Question about 2002 Yamaha YZ 426 F

3 Answers

It will not start and it backfire after valve adjustment. did i put the cams back the wrong way?

Posted by matte_peders on


3 Answers

tim mcgrath

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Master
  • 617 Answers

Sounds like you have timing off, reset timing chain crank at tdc cams at 9 & 3 o'clock marks on gear go along with head then after on release tentioner, then turn motor over with rachet to make sure its not hiting valves

Posted on Feb 04, 2010


Arnie Burke

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Yamaha Master
  • 6,480 Answers

Did u hav piston @tdc power stroke-valves shud slightly clic with ur hand after ajust-mite hav performed it at exhaust stroke! let me know

Posted on Jan 27, 2010



  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that got 5 achievements.


    An expert who has posted more than 50 answers, of which 90% or more were rated as helpful.


    An expert whose answer got voted for 20 times.

  • Expert
  • 67 Answers

1) The cams were in the wrong position or wrong stroke when clearance was measured. or
2) The shim change was mis-calculated or shims mixed up resulting in zero clearance causing leaky valve and the backfire. or
3) The cams were installed out-of-time after everything was installed including the cam chain tensioner. Note: if a valve was hitting the piston while kickstarting, it will be bent and will have to be replaced.

Posted on Feb 16, 2010

Add Your Answer


Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

2 Answers

No start on bear tracker 250 just backfires

then the timing is not set properly .

Jun 22, 2016 | ATVs

2 Answers

Whats the worst that could happen if I've adjusted valves incorrectly?

If the valves are too tight, they don't fully close. That can "burn" the valves, causing an expensive repair job to replace the valves. Too loose will make tapping noises and eventually can wear the cam.

Nov 14, 2015 | Cars & Trucks

1 Answer

Hi, ive got a 1999 g2 kawasaki zx6r been sat for 6 months+. ive changed plugs,battery, petral and pilet jets becoz to blocked, so put like for like back in. it only starts of bump and backfires realy bad...

Have a professional carb service and valves adjustment done.
Just replacing the idle jets will not clean the entire idle circuit. Mixture screws need to be removed, circuit needs to be cleaned out, re-installed,and properly adjusted for idle mixture.
If backfire continues valves need adjusting. Best to do both at same time to save on labor.

Apr 04, 2014 | kawasaki Motorcycles

1 Answer

My 1995 dr350se just wont run ... i have spark i have gas idk whats goin on can anyone help

Beings as the "valve cover" has the upper cam journals cast into them, did you retorque it properly, and to the correct specs?
Did you tamper with the rocker arm adjustments?
Did you remove the cam gear from the cam shaft? If so, did you reposition it correctly (didn't turn it one bolt hole?)

Jan 07, 2014 | Motorcycles

1 Answer

I have a Honda VT 1100 from 1990 It will not start and I have to control the timing between the camshaft and crankshaft if its okay Can you check this without taking valve cover of Know there are...

the cam timing marks are on the cams and the rocker cover has to come off to see them.
Honda usually leaves enough room for cam cover removal with out removing engine.
However why would the cam timing be out in one cylnder??? unless it was installed wrong and then the engine was put back in, but without seeing the cams you wouldnt know it was out.
If you suspect it due to a backfire, it can also be low ignition voltage, lean fuel mixture due to carb problems or loose intake manifold, and also tight valve clearances or a sticking valve, and again honda dont usually need an engine removal to check valve clearances.
If I remember after the cover bolts are removed, it wont lift straight up, but it will move back or forward and come off.
There is also the possibility Im completely wrong :{(

Apr 08, 2011 | Honda VT 1100 C Motorcycles

1 Answer

1992 f150 back firing throu intake when cracking throttle breifly-soundslike only one cylinder backfire. stock engine-5.8lw(efi) with headers and roller cam, engine recently rebuilt

backfire is the igniting of fuel in the intake. Can be, timing, valves not adjusted right, cam worn flat on one lobe are usually the first places to look.
check it out.

Apr 15, 2010 | 1999 GMC Jimmy

4 Answers

I broke the timing chain in my 07 honda 400 ex and me and my dad tore it down and it had been smoking and burning oil so we replaced the timing chain the thre bottom gears the piston and rings with wiseco...

you probably have time 180 degrees out....4 steps....(1)piston top dead center...(2) camshaft aligned with marks...(3) dist set for #1 cyl to fire ...and (4) timing marks on damper pulley aligned with marker on the cover or eng block...good luck

Mar 13, 2010 | Honda CRF 250 X Motorcycles

2 Answers

2000 jeep charokee 4 liter backfires

Put a vacuum gauge on it and see if you have a steady reading. You may have a bad cam lobe or partially burned valve which will show up as a quickly fluctuating vacuum reading. Backfiring is generally caused by the above or by the ignition being too far advanced (yours is not adjustable but if you had the distributor out?, you may have put it in one tooth off.)

Mar 04, 2009 | 2000 Jeep Grand Cherokee

Not finding what you are looking for?
2002 Yamaha YZ 426 F Logo

527 people viewed this question

Ask a Question

Usually answered in minutes!

Top Yamaha Experts


Level 3 Expert

3063 Answers

Neil Lancaster
Neil Lancaster

Level 1 Expert

14 Answers


Level 3 Expert

501 Answers

Are you a Yamaha Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides