Engine Mounting Bolts Destroyed

[HeadSmess]

i had one bike, decided to blow its crank seals and die on me... i ended up jumping on the thing a few times, venting.

the frame BENT before the engine moved

thats how tight they need to be

 

[Hello Moto!]

This makes me ask the question..Why does the Skyhawk frame come with the rubber motor mount cushion for the pedestal engine mount? It didn't take me long on this forum to realize that using rubber, especially thick rubber, is a bad idea. You just can't get a solid mount.

Just a thought...

 

[Luybaton]

I cant agree more here!!! This is SO important. I am a noob that learned the hard way. The comment also before about the engine case being soft is so true also.

What I do now when its engine mount time is this:

- First, make sure bike frame is secure, upright and level/close to final riding position etc(meaning if the wheels arent on it, just make sure the frame is not rotated way forward or back etc if that makes sense), best to have the front and rear wheels on bike and tight, I dont worry about getting the chain over the rear sprocket etc until after the engine is mounted perfect.

-Now find the sweet spot for the engine. Without any rubber or anything at all between the frame and engine (metal to metal) I lower it into the "V" trying my best to keep the frame tubes as perpendicular and flush as possible on either side. I want to gently shimmy it back and forth into place, NOT force it(this can cause frame stretch which is very, very bad!) Tap the engine a little on each side, rotate it, etc. try a few different angles and take your time. Every engine/frame combo "should" have a sweet spot, or at least a best position possible.

- After I have the engine perfectly wedged between the two frame tubes, making sure im fitting flush on both sides, hopefully have 0 or as little gaps as possible between frame and engine mounts. Its ok to have small gaps though if you cant avoid it. Now I JBWeld (2 part epoxy resin dries hard as metal) and literally fill in between the frame and engine mounts anywhere its not perfectly flush. This welds the engine in place.
This is all before I attach a single bolt or u clamp.


The next time I do this I want to use those awesome muffler u-clamps and fabricate stronger mounts like ive seen on some other bikes. Relying on the standard engine mounting brackets/bolts etc even if you do all of this perfect still can have issues/fracture/fail etc. I end up using no rubber/insulator at all except for a small thin layer with the u-brackets where they make contact with the frame to keep it from scratching it up.
Please share any other suggestions/tips.

View attachment 72221

First build/bike. "Funhog"

I am having a problem with the stock screw breaking off in the back side of the crank and my other motors piston blew u think I can take that crank and put the other cylinder and piston on? But another thing is the crank with the bolt broken inside is a Z-L (witch is good) crank my other one is some weird gcb1 or something.

 

[KCvale]

Nice build Learner.
I just had a repair in here that had those rim lights on it ;-}

I cant agree more here!!! This is SO important. I am a noob that learned the hard way. The comment also before about the engine case being soft is so true also.

The next time I do this I want to use those awesome muffler u-clamps and fabricate stronger mounts like ive seen on some other bikes. Relying on the standard engine mounting brackets/bolts etc even if you do all of this perfect still can have issues/fracture/fail etc.

The seat post is the power transfer point.
You want the engine mount to start there, dead square with the tube and tight, everything else you adapt.

All the front mount has to do is keep the engine from twisting.
With a V frame most times it will drop right in, but I build mostly beach cruisers and the front never works.

I use the SickBikeParts.com front mount system for convenience.
http://www.sickbikeparts.com/catalo...ducts_id=74&osCsid=jomh8j77rv7hsg6333pod6as10

It's a versatile package, and you will see it used on most all of my 2-stroke builds.
The trick is to get the right size muffler clamp to fit your front down tube.

 

[bakaneko]

Your bike looks very nice especially that tank. Also, how is your butt feeling from that seat... doesn't look very comfortable unless you have really nice roads by you.