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Timing Marks??

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I was checking my clearances last night and when aligning my timing marks, they just simply do not line-up. The arrow on the cam holder is either above or below the cam gear mark. I use both alignment marks on the right and left side. If I use the left side marks, ( sitting on bike ) and put it on the second mark then it is a little closer to the mark above the arrow on the cam holder. This is where I had it.

Where do you guys line-up your marks?

Is your marks dead on?

If mine will not line-up, am I better to be above or below the arrow on the cam holder, for timing ( advance vs. retard ) ??

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Ok here is the full documentation so if someone else searches, hopefully this help as it was not in my bike manual or the downloaded PDF full manual. The left side looking hole is way easier. I have provided all the supporting pictures.

Bestofmotocross.com Team AdverNETS

Rider: 122 Rob Gerwing with Team AdverNETS

2004 Honda CRF450 (Pictorial of Cam Timing Marks)


NOTE: Refer to your manual first, use these pictures as supporting documents that I created to help the process.

I hope this helps everyone out. I figured while I was doing my top end, I could provide some illustration to help out fellow TT'ers.

Cam Timing can be tricky if your not careful and I hope to save some people from destroying their valves or the infamous one tooth off problems or timing off ( backfire, won't start, runs bad ). Below I provided the pictures to help people see the cam timing marks for TDC and aligning the cam gear and timing chain.

Finding Top Dead Center (TDC)

Definition: Piston is at the very top of the stroke.

Left Side Alignment

Because the right side can be tricky as I illustrated at the end of this post and can put you off one tooth. I have found using the left side is easier and much more accurate. There is a cap hole to use, but I have illustrated with the cover removed AND with cover installed:

COVER INSTALLED (removed small round allen bolt plug) Not look GLASS!


Cam Lobes Need To Face Toward The Rear Of Bike (Intake Side Of Engine)


Cam Gear and Cam Chain

NOTE: Green String In The Piture! No matter how much of a hurry your in, put some kind of wire or string through the chain to prevent the chain from falling down. Once it falls down you will have more work ahead of you to just get it back up to the top.

If the chain comes off the bottom gear during re-installing the gear, lean you bike over to the right and have someone hold it and push the chain loose and let gravity let it slide back onto the gear. If this doesn't work you will have to take off the left side cover.

Quick Notes on old chains. As the chain wears, the timing mark alignment on the cam gear will not align exactly. My CRF450 the cam gear line is BELOW the arrow one tooth when I have aligned TDC. When I was aligned prefectly it backfired when trying to start so be aware sometimes you can be a one tooth off. This seems to be a know deviation with everyones bike. But if your timing chain is good, should line right up like below. You should never go more then one tooth in either direction from perfect mark alignment. If your mark doesn't line up perfect, make sure you turn over the engine with the spark plug out to check for any binding.


Optional Right Side Alignment:

This side is alot harder to line up and alot of people mess this up. Although I would like to note that it is nice to have the right side open to spin the crank by hand with a allen wrench in the crank bolt shown.




Another thing that is easy to do is forget to check your valve clearances. Make sure after reassembling the cam gear and timing chain to make sure everything is in spec.

What if bike feels very hard to kick over and you fear binding on your newly assemble cam or top end. Something everyone and I have run into is with a new cam it's easy to over look the valve clearance of the "Exhaust Decompressor". If this gap is incorrect, this can cause the bike to be very hard to kick over. If everything is aligned on the timing chain, this is the next place to look. The manual specifies .014" gap. I run mine at .010" and seems to start easier with the HotCam Stage 1.

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