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Discussion Starter · #1 ·
Here is the difference between the Yuminashi and GromFatherZ Cam Chain tensioner

Yuminashi comes in two colors blue or red and you use your stock/OEM pipe and top plug that contacts with the cam arm, on the right is the GFZ in silver and black.
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as far as pricing there is a big difference and it's your choice which model you like or price you can afford.
 

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Is this an issue with stock bore? In other words, is it mostly the BBKs that require an after-market cam chain tensioner?

i confess that I have not (yet) been confronted with any problems regarding my cam chain.
 

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Discussion Starter · #4 ·
Used on BBK kit is recommended since the High RPM and the spring loaded cam chain tensioner will not keep the chain from hitting the upper roof of the cam cylinder channel.

notice the two silver lines which is the cam chain hitting the roof.
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I’m reading up on BBk’s. What is different on these aftermarket parts Vrs stock? I understand what they are soposted to do, but how do these work better then OEM?


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I’m reading up on BBk’s. What is different on these aftermarket parts Vrs stock? I understand what they are soposted to do, but how do these work better then OEM?


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OEM Grom cam chain tensioner is designed for stock power levels with a mix of city and some highway riding. A lot of riders here do lots of freeway riding. Imagine driving your car at redline all the time. Then there are guys who are riding their Groms with considerably higher redlines. That's why all these aftermarket parts are made - the OEM parts can't handle this type of use.
 

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OEM Grom cam chain tensioner is designed for stock power levels with a mix of city and some highway riding. A lot of riders here do lots of freeway riding. Imagine driving your car at redline all the time. Then there are guys who are riding their Groms with considerably higher redlines. That's why all these aftermarket parts are made - the OEM parts can't handle this type of use.


Ok. I get that. My throttle is pretty much a on/off switch. LoL. But what’s different with the actual part. Stiffer spring, different arch angle? Looking at the lesser expensive A/M offering, still uses the OE shaft and cheesy white plastic cap that gets dented, thus reducing chain tension. I can see a billet bolt threw the bottom of the crankcase. But has to be something that makes it better, stronger,etc.


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I hear a noise when I'm decelerating, like maybe when it's passing from 4000-3000 rpms. I wonder if it's the cam chain rubbing.
In retrospect, this noise was the drive chain hitting the aftermarket swingarm. I broke the chain slider off from adjusting the chain too tight. I bought a manual cam chain tensioner from yuminashi but haven't installed it yet. The top of the cylinder still seems smooth. I've been running the takegawa tensioner arm and a hardened tensioner button. Rev limit was raised to 13,000 but probably less than 1000 miles ago.
 

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Stock has a long spring that fits inside the shaft to push it against the chain. These replace the spring with a solid threaded adjuster.
Actually, I think the Yuminashi is supposed to be used with the stock spring. I was turning the engine by hand without the spring installed and there was a lot of chain slack when the valve springs would compress, even with it tightened the whole way.
 
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