Saito 180 Help

[Matthew Clive]

I'm trying to run up my saito 180 in a new model before a test flight. I got it on ebay second hand ages ago and i cant remember if its been run before or not tbh.

I've warmed it up gently using a rich mix (3 turns out), let it cool and refired at 21/2 turns out and run it a big longer at tickover, which it holds no problem.

Now i've come to power up and once it gets to half throttle it abruptly stops with a bump. It doesn't matter whether i blip the throttle fast to that point or open it very slowly, it gets to the same rev range and just stops. It does this at any richness setting so i'm thinking this could be a timing issue?

What is going on please?

[Matthew Clive]

Hmm...just started it up again an its not sounding very healthy at tickover either, a bit rattlely.

[Mr.B.]

There are others on here with more experience than me (I'm sure they will be a long in a bit) but it sound like it's lean to me. I assume you have been adjusting the high speed needle, This does not affect the mixture below about half throttle. Try richening up the low speed needle, this is in the middle of the throttle arm. You can find the factory manual on the Sato web site for factory settings. Also check for air leaks around the the carb and intake manifold. The trouble with S/H engines is you don't know what has been fiddled with.

Oh, and when it stops with a bump it can throw the prop so keep well back and check the prop nut is still tight regularly.

Edited By Mr.B. on 14/06/2014 21:44:32

Edited By Mr.B. on 14/06/2014 21:46:38

[Former Member]

[This posting has been removed]

[Mr.B.]

I think the problem is Mattew can't set the top end because the engine won't transition to high revs yet.

[john stones 1 - Moderator]

Yep find factory settings then start from there.

John

[Phil 9]

how is the tank and tubing set up. Does tank sit at the right height for the carb and is the tank close enough. What size tank and tube are you using

are you running it inverted

If it has been sat around for a while the carb may need a clean out

It sounds to me that something other than the needle settings are causing a lack of fuel.

[Former Member]

[This posting has been removed]

[Masher]

I am also of limited experience with Saito 4 strokes but had very similar situation to you. For me, the "Mr. B." solution worked.

I have a Saito 62 and couldn't set the main needle to optimum. Mine idled well but wouldn't run above about 2/3 throttle. I used a rev counter to make sure it wasn't my ear and couldn't peak it up.

So I started to open up (richen) the low speed needle 1/4 turn at a time, waited for things to settle then re-tried the main needled. After about 3/4 turn of the low needle, I could now set main needle and peak up, then back off a bit.

Engine runs perfectly now. I did buy this as BNIB second hand so it may have been inadvertently adjusted

[Matthew Clive]

Thanks for the replies. Mr B - I'll have a go at turning out the bottom end needle later on today and see how it goes. It has already kicked the prop twice when it stopped.

I'm running it inverted with a 500cc tank butted up to the firewall, clunk line is in line with the carb.

Matt

[Matthew Clive]

Turning the bottom end needle seems to have no effect on the running problem.

I'm thinking that it might be a mechanical issue since it seems to grind to a halt rather than through lack of fuel.

Also, the position the prop stops in changes each time it runs. i.e. when i put the prop on, its near vertical at TDC but after its run, the prop is say 10 to 4 position at TDC.

[cymaz]

Posted by Matthew Clive on 15/06/2014 18:49:43:

Turning the bottom end needle seems to have no effect on the running problem.

I'm thinking that it might be a mechanical issue since it seems to grind to a halt rather than through lack of fuel.

Also, the position the prop stops in changes each time it runs. i.e. when i put the prop on, its near vertical at TDC but after its run, the prop is say 10 to 4 position at TDC.

The grinding might be a bad bearing. Check any O rings in the carb, they could be perished and leaking air into the carb which in turn will give you poor adjustment.

[Mr.B.]

I agree with Cymaz, if twiddling the low end needle in having no effect that would suggest an air leak into the carb or manifold.

You say the prop is slipping. and said before that it was running rough when you tried to open the throttle. If there is an air leak that would make it very lean. Leaner = hotter so ignition is becoming advanced and the engine is kicking back causing the prop to slip until it gets so bad it throw the prop off. This can make it seem to rattle or bang (what we used to call pinking in car engines).

The web site PV links to is a good one.

[YakMad]

I've had 1 Saito 180 and 2 150's in my time, the 180 always ran rough, it seems to be a trait of the larger Saito's, my 180 suffered from a sticky valve and required careful sanding/polishing of the valve stem to fix, it did run less rough afterwards. After you adjust the idle mixture don't forget to re-adjust the high end, on Saito's the idle mixture adjustment effects about 70 to 80% of the throttle range not just the idle.

[Andy Green]

I have a Saito 180, and the thing is (Was) brutal. I have tamed it somewhat by converting to spark using one of this guys conversion kits.

I still use glow fuel, but on spark. I'm happy to flick start now, and the tick over is nice and low.

Andy

[Matthew Clive]

Finally cracked it! There is a pressure nipple on the backplate which i hadn't seen before, i plugged it up an now it runs up much better. It seems to have a LOT of pressure behind it because it forced the first bit of fuel tube off it when i first revved up the engine!

This means i can hopefully fly the plane at greenacres this weekend. Fingers crossed!

Edited By Matthew Clive on 19/06/2014 20:58:20

[Steve Hargreaves - Moderator]

The nipple on the backplate is probably the crankcase breather Matthew...this needs to vent to atmosphere as it allows air to flow out as the piston decends & back in again as the piston rises.

It certainly shouldn't be blocked off.

But I'm not an expert on Saitos....should this breather perhaps be linked to the inlet manifold at all? is there a nipple on the manifold at all?

[Matthew Clive]

Oops, you're right Steve;

IMPORTANT !! The crankcase vent must be kept open to the atmosphere. This is NOT a pressure tap. It should not be connected to the fuel tank. Its purpose is to allow excess crankcase oil to drip out and it must never be sealed. It is convenient to connect about 4 inches of fuel tubing to this vent so that excess oil drips can exit outside the model; the fuel tubing is also useful because it is easy to squirt after-run oil into the crank-case through this tube. (see also the “Maintenance” web page).

The only other thing I changed on the engine was the prop for the same same size APC from a wooden one. Maybe that has made it run better.

[cymaz]

Oh no, the breather nipple on the four stroke must never be blocked off unless it is designed as a recirculating system.

[Steve Hargreaves - Moderator]

I think we may have hit on the problem inadvertantly here Matthew.....you were using a wooden prop???

Not a good idea on any four stroke as they need a bit of mass in the prop to act as a flywheel & store a bit of energy for the compression stroke.

As others have said the Saito 180 is a bit of a beast & has a very high compression ratio...16 maybe 18 to 1 at a guess......that big piston takes a lot of pushing up the bore. Add in a bit of pre-ignition & I think at higher throttle openings the wooden prop simply hasn't had the mass to turn the engine over compression & it's stopped....

APC is good....a heavier prop would be even better.....