Honda Grom Forums banner
1 - 5 of 5 Posts

·
Premium Member
Joined
·
57 Posts
Discussion Starter · #1 ·
Guys,
Just a note to anyone that has put a Crower, or other aftermarket cam in their engine with stiffer valve springs. The cam chain tensioning system in the Grom engine was designed for fairly light valve spring pressures, and mild cams. The Crower, and any other performance cam will have more aggressive ramps than the stock cam, which will use stiffer springs. What all this does in put more stress on the cam chain tensioner system. I noticed the cam chain react to the action of the cam & the springs when I built my test engine. My solution was to design a very simple spacer, that goes in the spring slot after the spring is installed, right before the hex nut is screwed in place. Look at the attached photo, I think it will explain itself. This spacer can be installed at any time, after the engine is built, by just removing the hex nut, and inserting it in the hole, seated on the nut. It increases the spring tension on the cam chain adjuster. I have 6 test engines with the spacer out there running, with no issues. I had 100 spacers machine, and I can ship them post pre-paid in the US for $9.50. If you have any questions, use the forum, or email me at [email protected].
Thanks
Brian S

 

·
Registered
Joined
·
43 Posts
Adding a little preload to the tensioner, isn't making a difference. The unit functions as a hydraulic pump. The spring is just there to move the plunger up to allow the oil to enter, when off-tension.
 

·
Registered
Joined
·
998 Posts
Adding a little preload to the tensioner, isn't making a difference. The unit functions as a hydraulic pump. The spring is just there to move the plunger up to allow the oil to enter, when off-tension.
BrianS said he has 6 Groms running this setup and I'm assuming on his BBK 170cc. I see he would not jeopardize his products if he did not test them first.

I'm assuming you are a Honda Tech with knowledge of how the CCT spring plunger unit works in the Grom or similar Honda engines.
 

·
Registered
Joined
·
4 Posts
BrianS said he has 6 Groms running this setup and I'm assuming on his BBK 170cc. I see he would not jeopardize his products if he did not test them first.

I'm assuming you are a Honda Tech with knowledge of how the CCT spring plunger unit works in the Grom or similar Honda engines.

The problem is in fact the tensioner blade the roller sits on and pivots against the tensioner piston.

Any increase in load actually splits the rubber on top of the tensioner piston leading to metal to metal contact, I have modified one by tig welding the end that fits against the tensioner piston rubber making it three times as wide to spread the load better and hopefully stop the rubber spliting as easily this was on a Malaysian MSX125 (Grom in Malaysia)
When the rubber splits you end up with metal to metal contact and a very noisy tensioner at idle and just above till oil pressure takes up the load.

Problem is when the tensioner does not work properly the chain whip causes most damage bent valves etc when you back off and there is no load on the engine
 
1 - 5 of 5 Posts
Top