Convert factory cam chain tensioner to manual - For $4 - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 10 Old 04-13-2017, 11:04 AM Thread Starter
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Convert factory cam chain tensioner to manual - For $4

So after going through 2 brand new factory tensioners in less than 1000 miles (original made it 28k), I decided that I wasn't going to buy another factory one to destroy my engine, and I also wasn't going to pay $50 for a bolt and nut shoved through a tensioner housing. Here is the original post with a video showing the symptoms and details of what I was experiencing: https://www.cbr250.net/forum/cbr250-p...ner-dying.html

So, since I had an extra (bad) tensioner laying around, I decided to do some surgery, find the underlying culprit, and solve this once and for all. So here goes. $4 in Lowes hardware and half an hour later, and no more ticking.

Supplies needed:
1 package of M6x1.00 40mm stainless steel bolts (need 1 bolt)
1 package of M6x1.00 stainless steel nuts (need 1 nut)
1 package of M6x1.00 stainless steel nylon lock nuts (need 1 lock nut)
1 package of stainless steel washers (need 1 washer)
Total cost: $3.96, and enough leftover to do 3 more tensioners!

Remove the hex cap bolt on the back of the tensioner and remove the small black o-ring. Do not lose this!



Remove the tensioner from the back of the motor with the two 8mm bolts on each side. Hold it in towards the motor when removing to prevent stripping the other bolt.

Remove the snapring from around the base of the plunger using a small, thin, flat head screwdriver and working around the housing a little at a time. Be careful to not warp/bend the snapring out of shape, as you'll be re-using this later. (Sorry, no pics of this. Needed two hands and didn't want anything flying out in my face.)

Once you have the snapring off, you can remove the plunger and all the guts of the tensioner. BE CAREFUL! There is a spring inside under tension, and it can slice you if it pops out.



Here are the parts in their glory. We'll only be using a couple going forward: 1. The housing 2. The snapring 3. The plunger. The spring, plastic sleeve, wormgear, and washer will not be used.



And this brings us to the crux of the tensioner debacle. The spring tension does both duties: Providing outward tension, and preventing the wormgear from backing off; there is no lock on the wormgear. Unfortunately, once the spring weakens to a point where it is no longer providing adequate pressure outwards, it is also unable to prevent the wormgear from backing off under vibration, allowing the cam chain to rattle around and make that cringe-worthy noise at idle.

Here, you can also see the end of my spring is also quite knarled. This thing was ready to let go.



Ok, now is when the magic happens. Take your stainless bolt, then place 1 regular stainless nut on the bolt, followed by 1 stainless washer, followed by the black sealing o-ring from earlier. Begin threading the bolt into the tensioner housing from the back side. Here you can see the order and the orientation.



You will want to move the nut to the head of the bolt so that you can bottom the bolt out on the housing as far as it will go. Make sure your o-ring is in the recession on the housing so it doesn't get pinched or torn.



Now grab your stainless nylon lock washer and place it on the end of the bolt that is now pushed through the housing. Use a 10mm wrench on the bolt head, and a 10mm socket on the nylon lock nut to tighten the nut until it is flush with the end of the bolt. If you feel paranoid, you may place some locktite on the threads before doing this.



Now back the newly completed bolt apparatus out of the housing until it hits the lock nut. Place the plunger back over the housing and lock nut, then reinstall the snapring.



Place the gasket back on the tensioner housing and reinstall in the bike.



Now make sure the o-ring is in its recession, and the washer is laying against it (this will keep oil from weeping out around the bolt). Turn the main bolt in finger tight until you hit resistance. I turned it one-half turn further, then held the bolt head with a wrench to keep it from moving while I snugged down the nut with another wrench to lock it in place.

Here is the completed install:



This may take a little adjustment. If you hear rattling after this, loosen the nut and turn the bolt head another half turn in. If you hear a whining sound on deceleration, then it may be a tad too tight and you should back off a smidge.

No rattles, no more failures, and no overpriced custom manual tensioners. Bling, blang, blao.

Tis better to be thought a fool and remain silent, than to open one's mouth and remove all doubt.

Last edited by cbrlocal; 04-13-2017 at 11:17 AM.
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The Following 9 Users Say Thank You to cbrlocal For This Useful Post:
don'tpanic (04-14-2017), jkv357 (04-13-2017), OleKennyRoy (04-13-2017), Parsec (01-17-2018), Sardo (05-19-2019), Schroeder (04-14-2017), shisoshin (04-14-2017), Stichill (04-21-2017)
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post #2 of 10 Old 04-14-2017, 05:49 PM
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That might come in handy one day.

My computer is fighting Aids and Cancer in it's idle time, and yours?
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post #3 of 10 Old 04-18-2017, 03:01 PM Thread Starter
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Bonus information: No more 5.5k RPM rattle! Must have been the slop in the tensioner construction or timing chain all along.

Tis better to be thought a fool and remain silent, than to open one's mouth and remove all doubt.
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post #4 of 10 Old 12-14-2017, 11:41 AM Thread Starter
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I have been informed by another member that my photos for this thread are no longer active because of Photobucket's updated 3rd party hosting policy, in which the host of the forum must pay Photobucket for the images to be hosted. Hogwash.

Anyways, here's a link to the album with the pictures. They aren't necessarily in order, but they're basically in reverse order for the process.

Cbr250r Cam Chain Tensioner Fix | Photobucket
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post #5 of 10 Old 12-14-2017, 03:53 PM
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'please update your account to enable 3rd party hosting'
with a tacho image with 100% over it, and 'go to photobucket' etc..

at first your images came up then replaced with a 'photobucket'
image,, but just repeated and the images stayed up..
[remember manual adjusters on earlier hondas
never having any problem with them
incl sohc 750/4's]
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post #6 of 10 Old 12-15-2017, 03:14 PM Thread Starter
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Quote:
Originally Posted by shisoshin View Post
'please update your account to enable 3rd party hosting'
with a tacho image with 100% over it, and 'go to photobucket' etc..

at first your images came up then replaced with a 'photobucket'
image,, but just repeated and the images stayed up..
[remember manual adjusters on earlier hondas
never having any problem with them
incl sohc 750/4's]
The new link in my previous post should go directly to the album; Photobucket hates embedding pictures on blogs, etc now if they aren't paid for hosting. Money grubbers.
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post #7 of 10 Old 08-22-2018, 04:59 PM
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thank guy...worked perfect...the only change I made was a 45mm long bolt and threaded the inside lock nut onto bolt until about 1/4 of bolt stuck out past nut and that went inside plunger to help support it like original setup


thanks again...easy, quick and no noise anymore
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post #8 of 10 Old 08-24-2018, 09:10 AM Thread Starter
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Quote:
Originally Posted by mwlehman View Post
thank guy...worked perfect...the only change I made was a 45mm long bolt and threaded the inside lock nut onto bolt until about 1/4 of bolt stuck out past nut and that went inside plunger to help support it like original setup


thanks again...easy, quick and no noise anymore
No problem; glad it helped. There's nothing like saving money and fixing a problem Honda has yet to rectify yourself.

Tis better to be thought a fool and remain silent, than to open one's mouth and remove all doubt.
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post #9 of 10 Old 08-24-2018, 05:02 PM
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Quote:
Originally Posted by cbrlocal View Post
No problem; glad it helped. There's nothing like saving money and fixing a problem Honda has yet to rectify yourself.

yup...thanks again for the idea, I love when someone figures out a way to fix something instead of throwing new parts on it...maybe cause I am cheap ..lol



my wife`s cbr has about 10k around town miles on it before it started to go bad, she is happy now which is good... she also has a red 2004 Aprilia tuono and a blue 2008 aprilia tuono but still enjoys cruising around on the cbr250r
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post #10 of 10 Old 12-09-2018, 03:28 AM
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Wow. seems like this bike tensioner stuff is kinda weak.

I remembered my friend told me that he needs to replace the CCT and the timing chain around 4-5 times.

And his bike mileage is barely touching 20k miles.

I already replaced mine 2 times.
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