just installed hotcams and now bike wont start?


14 replies to this topic
  • bolermountain

Posted April 12, 2008 - 04:15 PM

#1

I just installed the hotcams exhaust cam in my 01 Yz426, exhaust cam has the marks at 9 and 12 oclock and the intake is at 12 and 3. installed everything back together and when i went to start NOTHING. I got it to backfire or POP twice. Any ideas? Now in the manual it says on the rotor it has a line "I" to line up in the timing window but mine does not it just has some numbers with an "H" at the end that seemed to be TDC when i first dissasembled. Lobes are lined up just as it is in the hotcams instructions. Valve clearances are spec on but also noticed when turning motor over by hand before re-assembly the decompression mechanism on exhaust cam does not move when turning motor over? does this only happen when kicking over?


ITS RUNNING THANK YOU FOR ALL YOUR HELP ONCE I CLEANED CARB SHE FIRED RIGHT UP

  • grayracer513

Posted April 12, 2008 - 05:08 PM

#2

... noticed when turning motor over by hand before re-assembly the decompression mechanism on exhaust cam does not move when turning motor over? does this only happen when kicking over?

No, it only moves once it's started. It takes about 600 RPM to move the decomp flyweight outward.

With the engine at TDC, you can look down behind the camshaft at the top of the left exhaust lifter and see the end of the decompression pin. Move teh flyweight with your finger and you can see it retract. The retracted position is how it sits when running at any speed, from an idle on up.

The way it works is by extending out from the cam far enough that it lifts the valve off its seat as it passes over the lifter, releasing the first half or so of the compression stroke. This leaves the engine with enough compression to start, but not so much that a rider or a starter motor can't turn it over. As soon as the engine starts, the flyweight moves out, the pin is retracted, and the whole thing goes back to normal.

The 'H' you see should be directly to the left of the 'I', so that it says "HI". The H is for ignition timing checks. If you can't find the right mark, pull the plug and check for TDC with a Phillips screwdriver. While you're at it, put a new plug in the thing.

  • bolermountain

Posted April 12, 2008 - 05:14 PM

#3

Thanks for the info how the decompression cam works, also it definately does not have that "I" mark beside the H i will try thru the plug hole to find TDC, also it is a brand new plug in there.
Thanks again,

  • kirk_12

Posted April 12, 2008 - 05:48 PM

#4

Could be your timing i have an 01 yz426 an installd a hotcam an it done the same thing and it was one degree out of time

  • bolermountain

Posted April 12, 2008 - 05:55 PM

#5

How do I find out exactly, thanks again for the help, its just that weather is finally warm out and I have the itch

  • kirk_12

Posted April 12, 2008 - 07:34 PM

#6

no prob ... i feel ya i jus got mine shimd an ready to go .. make sure the punch marks on the top of the cams are straight up, and the e is level with the top of the head also the i.

  • bolermountain

Posted April 14, 2008 - 11:26 AM

#7

:thumbsup: Okay i did find the "I" mark in the window on TDC and then re-alighned intake and exhaust cams. I mean they are exactly as all the pictures say they should look like, went to start and nothing again. Took plug out and checked for spark and it was good. checked to make sure carb was getting fuel and that was ok. Not sure where to go from here? :thumbsup:

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  • grayracer513

Posted April 14, 2008 - 11:50 AM

#8

If you are using the "classic", "standard" method of pulling the choke and not touching the throttle, try changing up the routine a little.

Try giving it two or three twists of throttle, then starting as usual. If that fails to light it up, try opening the throttle very slightly off idle and cranking it while holding the throttle steady in that position. Sometimes, using the hot start along with the choke may help.

The 426 FCR is a touchy carb, and it doesn't take much to make it hard to start. Once you get it lit up, you can dial it back in and bring it back to normal.

  • bolermountain

Posted April 14, 2008 - 12:21 PM

#9

thanks again for the advise but that stll does not work either, tried choke/hotstart, hotstart only, etc still nothing, can;'t even get it to pop now.
Sorry for all the questions just want this thing to fire up. by the way before the new exhaust cam the bike would start first kick everytime(back with the old decomp lever days)

  • USED YZ426F

Posted April 14, 2008 - 02:12 PM

#10

Have you tried a new plug?

  • grayracer513

Posted April 14, 2008 - 02:16 PM

#11

He said:

it is a brand new plug in there.
Thanks again,



  • bolermountain

Posted April 15, 2008 - 08:01 AM

#12

I took some pics of cams installed with the "I" lined up in timing window do they look right to you? they do to me
http://i305.photobuc...in/IMG00052.jpg
http://i305.photobuc...in/IMG00053.jpg

Also because I think timing is good and I have good spark including new plug I assume I only have fuel left to figure out?
took carb apart and wrote down all the specs
Main Jet 162S
Piolt Jet 42
Starter Jet 72 or 12 couldn't see
Needle position 5
Main air jet 200
Pilot air jet 100
Pilot screw about 1- 3/4 turn out
Elevation here is 823 ft
Does this sound right or is this where my problem lies.

Bike is all stock minus the new exhaust cam
thanks

  • grayracer513

Posted April 15, 2008 - 08:52 AM

#13

It's sometimes hard to say from pictures, and timing marks on these rarely line up perfectly, but the exhaust cam bothers me a little. I usually ask myself if moving the cam one way or other would make it look closer to lined up, or further from it, but in this case, it looks like it would be about as far off either way you put it.

Let me ask you this: what's the cranking compression like?

  • bolermountain

Posted April 15, 2008 - 09:07 AM

#14

Thanks grayracer, Compression seems good when kicking it over, you can still feel what seems like TDC like before. I know what your saying about exhaust cam thats the closest it will come to 9 and 12 oclock moving one tooth either way makes it look way out of whack.

  • grayracer513

Posted April 15, 2008 - 12:58 PM

#15

I asked the compression question because cam timing affects the auto decomp system. It's supposed to release the first half of the compression stroke, leaving the engine with enough compression to run, but not so much that you can't turn it over.

If the cam is timed one tooth retarded (rotated back from its proper place) as I was suspicious that it might have been, your answer to the question would have been more like "It has almost no compression" because the effective compression stroke would have started 22 degrees too late.

It's probably a fuel or carb issue. Have you tried bump starting it?





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