Engine mount is driving me nuts.

[TehInteractive]

When I first built my bike, I was using a rubber shim inbetween the universal U bolt on my down tube to reduce engine vibration, but it turns out that because the engine wasn't solid on the frame, it was going cock-eyed to the left, causing slack in the chain and other issues, so I took my engine off and threw away the rubber shim, and put the engine back on.

It was running fine, then one day, I happened to look down after my bike was running weird and noticed that the right cap bolt's head snapped off, and the left one was just completely gone. So the only thing holding my engine on was a partial piece of bolt.

So then, I went to Ace and replaced the ****ty low grade 4.9 bolts I was using with black 12.9 grade allen head bolts. I tightened them down with new lock washers, and my bike rode great.

Then just yesterday, I looked down at my bike after it started riding ****ty again, and my left bolt is completely loose and is halfway out, and my right bolt fell out.

I just bought 4 more 6mm x 16mm 12.9 bolts and a pack of 6mm lock washers, and a bottle of blue 242 loctite.

My question is, do you guys think that torquing those bolts down with a generous amount of 242 blue loctite and lock washers will keep the bolts in place? If not, I'm open to suggestions.

 

[Mac]

Loc-tight is your friend!! I personally do not put a single bolt on my bikes' without Blue loc-tight. (Sometimes red, if I have a problem child), A good pre-ride inspection is another good idea, I get my allen wrench set, a 10 and 13mm, give everything a quick check before a ride, also look at your wheels, make sure there tight, give the spokes a "Harp" check, run your fingers over them, check the handle bars/neck by straddling the front tire etc... Anything you find here, won't break on you 12 miles from home!! Just my 2 cents.

Mac

 

[TehInteractive]

From my understanding of the back of the loctite bottle, it says:

Torque (in lbs.) / break

110/43

So that means that the Loctite bond will break with only 43 inch pounds of torque? Correct me if I'm wrong, but that's not a whole lot of resistance.

But anyways, I also plan on Loctiting everything I can, including all the bolts that hold my rear sprocket on once I replace the 4.9 bolts with 10.9 bolts one by one. However, those two head bolts are like, holding all of that load and vibration from the engine directly. It just doesn't seem like this stuff is going to work.

 

[GearNut]

Don't get too happy with torquing down any fasteners that thread into the engine case. The factory threads are weak and can strip out easier that you might think.
The stronger hardware you got is a necessity though.
Don't worry about the breakaway strength of Loc-Tite 242 blue either, I have been using it for years to "glue" Harleys together and it holds up very well. The trick is to be absolutely positively sure that there is no oil or grease anywhere on the threads of the fastener or case hole/ nut. Loc-Tite of any color will not lock against a lubricated thread very well at all.
Last thing, if you use it in the future, be careful with Loc-Tite 271 red. Concerning fastners of 1/4 inch or 6mm (stock HT engine fastners) the Loc-Tite can be stronger than the fastner and you can snap off the fastner before the Loc-Tite releases.

 

[bairdco]

before you try any type of loctite, super glue, or other magic bolt fastening system, make sure that all your mounts sit flush, that there's no gaps, no play, no nothing. you can easily grind down a stock mount with a dremel or a grinding bit and a drill to match the fit to your frame, just don't get to crazy.

basically, what i'm saying, is no bolt is gonna hold up to the torque of your motor if it's not mounted right in the first place.

the only thing i use loctite on is the set screw on the clutch flower nut, and that's as a preventative action, i never had one loosen up.

i actually use anti-seize compound on every external bolt on my engine (after upgrading all the hardware, to prevent stripping, seizing, binding, whatever. i like my bolts to come out when i want them to.

i've never had a problem with bolts loosening up. my pre-ride check involves looking at bolts to see if they appear loose. every few weeks i put an allen wrench on them and see if they turn. if they don't, i don't force them. and i'll maybe get a fraction of a turn on one now and then.

if you keep forcing them every day, they'll strip, flex, break, etc.

if you tighten it right the first time, it'll stay tight.

 

[Mind_Reader7]

On my first build I had problems of the bolts always coming loose/snapping.

Rip out all the studs/throw them away. Get some allen bolts, and put them in the motor, to make sure they're not to long. Then loctite them, install them as tight as you think you should (you shouldn't be using anything other than an allen key in one hand, if you need 2 hands, you're probably overtightening). Leave it overnight, and you're fine.

On my second bike, I have not had to tighten anything ever.

 

[2door]

Bairdco's above advice should be carved in stone and be included with every engine kit sold. Installed properly there is no need for thread locking compounds and no reason to expect fastener failures. Even the stock kit supplied hardware will suffice in most cases unless it is subjected to heavy handed wrenching and frequent retightening of fasteners.
In that case even the hardest alloy, not to mention the aluminum castings can be compromised and loose or ill fitting mounts will increase the chances of fastener damage and ultimate failure.
Tom

 

[bairdco]

thanks Tom. i know you agree. now, if we could just get everyone else to listen...

 

[Dave31]

thanks Tom. i know you agree. now, if we could just get everyone else to listen...

Hope this helps

http://motorbicycling.com/f30/re-engine-mount-driving-me-nuts-20782.html#post197722

 

[oldsurfer]

it says when you install your motor to put tape under the mounts to protect your frames paint.but i'm having issues like you that the engine ends up leaning to the left and throwing the chain....is it wrong to have tape under the motor mounts?

 

[oldsurfer]

my tahaiti bicycle has the large down tube and the standard seat tube size..the rear mount is the standard cast mount on the engine...the front is the sick bike parts u-bolt ..there is no grinding to get the monts to fit...yet my motor does to the left..i have electriacl tape under them as recomended in the instructions...what to do???

 

[KCvale]

How are you doing the front mount?
A picture would be nice.
If your motor fits nice and snug with kit mounting in the frames V it's not going anywhere.

 

[oldsurfer]

i have pretty much convinced myself that the problem is the tape under the mounts..it allows the motor to slip to the left because of the chain torque

 

[TehInteractive]

So it turns out that the threads inside the left side of the engine are 90% stripped, with the top 10% being the only threads that are holding the bolt in place. I can't even thread a 6mm bolt in with a lock washer because there's not enough thread.

Am I going to have to retap the threads to like, 8mm? I don't think, even with the amount of loctite I used, that this will hold up for very long.

My engine is still under warranty.

 

[bairdco]

under warranty, send it back. fix it yourself, tap it out.

 

[Flattracker]

I use a rear engine block spacer between the clutch cover and the seat post. You can use a thin piece of rubber inner tube between the block and clutch housing, and around the seat post. The block is just the right size to fit! I call it my "anti-torque" block. It keeps the engine perfectly straight in the frame by preventing the engine from shifting left. Mine fits so tightly that all I did was tap it into place with a hammer and it has not moved in 620 miles of highway riding. Or you can use zip-ties to hold it in place. This works so well that I consider it an installment REQUIREMENT for bicycle engines and it fixed my problem once and for all. I got tired of using my left knee to push the hot engine back into place while riding. At first I used a block of wood and hose clamp, than reading on a forum, I read that the rear engine spacer block fits perfectly and have been using it on my engines ever since! Not once has my engine shifted!

 

[Nashville Kat]

Here's what I do- it may sound halfassed but seems to work- I file down the original motor mount wide- to fit the frame you have to file and grind down even past where the studs go in- (this is done with them out, of course). Then I use LONGER studs- the first build I bought longer bolts at the auto store, and hacked the heads off to make studs- studs that are longer by at least 1/4" or more.

This time, the parts store doesn't have them- I ordered two more long BACK motor mount studs-
($3 plus ship- about $10)

Anyway after widening the motor's cast mount so it fits the over sized tube- thread the new longer studs in- they are about 1/8" inch closer together than the width of the frame tube-

With a large crescent wrench- carefully BEND THEM out to clear frame- HERE"S THE DANGER! DON'T SNAP THEM OFF!- very gently!

Then jam the motor onto the frame- I use pipe insulation foam between to cut vibration.
The mounting skratches the frame a little bit- but it's REALLY SOLID- I respray the frame slightly with similar color to prevent rust.

then VERY CAREFULLY, bend the longer studs back together-
It may help to pound lower steel mount a little flatter to widen it, but the less the better-
The studs can't loosen at the motor because they are literally slightly wrapped around the tube-

using rear studs, there is really ample length. Once the studs fit in the lower clamp hole again, double up the bolts to lock them on-

It's really very secure, but scratching the frame is the only real drawback- I'm sorry to hear that about the mount at Sick- is that the offset one- I was thinking that one might be the best adapter- I also see there's one out there that has two u-bolts- not sure which site I saw it at...

Anyway- once it's on- this method works great- NEVER moves.

still hoping they'll recast the mounts soon for wider tubes- it's easier to shim for smaller tubing than to have to adapt to bigger ones...

 

[KCvale]

Picture your motor and mounts being like a combination box/open end wrench laying flat on your work bench, the open end pointing away from you, the box end towards you.

For the most part your seat post is the right size for the stock mount and that is the box end.

The seat post isn't going anywhere so that is your motor torque pivot point.
The motor and chain torque will want to pull your wrench to the left so with your finger in the box end to act as the immovable seat post, pull the wrench handle to the left.

You can tighten the seat post clamp (box end) until the cows come home but it is going to pivot there if you don't secure the open end solidly to the front downtube it is going to pivot.

Most of the beach cruisers I have built have a slightly wider downtube that is farther away than a typical V frame.
The important thing is to get a bolt/stud on the right side of the downtube to act as a solid mount against the torque pull to the left if you can't get a full 360° solid bracket around it.

I usually use the extra front mounting block and longer studs in the optional motor mount kit, and like Nashville Kat I usually grind that block well into the stud holes to make it wider.

Then I just squeeze the front tube a quarter inch with a C clamp so the studs just fit past.

To fill in the little gap left in the mounting block I use some left over rubber-rag from the rear sprocket spoke mount. I have plenty left over from a couple of Jackshaft builds and it holds up much better than inner tube rubber.

With that right stud up against the downtube the motor simply can't pivot because that down tube isn't going anywhere either.

 

[culvercityclassic]

Wow...that clamp is doing some ugly things to that down tube. I would try to be a little more creative with the front mount...

 

[bairdco]

jeez. just when i thought KC had finally stopped telling people to crush one of the most important, load bearing tubes on a bicycle frame, here he comes again...

his method is no better than drilling a hole in the tube like the kit instructions tell you.

the most common place for a bike frame to crack is on the downtube where it joins to the headset. because of the forces on the bike, the downtube is continually being "pushed" on, from pedaling force and from every bump.

doing anything to compromise that tube is the worst thing you could do. if your downtube buckles, your frame folds in half, and you could lose some teeth or break your neck.

seriously.

i don't wanna hear "i've done this and never had any problems..." because it's one thing to do it on your own bike and take the risk of injury or death yourself, but to offer it up as advice to anyone, or to sell a bike to someone knowing it could injure or kill them is irresponsible, not to mention morally wrong.