maybe I need to close the gap closer to 0.04 mm.

I don't know enough about 4 strokes to know if this is a reasonable explanation.

I'd check it out, but I got the screw so tight the last time after it had worked loose that I can't adjust it now. I need a Saito box-end wrench...needle nose will only damage it at this point.

Jim

w8ye

My Feedback: (16)

If the valve is at .1mm it should be good enough.

The mixture on the four strokes is not that different from two strokes.

Hobbsy should file his report on his 45 MK II latter today. I think he actually has two of them.

Right now I feel like Hobsy does that you might be a little rich on the top end.

When setting the high speed needle, I move the needle around and see how the engine sounds. This old Saito, if you get it too lean, will just shut off. It is unlikely to backfire and throw the prop. Play with the high speed needle at full throttle a little and find out where you are at?

If you get the top end peaked, then throttle down and work on the low speed needle. I usually lean them a little and they idle better. Then I check the transition to full throttle. if the engine stumbles some -clears out- and speeds up it is still rich. If the engine wants to quit when you give it the thrttle from idle - the low speed is too lean.

You are not dealing with rocket science here. The Saito MK II is a gentle forgiving engine.

Maybe you should put your 40 on the stand and see how it responds and then try your 45?

Hobbsy

My Feedback: (102)

OK Jim and Jim, the HS needle on the 45 is 1.75 turns out from bottomed out and the LS needle is 2 turns out from bottomed out. Graupner 12x5

buzzard bait

Thaniks very much Hobbsy. Your old Saito looks pristine...other than that it looks just like mine.

For HS needle, that's about right where I was, but your LS needle is much leaner than mine. I'll keep that in mind.

I checked the exhaust valve again and the 0.1 mm slides in and out with no resistance, so I've tightened it up so that the .04 mm slides freely but the 0.1 doesn't fit.

I'll report again later. Thanks much for all the advice.

Jim

ArcticCatRider

My Feedback: (6)

Is the throttle barrel turning past WOT, closing a little?

buzzard bait

I wondered that too, but I don't know how to tell. The carb stack is curved, so there's no way to see inside.

Just tried again with a slight valve adjustment and a new OS F plug. Still not running right.

w8ye

My Feedback: (16)

Send it to Hobbsy and let him look at it?

buzzard bait

Success!! I had to abandon the notion that adjusting the valves caused the problem, even though there was no problem till I did that. But that's how it goes sometimes.

After lots of messing with needles and valves, I finally took out both needles, fired up my compressor, and blasted high pressure air through the carb. I also fitted a short piece of tubing over each needle, then re-installed. The engine worked very well right away. I got 9000 rpm on the 12x4, which is still kind of doggy, but it's definitely good enough for the Taube; transitions are all good now, which was my biggest concern. Throttle works normally thoughout range.

Idle is not ideal...about 2800 vs. 2400 before. But it will do. Seems a little rich, and the LS needle is pretty far out, but if I try to lean it out, then the engine dies when I throttle up. Leaving it as is, the engine works. HS needle is about where Hobbsy's is.

Thanks for pitching in everyone. Always helps to have help kicking around ideas. I'll post a pic of my Taube in a couple days. The Flair kit is a little different from the BUSA.

Jim

Gizmo-RCU

My Feedback: (27)

Just for grins pull the exaust and check for carbon on the exaust valve, my old 45 needed the carbon removed about two times a year! (castor fuel).

buzzard bait

Do you mean remove the valve cover on the exhaust valve? I've had it off a few times. How did you get the castor off?

Gizmo-RCU

My Feedback: (27)

Pull the muffler pipe off the head.....or just the pipe as some of the old ones did not have a muffler. Look into the port and you can see the valve. If it has much carbon you will see it no problem.
I used an old paper clip end to carefully push off the carbon until the valve was clean then a little air to clear the chamber. Stay away from the chamber walls it's self as it is much softer and could be gouged up by the steel clip.
Us a little care in putting the pipe back on as you do not want to cross-thread it.
This is a very easy process and takes very little time!!![8D]

buzzard bait

Thanks Gizmo. I tried to look inside, but couldn't see. I'd need a better light. But I did try poking around with a wooden toothpick with a bit of cloth wrapped on the end, and every time I stuck it in it came out with a grungy black spot.

I tried to get Hoppe's gun cleaner here, but can't find it. I'm thinking carb cleaner might help.

Jim

Hobbsy

My Feedback: (102)

Buzz, would it be possible for you to send me a copy of your 45MKII instructionsI seem to have only the parts page of mine. Thanks, Dave

buzzard bait

I'm sorry Dave, I don't have any instructions either. My engine came used on a plane, and I got my FA-40 used also.

Jim

Hobbsy

My Feedback: (102)

No problem mate, that guy at Bob's Engine Service has em for 2 bucks. I'll get a link for you.

Well, it ain't much, a mailing address and a list of what he has is all you get.

http://bobsengines.com/instruction_sheets2_04.htm

Patxipt

Hobbs, I'll send you the one you gave me a couple of years ago, I'll stick with a copy for myself. Will send it out tomorrow