Unusual Technical Support Request

[Jon Carleton]

I've learned a lot from this forum, as I have lurked a while. I fly gyroplanes and own a machine powered by a Yamaha Nytro 2009 FX-?? that had a problem the other day. It had an overheat issue...but then it got wierd:

* I left it to cool down after landing, and it was running well. I started it up once cold to be sure.
* The next day, it would not start. I ran a compression check and it was 50-0-50 (instead of 180-180-180).
* No oil in the water or water in the oil.
* Further inspection revealed the timing chain was loose. Very odd...this is a low-time engine (150 hours +/-).
* Installed new tensioner (even though the old one looked OK), but the chain "jumps" and becomes temporarily loose when turning the engine over by hand, so I haven't gone further. However, I did the cam alignment procedure when replacing the tensioner.

And so my questions:
1. This is a basic rookie question. The Service Manual talks about turning the engine clockwise for several operations. Is that clockwise from the cylinder 1 end or cylinder 3 end? I ask because the cylinder 3 end is where the crankshaft access is located and the TDC indicator. I can make a good case for either, but cannot find it spelled out.

2. I'm thinking my problem may be a deformed/broken chain guide. Must one remove the head to access the cam chain guides? (please tell me there is another way....'cause that would be really unfortunate).

3. I have not tried a compression check to see if anything changed after the cam alignment, nor do I know how far off it may have been prior to the process (my "helper" removed the tensioner as I was turning the engine to #3TDC, knocking the chain off before I could check prior alignment). The jumping chain bothers me as well.

4. Does this engine typically bend valves on a timing chain misalignment?

5. Please feel free to add any suggestions for elements I may have missed! Thank you in advance!

 

[thor452]

that motor is known for timing chain tensioner problems the original can stop working and allow slack and timing jump and valve problems. if you read this thread https://ty4stroke.com/threads/cam-chain-tensioner-replacement-3-cylinder-engine-05-07.90826/ faq section of the RS fourm

 

[MIViper]

The FX Nytro was a 1049 and the RS Nytro was a 973. Different engines?

 

[cannondale27]

Clockwise flywheel or 3 side. Counterclockwise Pto or 1 side.
https://ty4stroke.com/threads/alway...ent-issues-when-changing-clutch-parts.148632/

You should be able to see broken guide with valve cover removal and flashlight.

 

[Jon Carleton]

Thor-> Thanks for the link. It answered many of my questions.
cannondale27-> Thanks! Can one replace the broken guides without removing the head?
MIViper-> My engine is the 3-cylinder 1049. I do not know the 973.

To my question regarding bending valves with the cams out of sync: Does it happen? Can it happen? Or (I hope) is it not an issue with this engine?

 

[thor452]

I am fairly certain it can and will.

 

[MIViper]

MIViper-> My engine is the 3-cylinder 1049. I do not know the 973.

I was stating that you had an FX Nytro engine and the link was for an RS Nytro engine. I didn’t know if that link would apply to your 1049 engine or not?

 

[cannondale27]

It’s a interference motor so valves can hit pistons if out of time. Valve cover has a guide in it also so can jump time if engine turned with cover off. I believe lower guides replacement does require head removal but will check for you.

 

[Jon Carleton]

MIViper-> Based on the Service Manual, the process seems identical.

 

[stevewithOCD]

This is awesome!
Any pics of this thing?
Now MrSled has to make a Gyroplane section.........i don't even know what a gyroplane is, but it has a Yamaha motor in it so it must be cool...

 

[Jon Carleton]

Well, gyroplanes ARE awesome, and a Yamaha engine is an excellent powerplant for their application. Here is a video of one of my TangoGyro test flights (this gyroplane has the 3 cylinder carburated engine):

 

[KnappAttack]

If you spin a three cylinder Yamaha backwards it can and will skip the chain over the cam sprockets. I watched it happen myself and it does not take much reverse rotation to have it happen and come out of time.

The tensioner is hydraulic and ratcheting, when its at the end of one tooth and not quite enough to get to the next on the ratchet, the chain is very loose and will skip when spun backwards. Very poor setup and you'd think that Yamaha who is supposed to be an elite engine mfgr. would have fixed it by now, but nope.

 

[TrueBlue]

If you spin a three cylinder Yamaha backwards it can and will skip the chain over the cam sprockets. I watched it happen myself and it does not take much reverse rotation to have it happen and come out of time.

The tensioner is hydraulic and ratcheting, when its at the end of one tooth and not quite enough to get to the next on the ratchet, the chain is very loose and will skip when spun backwards. Very poor setup and you'd think that Yamaha who is supposed to be an elite engine mfgr. would have fixed it by now, but nope.

When you say spinning the primary backwards is that towards the front of the machine or to the rear of the machine.

 

[Jon Carleton]

I'm glad to see I am not the only one confused about which end is the "FRONT" with regard to spin. The motor needs to always spin clockwise with cylinder #3 as the front.

By the way, my problem turned out to be a head gasket issue. I have it apart now awaiting new gasket and head bolts.

 

[Agman 57]

Well, gyroplanes ARE awesome, and a Yamaha engine is an excellent powerplant for their application. Here is a video of one of my TangoGyro test flights (this gyroplane has the 3 cylinder carburated engine):

This is so Cool, do you mind me being nosey and asking “ Ball Park, how much does something like this cost?”