Plugs get fuel fouled after 50 miles

[Paul G]

Kaw 650. After about 50 miles the bike will barely run. Pull the plugs and they are wet. Fuel not oil. What could it be?

[Lord Grizzlon]

4give me if im wrong or way off base cause im not a mechanic, but maybe adjust your air/ fuel mixture or ur floodin ur carbs.

[sixtysix]

Choke partially on or broken, carbs mis adjusted or dirty, mice or other blockage in air cleaner, just to get you started.

[Bud Manley]

Same thing happens on my brothers old bike. Try changing the plug. If it fires right up then you've got problems. We never got his working. DAmnsest thing is when you pull the plug and tried kick starting it gave a spark. Just not enough to ignite the fuel. Really weak. I think he just need to replace electrical stuff on it (cap, rotor, coil)
Good luck

[Geezer]

There could be a few things at fault here but the most likely cause is the wrong jets. It's also psssible that somebody redrilled the pilot jets.

One thing I've found with Yamahas recently is that new Mikuni pilot jets are of a different design than the ones made in the 1970s but look similar to them and will install just fine but run so damn rich that it'll be puffing an weezing within a few miles. For me the diagnosis was easy, I only had one new jet and it was that cylinder that had the problem.

You could have a problem with the floats but then it would be flooding all over the place.

Geezer

[Lawrence]

(I have had similar probs on my old Hondas) - when the coils are not up to the job - you will have a spark that is visible (at the plug) but isnt strong enough - a quick test is to remove the plug cap and see how far the spark will jump from the end of spark plug lead to the frame (or stick a length of plug lead into cap to get same effect) The spark should jump 1/2 inch with a nice strong bright colour - a faint spark at 1/4 inch indicates the coils are not good enough (old hondas).

Check the carb floats etc aswell.

Note: Some bikes have spark pickups that activate the coils - when these pickups fail you get all the symptoms of bad coils, bad carbs, bad everything.

E/:?)njoy

[Paul G]

Problem solved

The carbs were removed and cleaned out. Some goo but not horible. Flushed out all the ports and passages. Reassembled and the bike runs once again. He has about 250 miles on it so far with no plug fouling and it runs good as ever.

Thanks for all the help. My friend is glad to be back on two wheels.