How can I determine the correct belt length for my honey's 657 after changing engines?

[ebinmaine 63,137]

So as most of you are well aware by now I had to take the Tecumseh 6 horsepower engine out of my honey's 657 because I am a crankshaft busting brute with a hammer.

Until I can locate another crankshaft I have installed a late 70s Briggs & Stratton 8 horse engine.

 

I was able to remove the drive pulleys from both engines and swap the Tecumseh pulley on to the Briggs & Stratton.

 

The Centerline of the crankshaft of the Briggs & Stratton is a little over an inch higher than on the Tecumseh. I thought I had accounted for that by moving the engine backwards towards the transmission about an eighth of an inch.

I believe that was not quite enough but it was the best I could do because of the locations of several different components.

 

When she puts her foot down on the brake it holds perfectly fine but the belt still spins with the engine. I may not have the belt guides in the correct position but the reason I think the belt is too short is because there's near-zero difference between brake off and clutch on.

 

I'll take pictures of the belt guides and try to figure out if maybe I need to move the position of them slightly.

 

 

Still, the ultimate question is -

Should I get a belt that is one or two inches or... What length...?? Longer?

Edited July 30, 2018 by ebinmaine

[wallfish 15,919]

Best to post a pic of what you got with the belt guard off.

 

The brake should be adjustable with a 9/16 hex nut.

The position of the idler pulley when the belt is engaged should be up near the top of the belt guard. This allows enough movement forward for the belt to slack enough to disengage the engine pulley.

 

You can test those little belt guide positions by having someone hold the pedal down and use a couple of screwdrivers to support the belt and note the locations when the belt stops spinning. Adjust those guides to those positions. It takes just a little practice but be careful doing this for obvious reasons

 

Edited July 30, 2018 by wallfish

[ebinmaine 63,137]

1 minute ago, wallfish said:

Best to post a pic of what you got with the belt guard off.

Hi John. I just put it on there while you were replying.

 

I did try to do that trick with a screwdriver pressing on the Belt. when it was running. I couldn't seem to find the sweet spot so to speak. I'm wondering if I need to move these belt guides to the forward holes which would place the guides clock positions more like at 1 and 5 instead of 11 and 7.

[wallfish 15,919]

How high is the idler pulley? You want that in a position so when it moves forward it will allow enough slack of the belt. If it's halfway down the belt is too short.

 

11 and 7 should be close to the correct positions. They should be set with about 1/8 th inch of room from the belt when it's engaged. Just did one at the big show and need to set them about 1/16 away. Use 2 screwdrivers if necessary but you can't get any of it to work if the belt is too short.

 

If you have an old belt around. Cut it, wrap it around ALL pulleys and mark the spot where the end meets the belt. Measure it and you are very close to the length you need

Edited July 30, 2018 by wallfish

[Lee1977 6,217]

I have made a couple engine changes and use the same belt. First you need to check the crank shaft height on both engines. on those old engines it should be close to the same height. Next you needed the front to back location of the crank shaft on the original engine. Your a little past the correct location on the original engine, maybe some one can measure that for you on a similar tractor with that engine. As with a lot of other thing it's "location, location, location".

Also the belt guard has a lot to do with the belt pushing forward to release the drive pulley. Do you have any slack in the belt when the clutch is depressed?

I would made another wire belt guard 1/2 inch longer for the lower one and see if that helped.

Here is a couple of pictures of how I got the crank shaft in the correct location when I installed a Brigg Vanguard on my C-120.

 

 

 

[953 nut 51,682]

The belt stops turning with the clutch depressed because the slack is resting on the bottom of the belt guard. As your crank shaft is now an inch higher there may need to be an alteration to the lower edge of the guard to make up for that. Try screwing a strip of 3/4" square wood to the inside it to see if that is the problem.

Edited July 31, 2018 by 953 nut