Has any Aussies fouled a plug or does the USA have bad fuel.

I have never fouled a plug in Australia even when my bike was running very rich and blubbering and running like a dog. (Brand new with over oiled air filter at 1300 metres(4000 feet). Maybe your fuel in the US is the culprit. 2000 WR, YZ timing, 42 pilot, 168 main, Staintune Exhaust with Baffle. DRQ needle 3rd clip, pilot srew 1 3/4 turns. I have been as rich as 45 pilot, 172 main, DRQ 4th clip, pilot screw 2 1/2 turns at 1000 feet and had no fouling. The DRQ is our standard needle and is richer than yours.


The DRQ you have is a richer needle than the '00WR in the US - DRS. Lucky for you guys. :)

However, the '99/98WR in the US had a DTM which is richer yet by 3 steps (last letter rich to lean, MNPQRS ).

Yamaha has jumped around alot in 3 years.

Interesting to know what is working for you is a smaller pilot jet. What was wrong with the #45 at 1 3/4 turns??

(Clark, DRQ#3 is about the same as DVP#5, a VERY good choice MKB)

Thanks for the summary,


I had the bike for about 12 months and I have about 13 plugs sitting on the bench. I never had a problem with the stock pipe on the bike, and for a while even with my new E-series the bike ran great. But then I started running OPTIMAX and several things started to happen:

1. while under heavy acceleration the bike started to break-down and fart around (like it was out of petrol)

2. while it never fouled a plug while riding it sometimes never started when cold or just washed.

At the time I was getting a bit upset as plugs aren't cheap and I was told by a dealer that once you'd fouled them they were no good, as sometimes I was only getting one ride out of them. It was only after some much needed help from the gurus from this site and a process of elimination on my behalf that I came to the following conclusions:

1. piss the OPTIMAX fuel off, being a denser fuel it doesn't atomise as well as PUL or reg.UL

2. when washing the bike, make sure that the exhaust is sealed from the water and when oiling you filter that you get all the excess off

3.changed to yz timing and used DR J's EKP needle on clip no 3 and adjusted fuel screw to suit

4. invested in a small blow torch and cleaned up 12 plugs all of which now work fine

I hope some of that can help some one else out there.

James with the 45 pilot it ran to rich (blubbered non responsive) down low up to the lower midrange. Turning the pilot screw in to about 3/4 turn fixed this at idle and just above, but it was still rich in the lower midrange. The 42 pilot fixed this because it has a bigger efect a bit further into rev range than the screw. Now my bike runs well at between 1 1/4 and 2 turns depending on conditions and altitude. Remember that I am using a Australian made Staintune Exhaust with a baffle. Without the baffle it needs a 45 pilot. The baffle is not very restrictive. It just brings the outlet down to about 1 1/4 inches instead of 2 inches without the baffle. It cuts noise by a huge amount and actually performs better than no baffle in the upper midrange and top end. It does loose a slight amount of response down low but is still gives great response. They also use stainless steel wire packing which needs no maintaince and they have a 5 year warranty. This is my 3rd Staintune on different bikes and I would not change to any other brand because of the build quality and features.

Maybe you guys bought two smokes and you just don't know it... :)

Both are interesting perspectives. I've been wondering if other countries needed different jetting based on fuels. Occasionally seeing different setups. MKB's description of a rich setting looks to be rich for here too.

(note:The Euro model carb needle -DRQ in clip#2 is close to the stock YZ400 DVR#4. DRQ looks to be best in clips #2 or #3)


I too wonder if its the fuels.

I always though our fuel over here was close to the worst in the world but there is no fouling probs.

Doesn't the gas in the US have some alcohol content in it?

What octane rating are you guys running?



**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Vist the Rubber Chicken Racing Online Shop

Discounts for ThumperTalk members.

I have my bike here in quebec canada for one year. I never fouled a plug and I've gone thru yz timing and many jetting setting with a restrictive exhaust (megamax2 with quiet core and just 6 disks). Even with 48 pj, 175 main and 2 turn (no air box top) I never fouled a plug even if the bike was obviously rich. My only problem is starting since I have the yz timing but once hot the bike start easily (almost barefoot possible). I went on water up to the seat with the muffler bubbling in water and the bike stopped and just a couple of kick and everything is fine. Do you thing that canada have the same gaz as US? I run the highest octane available at pump here, the 91. I thing gaz is a concern related with the setting and the atmosphere. Hard to tell which factor is the most important.

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