Loss of Power, Stall After Bumps

[Vision]

This morning I'm running an errand in an area of town with rough roads/bumps. On the way back on a perfectly flat smooth road going a steady 20mph suddenly the power to the rear tire ended (like I had let go of the throttle) and I was coasting and idling. I gave it throttle but nothing changed. While coasting and moving the throttle back and forth a few times the power to the tire reengaged.

A few minutes later the same thing happened but after going over a speed bump.

A few minutes later it happened again while on a flat road. 

Then when close to home I hit a bump and this time the engine died. After pulling over and waiting a moment it started back up again and I was able to make it home.

The fuel filter doesn't look dirty. Should it be replaced anyway?

The drive belt was replaced recently but there was no jerkiness to indicate the belt was having trouble engaging.

[Ruffus]

Don't have a cristal ball, but:
- my first suspect would be the renewed belt and CVT  clutch
(many years on the shelf, too long, too small, and so on...)

- next would be coil, sparkplug cable, cap and plug itself, somehow loose...

- then I would check fuel and air system
This is to be found.

[Stig / Major Tom]

I'm thinking something electrical is going on... like a loose sparkplug cap/wire. Ground cable loose/dirty. Battery cable (s) loose.

Stig

[CROSSBOLT]

I am with loose electrical...

[Vision]

Anyone think it could be the cdi?

[Ruffus]

Yes, could be a faulty CDI too, but start with inexpensive checking.

[CROSSBOLT]

Anyone think it could be the cdi?

Do what Ruffus said! Don't start throwing parts at the problem!

[Vision]

Agreed. I'm traveling the next few weeks and can't get at the bike, am thinking of ordering spare parts in the mean time.

[Vision]

Hey All, I'm embarrassed to say I think the problem was due to a spark plug needing to be replaced and its cap was knocked a little loose.

I usually replace the Iridium plug each spring after putting about 8k km on it a year. This spring I read that the plug can go something like 60k km before needing to be replaced so I didn't replace it. Does anybody else go through plugs like this?

[Neil955i]

One nil to the Mighty Stig!

[Vision]

Agreed Neil.

[jeeves]

Hey All, I'm embarrassed to say I think the problem was due to a spark plug needing to be replaced and its cap was knocked a little loose.

I usually replace the Iridium plug each spring after putting about 8k km on it a year. This spring I read that the plug can go something like 60k km before needing to be replaced so I didn't replace it. Does anybody else go through plugs like this?

Iridium plugs last much longer then regular plugs. Had an Denso Iriduim on my scoot for over 30000km, on my motorcycle (NGK Iriduim) they lasted over 50000km.
Changing it every 8k km is just a waste.

[Vision]

Just saying, I only get 8k km out of mine.

[stuo]

I vote "loose electrical".

Spark plugs rarely need changing. In the "old" days when we had leaded gasoline they would need cleaning due to the lead deposits on the electrodes, or fouling from an oil burning cylinder. Garages had sand blasting machines that cleaned plugs.

Iridium plugs last at least 50,000 miles due to the use of an iridium electrode, which has an extremely high melting point and doesn't burn away like the old steel electrodes did and which required periodic re-gapping. Platinum electrode plugs are long lasting, too, but apparently iridium is the latest winner in the high price spark plug market.

[Vision]

I use Shell Rotella T6 synthetic 5W-40 diesel engine oil and add 2oz of Techron to the gas tank at every oil change. Is it possible these are creating high temperatures that are eroding the Iridium plugs?