How To Turn Your Stock Acct Into A Mcct

[CFM-Z440]

Thumper talk sells a manual cam chain tensioner (mcct). It is very popular because it is believed that the stock automatic cam chain tensioner (acct) for the Z400 has too much spring tension which makes for a short timing chain life.


I'm too cheap to buy one, so I turned my stock acct into a mcct.


First, you need to put the engine at Top Dead Center on the compression stroke, then remove the acct and totally disassemble it. To do that, you will need a small punch to remove the roll pins that hold the end cap on the adjustment rod, and to remove the latch.

Here are all of the parts



Next you will need a 1/2" tap and a fully threaded 1/2" bolt and jam nut that match the thread pitch of your tap. I chose coarse thread because I don't want to put too much tension on the chain by accident. (less leaverage with coarse thread)

Thread the acct housing from the side that sticks out of the engine. I ran my tap in until the last set of flutes had reached the hole, then stopped at that point.





Next grind the latch down until it is just a round wheel. Try to keep it as big as possible, but it needs to be round and not very oblong. I also beveled the edges down when I got it ground down. This was too small to get much for pics of with my camera.




Next you will need to find a small screw to act as a space filler and as a thrust surface. It fits into the back of the adjustment rod where the spring used to go, and sits on the ledge. The bolt will push on this screw head.





Now put it all together. Make sure that your adjustment rod moves freely with no binding, and make sure that your adjustment rod is extended all the way before the bolt is threaded all the way in. You will not re-use either of the springs, or the plug. I put some grease on the threads of the adjustment bolt.



Here is the finished product.


All the way backed off



All the way extended




This thing did not cost me anything because I already had the extra pieces laying around the shop. The beauty of this mcct is that it is still not possible to run a worn out chain. The adjuster rod Does not extend any farther than it is supposed to. When your out of adjustment, you need a new chain.


To set the chain tension, make sure the engine is at TDC on the compression stroke, finger tighten the adjuster bolt, back off the tension just a little, and lock the nut down.



Done, nearly free mcct

[SVT]

Cool Beans
just need a fancier nut on the end like a acorn style

[CFM-Z440]

QUOTE (SVT @ Feb 28 2008, 01:01 AM)

Cool Beans
just need a fancier nut on the end like a acorn style[/b]

Yeah, I just went with what ever I could find around the shop

[z400kiksazz]

Do you just tighten it up like finger tight or something? or do you torque it down?


This will probally be another mod on my list, thanks!

[CFM-Z440]

QUOTE

To set the chain tension, make sure the engine is at TDC on the compression stroke, finger tighten the adjuster bolt, back off the tension just a little, and lock the nut down[/b]

Im looking into adding an o-ring or a sealing washer between the jam nut and acct housing now also to keep it from leaking. Pics will be up when I have done that.

[kfx400boy]

Vary nice, did you grind down the screw head to take the groves out for the screw driver.

[z400kiksazz]

how often do ya have to check it?

[CFM-Z440]

QUOTE (z400kiksazz @ Feb 28 2008, 09:35 PM)

how often do ya have to check it?[/b]

As often as the chain starts to get noisy.

[CFM-Z440]

Ok people, adding another step...



I used a counter sink to make a bevel in the end of the housing where the bolt threads in. This is where an o-ring will sit to avoid any leakage.





If you dont have a counter sink, a very large drill bit turned by hand might also make the same type of impression. A beveled stone for a die grinder may also work.


The o-ring came from our assortment at the shop.

[WheelieZ]

MAN YOUR A THINKER!!! THATS AWESOME!!

[z400rider1292]

wow i woulda never thought of that .
lol

[SVT]

well its already a sticky, my bad. doing this this weekend with my machinest buddy, goiing to do some improvising.

[CFM-Z440]

QUOTE (SVT @ May 20 2008, 10:14 PM)

well its already a sticky, my bad. doing this this weekend with my machinest buddy, goiing to do some improvising.[/b]

Post it up in here if you want. I left this topic open for a reason.

[TJ400]

QUOTE (CFM-Z440 @ May 21 2008, 02:06 PM)

Post it up in here if you want. I left this topic open for a reason.[/b]

this is a very cool mod!!!!!!

[camaro1976]

can't believe i missed this...

i was plannin on carving mine out on a lathe, but this will save me a bit of time.
great job chuck! :