Broken Cam gear Saito 270- Help
06-19-2004, 07:39 PM
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Broken Cam gear Saito 270- Help
William Robison and other Saito guru's,
I broke the teeth on opposite sides of one cam gear of one cylinder today in flight. I ran on one cylinder and I was able to land.
What now? Send it to Horizon? Any ideas how much it might cost to fix? Should it be taken apart and be totally rebuilt because of its age? Can I do this myself? Does the timing have to be set? Can I ask any more questions?
You get the idea about where I'm going with this. I'm no 4 stroke mechanic and I want it to be right...thanks
Dave
I broke the teeth on opposite sides of one cam gear of one cylinder today in flight. I ran on one cylinder and I was able to land.
What now? Send it to Horizon? Any ideas how much it might cost to fix? Should it be taken apart and be totally rebuilt because of its age? Can I do this myself? Does the timing have to be set? Can I ask any more questions?
You get the idea about where I'm going with this. I'm no 4 stroke mechanic and I want it to be right...thanks
Dave
06-19-2004, 08:17 PM
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RE: Broken Cam gear Saito 270- Help
Dave:
How do you know exactly what's broken if you've not taken it at least partly down?
My thoughts, off the top of my head. The first timing gear has broken, how about damage to the gear on the crank and the other driven gear? I'd tend to replace them all. And that means the cams themselves, and the tappets. Close to $100 for those parts. I'd also replace the valve springs, which will require machine work to the cylinders to fit the larger diameter springs. Or new cylinders. Machine work cost here zero as I'm set up for it, elsewhere around $100 estimated. New cylinders $200. New rings are a minor amount of the total, around $25-$30 the pair. Might have to be made specially since it's an old discontinued engine. Crankshaft bearings, $35 for a good set.
And another consideration. Did a valve hit the piston? That'll be a valve replacement also, if the piston is just slightly dinged it can be reused.
But yes, you can do it yourself, and yes, the cams have to be timed.
When you add up the cost you might just decide to buy a new one.
If you decide to fix it I'll give all the help I can, from advice through machining the cylinders for you, or doing it all.
However I thought I heard you say "...did you send a bill? My SeeEyetow 270 is in the mail to you today! Who needs Horizon we have Will Robison!" just a few days ago? Why did you fly the engine when you were going to send it to me? Granted, that was only three days ago, so should I expect it in tomorrow's mail?
Haw.
Let me know.
Bill.
How do you know exactly what's broken if you've not taken it at least partly down?
My thoughts, off the top of my head. The first timing gear has broken, how about damage to the gear on the crank and the other driven gear? I'd tend to replace them all. And that means the cams themselves, and the tappets. Close to $100 for those parts. I'd also replace the valve springs, which will require machine work to the cylinders to fit the larger diameter springs. Or new cylinders. Machine work cost here zero as I'm set up for it, elsewhere around $100 estimated. New cylinders $200. New rings are a minor amount of the total, around $25-$30 the pair. Might have to be made specially since it's an old discontinued engine. Crankshaft bearings, $35 for a good set.
And another consideration. Did a valve hit the piston? That'll be a valve replacement also, if the piston is just slightly dinged it can be reused.
But yes, you can do it yourself, and yes, the cams have to be timed.
When you add up the cost you might just decide to buy a new one.
If you decide to fix it I'll give all the help I can, from advice through machining the cylinders for you, or doing it all.
However I thought I heard you say "...did you send a bill? My SeeEyetow 270 is in the mail to you today! Who needs Horizon we have Will Robison!" just a few days ago? Why did you fly the engine when you were going to send it to me? Granted, that was only three days ago, so should I expect it in tomorrow's mail?
Haw.
Let me know.
Bill.
06-20-2004, 05:57 AM
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RE: Broken Cam gear Saito 270- Help
Bill,
I did take it down right there at the field. Had to see what was happening. The broken teeth were just sitting there inside. The gear on the crank seems to be ok and the other driven gear I guess is ok. They could both have some damage but the other piston turns and runs, remember it was running when I landed.
As for all the other stuff you mentioned, I'm trying to get out cheap as I couldn't afford a 300 twin right now without selling the plane. Go Figure.
$100 for parts...ok. Valve Springs, why machining? Don't the 300 parts fit except for the cylinders?
Man, you are talking almost $500 to repair, (that includes $100 for your machining). But even if you did the machining for me there would be a charge for your labor. It is certainly fair, I'm just hobby poor at the moment. That kind of money puts me in a used 300 twin anyway, which would fly the plane better.
Decisions, decisions.
Any Ideas on what caused it to break?
"...did you send a bill? My SeeEyetow 270 is in the mail to you today! Who needs Horizon we have Will Robison!" ...WHO WOULD HAVE KNOWN!!!!!
Thanks, I'll be doing some research trying to figure out what to do...Man this hurts!
Dave
I did take it down right there at the field. Had to see what was happening. The broken teeth were just sitting there inside. The gear on the crank seems to be ok and the other driven gear I guess is ok. They could both have some damage but the other piston turns and runs, remember it was running when I landed.
As for all the other stuff you mentioned, I'm trying to get out cheap as I couldn't afford a 300 twin right now without selling the plane. Go Figure.
$100 for parts...ok. Valve Springs, why machining? Don't the 300 parts fit except for the cylinders?
Man, you are talking almost $500 to repair, (that includes $100 for your machining). But even if you did the machining for me there would be a charge for your labor. It is certainly fair, I'm just hobby poor at the moment. That kind of money puts me in a used 300 twin anyway, which would fly the plane better.
Decisions, decisions.
Any Ideas on what caused it to break?
"...did you send a bill? My SeeEyetow 270 is in the mail to you today! Who needs Horizon we have Will Robison!" ...WHO WOULD HAVE KNOWN!!!!!
Thanks, I'll be doing some research trying to figure out what to do...Man this hurts!
Dave
06-20-2004, 08:07 AM
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RE: Broken Cam gear Saito 270- Help
I believe Bill is taking a rather pessimistic view of what is required. I would thoroughly clean and inspect the cam cases for each cylinder, the good cam gear, and the crankshaft gear. If no other damage is visible, replace the broken camshaft, time it, and go.
Cam tooth breakage on Saitos is nothing new. I have replaced several. I believe it is the result of detonation due to running too lean, especially with higher nitro fuel. Good luck.
Cam tooth breakage on Saitos is nothing new. I have replaced several. I believe it is the result of detonation due to running too lean, especially with higher nitro fuel. Good luck.
06-20-2004, 09:59 AM
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RE: Broken Cam gear Saito 270- Help
Dave:
The reason for replacement of all three gears is that whatever loaded one to the point of breakage also loaded the other two, probably less expensive to replace them that to have an X-ray inspection to be sure they aren't cracked and about to do the same thing the first gear had already done. Even though they may never fail, putting them back in is a crap shoot.
The earlier valve springs have a coil diameter of 6.95mm, with the bore in the cylinder just clearing them. The currently supplied springs are 7.25mm OD, and wont fit into the head.
It's not just a matter of an overbore, as the valve guide comes up inside the spring relief, and has to be left as original. o, a special cutter has to be made.
And you have a misconception about my work here, If I'm repairing your FS plane my shop charge is $150/hour, but for model engine repair the total cost is parts plus the return postage. No labor charge. In other words, your cost for my doing the machine work will be about $20 for postage and insurance two ways. My contribution to the hobby. (Call it a "Sport" and I'll charge you. Haw.)
Bill.
The reason for replacement of all three gears is that whatever loaded one to the point of breakage also loaded the other two, probably less expensive to replace them that to have an X-ray inspection to be sure they aren't cracked and about to do the same thing the first gear had already done. Even though they may never fail, putting them back in is a crap shoot.
The earlier valve springs have a coil diameter of 6.95mm, with the bore in the cylinder just clearing them. The currently supplied springs are 7.25mm OD, and wont fit into the head.
It's not just a matter of an overbore, as the valve guide comes up inside the spring relief, and has to be left as original. o, a special cutter has to be made.
And you have a misconception about my work here, If I'm repairing your FS plane my shop charge is $150/hour, but for model engine repair the total cost is parts plus the return postage. No labor charge. In other words, your cost for my doing the machine work will be about $20 for postage and insurance two ways. My contribution to the hobby. (Call it a "Sport" and I'll charge you. Haw.)
Bill.
06-20-2004, 12:51 PM
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RE: Broken Cam gear Saito 270- Help
Wow!,
That is very generous of you. I didn't know you worked on full size planes. I just went to the glider field last week and plan to take a sailplane ride soon. Maybe even next week. www.glider.org
It sounds like I need to save up for parts and send you a care package. I bet this motor makes enough power if properly running to fly this Eagle. If I could do this without the money for the pistons...you said cylinders not pistons eh? then it might be worth it. Thanks for the offer and I'll see what I can scrounge up.
If you need decals I can help there for you. I have a sign business.
Dave
That is very generous of you. I didn't know you worked on full size planes. I just went to the glider field last week and plan to take a sailplane ride soon. Maybe even next week. www.glider.org
It sounds like I need to save up for parts and send you a care package. I bet this motor makes enough power if properly running to fly this Eagle. If I could do this without the money for the pistons...you said cylinders not pistons eh? then it might be worth it. Thanks for the offer and I'll see what I can scrounge up.
If you need decals I can help there for you. I have a sign business.
Dave
02-23-2005, 02:50 AM
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RE: Broken Cam gear Saito 270- Help
Seeing as you know the 270 so well, My crankshaft is bent slightly. It still runs well but looking closely it is a little off. I wanted to replace it but I couldn't find parts. Can it be straightened and if not, do you know where I can get parts?
02-23-2005, 06:26 AM
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RE: Broken Cam gear Saito 270- Help
RJ:
The crank can be straightened. Replaement parts can be had from Horizon only if they fit current engines. Thankfully most service parts will interchange, or can be fitted with just a little rework. Piston rings have to come from Frank Bowman though.
Bill.
The crank can be straightened. Replaement parts can be had from Horizon only if they fit current engines. Thankfully most service parts will interchange, or can be fitted with just a little rework. Piston rings have to come from Frank Bowman though.
Bill.
02-23-2005, 11:40 PM
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RE: Broken Cam gear Saito 270- Help
Bill
I looked at Horizon Hobbies, they have most parts for the 270 but no crank. Are the crank and bearings for the 300 interchangeable? Would the average machine shop be able to straighten the old one, or should I send it somewhere?
Jason
I looked at Horizon Hobbies, they have most parts for the 270 but no crank. Are the crank and bearings for the 300 interchangeable? Would the average machine shop be able to straighten the old one, or should I send it somewhere?
Jason
02-24-2005, 12:07 AM
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RE: Broken Cam gear Saito 270- Help
Jason:
The 270 and 300 twins use the same bearings. One each MR6003, MR6200, and MR6903. The MR6200 should be a -Z, -ZZ, or -2RS type. The "Z" and "ZZ" have either one or two metal shields, leave them in. The -2RS has rubber seals on both sides, pop one out and put the remaining seal to the outside.
If the stroke is the same on the 270 and 300 the cranks should interchange, but I don't know the stroke on the 270. A good machine shop can straighten it if they have centers to work on something that small. Or if you want to send it here I can straighten it for you. Or I can do the entire repair if you wish.
Let me know.
Bill.
The 270 and 300 twins use the same bearings. One each MR6003, MR6200, and MR6903. The MR6200 should be a -Z, -ZZ, or -2RS type. The "Z" and "ZZ" have either one or two metal shields, leave them in. The -2RS has rubber seals on both sides, pop one out and put the remaining seal to the outside.
If the stroke is the same on the 270 and 300 the cranks should interchange, but I don't know the stroke on the 270. A good machine shop can straighten it if they have centers to work on something that small. Or if you want to send it here I can straighten it for you. Or I can do the entire repair if you wish.
Let me know.
Bill.
