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| *Vultures Knob>>>Bike Repair |
Please help with REPAIR INFORMATION for my antique early 70's Honda CB-125 with a NOISY TIMING CHAIN. |
I was told there was a design flaw (later corrected by HONDA in later versions) resulting in failure of the timing chain tensioner. I was also told there was a relatively EASY FIX to permanently correct the problem. If you know anything about this problem, will you please provide some details on how to do this repair ? I sure would appreciate ANY information you can provide, as this particular little bike is very much worth preserving, to me. Thanks for your help. Hey Saturn,,,I guess I'm almost outa time to ignore You,,,geez. Seriously I apologize,,,I just happened to stumble upon this question. A question about another 125 prompted me to look. And I SHOULD have explained the fix in 1st question. OK,,,it's Very Simple. So "Dumb Simple" it belies it's effectiveness. I am gonna skip all the History,,,but I assure you it's a well proven solution. And that's among a large variety of other alternatives,,,all of which were really Gross OverKill remedies. It's worth noting that the Original Configuration which is prone to failure was only a Marginal Fault. Just BARELY insufficient to be reliable. Which is why such a seemingly Simple patch is 110% Effective and reliable,,,,practically "bullet proof". ........................ FIX: Safety Wire the SnapRing. It's a "Tru-Arc" type of ring,,with a Hole in each end to accomodate using Snap Ring Pliers. Simply "Tie it Closed" with some good steel wire will prevent it from Ever coming off. Some details.... #1,,,Look Carefully at the Ring's Groove in the Shaft It should have a sharp/Square Profile,,,and not be "smeared" into a Taperor Angle which would allow Ring to be wedged Out of it's groove. That's IMPORTANT,,,it's worth using a Magnifying glass and Good Light to verify the Groove's condition. ~~~~\__/~~~~ = Not Good ~~~~)__(~~~~=No real good either ~~~~|__|~~~= "Normal" and Good ~~~~/___\~~~= "Ideal",,,if a bit exagerated ...................... Also ,,Those type of Clips have a "Top & Bottom" It's important which direction they're installed. They're PUNCHED out of a sheet of steel. One side is Ground Flat,,which produces a Sharp,Square Edge around ID and OD. The Other side is rounded. The Cross Section of the Clip is sorta like the Top Half of a Hamburger Bun.....lol Almost like "D". The SHAP,FLAT Side points AWAY from the Thrust. So that any thrust applied to the Clip makes the clip "Dig In" to the Groove,,, rather than being wedged out of the groove on it's more rounded Side. RIGHT: ~~~~|D|~~~ <<<---Thrust Wrong: Thrust---->>>~~~~\D/~~~~ That's exagerated,,& pardon my art,,,,, But You can see the difference in the Ring's ability to Bite and Hold a Thrust Load in the 2 different scenarios. On Small Diameter,,Shallow Grooves,,it's a Critical Difference. So on Your Engine,,,the Flat Side of the Clip points towrd End of Rod,,or Down Towards Ground. ................. On Safety Wiring the Clip... Use the largest wire that'll easily go thru the hole. Actual Safety Wire is Best,or course,, Music Wire (Guitar String) is next best. Really,,ANY steel wire will do. Most Important is to Shape the Wire so it's actually Tight and Support the ends of the clip. A simple U shaped piece slipped thru the holes and twisted tight yields a sort of OVAL shaped wire. When the whole assembly gets under Pressure,,,That Oval gets sorta Folded over and forms a Arc of wire joing the ends of the Clip. Which is SLACK that allows the Clip to Spread,,Defeating the wire's purpose. Fold the wire into the shape of a STAPLE. (same way You'd shape Resistor leads to install on a PCB). That produces a Straight Link from Hole-to-Hole. And when the Washer which bears against that Clip pressures down upon it,,,All remains STABLE and Tight. Twisting it tight on the Through side of the clip is not real critical. DONT Overtighten. Ya just wanna "tie off" the open ends of the wire That all may seem pretty Anal,,,,clip direction,,,and Wire Shape.etc. But it's a Very Small Joint,,bearing a Lot of Thrust Pressure AND a degree of Shock Load while under pressure. If Done Half-Azzed,,,it's Probably OK,,,,but still a crap shoot. If done Half-Right,,,It's BULLET PROOF. Recap: *Inspect Groove ,make sure it's still basically "Square" and not rounded/smeared off *Install Clip with Sharp Side DOWN *Bend some Steel Wire into a Square Cornered "Staple Shape" the width of the Clip's end holes to prevent the Clip from Spreading,,,Slip it Thru the Holes & twist it semi -tight. ------------------ SIMPLE as That,,,and waaay more solid than what's actually required. ****It's a 6mm Clip. It's Best to use an actual Honda Clip if it's not too much hassle to get one. Otherwise,,,a 1/4" clip from Auto Parts or Hardware store will work. They are a Bit Smaller than 6mm,,,but Not enough to require Over Stretching the clip to get it installed. Again,,,My Appologies for not saying in the first place. And for not checking back and answering This question sooner. I'm not 100% sure but on my cb 352 the cam chain was adjusted by spring tension and got loud when it was loose. On that one there was a cam adjuster on the back of the cyclinder about half way down, the locking bolt went in the top of the adjuster what you had to do was loosen the bolt then turm the eng over till the valves were about halfway open (there was a mark on the flywheel or something to let you know sry its been over 25 years since I had the bike so things are a little hazey) what that did was pull the cam chain tight on the front and put all the slack in the back and the spring tension would push the slack adjuster forward to tighten the chain. Lightly tap on the adjuster housing just incase the adjuster was stuck and then tighten down the locking bolt. Hope this helps |
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