Using the front engine Through Bolt tips/caution

Discussion in 'Frame Mounted Engines' started by WIZARDOFOZONE, Oct 16, 2007.

  1. Those who have a downtube too thick or wide for the standard saddle and clamp setup normally opt instead to use the included 3 hole bar with through bolt. Or use thier own thru bolt set up. This requires drilling a hole in the downtube. Just like to note a couple of things that might possibly occur with this method that are SO subtle you can drive yourself crazy trying to discover the problem ... it happened to me.

    If the frame is aluminum and you have added any type of rubber bushing or thick rubber washer to help isolate engine vibration, you might find after 50 or so miles of new engine use that the engine is either SLIGHTLY (almost imperceptably) or quite obviously TIPPING or LEANING to the left regardless of how tightly you have torqued down the front mount thru bolt.

    To see if this is so, just mount the bike and look straight down at the 4 bolts on the engine headcover. If the engine is leaning you'll see that the spark plug is favoring the left side of the mens framebar, and you'll only be able to see the 2 left bolts of the head because the other two are under the center bar as you are seated looking straight down from a 0 lean angle. There is an easy fix and but also a caution that goes along with the fix as well. The lean is caused by the hole being either drilled too large initially, but MORE probably due to the chain tension plus engine vibration causing a slow stressing and caving in via metal fatigue around the hole coupled with the spongy 'give' of the rubber bushing you used to dampen vibrations.

    To straighten the engine and allowing continued use of engine chain tension without the lean recurring, simply place a hoseclamp or nicely brush finished or chromed clamp around the exhaust tube at the curve right where it passes the bikes frame tube. As you tighten the clamp the exhaust tube snugs against the downtube and acts just like the coaster brake lever does, that is , it becomes a handle or lever for the entire engine which can no longer tip regardless of the chain tension you set.
    Now the CAUTION : After numerous inspections I find the exhaust right where the strap is attached suffers no effects at all while clamped this way and when superheated during engine operation. I also find after miles of use that the engine absolutely cannot move from its dead on straight up position. HOWEVER, ... if you begin to notice an ever so slight or medium or heavy darkening around the top left hand corner of the cooling fins, then what is occurring is that the straps tension to stop the engine from leaning under power is loosening either the left exhaust manifold nut, or is bending or causing loosening of the exhaust manifold engine stud (bolt) which raises the muffler exhaust manifold imperceptably up from the manifold gasket allowing fine as an airbrush misting of exhaust oil onto the fins. If so, then loosen the muffler clamp BEFORE you retighten the exhaust manifold nuts . Also check to see if the nut and bolt stud have spun out and away from the engine block threads. tighten the threaded stem back into the engine block before retightening the nut and I highly recommend using RED locktite on the stud and the nut. lastly, retighten the muffler clamp to again lock the engine into the straight up position. for added safeguard against oil misting from that area in the future you can also tighten the muffler clamp just a tad looser, which will allow a tiny and unnoticable partial lean of the engine to begin but this time its angle of left hand lean is controlled by you.
     

  2. KiDD

    KiDD Member

    This is a great tip for sure!
     
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