DIY: Manual Cam chain tensioner $:3

I Haven't seen any other CRF's with this DIY mod, I"m sure it's been done though, just never came across a DIY thread. So, for those of you who don't want to spend $100 on a Tokyo mods manual tensioner, here is your option. Cost from Ace hardware, $3.

Parts needed:

x1- 3.5" 5/16-16 SS caster bolt

x3- SS nuts that fit on that bolt

x- 5/16 flat washer

F size drill bit

5/16-16 tap

New OEM gasket (if you want)

30 mins of your time

Remove tensioner, remove snap ring from back side, remove all parts from tensioner, Drill hole larger with F size drill bit, tap new threads with a little cutting oil or motor oil. Grind or file head of caster bolt a little smaller to fit in the engine case hold better. Install caster bolt in tensioner, and install a 5/16 flat washer on the outside of the tensioner, then the three nuts as the pic shows. Then, your finished. Saved your self $97, so go buy yourself a new back tire with the savings.

To adjust, everything that I could find said, tighten it finger tight, start then engine and back it off listening for the chain to rattle, then tighten it back in with your fingers until the chain rattle goes away and tighten the nut down. You can feel it getting tighter as you turn it in with your fingers. I tightened it moderately (as in not turning it in until your fingers hurt, but got it snug) tight with my fingers, then tightened the lock nut. If you open the stock one up and feel the spring tension on it, it's not a lot, so your finger tight method is probably comparable to a tiny wound up wire. I didn't post a pic, but after I tightened the lock nut, The two outer nuts I used to turn it, I also threaded those all the way on against the locking nut, so now there are three nuts all side by side so there is no chance to back off.

The reason I did this mod is because I have heard of many cases that the stock automatic tensioner has fail and catastrophic engine failure has occurred and it ended up costing them $1500+ to rebuild their engine. I am moving overseas to a third world country where parts take at least a month to get, and they have to be shipped from Australia, so I am taking every precaution to bullet proof my bike.

photo1iev.jpg

Edited by narf_44

I like stuff like this, saves some cash for other go fast parts and it makes your bike more yours. One question why did you choose to use SAE threads and not keep it metric?

Because I had SAE taps and drill bits already

Got it, I was just wondering.

Have you put any miles on the bike since doing this DIY mod?

Just curious, why would I want to jimmy rig such an important piece on my engine when the stock Honda tensioner works better in every way??

Because I had SAE taps and drill bits already

I like the fact that you used a larger center adjuster bolt, have heard of some guys using a smaller 6mm center adjuster bolt which would probably be easier and not require drilling it larger but IMO 6mm is alittle too small.

One thing I would suggest to add to your post is how to adjust it, I think some guys dont consider doing this because of not knowing how to adjust it or thinking adjusting it is too complicated.

Just curious, why would I want to jimmy rig such an important piece on my engine when the stock Honda tensioner works better in every way??

Could you elaborate on how they're better in every way. I've seen major engine damage on more than one occasion from stock adjusters failing, and have never seen a manual tensioner fail. They're super easy to adjust (easier than adjusting your drive chain). I'm not knocking stock tensioners, but can't see in any way how they're better.

The stock adjusters get 'stuck'.

They work great, until they don't work at all.

I would prefer a device using grade 8+ hardened materials, and less exposure to impact.

Give me the MCCT over the auto unit any day .

The auto units also extend prematurely and retract due to failure

Edited by backyard hack

Just curious, why would I want to jimmy rig such an important piece on my engine when the stock Honda tensioner works better in every way??

One of the main reasons is because at high RPM, the automatic adjusters can potentially float a bit, allowing the chain to pick up some slack and jump a tooth.

An automatic adjuster is nothing more then a manual adjuster with a spring on it to apply a certain amount of tension. The amount of tension is a balancing act; too light and you don't keep slack out of the chain, too heavy and the chain ends up too taught. So if the chain guide presses on the adjuster with more force then the spring provides or the adjuster gets stuck, then you end up with a slack chain.

Note that you can just as easily have a problem with a manual adjuster. I've heard of them backing out. I've also heard of people that over tighten them and cause pre-mature wear on their chain and cam bearings. It's really not rocket science to adjust it, but you need to stay on top of it (like at every oil change).

But since I don't live on the rev limiter, I'm not too worried about the stock adjuster. If I had a R, a manual adjuster might be a better choice. But I also believe that the guy's that designed the motor are pretty smart and if they felt an automatic adjuster was better then a manual one, then that's why it has an automatic and not a manual one.

Last, while the aftermarket does everyone a great service coming up with things that improve riding, I also believe there are times when they market items that we are made to believe we need when we really don't.

Jim.

Need to remember the thing with these engines that cause the tensioner and cam chain problems is that they are capable of very high rpm and some of the bikes are often run at high rpm, but also the engines are acelerated and decelerated so quick. On aceleration the front of the chain is tight, on decel the back of the chain or the tensioner side gets tight. The conditions the tensioner has to deal with changes quickly and if it mal functions even briefly with the engine at high rpm its a problem, often times a big problem.

As far as adjusting a MCCT, it takes five minutes or less if you know how to do it. The first time you may want to go alittle slower but theres not much to it.

I always check or adjust mine with the engine at TDC, so if you can find TDC (of the comp stroke, same place you would check valve clearance) by turning the engine over by hand using the kickstarter, you can then loosen the locknut, and back off the adjuster bolt, and using no tools turn it out a turn or two with your fingers. Then slowly turn it in until you feel some light pressure because it made contact with chain guide. I normally will turn it in from there approx 1/4 turn, again using no tools just finger pressure. Tighten up the lock nut and your done. Maybe takes 3 minutes.

Edited by TDW

I was remiss too in not mentioning that this was a great post.

A little ingenuity can go a long way when your working on your bike.

Jim.

Can you re-post the photo of the DIY MCCT?  I know this is an old post, but I have just had 2 of the OEM ACCT's fail and want to mod the broken ones.

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