Cylinder pics....bad news?

Did it just start doing it one day during the middle of a ride?

Yes but it is much worse now and when it started it would kind of run good for a while then run bad, run good, run bad. Now it's always bad. The day it was good and bad the whether was real crazy and went from cold to hot to cold again so I figured that had something to do with it. I then rode it after that and just made the jetting super rich, but it still was running lean.

Have you checked the CDI and the coil? Why do you think that its running lean?

Yes I replaced the coil after I could not get a consistant reading at the plug wire end. I used a coil from a Yamaha R6 and it's a nice clean setup. Later I found out the end of the spark plug wire was the only issue with my stock coil, oh well. That was the only electrical test that was not within spec.

The spark plug is white for one. It runs lean because I just know what lean feels like and the bike is running hotter than before and spews coolent now and then. Some people say "with modern fuels you can't go by spark plug color, etc." Well I think that is somewhat BS because the plug used to be tan and my other bikes have tan plugs also.

Listen guys the bike does not gain any RPM after half throttle. How is this not a problem? I have tested everything several times and replaced things that were suspect or just for the hell of it. Nothing seems to be working. The shops around here are pathetic so they will be no help.

Anyone going to be in Ventura County sometime soon? Maybe someone else that knows a thing or two can check it out and see what I mean? PM me and let me know please.

Do your other bikes have the same carb? If you do then you could switch them out and see if the carb is the problem or not.

Well my friend has a wr426 so that would be the only carb I could swap. My other bikes are different bikes a CR500 and a ATC 350x they both have way different carbs.

I did already check out the needle jet and could not find anything wrong, it was not ovaled out.

So are you saying that if you time a WR with YZ timing there is still a difference from that to a YZ? I guess that could be but there are tons of threads on here and I've never seen anyone say that.

Depends on the year/model. The '03-'04 YZ450 and WR450 use the exact same intake cams, but later ones didn't, and the the 426's didn't either, as you can see. Setting the WR426 exhaust cam one tooth retarded from stock brings it very close to YZ timing overall, because there isn't as much difference in the intake as the exhaust, but yes, it's still a little different.

I'm positive it started acting funny before this, but I did have some welding done to my new muffler. We did a few tacs while it was on the bike, could that be my problem? Maybe the welder hurt something?

Where was the welder ground?

To the bike

To the bike

Perhaps a little more specifically?

Haha sorry I don't remember exactly. The footpeg most likely but it was about a year ago....

Where the ground is placed relative to the electrode defines the path the current will take. If it runs too close to paralleling part of the harness, there is a potential to induce voltages in the wiring that the CDI won't like.

Man, this is a hard one that I'm sorry to say I have no more constructive input on, but I'll keep watching with some popcorn to see how it turns out! lol (sorry)

But if I were you, at this stage I'd buy a CDI off ebay and a coil (instead of the R6 one) and put the timing and everything back to stock and take it from there...I think at least then your problems will become more obvious so that you can narrow it down, then go back to the mods...And I stick to thinking you should at least change the rings since they have over 20 hours and a hone job on the cylinder since new...

I may end up just selling the damn bike even though I love it. It's been a paper weight money pit for over a year now....

I have no answers and no nearby shop that would be any help.

You went this far...See it out...You can't be too far off...And you'll have a solid bike after all this mess...If anyone can get you back on track, GR will...Just follow advice, take the steps, pictures, notes, details, etc...Would suck worse to let this bike go and wind up with another used mess...

Yeah I hear and feel what you are saying. It's just been frustrating for so long, most of the time it's been down I just can't work on it because I've already tried and tested everything. I've taken lots of advice and done all the normal/ obvious things numerous times I've lost count.

It's just frustrating and I really need in person help. That's the only way it's going to get fixed, if someone in the know can ride it and feel what I mean rather than just reading it or hearing by word of mouth. My friends don't know enough about bikes to help out.

Well if I had more knowledge (& time) I'd show up with a twelver...But although I've taken quite a few bikes apart, they're pretty much always standard repair jobs, I suck when it comes to the head scratching stuff...So I wouldn't be much help...

I do really think it's time to step back to stock settings, along with a new CDI, new coil, new plug, fresh gas, clean filter, etc...Go back to stock basics, then see how it runs, then back to the mods...

And as long as you don't make him do too many face-palms, I'd bet GR can get you back running again...

If you want to take it to a shop, I can refer a great guy in Redondo Beach, CA but it's a big dealership (top dollar) and you should be adamant about it not being touched by anyone else there except him (Fernando at Del Amo Motorsports)

I may end up just selling the damn bike even though I love it. It's been a paper weight money pit for over a year now....

I have no answers and no nearby shop that would be any help.

dont ya just love modern 4stroke engine technology??? dontcha???

@TheStuz- haha gotta love it! I bought a cr500 recently that runs great....and it's simple/ easier to work on yaaay.

@Goose- I have changed to a new plug already long ago and also tried my friends stock coil. The coil isn't the issue as his coil and the R6 work the same. Mine stock one just had a bad connection to the boot. I put in fresh gas also, air filter cleaned. It's really not far from stock, just the free mods, ex hotcam and aftermarket exhaust. Those mods have been done hundreds if not a thousand times with no issues.

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