'98 WR400 fouling plugs after new parts

Valve are a little on the loose side, but not too tight.

Should I worry about the 12 vs 13 pins? I mean the 12 pin cam adjustment was supposed to work hand in hand with the gray wire mod correct? If I can avoid pulling both the cams I would like to do so. Going out right now to stair at it a little then probably give up.:eek:

Incorrect cam timing will cause the bike to run poorly hot or cold. Cam timing does not get worse as the engine heats up. Just not possible.

If the plug is brand new will it mask the overly rich conditions until it fouls up? And would the exhaust cam being off cause this problem? I'm just wondering how some new parts affected my jetting that much if that's what happened...

If the plug is brand new will it mask the overly rich conditions until it fouls up? And would the exhaust cam being off cause this problem? I'm just wondering how some new parts affected my jetting that much if that's what happened...



It's not affecting your jetting, it's affecting your timing. You are not 'rich' fouling, you are 'oil' fouling.

ok, I'm planning on making time to work on this a little after work. I'm inside most of the day today so when I get home I can handle the heat of the garage. I plan on putting up a pic of the timing. So far I have moved the exhaust 1 tooth clockwise...pretty easy to visualize. I'm just wondering if that is correct or not.

Also, how does one oil foul with timing? I though oil fouling was gooey and wet, carbon (excess fuel) dry and chalky. I have 4 new spark plugs so I'm going to get this thing running proper. I have until Sunday to do it...

Will 1 tooth make a huge difference in timing? Isn't it only like 3 degrees or something along those lines?

More like 10 degrees (maybe 9)-Divide 360 by the number of teeth on the sprocket.

Cam timing will not oil foul a plug. Only bad rings/out of round bore/incorrectly installed rings/bad head gasket/bad valves seals will cause oil fouling.

You need to put the cam timing back to stock. You made a lot of changes. You need to eliminate some of your modifications. I still think you have a stator issue.

Well I didn't have time after work...figures. I'm going to try my hardest to work on this tonight. I have to help a friend with his exhaust tonight too so we'll see how that goes. The flywheel bolt may or may not be on there for good. That will be a last resort. I want to just chuck this sucker on craigslist and be done with it...

EDIT: also.....I don't know what stock timing is! I've never been able to get all the punch marks to line up no matter how I position the chain. And does it look like carbon or oil fouling?

It is hard to tell from your pictures. They do not look oily though.

Ok, so I moved the exhaust cam 1 tooth clock wise and now it looks like this with a little pressure on the cam chain guide. This is as close as I remember getting it. Does it look ok? I'm a little hesitant to put it together with out someones "ok" as I obviously did it wrong the first time. There are also 12 pins between the top punch marks if it makes a difference?


The picture above is incorrect as the flywheel was not completely at tdc. Here it is with the tensioner in place.



Here is a video as well... I have a pretty crappy camera, but you can hear it stumble and backfire to a stall as I give it throttle, then I start it up and give it no throttle. It started 2nd kick and idled for ~4 minutes.


EDIT:also, the last plug I pulled wasn't completely carbon fouled.

That timing is off by at least a tooth or more on the exhaust, possibly one on the intake too.

Well it didn't work when it was set correctly? I'll move intake and exhaust both counter clockwise 1 tooth? I'm still confused as to if I want 13 or 13 pins between the top punch marks.

Sorry I'm so incompetent, I don't know why I'm having so much trouble with this.

Assuming you have a shop manual (which you should being it is a free down load from Yamaha) getting the cam timing right is simple.

First make sure you are at TDC on the flywheel.

You have the exhaust cam dot (dot towards the front of the engine) even with the gasket surface with slight CW tension on the cam. It can be ever so slightly above to accomodate chain wear. Not below.

Install the intake cam, again, the dot must align with the gasket surface when CW tension is applied. Install the cam chain tensioner. This dot is the rearward one.

Rotate teh engine slowly 360 degrees (one full cam rotation) Confirm whn the fly wheel is at TDC that the dots line up.

The manual that I am using (clymer) says that the the front AND rear punch mark of both the exhaust AND intake cams should be level with the top of the head. I have never had both punch marks on both cams level with either an old or new cam chain.

The YZ timing mod that I have looked up says that the exhaust cam should be moved 1 tooth clockwise from stock. I'm assuming this is done hand in hand with the gray wire mod unless I am completely wrong on this one. See here: http://www.thumperfaq.com/yz_timing.htm

In this image I posted on the previous page you can see that the intake cam has the rear dot right at the top of the head like you mention is correct in your previous post today however you said yesterday that the intake is probably one off.


I just went out now and moved both the intake and exhaust one tooth counter clockwise (note that on the intake cam, the rear punch mark is up and the front punch mark is down; not what you/yamaha manual recommend). The exhaust cam has the forward punch mark as close as possible to level with the head:


Here it is again with the exhaust cam untouched from the picture above, and the intake moved back to how I had it yesterday which is 1 tooth clockwise from pictured above, which is what you recommend:


However to get yz timing I need to only move the exhaust cam 1 tooth clockwise from pictured above in order to have 12 pins between the top punch marks. Which is what I initially posted on the last page IIRC.

What am I missing??:eek:


P.S. both of these pics were taken with the exhaust cam not bolted in, and tensioned with my finger in the tensioner hole.

Exhaust looks right, intake is off by a tooth It needs to be one tooth CCW to be stock.

You need to get your bike running before you look to 'hot it up'. Right now, you are advanced one tooth on the intake cam.

Grey wire mod has no bearing on the cam timing change. They are exclusive of one another. Both can yield high top end performance.

My point I made many posts ago, was addressing your running issues. You need to get the bike back to normal, address those running issues first.

Also, D/L and use the Yamaha manual. Clynmer is questionable.

The 2nd picture in the post above has the intake CCW 1 tooth like you recommend I change. The rear punch mark is far from level with the top of the head.

If you look closely you can see purple sharpie around the cam chain where the top punch mark is in the pics. To compare them....

Edited by nnamssorxela

I'm going to assume you got a little mixed up and I'm going to go ahead and set it up like the last picture and not the 2nd to last like you said in the last post.

The front of the exhaust and the rear of the intake cams are on the top of the head.

Will the fuel screw alone foul the plug?

Listen to William, download the Yamaha manual and set it according to what the WR manual says (which should jive with Williams description).

Clymers are nice but they cover a bunch of models, their pics, descriptions and specs get jumbled VERY easily and you'd never know any better.

Like was said, get it running correctly first before making any changes.


This is the manual that I downloaded:


says; "In order to be sure that the pistons are at top dead center, the match mark C on each camshaft (and it points to the front AND rear punch marks on BOTH cams) must be aligned with the cylinder head surface as shown in the illustration."

This simply is not possible. I'm pretty sure over the last 4 pages I have posted pictures of every combination of cam timing that is even close to having BOTH marks line up.

I posted a picture with the exhaust cam forward mark level and the rear mark up and the intake cam rear mark up and front mark below the head. He said that it was off a tooth and needed to be put CW 1 tooth on the intake cam.

So, I took a picture of the exhaust cam forward mark level and the rear mark up and the intake cam rear mark level and the forward mark up and then it was said that I need to move it 1 tooth CCW, which if you read back a little is contradicting the 2 things that were just said. I am becoming very frustrated.

I know it is difficult to diagnose things over the internet but I am trying to document this as much as possible to make it easier. I have had someone familiar with the engine try to set it up and you see where that got me. I have had very bad luck with taking this bike to ANY shop and after a lengthy talk with a certified yamaha mechanic I'm still in the same place....the cams don't line up!

At this point I'm not trying to "hop/hot/soup up" my bike. Yes I am young and yes I am stubborn but this is my first bike and it has been the biggest pain in the neck, but when the two manuals, and the people on the internet say different things, I can't help but begin to wonder. The only reason YZ cam timing was mentioned was because I figured that if the ignition was set to yz timing via the gray wire mod which was done by the previous owner, that the cams would have to be yz timed too. If I had the stock pipe, airbox, jets, valves, etc I would return it to stock and start from there, but I don't.

I have a lot of time and money into this bike. I do not take it to a shop unless I am completely stumped, and last time that caused more harm than not, so I'm trying to refrain from that. I hope you see where I'm coming from...I'm just looking for knowledgeable help.


So if it's not possible, then you have a cam chain issue.


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