Free Perf. mods ideas for 99 WR400

I've have had my plated 99 WR400 for a couple of months now and my best friend just baught a plated one today :bonk: . Now that we both have the same bike we would like to use one to modify and test against the other for a true reading on the perf. mods we make :cry: . Before we start go buying bolt ons. Can anyone tell us of some perf. mods to start with that don't cost anything :applause: . IE carb adjusts, exhaust tinkering etc. Thanks guys and I will post the results. It will finally be nice to mod one and ride the other stock one for a true feeling of the difference. :cry:

Best of all would be YZ time the cams.

Don't know if the grey wire mod applies?

Uncork exhaust

Open up airbox

Jet correctly to suit

yeah what matty said.

here is link on how to do it.

opening up the exhaust is a good cheap mod too

here is some pics of the inside of mine.

initially it only had a 22m or less than an inch out let, which i changed to 38 mm and opened up the baffle inside.

i drilled some extra holes(10mm) on the baffle you can see with 3 holes in it and enlarged the big hole with a tapered grinder bit out to suit the new outlet.

original outlet pipe (22mm)

this was standard or stock exhaust, yours maybe different in as much as you may be able to unscrew the end. aus version is a sealed unit. precision incision was made with angle grinder.

hope this is of some help.

good luck

You guys rock, keep the ideas coming im all for it. Thanks, I will try all these this weekend... ANY MORE???

You guys rock, keep the ideas coming im all for it. Thanks, I will try all these this weekend... ANY MORE??? :applause:

I have your same bike....some other "free" mods that I did were.

Cut the gray wire.

De-octopuss-ed the carb (removed the extra plumbing on the side of the carb)

Homemade version of the Power Now.

Accelerator pump mod (wheel collar mod)

All of these mods help to clear up the bog off the bottom.

Most can be found archived under Motoman's section.

Good luck


you will find one of the best things about owning a wr (or basically any high performance four stroke) is access to TT.

i say to new owners, dont touch it until you've checked here.

i really couldnt change my own oil without these guys(seriously) i changed it 3 times and filters( like i was told on here to do it every 500km or less) but didnt know there were two drain plugs until someone mentioned exactly how much oil they replaced. DUH ( 1.7 litres to be precise not 500 ml like i had been changing)

not only that, you can help others on simple stuff that the really smart guys are sick of telling people about, just by providing links like we do.

i get a buzz out of helping people even though i'm just recycling expert know how from here. I can ride, i just cant fix. at last look there is 81000 or so members who have real world and practical experience that can help with almost anything to do with 4 strokes, it's great. so far i would say i have saved well in excess of a couple of thousand dollars (aus or $150 US) in unnesscary trips to mechanics through here. even more had i taken it to a yamaha dealer.

good luck

Hey blue speaking of passing on good info...... No wonder I couldnt get the full 1.7 liters of oil out of my bike when I did my first oil change. Wheres the other drain plug? Theres two??? You might be laughing but I thaught the parts guy made me buy extra oil and was mad at him for a while...lolololol. Anyway. I dont think I will ever do anything to the bike without asking the thumper GODS here. Thanks again for everything. Ive only been on the site for a month or so and have refered 5 other riders that have joined this week. This site and the people on it are invaluable to me. Hate to sound redundant but thanks guys. Blubike, teamstreak, etc. You know who you are...

want more laughs?

well the other drain plug is on the front of the frame, I actually thought it was for an aftermarket sumpguard.

I'm enjoying the credit, but when you see what some of these other guys know..... I,m a dummy in comparison.

up in the top right corner is a 'search this forum' box.

first type your query into it and if you cant find it then start a thread.

I actually think that every question has already been asked, well almost.

when you see some of the stuff that the genuine 'gods' answer, i actually need an interpreter. the likes of indy450, simon@vic ncmountain man, toyota m tech(?) and my personal favourite frostbite and several more are the ones who really know these things inside out, literally. there is jetting info on here i doubt even Yamaha are as fully aware of( i have only ever drained water out of my carb) and stuff i genuinely believe yamaha should be using as testing and marketing templates for future models. and i referred another wr450 owner to here today, he said he'd never heard of it???? i said 'you do have the internet on?'

there is also a forum called Town Square.... dont go there.

good luck

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