Easy GY6 Cam Timing Guide

Top Dead Center refers to the piston being at the very top of its travel in the cylinder. Otherwise known as “TDC”.

This position is important when installing a new camshaft, because the cam must be set with the crankshaft at TDC.  If the camshaft is off by a tooth, the engine will lack power and risks damage to the piston and valves.

STEP 1: Align Flywheel Timing Mark and Index

Search the outer rim of the flywheel for the T and F marks, in between 2 lines “|T  F|”. The line to the left of the T is what we’re after. Rotate the crankshaft so the T line is aligned with the index on the crankcase (as pictured).

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STEP 2: Align Camshaft with edge of Cylinder Head

Rotate the camshaft so that the two hash marks and smaller holes are exactly aligned with the edge of the cylinder head.

If your new cam has multiple large holes: Make sure that the “A” number of your cam is visible and rotated away from the engine as seen in the picture.

Or if your cam only has one large hole: On stock cams and some aftermarket cams there is a single large hole in the cam gear instead of an “A” number.  In this case, make sure that the large hole of your cam is visible and rotated away from the engine, shown in the red area box below.

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You’re in-time!

Reinstall your timing chain and rotate the crankshaft a few times, double checking the flywheel-to-index and hashes-to-head alignments.

7 thoughts on “Easy GY6 Cam Timing Guide

  1. Avatar Bernie Fields Gray, TN

    Barry and Travis
    You have been so very helpful to me. I know I have asked a miilion questions but you have been so helpful and patient. I really really appreciate all your help. You both are so knowledgable on the GY6 engine and Crossfire 150. Thanks a million!!! And……..love this website!! It helped me so much!

  2. Avatar How-To: Get an engine for your Crossfire 150R | BD Technical Center

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  3. Avatar michael Teel

    What does the F mean… And what about lines in-between. How many degrees is each line

  4. Avatar stupid

    What if by chance a person removed the timing gear from the cam to replace a beating and did not pay attention to the way it came off and put it on all wrong. Then what would this person do to time it

    • Travis @ Buggy Depot Buggy Depot

      In all fairness, that sprocket isn’t really meant to come off. Getting it back on correctly is a feat not often seen. The easiest fix would be to buy a new camshaft at this point. Otherwise you’ll have to come up with a way to re-index the cam sprocket with the shaft. Not impossible, but usually not how I’d recommend to spend a weekend with limited chance of success. New cams are reasonably inexpensive. https://www.buggydepot.com/product/115/camshaft-standard-spec.html

      • Avatar stupid

        That as it may, is there any way to time it now?

        • Travis @ Buggy Depot Buggy Depot

          I really don’t want to say no, but there isn’t a clear method for indexing with common tools. The unique design of the tool needed to index a GY6 cam isn’t something I’ve had to work out before, and nothing reasonable immediately comes to mind without involving a 3D printer for a one-time-use indexer, or a couple afternoons on the Bridgeport if I wanted to make it a production tool.

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