I have a Saito 300 Twin with the single carb. I've been breaking it in on the bench and tonight I decided to check my cylinder temps with an Infrared Gun (from my RC car days). With the engine running about 1/2 throttle I have a 40 deg difference in temp. between the 2 cylinders. Looking at the way this is made I noticed that one intake runner is shorter than the other. The cylinder with the shorter intake runs richer, cooler temp, while the cylinder with the long runner runs leaner, hotter temp. Makes sense that the fuel would take the shorter route which is the path of least resistance. This engine was designed this way and with unequal intake lengths and only one carb feeding both it will never be balanced.

Does anyone know why Saito did this???

On the other hand, on my Saito 130T with dual carbs I can get the cylinders running within 5 degrees of each other

I'm stumped![&:]

Meesh:

Differences in the valve clearance will make a lot more difference that the inlet runner length. And even production tolerances in the glow plugs. Switch the plugs side to side and retest, check the valve lash and retest.

The nastiest I've run into on a Saito twin was ONE cam one tooth out of time.

Bill.

Hi Bill,

I bought this used on Ebay. Owner said it had only been run once on the bench. By the condition of the motor I believe him.

I will check the valve clearances. If the motor has not been disassembled what are the chances it is out of time?

I had the 300 Twin and had to to run an on board glow to keep both cyls. burning. It was sometimes hard to notice if one side was not firing and the only way I could tell was by putting my hand close to the exhaust pipe of each cylinder and the one that was not burning was much cooler exhaust than the other. It was hard to tell even in flight until I ran the onboard glow...this may not be what is going on with your engine but I just wanted to tell you about it....other than that it was the finest engine I have ever owned in 30 years of R/C and I plan to get another 300 befroe I croke.

Robert:

The one I found the off cam was supposed never to have been pulled down.

It's easy to check. With the plugs out and the rocker covers off to check the lash, turn the crank and watch the rockers. Going in forward rotation you'll see the exhault open, and then as it's closing you will see the inlet start to open. If the cam is timed correctly you will see the two valves equally open when you feel the crank move the pistons past TDC. The two cylinder's overlap points should be exactly one turn of the crank from one to the other.

Ifthe engine is new, with the rockers unworn, you can do an accurate valve adjustment using a feeler strip. If the rockers have any wear you can not. The end of the valve stem will wear, and a groove will wear in the rocker. This is aggravated by oil deposits and gum build up on the rocker face. You might get a good feel with a 0.002" strip, and still have 0.005" actual valve lash. The only way to know for sure what the clearance is requires using a dial gauge. The two pictures attached show the overall set up, this is on an FA-80, but it's the same for all Saito enginesx, whether one, two, three, or five cylinders. The second shot is the plunger of the dial gauge sitting on the rocker arm, as close to being in line with the valve as you can set it. By reaching under the valve end of the rocker with a small screwdriver you can lift the rocker, and read the actual lash.

Now. How many people have that dial stand? And how many are willing to ship their engines to me to have them adjusted? Right. There's a better way, a consistent way, and it's easy.

With the piston at TDC and the valves in the overlap position, turn the crankshaft exactly one turn. If you want to try your feeler gauge go ahead, then set it down and do not pick it up again until it's time to put it away. Loosen the locknut on the adjuster screw, and with your allen key turn the screw back and forth, make sure it turns freely. You noticed, as you turned it in it got a little snug at one point. Look at the valve as you turn the screw in. You will see the valve start to open as you keep turning it. Back the screw out to where it's free again, and turn it back in until you are just at the point where the valve would start opening if you kept going. this should be exactly zero clearance. Hold the screw right there, and tighten the locknut. The threads will distort a little, and if you got the screw just right before you tightened it you will have right at your 0.001" lash. Practice it, do it five or more times to get the feel. Once you have it you will find this method is very consistent, your valves will be as close as they can be done without using the dial gauge. After you do one side switch and do the other cylinder. You will be able to wiggle the rockers and feel the clearance. Easy, fast, and accurate.

Hope this helps you find the problem.

Bill.

Here's the rig for an installed engine, with the flexible clamp-on dial stand.

Bill.

Bill,

Thanks for the wonderful explanation and the pictures. When I was a kid I owned a new 1969 Chevy Z-28 Camaro that had solid lifters in it. Every 1000 miles I got out the dial indicator and set the valve lash just as you described here. I guess basically most engines with overhead valves and solid lifters are the same, just different sizes.

I will check first to see if the timing is off then I will adjust the valves. Again, thank you for your very detailed explanation.

Bob

William,

I went to check the timing tonight. I pulled the valve covers and saw huge clearances in the valves. Got my feeler gages out and measured .025"-.030" gap on all 4 valves. This was checked with each cylinder at TDC on the compression stroke. I also found one rocker arm pivot very loose. Checked the timing and it seemed fine. I adjusted the valves per your instructions then checked to see that the intake runners were not loose. They were snug. I see no wear on any of the valve train componenets. Is it possible the clearances were set loose like that at the factory??

Thanks again!

Bob

Bob:

Not probable, but it could have happened.

Make sure you have the wiggle in all the rockers, then run it. If you have a Raytek or similar check the exhaust temperatures, best way we have to be sure both cylinders are running together.

Bill.

I have a Raytek. That's how I measured the cylinder temps.

Thanks!

Bob:

I know about your Raytek. After I made the last post I reviewed the thread, you said in post #1 that you had it.

And you're welcome. Let us know how it runs with the proper set-up.

Bill.

Bill,

I might run it tonight after work if I have enough daylight left.

Hi William,

Ran it tonight. Cylinder head temps were within 8 deg F of each other.
Now that's more like it.

Thanks again for the help.

Bob

Bob:

Glad it came out fine.

And glad to be of service. That's what we're here for.

Bill.