Problem Yamaha GP 800

[Jajobe]

Good day everybody
After cleaning up the my Jet (Yamahe GP800) I trailed into the water. After warming up the engine, I rev up the Jet. Rpm went normally high, but the speed has not been reached. Only 30mph were Topspeed although the Rpm was normal as usual. What could be the reason? Impeller is normal and is not damaged or clogged. Does ne idea? Compression perhaps?
At idle the engine doesn`t run very nice and has some misfiring. Also at full throttle are some misfiring.
Has anyone some ideas?
Sincerely Jannik

Sorry for my bad english, because i`m form Germany and try it to translate in german with Google Translate

[birdgod]

Check spark plug?

[Jajobe]

Check spark plug?

Thank you with that idea. I will Check this at the weekend.
If the spark plug works normal. Any other ideas?
Greets Jannik

[txredxj]

Check compression

[Jajobe]

Check compression

If the compression ist`t normal the rpm also should`t be normal, or?

[Prism]

I agree. Sparkplus or ignition wires. The misfire is the most likely cause of the low speed.

[04gtxsc]

How old is the fuel?

[Jajobe]

How old is the fuel?

The fuel isn't old. I tanked up the Jet the day before at a normal gas stadion. And the fuel was empty before I tanked up. So there was`t old gas in the tank anymore.

[pantherdawg]

Running on one cylinder, either plug wire, or.............bad news

[Jajobe]

I found my problem.
It was the spark plug. Both spark plugs were damaged.
Now with new pair of them the jet runs fantastic
Thank you for your help