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Bill, Mike Carpenter

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OK Fella's,

I am now re-assembling my bike after pulling the airbox.

I know we checked it, but I need a little re-assurance. Is everyone absolutely sure (in your most honest opinion) that my engine is indeed YZ timed?

I am still trying to locate maybe 10hp. Is there anywhere else I can verify my cam sprocket positions other than the one article on this websight?

If you recall, when I installed the DVP, I had to put the stock WR air jet in, not the 100 YZ jet. I do have the yz jet installed now. I am also looking at puting my EMP, #4 or 5, in place of the DVP, plus a 178 MJ. Maybe I can find some lost HP...???

I am going roostin' on Saturday, the family is off to PA for 8 days, and I need to blow off LOTS AND LOTS of energy!

That followed by a horendous night of drinking Sam Adams!!! :)


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat.

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Hi Kevin-

Glad to see you're working on the bike.

Yep, it was YZ timed, at least by visual inspection. I don't recall looking at the alignment marks on the crank, just the cams Could the chain have come off the crank? Pull off the caps again and make sure the "I" lines up when checking the cam timing.

Just a thought.

Other thoughts:

--Purchase new header-to-silencer gasket. Do not bend this area much, just twist on the pipe slowly. It may have still been leaking after our aluminum foil warp job :) I noticed the pipe was a tight, bending sort of fit. Loosen the entire system, then tighten from the header back maybe that will align the system better and keep it from leaking.

-- Airbox defective. I sort of doubt it make the bike run like it did, though. What about the hot start mod you had to make? Is it sealed real well?

--Valves loose and not closing enough?

--Scored cylinder you mentioned. Have you done a leakdown? It DID feel like the compression just wasn't there. If you don't have access to a leakdown kit, at least try to turn over piston with kickstarter w/o compression release when cold and warm. At 195 lbs, I can't kick the bike through cold or warm-with all my weight on the starter.

You're should behave similarly, except if you haven't run the bike for many weeks, oil may have dripped away from the piston rings and will render the seal much less effective (see Boit's post)

-- TPS- what ended up with this? Was it tested for resistance properly?

I don't know if one or many of these things are wrong. It did not feel electrical to me, and I know you already troubleshot this system.

I am guessing low compression, as it felt like the YZ powerband more than the WR, just much less of it. It also carburated fine to me. If you suddenly get you're power back, I would recommend

--Carb float height. I noticed you tended to manhandle the carb like some red-headed step child. Did you possibly change the adjustment without knowing it? Just an observation that is probably not causing the 10hp loss, but can contribute of course.

-- The Taffy jetting you had in there may not have been too bad if the real problem gets fixed. Experiment more with the E series needes, clip #4 (EKP or EKN) after the HP comes back.

There's tons of power in there, we promise :D

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Good to hear your trying to get the beast straightened out. Are you also using the YZ start jet (65)? And I'm using the 175MJ.

Are you planning on trying the changes without the CF airbox? You may want to, until you get some of the lost power back.

Good luck and let us know how it turns out.

Bill :)


99 WR400f, YZ timed, MX-Tech suspension, Scotts steering damper, White Bros E-Series (12 discs), tapered header and a/f. Kouba T-handle for the fuel screw. Works Connection billet throttle tube and frame guards. Cycra Pro-Bend, triple clamp mount handguards. Thumper Racing rad guards, Renthal Jimmy Button highs, YZ Tank and IMS seat, YZ number plate, odo removed, EKP, 48PJ, 175MJ at 500-1000' Thanks James Dean!

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How about an exhaust valve problem? Compression Release cable too tight?

I am at work right now looking at all possibilities.

Here is my list:

1 - TPS

2 - ignition timing

3 - Throttle Stop (STILL!)I do note that the throttle stop is allowing the slide to open further than the venturi opening, not much, but definitely more than necessary.

4 - valve clearance

5 - Compression Release

6 - YZ timing

7 - binding underwear...OOPS, that is another problem of mine. It is kind of personal, but you can read about it at www.impotence.com :)

Any other ideas?

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Found 2 of 3 intake valves tight and out-of-spec. One was .102mm (very tight fit w/ feeler gage). Cannot get bucket off of the other valve to check shim #.

Both exhaust valves are SAT.

Looked and re-looked on the YZ timing. It does appear everything is SAT there as well.

Should have it all back together tomorrow. Hopefully some long lost HP is back (doubtful).

Mike: e-mail me. I may have something for you.

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