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Birdy426

426 Valve Job...To lap or not to lap?

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I'm doing a complete rebuild on my 01 426. Got the valve seats cut and porting done by Gorr, and am getting ready to put in new stock Ti valves, new springs, keepers, etc. This to go along with a new crank and 13.5:1 piston.

In looking at the Yamaha shop manual section dealing with replacing the valves, it says to lap them with coarse, then fine lapping compound.

I've read several posts about Ti valves and the Titanium Nitride (or whatever other hardened coating they put on 'em) that say to not lap the valves. Makes sense.

What say you, TT experts? Lap or not? Anyone care to share?

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I have read the same but my manual has served me well though.

I would call Eric Gorr and ask him, you got the head done by him, he should be more than willing to help, plus this is his livelyhood.

Sounds like a cracker of an engine mate!

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I have never done my four stroke yet but I did do a street bike an old KZ 1000 no ti valves so sorry can't help but I sure would like to know how well you get it running like to here a ride report when your finished with it.I would love to do the same exact thing to my 02 WR 426. :thumbsup: That thing sounds like it should get it pretty damn good. :thumbsup:

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I would call Eric Gorr and ask him, you got the head done by him, he should be more than willing to help, plus this is his livelyhood.

I called Eric, but he was not around. I left a voicemail asking the question. I will post his answer.

Yup, the motor should rock...Here's the complete rundown:

Porting and valve job by Gorr

Wiseco 13.5:1 piston

All new Valvetrain (stock Ti valves)

HotCams Intake and Exhaust cams (autodecomp, of course)

New Crank and main bearings

New clutch (all the pieces)

PowerNow!

Boyesen Quickshot

JD Jet Kit

Twin Air Powerflo kit (the filter cage is SWEET!)

YZ exhaust can with PMB end cap and silent insert

Opened up the airbox

Gray wire disconnected

Air Cut Valve plugged

It ought to be an interesting ride. I'll post a report when it's done

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I can't wait to hear about this one. I will be watching. Did you have any Head porting done if so what did they do and how much did it cost? I am assuming that your cylinder was good or maybe a wiseco big bore kit would be nice if this is not the case please give us the details. What about new cam chain and crank main bearings some say these items need to be replaced during major overhaul is this true?

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I can't wait to hear about this one. I will be watching. Did you have any Head porting done if so what did they do and how much did it cost? I am assuming that your cylinder was good or maybe a wiseco big bore kit would be nice if this is not the case please give us the details. What about new cam chain and crank main bearings some say these items need to be replaced during major overhaul is this true?

Yup, cylinder was in good shape. Lots of crosshatching left, and piston/wall clearance was right at the mid point of wiseco's recommendations. The port job is what I would call "Stage 1", that is, cleaning up all the casting flash, abrupt changes in cross section, and mild reshaping, polishing the surfaces, then grit blasting the intake. Some additional recontouring near the valve poskets, and tapering of the swept surface of the valve guides. Looks trick. As far as cost, Eric Gorr (forward motion) lists $150 for this service on his website. I picked up a "garage sale" head that had the porting, valve seats cut, etc for $300.00 (a steal, as the machine work alone is worth that).

New cam chain and main bearings go along with the new crank, as replacing the crank was the start of the overhaul (primary drive nut backed off, and f'd up the splines on that side of the crank)

Should be another week or so for all the parts to arive, then I'll post a ride report.

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wow 13.5 sounds like a huge amount of compression :thumbsup: But then again thats what I thought when i seen the stock is 12.5 on my wr426. So what kind of gasoline are you gonna use? Also I have a hard time even finding 91 octane around here. You guys think it be all right running 91 octain gas and a few squirts of octane boost in my 426?

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The 13:1 and hotcams work well together. I normally run a mix of 50/50 VP red and pump premium (91 octane, avg method, here in Cali). I have, on occasion, run 100% 91 octane pump poremium with no ill effects.

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I spoke to Eric Gorr this afternoon, and he reaffirmed...DO NOT LAP TI VALVES. I'm not sure why my factory Yamaha repair manual says to...nor could my local Yamaha dealer 'splain...

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I spoke to Eric Gorr this afternoon, and he reaffirmed...DO NOT LAP TI VALVES. I'm not sure why my factory Yamaha repair manual says to...nor could my local Yamaha dealer 'splain...

Well there you go! Are you just going to put em in, check for leakage then go?

Have you got that baby back together yet??? You must be getting itchy.......

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I spoke to Eric Gorr this afternoon, and he reaffirmed...DO NOT LAP TI VALVES. I'm not sure why my factory Yamaha repair manual says to...nor could my local Yamaha dealer 'splain...

I don't think the Yamaha manual has been updated for the Ti valves. When the 426 had SS valves it was okay to lap those in. Its probably one of those things that got overlooked.

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When did the 426 have SS valves?

The 2000 model used the same SS valves as the 400 did. You can use these in the '01/'02 426 IF you use the springs from the '00 model as well.

Whenever replacing any valve, it's absolutely imperative that the valve seats be correctly refinished, or the new valves will fail to seal, perhaps from the beginning, and won't last at all. This is even more important in an engine using Ti valves, since, as has already been pointed out, you can't lap them.

As for the inclusion of outdated info in service manuals, it happens all the time, and the person you need to talk to about it is the technical editor.

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Gray:

Are the Ti keepers and retainers compatable with SS valves and heavier springs? or should one replace the keepers and retainers?

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The 2000 model used the same SS valves as the 400 did. You can use these in the '01/'02 426 IF you use the springs from the '00 model as well.

Whenever replacing any valve, it's absolutely imperative that the valve seats be correctly refinished, or the new valves will fail to seal, perhaps from the beginning, and won't last at all. This is even more important in an engine using Ti valves, since, as has already been pointed out, you can't lap them.

As for the inclusion of outdated info in service manuals, it happens all the time, and the person you need to talk to about it is the technical editor.

Ok. Thanks. I'm new to the WR. I had thought they were Ti way back with the 400.

Since I can't lap, I'll check the fit with dye and get seat cleaned up if necessary. I have a 94 KLX I bought new that has 50-70k miles that has never had the seats re-cut. Just lapping. But the seats are very hard in the KLX.

I just read that the new YZ has only four valves. Wonder why they went back? I thought the lighter intakes was supposed to be the ticket to longevity.

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Gray:

Are the Ti keepers and retainers compatable with SS valves and heavier springs? or should one replace the keepers and retainers?

The retainers are the same on both, but the keepers (cotters) need to be replaced to match the valves.

Since I can't lap, I'll check the fit with dye and get seat cleaned up if necessary. I have a 94 KLX I bought new that has 50-70k miles that has never had the seats re-cut. Just lapping. But the seats are very hard in the KLX.

I just read that the new YZ has only four valves. Wonder why they went back? I thought the lighter intakes was supposed to be the ticket to longevity.

There is almost nothing harder than the coating on a titanium YZF valve. Get the seats touched up.

The number of valves never had anything to do with reliability. Note that the YZF has the same number of exhaust valves as everyone else, and they're more durable, too. The reason they went to a 4 valve head was for more top end power.

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There is almost nothing harder than the coating on a titanium YZF valve. Get the seats touched up.

The number of valves never had anything to do with reliability. Note that the YZF has the same number of exhaust valves as everyone else, and they're more durable, too. The reason they went to a 4 valve head was for more top end power.

There may be a first someday, but so far in my 50 years of motorcycles and cars, I've yet to take one to a dealer or a mechanic even though I have consulted them at times for certain. At only $16 I think I'll get a SS valve just for lapping and then check the fit of the Ti valve. I have a 20X optical micrometer that I use to check the contact width and placement and also surface condition.

Exhaust valves can be and in fact are smaller than intake valves since the gases are forced out. The intakes need to be as large as possible since the gases are simply drawn in by vacuum. But if they are too large, valve float becomes a problem at high RPM's with resulting valve damage.

Using three intake valves allows a larger intake cross sectional area using smaller valves. The smaller valves reduces or eliminates float at higher RPM's thereby increasing reliability. Or perhaps longevity would be a better word.

I do not understand how more top end power is achieved with two rather than three intake valves.

And if there is nothing harder than the coating on a titanium valve face, I do not understand why it would hurt to lap with the titanium valve. That said, I will certainly defer to Eric Gorr's advice on not lapping them.

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