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426 has arrived, questions for thumper veterans !
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Posted by: zx7king---------------------

Hello all,

I am new to this forum, and am very impressed. I was a roadracer (zx7 superbike) but went to dirt about 4 years ago. Since then I have had 97 yz250, 00 yz250 (for sale) and am now the proud owner of a 02 yz426f. Obviously I have experience with four strokes from my roadracing days, but still would like to ask the thumper veterans some generic questions. Since the 426 does not have degreeable cams, I will do all of the work myself.

Oil preference?
Do you index your plug?
How often do you check/adjust your valves?
Octane?
How often do you change your oil/filter?

Thanks in advance for the advice

,
Charles

Posted by: Scott F---------------------

Quote:

Originally posted by zx7king

Oil preference?

A lot of people choose Mobil1 15W-50 (non EC) red caps. A lot don't.

Do you index your plug?

I haven't heard of anyone doing it, so why don't you try it and report back?

How often do you check/adjust your valves?

Rarely. You can check them when new, then check every few months to verify that they are still in spec.

Octane?

Most riders are happy with 92 pump gas, others prefer race gas.

How often do you change your oil/filter?

Every hour of runtime during break in, every 3-5 hours after. The filter can be cleaned and reused indefinitely.

Thanks in advance for the advice

Here's some more. Check out ThumperTalk.com for an excellent YZ426F forum.

Posted by: zx7king---------------------

Thanks Scott F, I will check out Thumpertalk.com.

Posted by: J.B.426---------------------

Good advice from Scott.

I use Mobil 1 15w50 and it seems to work well for me. A lot of people use this oil because it is readily available most anywhere, performs well, and the cost is reasonable. Many motorcycle specific oils are great, but they are usually pretty expensive.

I change my oil about every 4-5 hours and reuse my oil filter. I'm on my second OEM oil filter in almost 2 years, inspect and reuse.

I have not indexed my plug, but it may something worth while.

I use the highest octane pump gas which is 91 around here. It works fine, I just try to keep it fresh and get it from a busy gas station. Race gas would likely be better overall once jetted for it but availability has prevented me from trying it.

I checked my valves after break in and they were within spec. I also rechecked a few months later and they were still within spec. Depending on how much and how hard you ride, I would say every 6 months to a year should be fine, more with more seat time. The valves have proven to hold up great on this bike.

Posted by: zx7king---------------------

Thanks for the info...

What do you all use to clean your oil filters with ??

Charles

Posted by: Rich Rohrich---------------------

Quote:

Originally posted by zx7king
Do you index your plug?

The way the combustion chamber and piston crown are laid out there isn't any shrouding of the flame front so it serves no purpose. Even on the 14:1 engines we've built there hasn't been any measurable difference indexing to the intake or exhaust side of the chamber. One less hassle to be rid of

Posted by: J.B.426---------------------

I clean the oil filter with contact or brake cleaner, spraying from the inside out.

Posted by: zx7king---------------------

thanks !

Posted by: Hick---------------------

You can degree the cams with aftermarket gearwheels from Falicon (you probably already know this).

A few guys on Thumpertalk, the site mentioned above, have tried this, and somebody claiming to be Ferry’s wrench (heck, I believed him) even offered these specs as working the best on the factory bike:

103 Intake
107 Exhaust

lobe centers.

I believe stock is 113 and 101.

You might check your valve clearances anyway, but I’ve gone over 50 hours on my ’00 and now my ’01 before they needed any adjustments. My ’01 is getting close but is still in spec. The exhaust does seem to tighten up first.

In addition to the filter, you may consider an inspection and cleaning of the screen in the bottom of the in-frame reservoir (the other side of the fitting that feeds the pump/motor) after the first few oil changes. I can’t imagine this screen getting totally obstructed by debris but I promise you will find some on there.

A lot of motocrossers swear by racing gas, and DRN/Rich Rohrich et. al. is the best place to find out what works the best, but there are just as many guys like me who think super unleaded is just fine, thank you.

Hope this helps.

Posted by: zx7king---------------------

Thanks everyone for the feedback !!!!

Charles

Posted by: sfc crash---------------------

hmmm.i use racing gas..why? hmm..can't remeber, 5 gals 35$+ $. i use yamalube, why?..hmmm, i think cause i'm scarred of screwing something up(see race gas) now then, whats all this about cleaning\changing oil filters:mad: hmm...better check into that more.

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426 has arrived, questions for thumper veterans !

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