hdwrench1
Member
- Joined
- May 8, 2011
- Messages
- 69
- Reaction score
- 5
Hello All,
Since I bought this KBC 9 x 20 I've had constant problems with the 7 mm drive belt. I used to go through a belt in a month. I adjusted the motor , shimmed the pulleys and checked everything and still had problems with belts twisting at the idler.
After watching the idler and belt at various speeds I determined that the ilder was cocking just enought under load to push the belt to the outside of the belt patch. Some serious head scratching went on until I thought about some various sport bikes that I've had the pleasure of working on (wink) and their final drive idler system. They use a plastic guide with the chain width machined into it.
So I took off the stock idler and measured the length and bearing bore. I cut a piece of round stock off and finished the OD to 1.970 inches and bored the center out for the stock bearings out of the old idler. Then the OD was turned to 1.724 keeping a shoulder on either end with the 1.970 OD. Then I installed it on the lathe and marked the belt position on the 3 outer speed settings and machined 3 separate grooves with a square narrow cut off tool. These were cut to a finished OD of 1.675 inches. The belt grooves got a polish with some green Scotch Bite to eliminate any burrs that could transfer to the belts outer finish.
Photo attached of the new idler.
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I also looked at the lever which transfers pressure to the belt and it was very tight. I put a cotter pin in the top washer that the spring attaches to and bent the tangs to make it exactly .875 inches long. The spring now has less pressure effect on the belt and the result is great. I've put about 6 weeks on this belt so far and no twisting at any speeds. I wanted to wait to see if this was going to work before posting it and I use the lathe a few hours a day at work without any issues at all.
I hope this will help anyone else out that is having the same issue with their 9 x 20.
Since I bought this KBC 9 x 20 I've had constant problems with the 7 mm drive belt. I used to go through a belt in a month. I adjusted the motor , shimmed the pulleys and checked everything and still had problems with belts twisting at the idler.
After watching the idler and belt at various speeds I determined that the ilder was cocking just enought under load to push the belt to the outside of the belt patch. Some serious head scratching went on until I thought about some various sport bikes that I've had the pleasure of working on (wink) and their final drive idler system. They use a plastic guide with the chain width machined into it.
So I took off the stock idler and measured the length and bearing bore. I cut a piece of round stock off and finished the OD to 1.970 inches and bored the center out for the stock bearings out of the old idler. Then the OD was turned to 1.724 keeping a shoulder on either end with the 1.970 OD. Then I installed it on the lathe and marked the belt position on the 3 outer speed settings and machined 3 separate grooves with a square narrow cut off tool. These were cut to a finished OD of 1.675 inches. The belt grooves got a polish with some green Scotch Bite to eliminate any burrs that could transfer to the belts outer finish.
Photo attached of the new idler.
I also looked at the lever which transfers pressure to the belt and it was very tight. I put a cotter pin in the top washer that the spring attaches to and bent the tangs to make it exactly .875 inches long. The spring now has less pressure effect on the belt and the result is great. I've put about 6 weeks on this belt so far and no twisting at any speeds. I wanted to wait to see if this was going to work before posting it and I use the lathe a few hours a day at work without any issues at all.
I hope this will help anyone else out that is having the same issue with their 9 x 20.
