Yz426f hot cam starting problem


18 replies to this topic
  • mariku

Posted March 16, 2015 - 02:38 PM

#1

I recently decided to show some love for my yz426f by upgrading to an auto decompression Hot Cam (exhaust only).
While I was at it, I decided to reshim all valves and throw in an Iridium spark plug.
I used Carb cleaner to clean the carb, put new oil (1.7 Liters in the frame) and an oilfilter in it, drained and replaced the coolant (1.2 Liters through the radiator cap) and reassembled everything.
I made sure that I was at TDC (second I mark I-I mark on the flywheel) and the cam lobes facing outward in the opposite direction, and the 9 o clock, 12 o clock and 3 o clock on the front on level with the cilinder.

Today I finished reassembling everything but the damn thing wont start! Before I took it apart it ran like a train..but now it only Shoots flames sometimes when I kick it and it puffs out grey/white smoke from the exhaust!
The carb is leaking gas from the hose on the bottom of the basket where the float is in. I checked the float and it closes correctly. I replaced the iridium spark plug with the original one but doesn't make a difference:(
I'm about to push the damn thing into the lake:( Please help me out so I can enjoy my beloved 426 again:(

  • Krannie McKranface

Posted March 16, 2015 - 03:10 PM

#2

Float seal?

Float needle?

 

Slide plate in upside down (hole goes on the bottom) ?



  • mariku

Posted March 16, 2015 - 04:03 PM

#3

Float seal?

Float needle?

 

Slide plate in upside down (hole goes on the bottom) ?

Hey friend!

I checked the float by blowing through the fuelhose into the carb while holding the float up, first it leaked air, but after I cleaned it a bit it does not leak air anymore. Still it wont start!

It is 1:00AM here so I will check the Slide plate tomorrow and update for you!

I really appreciate your help!

Here are 2 videos I made:






  • stevethe

Posted March 16, 2015 - 04:09 PM

#4

Two other things. Get a picture of the cam and timing marks by goggling it to be sure you got it correct.
If your bike sat for a while the pilot jet could still be somewhat plugged. Buy a brand new one.

  • mariku

Posted March 16, 2015 - 05:55 PM

#5

I used the manual and YouTube for timing, so I think its ok. If I cant figure ths problem out tho I will take the valvé cover off again to confirm I did right. Do you think this sounds timing related?

  • stevethe

Posted March 16, 2015 - 06:12 PM

#6

447916183_a68c2-L.jpgTDC_zps261e4208.jpg



  • mariku

Posted March 17, 2015 - 03:59 AM

#7

I just took the carb off and made this video for you guys. Is there anything else I can/must check about the carb?

The screws are 170, 72, 42

  • mariku

Posted March 17, 2015 - 04:00 AM

#8



  • mariku

Posted March 17, 2015 - 05:01 AM

#9

I Just Pulled the valve cover and came to the conclusion that The I-I mark on the flywheel does NOT line out exactly with the groove on the flywheel-cover. Instead the groove lines out exactly on a dot (which I didnt put, it was there since I got the bike). As you can see in the video (if you look closely), the dot is like 5mm to the right of the I-I mark so it is reallyyy close but not aligned. Could this be the issue??



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  • stevethe

Posted March 17, 2015 - 05:27 AM

#10

I Just Pulled the valve cover and came to the conclusion that The I-I mark on the flywheel does NOT line out exactly with the groove on the flywheel-cover. Instead the groove lines out exactly on a dot (which I didnt put, it was there since I got the bike). As you can see in the video (if you look closely), the dot is like 5mm to the right of the I-I mark so it is reallyyy close but not aligned. Could this be the issue??

 

As best as I can remember you do not line up with the I-I mark. You are looking for the single top dead centre mark it should be to the right of the I-I mark.



  • stevethe

Posted March 17, 2015 - 05:32 AM

#11

 

Two things I didn't see a squirt of the acc. pump. More importantly new pilot jet required.



  • mariku

Posted March 17, 2015 - 05:58 AM

#12

Can you explain what you mean with the squirt?
Which pilot jet should I buy?

  • Krannie McKranface

Posted March 17, 2015 - 06:08 AM

#13

SLIDE PLATE IS IN UPSIDE DOWN!

 

That is why it is running like crap.

Hole goes on the bottom...........

 

Your acclerator pump is not working either

Pull it apart and service

 

While you are in there you can also upgrade it

 

Read this thread

 

http://www.thumperta...p#entry11143305



  • mariku

Posted March 17, 2015 - 01:24 PM

#14

Thanks ! I will try this tomorrow. Can you tell me how you you saw that the accel. Pump is not working, so I know how to test them in the future?

  • stevethe

Posted March 17, 2015 - 01:30 PM

#15

Thanks ! I will try this tomorrow. Can you tell me how you you saw that the accel. Pump is not working, so I know how to test them in the future?


They squirt gas from the little brass post in the throat of the carb. I didn't see any gas squirt out.

  • Krannie McKranface

Posted March 17, 2015 - 03:51 PM

#16



  • mariku

Posted March 18, 2015 - 09:30 AM

#17

The carb was not connected to the gastank when I made the video.

I made this video to show the timing, does it look good or wrong?



  • mariku

Posted March 18, 2015 - 09:40 AM

#18

It is not a WR btw, it is a YZ, Im not sure if that makes a difference for you guys tho, I think my YZ has a WR flywheel because I run lights without a battery.

  • Pooley

Posted March 18, 2015 - 10:39 AM

#19

Take a picture of the other side of the cam as well, so that it shows the lobes.  If I remember correctly, they should pointing in opposite directions (sort of at 10 and 2 oclock) with the piston at TDC, and the punch marks do not line up perfectly level with the cases, but slightly raised up.






 
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