Crank balancing results?

When I lose a screw and nut due to vibration, I replace the nut with a nylock. So far I have never had anything fall off when a new nylock nut was used to hold it on.

Balancing a single cylinder engine may not help as much as you would hope. Make sure your front engine mount is as rigid as possible. Drilling the frame and/or extending the front engine mount will make the problem worse.

I would also like to know if anyone has gotten a substantial benefit from balancing one of these engines.

i used rubber handle bar grips under my mounts and made sure my mounts were tight and that the engine does not move.my vibrations used to shake your teeth out but now i have almost 0 vibrations at any speed.i have extended front and rear mounts. my nuts are all double nutted. i also have rubber peddals from a exercise bike. i also add 3 gaskets to my clutch cover and no more clutch noise. the only noise i ever hear is a ringing,so im going to add some rubber hose pieces to my engine fins,that should take care of that.

Truing the crank would likely do you wonders, machine shops or 2 stroke tuners with the knowledge and equipment to do that job cost money though. Likely 100 bucks or so when all is said and done...that's if you can get the crank out and back in yourself.


MotoRapido Service 2

Heres some stuff I found on crank balancing,hope its what your looking for. http://motorbicycling.com/f13/homemade-crank-balancing-4498.html http://motorbicycling.com/f13/transfer-port-modification-pictures-results-here-5985.html The second one has info about crank balancing you just have to read through it.

the rubber behind my mounts is almost the same as how they mount engines on motorcycles,works for them and works for me. i used black fuel line hose pieces between 4 of my fins on top,not all of them, and air will still flow just fine.

30mph cruise/35mph top speed and fast acceleration @ 200mpg, 0 vibrations, nothing comes loose, i must be doing something right. my engine still starts with the first pull of the pull start.

Cabinfever1977 – you either got lucky or took the time to address the other issues that present themselves when you have an isolating engine mount. An isolated mount will let the engine vibrate more but, when done correctly, the rider does not feel anything. So it can give the smoothest feeling ride. Since the engine is actually moving more, you need to lock everything down well on the engine. The muffler may also need to be rubber mounted in relation to the frame. Even so, the stresses on the exhaust studs can be very high when the engine vibrates more. You may also be putting more cyclical stresses on the engine mounting studs so they may be subject to fatigue. It may be a good idea to replace the low quality mounting studs on these engines, but the stock hardware works fine if you have the engine securely and solidly mounted in a correctly sized vee shaped frame. However, if your isolating mounts are very compliant so the engine moves freely throughout the vibrating motion, then your stresses on the mounts should be reduced significantly. But then you may have more problems with the exhaust and possibly chain vibration or jumping.

So my recommendation is do one or the other. Mount it as solid as possible (the easy way). Or if you are going to rubber mount it, use mounts that allow enough motion to work. Actually, these bikes are about experimenting. So try what ever you want and report back how it works. Be prepared to experiment. I see a lot of unique solutions on this forum that would not have come about if everyone just did it the standard way

i have a custom engine and muffler mount on the front.

Scotchmo,

This set-up worked perfect, except under acceleration. Under acceleration the engine would deflect slightly...It wasn't enough to cause any problems, but I know the average user wouldn't like it.

ENGINE MOUNT

I have been waiting for several months to get isolators of a higher durometer from the manufacturer.

Jim

Jim that engine mount is great,it would be awsome to mount my motor.
if i had the money id buy one in a minuite. i still cant wait for it to be for sale.

its good im not a average user.


karl

Rockenstein said:

Truing the crank would likely do you wonders, machine shops or 2 stroke tuners with the knowledge and equipment to do that job cost money though. Likely 100 bucks or so when all is said and done...that's if you can get the crank out and back in yourself.


MotoRapido Service 2

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Rock,

You're right: but,

I have torn down a few engines where "truing" was not limited to the usual aligning of the two crank halves about the rod pin. These cranks were either bent when they were pressed together at the factory; or the pin hole was drilled and reamed at an angle. Either way the end result is a crank that wobbles.

One was so bad that the bike was not rideable...It vibrated that bad through the entire RPM range.

Jim

Cabinfever1977 said:

Jim that engine mount is great,it would be awsome to mount my motor.
if i had the money id buy one in a minuite. i still cant wait for it to be for sale.

its good im not a average user.


karl

Click to expand...

Thanks Karl,

I have been waiting WAY too long for several suppliers to make more isolators...they just aren't getting the big commercial orders like they used too.

One supplier told me that they have a customer that orders 35,000pcs every quarter. This was in February. They still haven't had an order. I had figured on buying 500pcs, which would be enough for 125 mounts.

I need the isolators that are shown in the pics in a 90 durometer neoprene. The isolators that are shown are 60 durometer natural rubber.

Jim

Creative Engineering – It looks like you spent some time and effort to work things out. It looks good but here are some concerns of mine (may or may not actually be a problem for you):

With that type of mounting, you may need a three point setup. I know that you already have four, but they are arranged as two closely spaced pairs of mounts.

The isolator that you used look like the kind composed of rubber with a stud molded into each end. The problem with those is that if they shear, the engine is loose. A better approach would be to use isolator bushings and longer studs coming out of the engine. Use clearance holes instead of slots on your mount. The clearance holes accept the small diameter of the rubber bushing. The step on the rubber bushing is ½ the plate thickness. So the mounting plate is trapped between two rubber bushings at each stud location. Use a washer and nylock or double nut the lower bushing. That may also help restrict the side to side motion of the engine. This setup will eliminate the shearing action on the rubber. This setup will have the rubber in compression at all times.

If someone wants to design the best possible mounts for a motorcycle engine, they should study the 1968-1975 Norton Commando. The Norton engineers came up with a system that took a 1950s design long stroke motorcycle engine that vibrated so bad it was barely rideable, and made it one of the smoothest bikes of it’s time. It competed well against the newer four cylinder motorcycles of that time. I think someone else at this or another forum has attempted this. The Norton mounts let the engine move up and down considerably, but it was shimmed to restrict side to side movement. The swing arm was part of the engine assembly so motion of the motor had no affect on chain tension and vice versa. They did use isolators like you use but only to steady the head and support the mufflers. These small displacement bicycle engines are not going to have the severe vibration of that engine, so maybe it is not even needed.

Those other machined parts look beautiful. Keep experimenting but for simplicity’s sake, I’ll stick with solid mounts.

Creative Engineering said:

Rock,

You're right: but,

I have torn down a few engines where "truing" was not limited to the usual aligning of the two crank halves about the rod pin. These cranks were either bent when they were pressed together at the factory; or the pin hole was drilled and reamed at an angle. Either way the end result is a crank that wobbles.

One was so bad that the bike was not rideable...It vibrated that bad through the entire RPM range.

Jim

Click to expand...

That's not good news Jim although given where these things are manufactured and how much we pay for them I can picture crank parts being drilled, or pressed together, in machines and fixtures that are not square. Luckily mine wasn't so bad...my next one might not be though.

I originally used inner tube on my motor mounts. I had alot of vibration. I just installed a shift kit. The new rear mounting that came with it is very solid to the frame. I removed the front mount padding and solid mounted the front too. Now I know I don't have a left side chain anymore but my vibrations are almost totally gone. Locking the engine down really helped.

I sent my engine to Jim to have it balanced; he said that he'd be done soon. Once I have it and install it, I might make a thread describing how much it vibrates.

i cant wait to see the results ht2005.

HT2005 said:

I sent my engine to Jim to have it balanced; he said that he'd be done soon. Once I have it and install it, I might make a thread describing how much it vibrates.

Click to expand...

HT,

How is your latest engine performing?

I went through my orders this afternoon and I am nearly caught up! That means it's time to play...and your engine is going to be at the top of the list.

I've got my, Schwinn Jaguar, test bike ready. I'm going to put your engine in it "as is" just to see what it "was" doing. From there I'll modify it based on what it needs.

Jim