ComposiMo Fabrication Stretch Kit Installation for the Honda Grom!


Thanks for purchasing the Stretch Kit for the Honda Grom! This is a basic installation guide, and i tried to cover everything, but use your best judgement along the process. It is recommended that this kit is installed by a professional mechanic!



Ok, heres our Grom on the lift getting ready for its new stretch!


First we'll remove the stock rear sub-fender/splash guard


Next, locate the Master Link on your chain. If you are using the stock chain, it'll be the painted link as seen in the pic... Pop the clip off with some needle-nose pliars, and remove the link.


Next, use a 10mm and 12mm wrench to remove the chain tensioner nuts...


Next, you'll want to support the bike in a secure manner so that the rear wheel is off the ground, and the bike is fully supported...

IMPORTANT: BE CAREFUL here to not let the bike fall... This bike is mounted to a motorcycle lift with a clamping front wheel chock, and I used a motorcycle flat-jack and a 2x4 piece of wood to hold the bike up using the header near where the header bolts to the frame. If your header doesn't bolt to the frame like this, its probably best to go right to the motor or rear swingarm itself instead of the header. Use your best judgement here as to what will be best for YOUR BIKE and how your bike is being secured!!! We are not responsible for you not supporting or holding your bike properly during this process!


Ok, now that the rear wheel is off the ground, its time to pull off the rear axle. The nut on the axle is a 19mm, and the bolt head is 14mm.


Ok, now that the rear wheel is off, you'll also want to remove the stock chain tensioners and remove the stock chain so that you can start putting everything back together again...


Here is one side of the stretch... there IS a left and a right side, so make sure you have the correct stretch piece on the correct side. The side pictured here is the left-side.


You want to slide the stretch into the back of the swingarm. This can be a VERY tight fit. Also, the ends of the stock swingarm sometimes has some "burrs" and flashing on the inside of the edge of the arm where it was cut. Take your time here, and file the inside edges, etc to help the process go smoother.

IMPORTANT: It is easier to put the stretch INTO the arm then backing it back out. At this point you'll want to decide what length you want to have the bike be... because if you push it all the way in for the shortest stretch and then decide you want the longer stretch it can be a pain to pull the stretch back out (this is completely doable of course, just a pain). If the fitment is still a bit too tight, you can use a 2x4 and hammer to tap the stretch piece into the swingarm like this... BE CAREFUL, as it is easy to damage the piece doing this!


Once the stretch is in, this is what you'll want... the shorter of the two carriage bolts goes into the left side swingarm, and the longer bolt goes into the right swingarm since the right side has the brake bracket also.

IMPORTANT: The Carriage bolt should ALWAYS be set to the FRONT of the rectangle cut in the side of the swingarm!!! I know its tempting to slide it back for even MORE stretch, but then the extension can physically slip/slide forward in the swingarm while riding, which can cause you to lose the chain, or possibly have other problems!!! Do not slide the bolt to the back of the hole! It should look like this:


On the right side stretch, you'll want to install the rear brake caliper bracket like this... Leave the carriage bolt nut a little bit loose so that it can move around still, since it'll need to move a bit to fit the caliper correctly. You don't actually fully tighten this nut until after the chain is tensioned, since the caliper will need to move/rotate a little bit as you spin the adjuster.


Next up is to adjust the rear brake line for the added stretch.

IMPORTANT: If you do this JUUUUUST right, you will not lose any fluid, and likely won't have to re-bleed the rear brake system, but it is always a good idea to check and bleed the rear brake after doing this just to be on the safe side!!!

Here is the stock rear brake line... you can see how it has a little loop built into it. By straightening this loop out a little bit, the stock rear brake line can fit even with the longest stretch option...


Using a 12mm wrench, you can loosen the banjo bolt JUUUST enough to be able to rotate the fitting, but not loose enough to allow fluid to escape! If you do this right, you won't lose any fluid, and any air introduced into the line will be minimal, requiring far less work to bleed the brakes to check for air.


When done, you'll have rotated the banjo at least to the 90 degree point. Take SPECIAL care to make sure the brake line is not too close to any exhaust system that you may be using... make sure you have enough length in the line for the caliper, but if you need to rotate it more to clear the exhaust, definitely do!


Next up, put the rear wheel and axle back in so that you can attach the rear brake caliper... Everything should look like this at this point:


With the caliper installed, you can see here how the locating boss on the caliper bracket slides into the channel on the brake caliper bracket... because of how this slides and rotates, you should still have the right side carriage bolt loose enough to allow this bracket to move around!


IMPORTANT: Once the caliper is installed, double check the proximity of the rear brake line to the exhaust pipe!! If it is too close, rotate the banjo fitting more to create additional clearance!



OK! Now you are almost done, now it is just time to install the chain, set the tension, and finish tightening up the bolts!



Chain Installation


The Grom comes from the factory with this same exact chain (D.I.D. 420D)... you should order the chain with 132 links... You WILL wind up removing some links to get the exact stretch you want, but better to be a few links too long than too short ;) here is a picture of the part number for this exact setup:


This chain is available from any local motorcycle shop, or can be purchased cheaply online. Expect it to be around $30 for the chain.

You will also need a Chain Break tool... i use this one made by Motion Pro, and available at any local motorcycle dealer, or online...


First thing you'll do, is rotate the adjuster so that the axle hole is towards the front of the bike... You want to have as much distance of adjustment as possible to get the best tension on the chain. Then, drape the chain over the rear sprocket, and pull the chain tight when you do this. You are trying to line the chain up so that you have the links looking like this...


When you have the chain set like this, you'll see that we can push out the pin in the chain on the bottom link where my index finger is, and we'll have two open holes side-by-side to put the new Master Link through...

Once you have chosen the link to remove, you'll use the chain breaker tool to remove the link pin like this:


At which point you'll be left with this:


Once that is done, you'll see here where the two links come together you have the two open holes in either end of the chain... this is where we'll install the new master link that came with the chain.


IMPORTANT: It is highly advised that you do NOT re-use the stock master link... always use the master link that comes with your new chain!!!
*** Because we are using the EXACT same chain that came on the bike stock, it is advised to put the stock master link and clip into a small baggy or something and keep it under the seat of the bike... I've had the unfortunate pleasure of having a master link come off while riding, and i wish like hell that i had a spare on the bike somewhere... This is just a bit of added insurance in case you need the road-side repair.


Next, just reinstall the master link and clip the same way the original one came out...


Next up, use the same chain tension specs that are on the label on the side of the swingarm, but to adjust tension with the eccentric adjusters on the new stretch kit, you'll use the included spanner tool, and loosen the clamp bolt on the rear of the stretch. Also, make sure that your rear axle is loose at this point as well.

As you rotate, be sure that the marks line up from left-to-right to make sure that the axle is straight, and that both sides are adjusted the same! Also, only rotate the adjuster so that the axle is on the top-half of the 'circle', and the mark on the adjuster is on the bottom side so that it can line up with the adjustment lines!

Once you are done adjusting, the spanner tool is made so that it fits perfectly inside the small tool area in the under seat storage, and hardly takes up any storage space. You should also add a small 6mm Allen key to your under seat storage as well so that you can adjust the chain tension road-side if needed.

IMPORTANT: Be sure to use Loc-tite on the adjuster bolt... this will prevent it from possibly coming loose and allowing your chain tension to loosen!!


At this point, tighten up all of the bolts on the swingarm, and the stretch is installed! Be sure to double check that both carriage bolt nuts are tight on the right and left side of the swingarm, tighten the rear axle, and double check that the chain tension has not changed. Also, be sure to double check that the clamping bolts for the adjuster are tight.


And thats that!