Reduced from 14T to 13T at the front, increasing torque at the wheel and improving acceleration.
BHPian Mr.Sleeper recently shared this with other enthusiasts.
This was a time-intensive mod due to the research and trial and error that went into it but was worth it as it could be a possible fix to an issue a lot of CB350 owners face. This issue wasn't discussed much on team-bhp or YouTube either so I'm excited to share my findings.
I live in a hill station currently and riding the CB on hilly roads with its tall gearing is really annoying. The higher gears are rarely useful and you have to really push the bike to make quick overtakes. It is almost impossible to cruise sedately at low revs in uphill or city sections. Better low-end power would mean easier riding on uphill roads and quicker initial acceleration. I was checking out possible fixes to make the bike more tractable and read about changing the sprockets to alter the gear ratios.
The basic rule of Thumb is:
More teeth in the Rear (or) Fewer teeth at the Front = more torque at the wheel, quicker acceleration, reduced top speed
Fewer teeth at the Rear (or) More teeth at the Front = higher top speed, better mileage, reduced pick-up
There was very little information related to gear ratio altering of the CB online. Came across a thread on the CB350 Owners Facebook Group where a few owners had experimented with various sprocket combinations to improve tractability. After going through the entire thread this is the summary:
Stock: Front 14T, Rear 35T, Chain Link 104
Combination 1: Front 13T, Rear 35T, Chain Link 104
Pros:
- Stock chain and rear sprocket can be used
- Only front sprocket needs replacement
- Noticeable improvement in low-end power
- Easier to ride in city or hilly roads, fewer gear shifts needed
- Cost Effective
Cons:
- Top speed drops noticeably, while the bike can reach 120, it seems strained, Vibration-free cruising speed has come down to 90-100 km/hr
- Mod not suitable for owners who do a lot of highway riding as the bike seems a little strained while maintaining speeds above 100 km/hr
Combination 2: Front 15T, Rear 41T, Chain Link 105
Pros:
- According to owners' feedback this combination provides good rideability at low speeds without greatly reducing the top speed
- A more complete mod as it makes the bike tractable in a variety of riding situations
- Does not compromise the highway riding capability of the bike
Cons:
- Expensive as it needs replacement of both front and rear sprockets
- Custom 15T front sprocket must be purchased (Rs.1500 from GP Racing Chennai)
- Rear sprocket is from the CB500X (Rs.1805 from Honda Genuine Parts)
- Extra link must be added to the chain which requires a skilled mechanic
As my primary usage was city and hilly sections where I rarely cross speeds of 100 km/hr, I chose to go with Combination 1 as it was cost-effective and met most of my requirements.
Approach 1:
A Mumbai-based CB rider shared on Facebook that he used the front sprocket of the Suzuki Gixxer 250 which is 13T. It was not a direct fit as it does not have the screw holes of the OEM sprocket and he had to use two 24mm outer circlips and a 25mm big dollar washer to lock the sprocket into place. According to the rider, the jugaad works fine and he has been using this setup for quite some time. The Suzuki sprocket cost just Rs.270 therefore I decided to give this jugaad a shot.
My mechanic warned me during installation itself that fitting a sprocket this way could be very risky since it is a part that receives significant torque. I contacted the rider who had done this mod and he assured me that it should work fine. Used the washers and spacers to lock the sprocket into place. The mod worked and the desired gearing changes were observed. However, under high revs, there was a loud and noticeable clatter from the front sprocket area. Also, the gear shifting felt completely crude with the gear shifts requiring a lot of effort to slot into place. Overall even though the jugaad worked and the low-end torque issue was solved, it didn't feel like a refined and permanent fix and there was always a fear that it would all break and come loose anytime.
Approach 2:
Unhappy with the earlier fix started searching for more permanent solutions. Came across GP Racing, Chennai (9841059988), they make custom performance parts for Indian market motorcycles. They make 13T and 15T front sprockets for the CB which are of OEM specifications and a perfect fit. Contacted Mr. Ganesh who was very kind and helpful with the ordering and shipping process. The sprocket cost Rs.1500 and was delivered within a week. The sprocket was well made and had two screw holes just like the OEM sprocket and therefore could be screwed into place perfectly. No more loud clatter or vibrations at higher revs and gear shifts felt precise again. I would strongly suggest anyone looking into a sprocket swap to avoid the jugaad and go for this approach as it provides a better sense of safety and satisfaction.
Observations after 13T Swap
Pros:
- Noticeable improvement in acceleration at low revs, Quick overtakes are easier
- Can ride at higher gears in uphill sections
- Bike can start off from 2nd gear quite easily, shows improvement of low-end torque at the wheel
- Bike can maintain city speeds at 3rd gear effortlessly, used to experience lugging earlier on the stock setup
- Minimum speed for 4th gear is 40 km/hr
- 5th gear has finally found its purpose, minimum speed of 60 km/hr, after which you can cruise effortlessly without any hint of engine lugging
- Improved mileage at lower speeds
Cons:
- Top speed has dropped by around 10 - 15 km/hr (speedo indicated 120 km/hr is the new top speed)
- Engine is strained after crossing 100-105 km/hr
- Reduced mileage at higher speeds
- Possibility of speedo error (TBhpians I am not sure of this, someone please explain if possible)
I know people who like the tall gearing of the CB claiming that it gives the bike a completely unique character in the segment. I myself enjoyed the stock gearing when driving through empty roads and highways. Unfortunately for my use case, it just wasn't suitable. Many owners and Automotive reviews complain about the gearing claiming it requires lot of shifting when driving through busy traffic. I have even read about a few owners selling their CB after getting fed up due to this!
The sprocket change has definitely improved the tractability and peppiness of the bike. I am extremely happy with the results and would recommend this mod to owners facing the same issues as me.
Check out BHPian comments for more insights and information.