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Discussion Starter #1
Alright, as many may know the crf50 rear sprocket has the same inner hole diameter, stud pattern, and stud hole size. the only difference is the CRF50 rear sprocket has tapered holes and the grom does not.

Solution, simply turn the 4 nuts that hold the stock grom sprocket on around, so the rounded edge of the nut faces inward to align with the tapered hole, use some locktite and call it good.

Cool thing about the CRF50 rear is they offer larger rear sizes for cheap.... IE the JT Sprockets JTR1213 smallest size is a 37 (3 teeth larger than the stock 34).

If you do the math... this is almost exactly the same as ever popular dropping 1 tooth in front (14/34 = 2.428:1 15/37 = 2.4666:1) But this has a benefit of keeping a larger diameter front for less chain wear... and it makes things cheap if you are replacing both front n rear sprockets n chain like i was. (420 stock pitch chain)


The JTR1213.37 is all of 17 bucks n change on amazon

The JTF249.15 (15tooth front) is all of 8.79 on amazon


Also the JTR1213 rear is a nice black finish that blends in nicely with my black grom!
 

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Resurrecting this because searching for info results in hundreds of pages. Holy moly.

Anyways, instead of starting a new thread, again. I'll ask here. I'm sure it's been asked a million times, so sorry.

On my CRF250L, a popular upgrade was a 1 tooth smaller front sprocket. The CRF250L's are 6 speeds, and the bike didn't have enough power to overcome the stock gearing. Going down 1 in front actually increased the top speed for most people. I say most because the smaller guys didn't have a problem with stock gearing. Well, the Grom has even less power than the CRF, so does the same apply here? Will going to a 14t front increase top speed for a bigger guy? I know it sounds a$$ backwards, but it worked on the CRF. Wondering if the same holds true here.
 

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16/32 that is all you need for BBK if you want speed and high end top speed make sure you get the PBI sprockets made in the USA, P/N 3015-32 rear silver, P/N 321-16 C/S front. Home
 

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I don't care too much for top speed. Just curious if a 1 tooth smaller sprocket will increase top speed as a side effect.
 

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Resurrecting this because searching for info results in hundreds of pages. Holy moly.

Anyways, instead of starting a new thread, again. I'll ask here. I'm sure it's been asked a million times, so sorry.

On my CRF250L, a popular upgrade was a 1 tooth smaller front sprocket. The CRF250L's are 6 speeds, and the bike didn't have enough power to overcome the stock gearing. Going down 1 in front actually increased the top speed for most people. I say most because the smaller guys didn't have a problem with stock gearing. Well, the Grom has even less power than the CRF, so does the same apply here? Will going to a 14t front increase top speed for a bigger guy? I know it sounds a$$ backwards, but it worked on the CRF. Wondering if the same holds true here.
Short answer is yes. On a stock Grom going to a 14 tooth front for a big guy over 200lbs will give you more use of 4th gear and likely more top speed. Just remember unless you get something to correct it the speedo will now read about 3mph faster than you are actually going.
 

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FYi.... going -1 up front (equiv. to +3 rear) will improve lower torque, but will sacrifice top end. In other words, you'll get up to speed a bit quicker, but will lose some top speed. The inverse: +1 up front = -3 rear ;)
 

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Discussion Starter #8
FYi.... going -1 up front (equiv. to +3 rear) will improve lower torque, but will sacrifice top end. In other words, you'll get up to speed a bit quicker, but will lose some top speed. The inverse: +1 up front = -3 rear ;)
The problem is the grom simply does not have the power to pull through 4th gear going -1 in the front (or +3 in the rear like i did) yeilds a grom that has a faster top speed and gets there quicker.

I am so glad i went with the 15/37 sprocket combo, less wear on the chain and way more pep in its step.
 

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The problem is the grom simply does not have the power to pull through 4th gear going -1 in the front (or +3 in the rear like i did) yeilds a grom that has a faster top speed and gets there quicker.

I am so glad i went with the 15/37 sprocket combo, less wear on the chain and way more pep in its step.
Exactly what I figured. Thanks for reply. Just ordered the 14t sprocket. On a bigger bike going down in front lowers top speed, but on smaller bikes it seems to have the opposite effect because of HP deficit.
 

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Discussion Starter #15
sort of. the 50 sprocket has a countersunk hole.

however this is correct:
JT Sprockets: Catalogue

correct, as denoted in the first post, the CRF50 / XR50 rear sprockets (crossed referenced and those two models are the same) have different holes, but dont pose an issue. Had mine on for 1200 miles without problem.
 

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I put the xr50 sprocket on and torqued the nuts down.
I put a marker on the nut & sprocket incase they back off I can see it instantly.
The stock nuts with the xr50 sprocket worked perfect together even with the bevel in the sprocket.
it moved the rear wheel all the way forward, even better for wheelies.
rode for 20 miles with wheelies, drag raced a z125 and top end on the freeway with no issues & bolts still in place.
we used an app on the phone for max mph, it said I did 69mph on the app, bike said 72mph when I hit the cut off. That's telling me the cluster isn't that far off if the app is accurate though.
Best free mod ever. Well worth going 3 up or 1 down in the front as its about the same
 
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