Author Topic: GT Vibrations! (Read 9271 times)

hpwaco · **on:** March 30, 2019, 04:10:18 pm

Past the 4000 mile mark and still waiting for the vibrations to decrease! At least I can see out of the oem style bar end mirrors. Maybe a Carberry plate - or a new 650!

kelsoo · **Reply #1 on:** March 31, 2019, 05:20:23 pm

On my GT it's very noticeable through the whole bike. Footrests, tank when I grip with my knees as well as hands. Just back from a 60 miles ride and 30 minutes has past and my fingers and especially right hand thumb is still vibrating/tingling. My bike was new in December and has done 1400 miles and appears to be vibrating more than it did before, though I've gradually been increasing the speeds so it maybe has made it more noticeable. I'm actually quite worried about Vibration white finger (VWF) it so bad.
I'll let you test the Carberry plate :-)

Rusted535 · **Reply #2 on:** March 31, 2019, 09:55:33 pm

What speed and rpms are you mostly riding at?

Richard230 · **Reply #3 on:** March 31, 2019, 10:56:02 pm

Foam slip-over grip covers as sold by Grab On and other brands, help to cut the vibrations felt though the handlebars. They retail for around $15 or less and only take a couple of minutes to install.

GlennF · **Reply #4 on:** April 01, 2019, 12:24:58 am

Some UCE engines just vibrate more than others.

hpwaco · **Reply #5 on:** April 01, 2019, 02:05:53 am

I usually ride at about 50-55 mph on local roads. I have Grab On foam covers but they don't help. 60-65 mph and over 3000 rpm brings on the hand numbing buzz. I've checked all engine mounting boots but haven't tried the "loosening/tightening with the engine running" suggestion.

Grant Borden · **Reply #6 on:** April 01, 2019, 02:39:48 am

The loosening/tightening of the engine mounting bolts with the engine running greatly reduced the vibrations on my C5, when I changed the stock silencer for a free flowing one it got even smoother.

Grant

UncleBuck82 · **Reply #7 on:** April 02, 2019, 01:57:59 am

...loosening/tightening of the engine mounting bolts with the engine running...

What sorcery is this?

Grant Borden · **Reply #8 on:** April 02, 2019, 03:45:05 am

It works on most. You can decide what kind of sorcery it is.

Grant

Arizoni · **Reply #9 on:** April 04, 2019, 12:32:04 am

Quote from: UncleBuck82 on April 02, 2019, 01:57:59 am

...loosening/tightening of the engine mounting bolts with the engine running...

What sorcery is this?

It's really not sorcery.

When a frame is built the engine mounting holes on the frame aren't in the exact location to always mate with the holes in the engine.
When the factory assembles the engine in the frame they force the bolts thru the holes and tighten them up. This creates stresses in the frame and in the engine case that can cause a slight warping in the case. This can cause the bearings to be slightly misaligned.

By loosening up the engine mounts and running the engine for a while the engine and the frame will move a little bit to improve the bolt alignment and reduce the stresses in both the engine and the frame. In the process of doing this, often the vibrations will go down.

This sort of thing isn't needed with an automobile engine because they are almost always "soft mounted" in flexible engine mounts that absorb the misalignment but the Royal Enfield engine is "hard mounted" to the frame.

UncleBuck82 · **Reply #10 on:** April 04, 2019, 10:56:31 am

Thanks Arizoni.

That explains it completely for me. My GT doesn't feel like it vibrates that much, but I'll give that a whirl.

I'm used to that kind of interference fit in sheet metal; wasn't expecting it in an engine.

Arizoni · **Reply #11 on:** April 06, 2019, 12:08:16 am

I should add, the main reason the RE singles vibrate as much as they do is because of the way the crankshaft is assembled.

There is a heavy flywheel with the alternator shaft on one side and another heavy flywheel with the power output shaft on the other side. Connecting these is a crankpin.
When they assemble the three pieces (with the connecting rod and bearing on the crankpin) they don't always get the two shafts on the flywheels on the same axis or centerline. The two shafts are supposed to be lined up with one another and a very small error in this alignment will cause the engine to vibrate.

That's why some of the RE engines like the one in mine doesn't vibrate much at all. Others engines can vibrate pretty badly.

There's nothing that can be done about this alignment without a total engine tear-down so lets hope the old "loosen the mounting bolts trick does the job for you.

wildbill · **Reply #12 on:** April 06, 2019, 01:20:16 pm

or you could buy an interceptor and solve the vibration problem completely. not sure about the fuel cap though..lol

kelsoo · **Reply #13 on:** April 06, 2019, 03:21:51 pm

I refitted my short straight through exhaust pipe that is joined via springs to the header pipe. Greatly reduced the vibration.

ace.cafe · **Reply #14 on:** April 06, 2019, 03:25:18 pm

Quote from: kelsoo on April 06, 2019, 03:21:51 pm

I refitted my short straight through exhaust pipe that is joined via springs to the header pipe. Greatly reduced the vibration.

That is an interesting idea. I never thought of doing that. Glad to hear it worked!

heloego · **Reply #15 on:** April 07, 2019, 03:00:54 pm

The "loosen the mount bolts with the engine running" really did help my vibration issue. Now the only vibes felt are at speed (70-75mph) and in the right foot peg on acceleration. Smooths out as soon as I reach a stable speed. I can live with that.

Good Vibes · **Reply #16 on:** August 10, 2019, 01:43:40 am

Hi Grant, can you explain a little more the process of loosening & tightening with engine running. Is that on centre stand with engine idling, and does it include head to frame bolt etc?

ace.cafe · **Reply #17 on:** August 10, 2019, 01:13:57 pm

We are working on something to reduce GT vibrations, but we are not ready to discuss particulars yet. Prototypes tested and working well.

Grant Borden · **Reply #18 on:** August 11, 2019, 08:41:57 pm

Good Vibes,

I loosened all bolts slightly, bike on side stand idling, retightened head bolt to frame last. Bike did not vibrate very bad after this procedure, after installing the Carberry vibration plate it got better. Still vibrates but not very bad nor is the vibrations objectionable for a single cylinder engine.

Grant

Bannocksgt535 · **Reply #19 on:** May 25, 2020, 07:48:01 am

I just had the best ride ever today. Over the last two and a half years of ownership I have fitted a Carberry plate, put a free flow filter on, fitted a wild boar exhaust and small baffle, installed a powertronic ecu and finally some foam grip puppies. At every stage the vibes reduced to a very slight buzz in the fingers. I know the vibes will always be there, it's the nature of the beast, all these mods have meant that today I could just ride without worrying about numb fingers. So happy today!