Saito 80 overhaul problems
06-18-2003, 12:13 PM
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Saito 80 overhaul problems
I have recently compltetly rebuilt a SAITO 80. Everything seems fine except that will not run beyond 3/4 throttle. Could I have the valve timing off?
06-14-2004, 10:09 PM
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RE: Saito 80 overhaul problems
Doyne:
You could indeed have the cam out of time. It's easy to do.
Here's how to check without taking the engine apart.
If the engine is cowled, pull the cowling off. Leave the prop on the engine, or put it back on. You wont need the spinner, you can leave it off. The prop is just to make it easier to turn the engine, it's not necessary either. Pull the glow plug and both rocker box covers. Now turn the engine in forward rotation. You will see the rocker open the exhaust valve, with a little more turning it will start closing, and then the intake will start to open. rocking the crank back and forth you will be able to see the approximate point where both valves are open the same amount. This is the "Valve Overlap" point. Stop there, stick a toothpick or similar dowel into the cylinder through the plug hole. Using the toothpick to feel the piston position, rock the crank again. If you find the piston is not at top dead center at the point of valve overlap the cam is out of time. It wont be just a hair, the timing gear teeth are coarse enough you wont miss it. Even one tooth will leave a good bit of piston travel either before or after TDC at the overlap point.
This is a "Cut and Paste" of my post on another thread, the fellow asking there had a similar problem. Have not heard from him since, don't know if it did him any good or not.
If the timing is off, you'll have to pull the cylinder off again to correct it. You can't get the push rod tubes out of the way otherwise,
Retiming? See my next post here.
Bill.
You could indeed have the cam out of time. It's easy to do.
Here's how to check without taking the engine apart.
If the engine is cowled, pull the cowling off. Leave the prop on the engine, or put it back on. You wont need the spinner, you can leave it off. The prop is just to make it easier to turn the engine, it's not necessary either. Pull the glow plug and both rocker box covers. Now turn the engine in forward rotation. You will see the rocker open the exhaust valve, with a little more turning it will start closing, and then the intake will start to open. rocking the crank back and forth you will be able to see the approximate point where both valves are open the same amount. This is the "Valve Overlap" point. Stop there, stick a toothpick or similar dowel into the cylinder through the plug hole. Using the toothpick to feel the piston position, rock the crank again. If you find the piston is not at top dead center at the point of valve overlap the cam is out of time. It wont be just a hair, the timing gear teeth are coarse enough you wont miss it. Even one tooth will leave a good bit of piston travel either before or after TDC at the overlap point.
This is a "Cut and Paste" of my post on another thread, the fellow asking there had a similar problem. Have not heard from him since, don't know if it did him any good or not.
If the timing is off, you'll have to pull the cylinder off again to correct it. You can't get the push rod tubes out of the way otherwise,
Retiming? See my next post here.
Bill.
06-14-2004, 10:50 PM
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RE: Saito 80 overhaul problems
Larry:
The only hard part about removing the crank is getting the prop drive washer off. It takes a strong puller to do it, and until it is off you aren't going to move the crank. See first picture.
The cam timing is easy. You can make a timing tool, recommended, you can use a push rod or small screwdriver, or you can eyeball it.
Look at the cam. As you turn it a 2mm hole (second picture) will be seen in the base circle of the intake lobe. With the intake tappet pulled out of its guide, the timing tool is put in the place of the tappet, and the end will engage the hole in the cam. Then, with the crank turned to TDC the cam and cover assembly is installed. It's that simple.
How do I get a timing tool? Use a length of 4mm or 5/32" wire, turn or grind the end to have a 2mm section on the end. Third picture.
How do I know the crank is at TDC? Looking into the crankcase where the cylinder mounts, turn the crank to center the crank pin at the top. The timing gear teeth are coarse enough that close is good enough, your eyeballs will get it within a few degrees. Fourth picture.
How do I do it with a push rod or small screwdriver? Exactly as you did with the timing tool. Stick it through the tappet guide and into the hole in the cam. You have to be more careful this way, you will have enough clearance that you can get it off by a tooth. Just keep the hole centered in the guide as you put the assembly in place.
How do I eyeball it? Same way, except now you are watching through the tappet guide to be sure the hole stays centered. Not recommended, too many ways to hold the cam with a probe of one sort or another.
The "Official" timing mark on a Saito camshaft is a drill mark on the forward face of the gear, this mark is straight down or straight up when the piston is at TDC. The problem is there is no way to see it with the engine assembled unless you pull the front crankshaft bearing. And even then, there is no matching mark on the crank or crank gear.
The only hard part about removing the crank is getting the prop drive washer off. It takes a strong puller to do it, and until it is off you aren't going to move the crank. See first picture.
The cam timing is easy. You can make a timing tool, recommended, you can use a push rod or small screwdriver, or you can eyeball it.
Look at the cam. As you turn it a 2mm hole (second picture) will be seen in the base circle of the intake lobe. With the intake tappet pulled out of its guide, the timing tool is put in the place of the tappet, and the end will engage the hole in the cam. Then, with the crank turned to TDC the cam and cover assembly is installed. It's that simple.
How do I get a timing tool? Use a length of 4mm or 5/32" wire, turn or grind the end to have a 2mm section on the end. Third picture.
How do I know the crank is at TDC? Looking into the crankcase where the cylinder mounts, turn the crank to center the crank pin at the top. The timing gear teeth are coarse enough that close is good enough, your eyeballs will get it within a few degrees. Fourth picture.
How do I do it with a push rod or small screwdriver? Exactly as you did with the timing tool. Stick it through the tappet guide and into the hole in the cam. You have to be more careful this way, you will have enough clearance that you can get it off by a tooth. Just keep the hole centered in the guide as you put the assembly in place.
How do I eyeball it? Same way, except now you are watching through the tappet guide to be sure the hole stays centered. Not recommended, too many ways to hold the cam with a probe of one sort or another.
The "Official" timing mark on a Saito camshaft is a drill mark on the forward face of the gear, this mark is straight down or straight up when the piston is at TDC. The problem is there is no way to see it with the engine assembled unless you pull the front crankshaft bearing. And even then, there is no matching mark on the crank or crank gear.
06-15-2004, 10:38 PM
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RE: Saito 80 overhaul problems
William
Thanks so much for your post. I was able to get the prop drive washer off by cutting out a piece of 1/8" steel the exact size of the groove in the drive washer. I then put a 5 mm nut on the prop shaft and tapped it with a hammer till the crank shaft came out. The technique for aligning the camshaft will be very helpful when it comes to reassembly.
Where is the best place to order parts for a Saito?
Thanks again for a great post!
Thanks so much for your post. I was able to get the prop drive washer off by cutting out a piece of 1/8" steel the exact size of the groove in the drive washer. I then put a 5 mm nut on the prop shaft and tapped it with a hammer till the crank shaft came out. The technique for aligning the camshaft will be very helpful when it comes to reassembly.
Where is the best place to order parts for a Saito?
Thanks again for a great post!
06-15-2004, 10:55 PM
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RE: Saito 80 overhaul problems
Larry:
Everybody selling Saito parts in the USA has to get them from Horizon Hobbies. Your LHS might give you a part of their markup, or charge full retail. In either case you'll have to pay the local taxes on them. Unless you have a good LHS you want to support it's fastest and easiest just to get Saito parts directly from Horizon. You will save the local taxes but the shipping and handling charge ($7.99 per order) will be added. When I restock parts I try to make as big an order as I can, that spreads the $8 P&H over a greater number of parts, adding less to each one.
Bill.
Everybody selling Saito parts in the USA has to get them from Horizon Hobbies. Your LHS might give you a part of their markup, or charge full retail. In either case you'll have to pay the local taxes on them. Unless you have a good LHS you want to support it's fastest and easiest just to get Saito parts directly from Horizon. You will save the local taxes but the shipping and handling charge ($7.99 per order) will be added. When I restock parts I try to make as big an order as I can, that spreads the $8 P&H over a greater number of parts, adding less to each one.
Bill.
06-21-2004, 09:13 PM
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RE: Saito 80 overhaul problems
William,
After reassembling the Saito 91, although it ran nicely on a test stand, it does not have the power or compression as a new Saito 91 that I have. The rebuilt engine has a new ring, new cylinder, and new bearings. I have used the old valves and valve springs. Should I have replaced these parts as well? I was very carefull to get the timing right on. The valve clearance was also checked and rechecked. My thoughts are that with better compression, better performance will follow. Any thoughts?
After reassembling the Saito 91, although it ran nicely on a test stand, it does not have the power or compression as a new Saito 91 that I have. The rebuilt engine has a new ring, new cylinder, and new bearings. I have used the old valves and valve springs. Should I have replaced these parts as well? I was very carefull to get the timing right on. The valve clearance was also checked and rechecked. My thoughts are that with better compression, better performance will follow. Any thoughts?
06-21-2004, 09:54 PM
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RE: Saito 80 overhaul problems
Larry:
Many possibilities. How much time does it have since the major? Remember the new ring has to seat just as it did in the new engine. If that's it the power will come back as it runs.
Did you check the valve sealing? No, it's not too late. Set the piston about 1/2 way up the compression stroke, pull the plug, the intake stack and the exhaust. Fill the cylinder with fuel, put the plug back in and turn the crank pushing the piston up. If you have enough valve leakage to worry about fuel will run out of one port or the other. If it's just seepage don't worry about it. If, however, the fuel comes out in a free stream pull the cylinder off and fix the problem before the ring does any more wearing in.
Another possibility is the bearing fit. Some Saito cases are a bit small in their bearing bores, putting too much squeeze on the bearings and making them bind. When you assembled the crank into the bearings did the crank turn freely, did it spin and always stop with the ounterweight at the bottom? A little stiffness is OK with new bearings, but it should at least have looked like it wanted to roll to the bottom.
Next thing that comes to mind is the timing gear lash. Did you use a new gasket when you put the cam carrier back on? Again, easy enough to check the free play. Turn the engine to TDC between the compression and power strokes. The valve overlap will hold the cam, you should feel just the slightest amount of free play when you barely turn the crank back and forth. If you feel it you're OK.
If everything checks ok, then just run it, and let the ring seat, and the power will come back.
One final point. Saito has a nasty habit of changing things without telling anybody. Your old engine could be giving as much power as it ever did, and your new engine has the "S" cam and the wide tappets. And if it does your old engine will never match the power of the new one. two ways to tell. Get your dial gauge and degree wheel out, check the cam profiles on both engines. The other way is to take the new engine apart and look at the tappets, see if the cam has an "S" next to the timing mark. What makes it nastier is that it could have the "S" cam and the old style cylindric tappets, this makes it sort of an intermediate cam between the old one and the "Full house" "S" cam installation.
Sorry if I got too detailed, most likely it just needs time to seat the ring.
Bill.
Many possibilities. How much time does it have since the major? Remember the new ring has to seat just as it did in the new engine. If that's it the power will come back as it runs.
Did you check the valve sealing? No, it's not too late. Set the piston about 1/2 way up the compression stroke, pull the plug, the intake stack and the exhaust. Fill the cylinder with fuel, put the plug back in and turn the crank pushing the piston up. If you have enough valve leakage to worry about fuel will run out of one port or the other. If it's just seepage don't worry about it. If, however, the fuel comes out in a free stream pull the cylinder off and fix the problem before the ring does any more wearing in.
Another possibility is the bearing fit. Some Saito cases are a bit small in their bearing bores, putting too much squeeze on the bearings and making them bind. When you assembled the crank into the bearings did the crank turn freely, did it spin and always stop with the ounterweight at the bottom? A little stiffness is OK with new bearings, but it should at least have looked like it wanted to roll to the bottom.
Next thing that comes to mind is the timing gear lash. Did you use a new gasket when you put the cam carrier back on? Again, easy enough to check the free play. Turn the engine to TDC between the compression and power strokes. The valve overlap will hold the cam, you should feel just the slightest amount of free play when you barely turn the crank back and forth. If you feel it you're OK.
If everything checks ok, then just run it, and let the ring seat, and the power will come back.
One final point. Saito has a nasty habit of changing things without telling anybody. Your old engine could be giving as much power as it ever did, and your new engine has the "S" cam and the wide tappets. And if it does your old engine will never match the power of the new one. two ways to tell. Get your dial gauge and degree wheel out, check the cam profiles on both engines. The other way is to take the new engine apart and look at the tappets, see if the cam has an "S" next to the timing mark. What makes it nastier is that it could have the "S" cam and the old style cylindric tappets, this makes it sort of an intermediate cam between the old one and the "Full house" "S" cam installation.
Sorry if I got too detailed, most likely it just needs time to seat the ring.
Bill.
