i'd like to know your experience on this. what you put it down too?
did you find a cure?
did the bike run ok when it happened or was it useless?

Taffy

ps not one of the 630 of you has measured a YZ base gasket yet! shame on yer

I thought you had it all figured out Taffy!

If I have to split my cases I will gladly measure the base gasket (’00 426). I have calipers but no micrometer. I’m assuming you want to know how thick it is… I must’ve missed the original question. Why do you want to know? Thinking of punching out a YZ cylinder?

I’ve seen lots of four strokes make their headers glow. Lock yourself in your garage with the lights off and yours will do it too.

My buddies XR 650 does it, as does my other friends’ TRX 400s. I wondered why street bikes don’t until you (I think it was you, maybe it was some other foreigner ) pointed out they have twin walled construction.

But the first time I saw this on my 426 I did freak out a little bit. I was playing with the idle mix with the bike idling on a stand in my garage. It was dark and one of my lights in the garage had burned out. I looked down and I thought my pipe was going to melt. It did not. I lept to the conclusion that my adjustments of idle screw had led to overly lean bike and hot pipe. I richened it to the point where it barely ran and the pipe would get red in the same amount of time (about one minute I think) regardless.

I’m sure it has gotten much hotter a hundred times, but in broad daylight where the glow is not noticeable.

The headers on my Camaro will glow a bit too, and they are not cheap headers.

It scared me to death the first time I saw mine glow, I was sitting at the gate and looked down and wow! I asked around and found that everyone else's 426 pipes glow when idling and they told me not to worry about it, so I don't. I have found that I can sit at the gate on a night race and let it idle and get really bright and red and pretty, wait 'til they starter is about to drop the gate, then poke the 2strokers on both sides of me and point to it, they are so surprised and hehehe I almost always get the holehsot, works every time except some of them are getting wise to this trick hehehe...

Mike

Hey Taffy,

My pipe glowed from the day I got her. Being new to the dirtbike scene, I had no clue about why it was doing this. I'd never seen anything like it before.

The pipe was cherry red within 2 minutes of starting, and at the same time the bike was throwing anti-freeze. Even when thumpin, the pipe glowed bright cherry red, and anti freeze was still coming out the blow-by. She'd empty 1/2 - 3/4 of the fluid each time out.

I checked the owners manual again and Yamaha said not to let the bike either idle for over 2-3 minutes, or let it stand running. I wasn't doing that, but I made sure I did exactly what they said to do.

After about three more trail rides of this, I, through THUMPERTALK, hooked up with Mark at 2 Dad's Racing. Mark spent time quality time with me. He asked me questions, such as altitude, what gear level I was running in, and my riding conditions/style, terrain, etc. He was very thorough.

The problem: jetting.

Mark knew the dealership I bought it my bike from quite well. He voluntarily made a phone call to their service dept. He explained the issue to the head mechanic, and the bike was brought in for service.

Yamaha, the dealership, and I did get into an argument over who would pay for any repairs. Both Yamaha and my dealership took the position that the overheating was my problem, not theirs, and was not covered under warranty. After much discussion, and justified pressuring, they finally relented on a "good will" jesture. Yamaha approved the claim for rejetting the bike.

The dealership checked the overheating issue, and the cherry pipe. By my request they also tightened my chain, and changed the oil w/filter.

MY DEALERSHIP CLAIMS THE BIKE DIDN'T NEED TO BE REJETTED. They checked the cooling system...nothing. They explained that the pipe from the manifold to the muffler joint right infront of the kick starter is single walled, and very thin. This causes the pipe to glow cherry red.

Ever since coming back from the dealership that day, the bike hasn't overheated, nor has the pipe glowed cherry red. The bike also has run differently ( better throttle response, less bogging ). I know what they said, but I don't believe it. Something was done to that bike. She runs different...better...and Im not complaining about it either!

All my overheating/pipe issues were witnessed by other riders who collectively have over 50 years of riding experience.

I'm not knowledgeable or confident enough yet to tell you its your jetting. See what the other guys say. If you're new, I pray you don't receive the same criticism I have for being "wet behind the ears".

Whatever happens let me know. Im behind ya 100%.

God Bless!

Randy
YZ426 Kicks

mikeok

very very funny! you painted a picture that had me chuckling! great stuff.

the base gasket was simply a request recently for someone to measure the thickness in thou. the WR is .020" (.5mm) & rumour has it that the YZ is thinner.

i don't have a red pipe! but i'm getting the picture ready for my cam timing experiments. the camwheels arrived yesterday & are precision made bits of gear.

i won't have time this weekend to try some changes & i race the week after so it's out then as well.

Randy, did they ever say what they did to your jetting or did they keep stum.

Taffy

Hey Taffy,

They said absolutely nothing, nada, zilch, zoink, not even a sheepish smile, or stupid grin...Just it didn't need it.

Makes me think..how 'bout you?

Thanks,

Randy
YZ426 Kicks

i've got a bike that suddenly doesn't want to pull clealy in top & top of the revs. once i get that sorted i will have a go at the valve timing.

you know i spent my hard earnt dollars on these variable cam sprockets so if i find nothing can be improved you can all have a chuckle.

as for the problem with your bike? i think that someone somewhere in the usa has had the same problem & it's been sorted in a similar way. it's a case of who & how?

i'd love to know about some of those confidential yamaha service bulletins on the various model problems.

Taffy