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L600 flat head belt size needed

edisondiamond

Registered
L600 flat head (5M21), what is the correct length of belt. I know the width etc. The one I got is just too short, it will work for now but don't want to put too much pressure on the water pump bearings. I did the string check and got 28" but as most are OD mesauremnt, not a lot of help in this case. Thinking maybe 33 OD?
Thanks
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Both of mine are off, and measure 30-1/2”. The one that had been on the running engine is a Napa 4L300W.

Come to think of it, I want to say that belt was pretty tight, with no room for adjustment. I might be inclined to try a 4L31.

Keith
 
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When faced with such a situation, I usually raid my wife's sewing supplies and steal her cloth measuring tape. It easily conforms to the circumference and gives you an accurate measurement, unlike a steel tape.
 

edisondiamond

Registered
Is that 31 the inside or outside size? The one that I have now is 31 outside. The original belt shredded it self and was stretched as it is. The 4L would be for 1/2" wide belt, mine is 5/8".
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
That’s outside. I have an old, narrow six foot tape that is flat, and works well for these measurements.

Yeah, 5/8 would be 5L, too wide, I think, but would need to be longer since it’ll ride higher in the pulleys. A 5L31 would probably be too short.

I’d still recommend trying a 4L31. My 4L30 was functional, but seemed too short.

Keith
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
A B section belt... is the same as a 5L? Man it’s been a long time since I’ve fooled with such fun stuff.

That fan and pump aren’t going to be taking a great deal of power. I’d think an A section or 4L would be adequate. Pulleys might even be too small in diameter for the bigger belt?

I’ll go see how mine fits the crank pulley.

Keith
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Oh wow, I stand corrected! I’m glad I checked. The 4L belt works, but the crank pulley is definitely designed for a 5L / B section belt. 431AC60A-570E-4937-A349-E7448588B444.jpeg
 

edisondiamond

Registered
As it is now, the adjustable pulley is completely back off and belt is riding on the hub with very little give. You can just see the hub peeking past the belt on the front side in the second photo.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Yeah, I saw how far apart you had to spread the pulley halves too. That arrangement is driving the pump and fan particularly fast. Must be noisy!

Keith
 

edisondiamond

Registered
Not yet(noise)! That is why my next step after I get output sorted, is belt and muffler. My ears are ringing now from just a short test run. :whistle:
New belt is on its way.
 
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edisondiamond

Registered
Ok so I got the 6930 belt, it to rides on the water pump hub. It does fit better in the crankshaft pulley however. I will measure the pulley. jackO, I wonder if we have different size crankshaft pulleys? I will check mine later.
 
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