Engine mount bolts keep breaking. Help!

Dyetube

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Oct 1, 2020
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I have built my first motorized bicycle but for some reason, one of the two front engine mount bolts keeps breaking in two. The motor I have is from Gasbike.net (https://www.gasbike.net/collections/engines-only/products/black-stallion-66cc-80cc-engine-only) I had to buy the rubber engine mount kit because the motor isn't long enough to fit on my bike (it's an Ozone Beach Cruiser sold only at Academy sports): https://www.bikeberry.com/bbr-tuning-vibration-motor-mounts.html

This will be the second Time I have had to had a bolt extracted from the engine. It's always on the front as well. See the attached pictures. Here's some things that might be relevant:

1. The bike has no shocks/suspension/etc...
2. The bike REALLY vibrates.
3. I used blue loctite on all the bolts/nuts and don't over tighten them. They are m8 1.25 size bolts for the engine mounts.
4. The top of the motor is CNC and aftermarket (the CNC head came with the motor. It's a 66cc motor) and the Carburetor's air filter is aftermarket (I have a CNC velocity stack coming for the Carburetor: https://www.gasbike.net/collections...roducts/cnc-velocity-stack-for-nt-carburetors).

I'm using all the supplied mounting hardware properly (or at least I think I am).

This is a daily to and from work bike for me until I save enough money for real transportation. I really don't want to keep throwing money into the bike, I'd rather save that money for my next motorcycle.

Help me please!
 

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Davideo

Active Member
Feb 25, 2020
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I have built my first motorized bicycle but for some reason, one of the two front engine mount bolts keeps breaking in two. The motor I have is from Gasbike.net (https://www.gasbike.net/collections/engines-only/products/black-stallion-66cc-80cc-engine-only) I had to buy the rubber engine mount kit because the motor isn't long enough to fit on my bike (it's an Ozone Beach Cruiser sold only at Academy sports): https://www.bikeberry.com/bbr-tuning-vibration-motor-mounts.html

This will be the second Time I have had to had a bolt extracted from the engine. It's always on the front as well. See the attached pictures. Here's some things that might be relevant:

1. The bike has no shocks/suspension/etc...
2. The bike REALLY vibrates.
3. I used blue loctite on all the bolts/nuts and don't over tighten them. They are m8 1.25 size bolts for the engine mounts.
4. The top of the motor is CNC and aftermarket (the CNC head came with the motor. It's a 66cc motor) and the Carburetor's air filter is aftermarket (I have a CNC velocity stack coming for the Carburetor: https://www.gasbike.net/collections...roducts/cnc-velocity-stack-for-nt-carburetors).

I'm using all the supplied mounting hardware properly (or at least I think I am).

This is a daily to and from work bike for me until I save enough money for real transportation. I really don't want to keep throwing money into the bike, I'd rather save that money for my next motorcycle.

Help me please!
Dye.t
From the pictures that you posted it looks to me that the engine is not lined up with the bike's frame and you only seem to have one attachment from the front of the engine to the mount attached to the bike's frame plus as mentioned the engine has to be firmly attached. Those are some of the reasons that you have so much vibration. I used two 8mm studs screwed into the engine attachment point and 4 8mm nuts to attach firmly to a flat strap which in turn was attached to a U bolt located around the bikes front downtube. All the bits and pieces came with the bike engine kit.
 

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Dyetube

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Oct 1, 2020
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Dye.t
From the pictures that you posted it looks to me that the engine is not lined up with the bike's frame and you only seem to have one attachment from the front of the engine to the mount attached to the bike's frame plus as mentioned the engine has to be firmly attached. Those are some of the reasons that you have so much vibration. I used two 8mm studs screwed into the engine attachment point and 4 8mm nuts to attach firmly to a flat strap which in turn was attached to a U bolt located around the bikes front downtube. All the bits and pieces came with the bike engine kit.
This looks interesting. Lots of space in there though.
 

Dyetube

New Member
Oct 1, 2020
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Dye.t
From the pictures that you posted it looks to me that the engine is not lined up with the bike's frame and you only seem to have one attachment from the front of the engine to the mount attached to the bike's frame plus as mentioned the engine has to be firmly attached. Those are some of the reasons that you have so much vibration. I used two 8mm studs screwed into the engine attachment point and 4 8mm nuts to attach firmly to a flat strap which in turn was attached to a U bolt located around the bikes front downtube. All the bits and pieces came with the bike engine kit.
It also looks like your muffler is not attached to the bike. Does this help as well? Mine is loosely attached with the piece that came with the kit.

Also, I think I see what you are doing on the mounts. I will probably give this method a try since I have all those pieces.
 
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Davideo

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Feb 25, 2020
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It also looks like your muffler is not attached to the bike. Does this help as well? Mine is loosely attached with the piece that came with the kit.

Also, I think I see what you are doing on the mounts. I will probably give this method a try since I have all those pieces.
Yes give it a try with the studs and nuts it allows for adjustment and snugging up and it doesn't cost anything as well. No, I did not attach the muffler to the bike and after a year or so of riding there have been no issues. I suppose it could become bent if you strike it on a high curb or step but if you are careful there should be no problems.
 

Dyetube

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Oct 1, 2020
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How does this look? It still vibrates more than I think it should. This is first build so not sure how much vibration is too much... also, oil is dropping (very slowly mind you) from the muffler. Is this normal?

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Davideo

Active Member
Feb 25, 2020
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How does this look? It still vibrates more than I think it should. This is first build so not sure how much vibration is too much... also, oil is dropping (very slowly mind you) from the muffler. Is this normal?

View attachment 105837 View attachment 105838 View attachment 105839 View attachment 105840 View attachment 105841 View attachment 105842
Looks good! I like it, fewer parts than my front mount. Keep an eye on the nuts and studs from time starting before every ride in the beginning until you gain confidence in the mounts. The drip of oil from the muffler is normal after a run. I usually put a can or rag under to catch the drips. Vibration in the bike frame is normal and is acceptable as long as the engine is not moving relative to the bike frame. Enjoy riding your first build.
 
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Dyetube

New Member
Oct 1, 2020
8
3
3
54
Looks good! I like it, fewer parts than my front mount. Keep an eye on the nuts and studs from time starting before every ride in the beginning until you gain confidence in the mounts. The drip of oil from the muffler is normal after a run. I usually put a can or rag under to catch the drips. Vibration in the bike frame is normal and is acceptable as long as the engine is not moving relative to the bike frame. Enjoy riding your first build.
Great! Thanks for the advice! I'll keep a good eye on things for sure.
 
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allen standley

Well-Known Member
Oct 22, 2011
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Bangor, Maine
I have built my first motorized bicycle but for some reason, one of the two front engine mount bolts keeps breaking in two. The motor I have is from Gasbike.net (https://www.gasbike.net/collections/engines-only/products/black-stallion-66cc-80cc-engine-only) I had to buy the rubber engine mount kit because the motor isn't long enough to fit on my bike (it's an Ozone Beach Cruiser sold only at Academy sports): https://www.bikeberry.com/bbr-tuning-vibration-motor-mounts.html

This will be the second Time I have had to had a bolt extracted from the engine. It's always on the front as well. See the attached pictures. Here's some things that might be relevant:

1. The bike has no shocks/suspension/etc...
2. The bike REALLY vibrates.
3. I used blue loctite on all the bolts/nuts and don't over tighten them. They are m8 1.25 size bolts for the engine mounts.
4. The top of the motor is CNC and aftermarket (the CNC head came with the motor. It's a 66cc motor) and the Carburetor's air filter is aftermarket (I have a CNC velocity stack coming for the Carburetor: https://www.gasbike.net/collections...roducts/cnc-velocity-stack-for-nt-carburetors).

I'm using all the supplied mounting hardware properly (or at least I think I am).

This is a daily to and from work bike for me until I save enough money for real transportation. I really don't want to keep throwing money into the bike, I'd rather save that money for my next motorcycle.

Help me please!
Forward engine mount is Upside -Down... Should be this way.