CB125 cam chain tensioner question

[grapedrank]

I have a CB125 (bored to 150) engine that I partially disassembled to clean & paint. Bike is intended for race use only and has been used in the past as a bucket racer before I bought it.

I removed the stator/gen, cam chain and tensioner initially. Now putting the cam chain tensioner back together I have found I am missing the tensioner bar (part 6 in diagram). I didn't take any photos during dismantling of the engine though I do not recall seeing the part and it is not anywhere with the parts I have (I sorted all the parts in zip lock bags). On closer inspection of the rubber cam chain tensioner there are deep grooves carved into it at one end. I would suspect this is from being run without the adjustment bar at all.

I assume that when the tensioner adjustment bolt is tightened, the tension on the cam chain is relieved. I am after opinions on whether I need or should have cam chain tension adjustment, keeping in mind the bike is for race use only and will be mostly operated in the upper RPM range.

 

[Bert Jan]

assuming you're talking about a twin, the bar #6 is the actual piece holding the camchain tight. The spring #5 is the applying force onto the camchain tensioner, and the bar #6 makes sure the metal arm #4 can not go up, making slack. You could permanently fix the right arm of piece #4, in such a way the vertical piece of #4 can still rotate and take the slack in the chain. Do not fix the whole piece permanently as some slack is needed to operate ok. Thats how i did it on my 125k5 back in the days. When you're talking about a single, i don't know for sure.

 

[Texasstar]

I have a CB125 (bored to 150) engine that I partially disassembled to clean & paint. Bike is intended for race use only and has been used in the past as a bucket racer before I bought it.

I removed the stator/gen, cam chain and tensioner initially. Now putting the cam chain tensioner back together I have found I am missing the tensioner bar (part 6 in diagram). I didn't take any photos during dismantling of the engine though I do not recall seeing the part and it is not anywhere with the parts I have (I sorted all the parts in zip lock bags). On closer inspection of the rubber cam chain tensioner there are deep grooves carved into it at one end. I would suspect this is from being run without the adjustment bar at all.

I assume that when the tensioner adjustment bolt is tightened, the tension on the cam chain is relieved. I am after opinions on whether I need or should have cam chain tension adjustment, keeping in mind the bike is for race use only and will be mostly operated in the upper RPM range.

is it a cb125t?

 

[xb33bsa]

yes you MUST have cam chain tension adjustment
this is not something you can modify,make it original like in the diagram