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Mclane 20" 3.5 rp7 Help Needed!

Posted by smalllawnbigdreams none (My Page) on
Sun, Oct 6, 13 at 21:09

I picked up a Mclane second hand as a project first, and to help improve my lawn second. The engine started up first pull, but the mower needed a back-lapping and reel to bed-knife adjustment. Upon adjusting the reel, I realized the drive chain for the reel (called the side plate chain in the owner's manual) is veeeery slack. So slack that it is making contact with the front chain guard mount, and has worn a small groove in the front mount. Some questions: #1 Is there a way to tighten the tension on this belt without adjusting the reel away from the bed-knife? (which would stop the contact, but not cut grass) #2 Is it possible that this mower (2001) has a chain that is simply worn out/stretched? #3 Is it possible that the mower has been backlapped/sharpened enough over the years that there is no meat left on the bone (bedknife or reel) and any adjustments will make this chain slack.
Taking out a link makes the chain too short. The mower is set at the factory setting for the back axel. and the front settings have made no difference in the chain tension. Any help is appreciated.

This post was edited by smalllawnbigdreams on Sun, Oct 6, 13 at 21:28


Follow-Up Postings:

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RE: Mclane 20" 3.5 rp7 Help Needed!

Did you take out a full link (2 pitches)? or a half link (1 pitch).

Half link should be what you need if chain is as loose as you say.

You need to purchase a chain breaker and then a half-link (or offset link). Your chain is ANSI# 41.


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RE: Mclane 20" 3.5 rp7 Help Needed!

Your chain has 1/2" pitch.
You should be able to get a good idea of wear by simply using a tape measure if you can get the chain off and lay it down on the scale.
Pull tension on the chain to take out the slack.
BTW, bicycle chain is also 1/2" pitch.
Single speed chain "might" work as a replacement??
Derailleur geared bikes use a narrower chain although it is also 1/2" pitch.
A bike chain is considered worn out when 12 link SETS (inner + outer link) reaches 12-1/8".


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RE: Mclane 20" 3.5 rp7 Help Needed!

Thank you both for the reply. I found a replacement chain cheap (and new) for less than the cost of a chain breaker and half link. If it doesn't fix the problem I'm out a few of bucks and and can still modify the new chain. I'm going to go for the simple fix first and see what happens. Thanks again!


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