Author Topic: Normal?  (Read 1752 times)

Offline Waggles

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Normal?
« on: October 11, 2012, 11:01:29 AM »
My F1 is bedding down nicely now and is pretty much as I remember the one I had new in '76, but for one thing, I get quite a buzz of vibration through the bars from around 50 mph onwards. Now it could be selective memory but I do remember the bad as well as the good ( like the gearbox that feels like pushing a knife through a bag of marbles at low revs  :) ) The vibration was enough to make my hands numb after 100 miles if I gripped the bars tightly.

Before I go through the tuning and checking of engine mounts etc is this normal and I have just forgotten? I don't remember feeling the need to rubber mount the bars on my original one!

Offline Spitfire

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Re: Normal?
« Reply #1 on: October 11, 2012, 12:31:13 PM »
I don't remember it as that bad but I did have to rubber mount my wing mirrors when I bought the bike in 76, these were removed when I rebuilt the bike but have since been reinstated !

Cheers

Den
1976 CB750F

1977 CB750F2 In bits

1964 BSA A65R In bits

Offline ST1100

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Re: Normal?
« Reply #2 on: October 11, 2012, 04:22:46 PM »
The vibration was enough to make my hands numb after 100 miles if I gripped the bars tightly.

Are the carbs properly synced?
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Re: Normal?
« Reply #3 on: October 11, 2012, 10:14:50 PM »
Try checking the valve clearances to make sure nothing has got tighter.

Also the ignition advance when running at max advance for both coils and not just look at one.

Check that the compression levels are within range for all cylinders.

Offline Waggles

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Re: Normal?
« Reply #4 on: October 12, 2012, 07:35:56 AM »
So the general concensus is it shouldn't be like that?

The carbs were synced about 1500 miles ago also the ignition timing etc didn't check compression over and above all cylinders have good compression by feel

Probably about time to service completely again as I expect things will have settled. Seems to run fine though

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Re: Normal?
« Reply #5 on: October 12, 2012, 07:27:02 PM »
Fours are a little bit "fizzy" anyway and with no rubber in the engine mounts you're going to get some through to you, but anything particulary unequal must go towards increasing that.

I don't recall having any particular feelings as you describe, but a friend of mine who rode them at the same time as me has more recently found that his tolerance of this is much lower now than then if that makes sense.

One contributor to the feeling at the bars is a lot of newer stuff runs with bar end wieghts that specifically try to damp that effect out, so could account for some of the difference. Also the vibration masses are smaller on new stuff anyway.

My feelings about picking up vibes can often be an early detection of some inbalance even if power is unaffected, so worth a reasonably careful check through settings to make sure nothing is far away from spec.

Offline Waggles

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Re: Normal?
« Reply #6 on: October 15, 2012, 10:16:44 AM »
I haven't actually ridden a modern bike so wasn't comparing it in that way just from what I remember ( which is a little faded now! )  and I know what you mean in that ALL my 'tolerances' are lower these days  ;)

She's coming up due for a service anyway, I will just make it a big one! my money is on the carbs having drifted out of sync

 

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