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Thread: Rear Engine Mount Design Differences - Strength and Reliability?

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    Rear Engine Mount Design Differences - Strength and Reliability?

    I am doing a ground up build and seeking advice on which route to take.

    If you had to pick between the 86/87 2 bolt/swingarm pivot bolt style rear engine mount, or an 88/89 style single bolt frame mount, which would be the better of the two options for strength and reliability? This discussion should ignore swingarm length as it will be the same in either case.

    My initial impression is the 86/87 style puts the least torque strain on the engine cases and other frame mounts since it turns the 2 bolt points into a solid swingarm mount like used on newer ATV's (TRX450R). I'd take a guess this would be useful for higher power motors. However, since the 86/87 design splits the swinger pivot into two pieces, I could also see this causing more flex/torsion forces on the frame and pivot bolt during suspension movement. The 88+ design decouples the motor completely from shock forces going through the swingarm and may prevent vibration/stress from being transmitted to the engine under hard impact.

    These are all theories (wild ass guesses) and I'd be interested in knowing how the design change translates to real world results. Does either style have a notably different track record? How do most racers pick between frame styles to do their build?

    Are there any other factors to consider one over the other?

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    Racer jwraymond6's Avatar
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    If your going with a Lsr frame like discussed in your other thread I believe all LSR frames are based off the 88/89 plat form so you wouldn't use the 86/87 rear mounts the Lsr frame already has them incorporated in at least mine does
    99 Lsr TRX310R
    87 250r currently getting a 363 sphynx built by Pete @ hybrid engineering

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    When I spoke to them they offered me the option of either of the two styles. It would appear that the 86 swingarm and mount would work on an 88 frame but not the other way around. Just for point of discussion it might be nice to know still which design is better and why.

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    Racer jwraymond6's Avatar
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    Quote Originally Posted by CTGT2005 View Post
    When I spoke to them they offered me the option of either of the two styles. It would appear that the 86 swingarm and mount would work on an 88 frame but not the other way around. Just for point of discussion it might be nice to know still which design is better and why.
    Didn't know they offered it in both if you use a 86/87 swing arm on a 88 you don't use the rear mount but you would have to make a spacer to go in between were the mount would have gone


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    99 Lsr TRX310R
    87 250r currently getting a 363 sphynx built by Pete @ hybrid engineering

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    Could be a disconnect between the sales guy and the engineering guy. He asked what year engine/swingarm I was planning to use. I will clarify today when I call back.

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    On there site they say it's based around a 88 frame http://lsracing.com/honda-trx250r-at...atv-utv-racing

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