How hard do you tighten engine bolts?

Steve73

Active Member
#1
I've always really wrenched down hard on those bolts holding the engine in place. Is there a general torque value that people use when tightening down their engines to the frame?

Thanks for your response. :)
 
#5
I started using Belville washers between the nut and engine plate and have had a lot better luck with the engines staying put where I wanted it to be. The washers are cone shaped, barely, which helps for proper pinching to hold everything together.
 
#8
German Torque. Gutten Tite. I use serrated fasteners as well, 5/16-24 grade 5. The reason I don't measure torque on these, is because 99% of the vintage minibike engine plates out there flex up against the engine base plate. Flat heads anyway. Never installed an OHV, so don't know if they are truer. Never had an engine slip.

Point is, if I tighten up the rear bolts first, tightening the front bolts will move the engine forward, so it's a delicate balance in tightening and maintaining alignment and chain tension all at the same time. Just my experience.

Note that there are torque specifications for various fasteners using size, material and thread as a guide. My dry 5/16-24 grade five bolts need 231 inch pounds according to this chart from Fastenal. https://www.fastenal.com/content/feds/pdf/Torque-Tension Chart for A307 Gr5 Gr8 Gr9.pdf
 
#10
if I tighten up the rear bolts first, tightening the front bolts will move the engine forward, so it's a delicate balance in tightening and maintaining alignment and chain tension all at the same time. Just my experience.
This is how I do it also. RR, LR, then the front. If the engine moves a 1/16" it can go from too tight to too loose.
 
#11
SAE has general torque values for different size fasteners.

Generally max for grade 5:

1/4.......8 ft. lbs.
5/16.....17 ft. lbs.
3/8.......31 ft. lbs.
7/16......49 ft. lbs.
1/2........75 ft lbs.

Blue LocTite is good too.
 
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#13
Thank you to everyone for your help. While getting the engine tight I noticed a hole behind the engine. Found a bolt I had that fit kinda and this is what seems to be making a whole lot of difference now. Took off for a 30 min. Ride and so far great!
20200404_151319.jpg
 

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