618 vibration

[powerfly]

Hi there,
Do any users of 618 engines have a vibration problem when giving full power?

I have a 618 in my trike and find that i take off at 6200rpm and all is smooth and climb like a home sick angel. When i give full power i find there is a vibration on the engine or prop. It only comes from full power. Any ideas?

NOel

[ZU-CDW - Shark]

Hi Noel,

From my personal experience regarding props and vibration the cause can be numerous e.g. Prop mounting flange could be bent, the main bearing on the crank could have shifted from a prop strike or the prop could be out of balance.

I suggest you remove the prop and do a test on the mounting flange with a micrometer to test if it is bent. If that is fine try to get a balanced prop and test or alternatively send the prop in for a balance test with Denecker. Also check that the pitch on all the blades are the same, given that it is not a wood prop.

I do not know if the carb balance would affect the vibration over 6200rpm as you have stated that it runs smooth up to 6200rpm.

I personally have a 618 on my trike with a slight vibration below 4500rpm which is prop related and decreases as the rpm climes.

I hope you find that the cause is the prop.

[Griffin]

I suggest you remove the prop and do a test on the mounting flange with a micrometer to test if it is bent.

How would you check with a micrometer? Do you mean a dial guage?

[powerfly]

Howzit Shark,

Cleaned carbs, jetss, etc...

Measured blade pitch and all fine so it needs to be prop balance. Going to try a new prop and see the diffs.

I hope it is not the crank...cant afford....

Shot

[Rudix]

Howzit Shark,

Cleaned carbs, jetss, etc...

Measured blade pitch and all fine so it needs to be prop balance. Going to try a new prop and see the diffs.

I hope it is not the crank...cant afford....

Shot

It is worth looking at the RAVE valves, when mine gets dirty they stick and it causes a vibration as well. If you have the over-ride option installed you can try playing with that in the air to see if it helps.

I have also found that by adjusting the spring tension (using the red caps) you can get it to run smoother, as you decrease the tension by screwing the caps out it should get smoother (RAVE valves opens earlier) but you get to a point where the mid-range suffers and you end up with a "flat spot" that can be scary on take-off !

Good luck,
Rudi