CRF's Only Forums

Hi guys

I am having such a headache with my crf 250r 2008 and I am loosing sleep over it!

So I have recently re shimmed the bike as the valve clearances where way out. New shims are in and all valve clearances are spot on.

Chain tensioner working perfectly and cam chain in good condition.

On the right hand side of the bike I can get the timing lined up but the hole on the left side for the spark timing is slightly out... but when I go to adjust it, my right side is then out of line...


My bike will not currently start, its back fireing eveey 3/ 4 kicks when I try to kick start it

And my kick start compression doesn't seem to be as strong as it used to be!???


Helpppoo

Welcome to the site !!

We need to clarify some things so we can see if there is anything you missed ......

First ..... You said you recently adjusted the valves , and now are having issues with it starting ....... Was it running/starting fine before the valve adjustment ?? , or did it have the same symptoms before the adjustment ?? ....

You also said the timing marks are not in alignment when checking each side .... where are the marks on the Cam Sprocket when this is taking place , are they both level with the head and the cam lobes facing 2 O'clock towards the rear ??? , and if so , which of the other 2 marks are aligned when the cam sprocket marks are level ?? , if it is the clutch side , then I would say you are 1 tooth off , if it is the ignition side , then I would say the timing chain is stretched ...

So most likely the Timing Chain is stretched , OR when you did the adjustment you got the timing 1 tooth off ...... if you are confident the valves are in spec , then timing would be the issue , if the lash was below 0.004 then I would say the issue is the valves are toast (Intakes) and need replaced .... which would also explain the lower compression , if the valves are not seating , your compression will be lower ......

All 3 marks need to be aligned , the 2 on the cam sprocket should be level with the head like this -o- , the timing mark in the small round hole , and the dot/triangle on the clutch side , ALL 3 need to be on the marks , if not it only leaves 2 possibilities , either timing off 1 tooth , or stretched timing chain ..... Report back with findings .... and/or add any info you left out as I mentioned above ......

Backfiring is a sign of timing off , or a valve open/not seated/worn ......

On a related note , once the valves start moving , then it is only a matter of time before they go again , or completely , and you will need to do a valve job , you may get 1 ride out of them , or 50 , there is no telling when they will zero out again , once you get to the smallest shim , then you are done adjusting and have no choice but to replace then or the head .... if you are not racing , then I would suggest going to Stainless Steel Intakes , you will lessen the need for adjustments and replacement by 2 to 5 times or more depending on what you do with the bike , if just play riding , you could get 10 years out of them before any adjustment is needed

Hey, thank you so much fornthe warm welcome.

The bike would not kick to start with, it would only bump start, occasionally it would start when stone cold, but after that it would have to be bump started.

I am going to attach some photos for you. The cam lobes are facing 2 O'clock and the marks on the cam wheel are dead center with the top of the head.

I can get everything to line up but the clutch side is out slightly to the left as you can see in the photo you can not see it.

There is a slight wear mark on the intake cam lobe but no damage at all as seen in the photo... as I am kick starting it it is not starting but after 3/4 kicks it will back fire and the compression feels weaker than it used to..

My old valve intake clearances where left, 0.25mm right intake 0.05mm

Exhaused clearance was 0.10mm left and 0.10mm

My new shim sizes are intake left 1.8 intake right 1.7

Exhaust left 2.4 exhaust right 2.5

Both intake clearances are now reading 0.30mm left and right

Exhaust left and right 0.28mm


When trying to upload photos it is saying file to large?

Thanks

To upload a picture , you need a hosting site like IMGUR (free) or Photobucket (they charge a lot) , to host the picture , you upload them from your PC/Phone , and they will have a link to the image for Message Boards and Forums , you copy , then paste that link in your post ............................. it will look like this [img]https:/ /i.imgur.com/HnPmgXU.jpg[/img]

But show up like this

Awesome, I think I have done this

The mark on the left side in the inspection plug is more important that the one on the right. My right side always looks off by a little. Before I take it apart for the first time, I line up the cam sprocket precisely, and use a punch to make a new mark on the right side where my eye thinks it is.

I am thinking when you did the Balancer Shaft , you got the alignment off ..... Look at this (Also , you can post more than 1 image per post)

Hi Jim, I haven't touched the balancer mate

OK , so if you align the Balancer and the Crank mark , where does that put the Cam marks ??? , if Balancer was not touched , then it has to be a tooth off on the cam itself ....

Re-align the Crank/Balancer marks and then set the Cam sprocket to match them and you should be good I would think .....