2007 EC300 loose engine

[Davehuge]

Originally Posted by risk74

I was constantly tightening the motor mount bolts and breaking head stay bars on that particular bike.

That's interesting, it sounds to me like the frame that was at fault, out of tolerance, wider at the swinging arm pivot than it should have been. So when you torqued the swinging arm pivot it was tightening against the tension of the frame, not against the crankcases.

This would have meant the engine was still free to move about, hence putting strain on the head stay bars, fatiguing them until they snapped.

Anyway, that's my theory!

[Col]

I finally got time to strip it down.
As feared, it looks like the cases are badly ovalised at the swingarm mount.
But the gap is massive between the bolt and the hole, seems too big to have been caused by a lose bolt and vibration.

I can try to drill the cases back to a round shape and make a sleeve to go in there, the tricky bit will be getting it exactly right so that the other mount points all line up perfectly





Any more thoughts before I do something I?m almost certainly going to regret!

[Davehuge]

Maybe someone's going to shoot me down in flames but in my opinion...

Yes it looks terrible, however I wouldn't worry too much about the excessive clearance around the swinging arm pivot bolt. I don't believe it's the nice tight fit of the pivot bolt in the casing that locks the rear of the engine in place, it's the bushes and spacers, etc. clamping the engine in place when the pivot bolt is tightened to the correct torque.

I would leave the hole as it is. Square off the casing around the hole then rebuild it and add spacers/shims to get a nice snug fit. Then when the pivot bolt is tightened it will clamp the engine, locking it in place.

Anyway, that's what I would try. If it doesn't work then go down the route of boring the casings out (if there's enough meat in them?) and adding a sleeve. If you do end up fitting a sleeve then ensure it's shorter than the hole in the casing, so the engine casings can be clamped. If the sleeve is too long it will just clamp the sleeve leaving the engine loose and causing a similar problem all over again. I hope this make sense!

All the best, Dave.


By the way... I remember reading some models have different diameter pivot bolts. Do you know if this is the original engine that came in the frame? Maybe the engine's been used in a different frame with a larger diameter pivot bolt?

[Col]

Thanks Dave,

I was wondering whether it?s mainly friction that should be holding it there.
I?ll check all of the spacers & bushes for the swingarm etc against the parts diagrams. At least I got the swingarm bolt out ok, good opportunity to grease everything up etc
I think it’s the original engine, the serial starts 250607 which could correspond to a date, it’s a 2007 bike

[Col]

Well, the swingarm bushes are there and the upper rocker arm support spacers are so I can?t see that anything is missing.
The nut was very stiff on the swingarm pivot bolt, I?m wondering if is was stopping before everything was properly snug and allowing the movement.
I’ll order some new rocker arm support just in case they are worn as mentioned earlier.

Edit: just had a look at those rocker arm supports and they do look very worn, especially on the inside where the engine contacts them.

[Davehuge]

Originally Posted by Col

The nut was very stiff on the swingarm pivot bolt, I'm wondering if is was stopping before everything was properly snug and allowing the movement.
I?ll order some new rocker arm support just in case they are worn as mentioned earlier.

Well it sounds like you've found out what caused the problem in the first place.

[Zman]

That is a HUGE gap and I would bet that the clamp load will not be enough to hold the forces on the engine. I would drill the cases larger and insert a bushing to take up the gap.

[Davehuge]

If you do decide to drill the cases and fit a sleeve or bushes, it's going to be tricky to get the correct centre for the hole. You'll need to devise a method of finding the correct centre for the new hole and ensuring it's drilled or bored in the correct position.

[motopsycho87]

I haven't read all the posts in this topic, but on both of the ec300s I've owned they have had play on the swingarm bolt, the reason being that the nut tightens on the shoulder of the bolt before it tightens on the frame. The cure, use a couple of washers larger than the largest diameter of the bolt (not the undersized threaded section).

[Davehuge]

Originally Posted by motopsycho87

On both of the ec300s I've owned they have had play on the swingarm bolt, the reason being that the nut tightens on the shoulder of the bolt before it tightens on the frame.

That's interesting...