Not starting very good post YZ cam swap - help?


7 replies to this topic
  • SJMC_DON

Posted May 15, 2008 - 05:28 PM

#1

Just completed a cam swap in my 07' to 06' YZ cams. Everything in regard to cam timing and valve clearances is spot on. The bike is running strong, (atleast it is in my driveway, I have to get it out and really test it out still).

My problem now is with starting. It seems to kick start just fine but it won't start real easily with the e-button. It takes a while and only then with the hot start pulled in, even when cold...

I have a 48 Pilot, 168 Main and the needle is from the GYTR AIS kit set with the clip in the 4th position. My garage is about 400 ft above sea level and spring has finally sprung here with 60 deg temps...

Even before the cam swap I would have to use the hot start occasionally when e-starting so I figured I am rich some where in the circuit but not sure where as I am somewhat challenged in understanding all the aspects to properly jetting this bike.

Anyone have similar symptoms after a cam swap or can you direct me to which jet is setting the mixture when starting.

Thanks!

Don

  • honeycutt

Posted May 15, 2008 - 05:36 PM

#2

Not sure about this but would it have anything to do with auto decomp on the WR cams and the YZ not having it? I have heard that the e-start has trouble with some high compression pistons and some cams. Like I said not sure but someone will chime in that knows for sure!

  • SJMC_DON

Posted May 15, 2008 - 05:39 PM

#3

Honeycutt - Thanks for the reply. The YZ exh cam has the auto de-comp pin and it is working great. I think it even kicks a little better now with the YZ cams installed. Piston is OEM WR... I hope your right in that some of our WR bretheren will chime in with an answer.

Thanks :thumbsup:

  • tweav

Posted May 15, 2008 - 07:07 PM

#4

Ok my 07 does not start the same ether , But it still starts ok . The e-z button is a bit odd now , It kind of sounds like it has very little compresion . but kicking it is easier now . what the deal is the yz ex cam is dumping more compression because the pin hits sooner . As far as my jetting goes I'm running a 42 pilot and a 150 mj at 700 ft . but I think I'm just a tad lean at WOT I'm going to swap in a 155 mj . My bike started like crap until I leaned it out it was running major rich according to the wide band o2 sensor with the stock 45 pilot 11.2 to 1 at idle . my accel pump also did not work from stock , according to the wide band it would go off the chart lean at over 18.99 to 1 when I'd crack on it . so I put on a Rd powerbowl to fix the pump . I Think you should get some o2 readings from your bike , to see where your at . your jetting is most likey to rich at idle ,but with out knowing that your accel pump is doing it's job right I'd be afraid to lean out the pilot because your pilot will lean the bike out the whole way thru the rpm range . and we all know too lean will kill an engine. Take it to a Dyno

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  • MaxPower

Posted May 15, 2008 - 07:09 PM

#5

[COLOR="Green"]Did you install OEM cams or aftermarket cams?
In my 04 I just switched out the exhaust. No reshimming needed
I have to use the hot start pretty much all the time but for the first start up.
Wait till you take it out and really give it the stress test.It really runs like it was made to run.I love my bike now.

Sorry I can give you what you need for the cold starting. I just wanted to tell you it will be worth the effort when you do get it sorted.
[/COLOR]

  • SJMC_DON

Posted May 15, 2008 - 08:28 PM

#6

Ok my 07 does not start the same ether , But it still starts ok . The e-z button is a bit odd now , It kind of sounds like it has very little compresion . but kicking it is easier now . what the deal is the yz ex cam is dumping more compression because the pin hits sooner .


Exactly what mine is doing. OK, this makes sense to me

As far as my jetting goes I'm running a 42 pilot and a 150 mj at 700 ft . but I think I'm just a tad lean at WOT I'm going to swap in a 155 mj . My bike started like crap until I leaned it out it was running major rich according to the wide band o2 sensor with the stock 45 pilot 11.2 to at idle . my accel pump also did not work from stock , according to the wide band it would go off the chart lean at over 18.99 to 1 when I'd crack on it . so I put on a Rd powerbowl to fix the pump . I Think you should get some o2 readings from your bike , to see where your at . your jetting is most likey to rich at idle ,but with out knowing that your accel pump is doing it's job right I'd be afraid to lean out the pilot because your pilot will lean the bike out the whole way thru the rpm range . and we all know too lean will kill an engine. Take it to a Dyno


Thanks for the input :rolleyes:

And Maxpower, yes they are OEM cams. The intakes are different on the 07's too. I wonder if the hotcams WR cams would have the same decomp issues? If it is infact an issue:excuseme: I hope it's not, I had it working good for race starts before I started this little project :thumbsup:

  • beezer

Posted May 16, 2008 - 06:28 AM

#7

My 08 with a YZ exhaust cam won't start easily cold with the e-start either. I used 08 YZ jetting with a Dr. D pipe and it runs really, really good but I always start it with the kickstarter when cold.

Sometimes even when hot the e-start gets hung up on a compression stroke and won't turn the motor over. I noticed that the hot start helps.

My 05 doesn't like to start cold with the e-start unless it's 70 degrees or more.

  • MountainMax

Posted May 18, 2008 - 01:05 PM

#8

my 06 never started easily with the the magic button when i put on my 05 yz cam either, but after re-jetting it made it better, not like stock but acceptable, she starts about 75% of the time now withough kicking her over.




 
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