Author Topic: vibration (Read 4808 times)

6adan · « **on:** October 18, 2005, 07:21:30 PM »

New to this site but have a vibration in the handlebars of my 1970 CB750. Has anyone have an idea what it may be? I have checked timing and even checked chain. Thanks Dannie

skamania19 · « **Reply #1 on:** October 18, 2005, 07:44:38 PM »

Almost all motorcycles have some vibration in the handlebars, some much worse than others. What kind of vibration? Are you talking a high frequency vibtation that makes your hands/fingers tingle when you stop? Or a lower frequency vibration more like a shudder?

6adan · « **Reply #2 on:** October 18, 2005, 08:17:12 PM »

High frequercy it makes my hands tingle. I don't remember it doing this when it was new. Of corse both of us have gotten older sence 1970.

skamania19 · « **Reply #3 on:** October 18, 2005, 10:44:55 PM »

If your grips are original they might be brittle. I'd try some softer grips like gel grips. There have been other threads here with similar problems. Try searching this site for handlebar vibration and you should find more suggestions. Also, if you happen to have reduced circulation in your extremities for medical reasons you'll be more affected by vibration.

Raul CB750K1 · « **Reply #4 on:** October 18, 2005, 11:53:10 PM »

Prognosis: You have a Harley with Honda badges.

6adan · « **Reply #5 on:** October 19, 2005, 07:15:39 AM »

Not a Harley you can't see the bars shake from 50 ft away.

eldar · « **Reply #6 on:** October 19, 2005, 07:35:34 AM »

Or the engine lurching all over in the frame

Einyodeler · « **Reply #7 on:** October 19, 2005, 07:39:45 AM »

You might want to try Bar End Weights , I use them on the old Harley and they really do dampen the vibration.
Here`s a link:

http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=591365&store=&catId=410&productId=p591365&leafCatId=41005#altImages

Raul CB750K1 · « **Reply #8 on:** October 19, 2005, 07:58:36 AM »

There is an old wive's tale that there was a spot on the CB750 engine where you can put a coin standing with the engine idling and the coin stayed upright!

I don't have any noticeable vibration in my 71 750. On the contrary, my modern thumper vibrate much more, even with handlebar weights. I guess it is a problem of incorrect carb synchronization, or one of the cylinders not firing correctly. Check the RPM where you get the most vibration and rev the engine on a standstill on neutral. If the vibration disappears then it's probably a bad balanced front wheel. Check if the vibration increases with RPM or speed: engage the clutch while coasting at 60-80 mph and let it idle. If the vibration stays then it's time to balance the wheel.

Raul

Raul

dusterdude · « **Reply #9 on:** October 19, 2005, 08:03:06 AM »

i get it too,but im not going to blame the bike itself until i get my front end situation straightend out,then we`ll see.

78 k550 · « **Reply #10 on:** October 19, 2005, 07:12:01 PM »

6adan,
Tell us more. Has the bike been sitting? How much fluid is in the front forks? new tire, old tire? Is it balanced?

Paul

ElCheapo · « **Reply #11 on:** October 19, 2005, 07:56:15 PM »

No bad vibes here on the 75 cb750. I always say keep it simple and start with the easy stuff, because when you come backwards to it you feel real dumb when you find it. Go through your standard tune up inspection including the carb synch. I would look for things to be off just a little bit. Start by looking at your plugs. Do they all match in the color and pattern? With the exception of a small amount of oil.

My old GSXR 7/11 used to give me the stinging hands when it needed a serious tune up.

Really guys let me know if I am just making noise.

6adan · « **Reply #12 on:** October 20, 2005, 01:53:24 PM »

Thanks everyone tire is new and balanced,dose not feel like tire,very high picthed vib.When I tryed to synch #4 was pulling more vac than others even at idle with all slides closed I guess this could be the problem but don't know how to fix. What could cause one cylinder to pull more vac than the others with all slides the same?I have checked timing,got a new set of plugs to put in will see if that helps also. Dannie

Bob Wessner · « **Reply #13 on:** October 20, 2005, 01:58:31 PM »

Your bike is a '70 750, you have four separate cables to the carbs right? If so, they get out of sync very easily. Anyone fiddling with the carbs can result in needing to resync them. The adjustments are via the individual carb tops, brass fitting with a lock nut. They are easy to work on, you just need to adjust them more frequently than the later years where the carbs are linked via a shaft.

Dennis · « **Reply #14 on:** October 20, 2005, 02:22:03 PM »

Quote from: Bob Wessner on October 20, 2005, 01:58:31 PM

Your bike is a '70 750, you have four separate cables to the carbs right? ...... They are easy to work on, ........

"They are easy to work on, ........"

Did Bob REALLY say THAT?

Bob Wessner · « **Reply #15 on:** October 20, 2005, 02:38:45 PM »

Yup, he did.

I just had to do it more often than most.

dusterdude · « **Reply #16 on:** October 21, 2005, 06:13:48 AM »

dennis,he would,bob is a carb guru now,nothing about carbs is difficult to him

eldar · « **Reply #17 on:** October 21, 2005, 08:34:48 AM »

I think the big question is......how much vibration is a little or a lot? When I first started riding my bike again, my hands would tingle a bit. I have done some tuning and gotten usedto the bike and now I do not have the tingle. But does that mean the vibration is less or did I just get used to it and adapt and now it just no longer happens.
My mirrors do shake too much to get a clear picture if my hands are off the bars, but then the bike has always done that and I do not have any rubber grommets between the mirrors and the mounts.
So maybe some one could give an example of what might be too much vibration. nothing rattles on my bike either.

mrbreeze · « **Reply #18 on:** October 30, 2005, 12:20:28 PM »

I noticed a couple of times when synching my carbs that in between adjutments I could get the front brake lever to start shaking around at an idle. When you get it dialed in,the shaking went away.

SteveD CB500F · « **Reply #19 on:** October 31, 2005, 06:15:08 AM »

At anything more than 70mph (500/4) my mirrors vibrate making it impossible to see anything behind me. At night, the following headlights appear a circles of light (when I'm not looking at my elbows that is...)

I have David Silver mirrors on my bike as it didn't have any when I bought it.

So, two questions:

1. Do my mirrors vibrate more than they should/did?

2. Anyone tried any wider mirrors or extensions? (I had a bar-end mirror in the 70's (avatar) but don't want one now - prefer the "stock" look)

MRieck · « **Reply #20 on:** October 31, 2005, 08:58:40 AM »

Quote from: Bob Wessner on October 20, 2005, 01:58:31 PM

Your bike is a '70 750, you have four separate cables to the carbs right? If so, they get out of sync very easily. Anyone fiddling with the carbs can result in needing to resync them. The adjustments are via the individual carb tops, brass fitting with a lock nut. They are easy to work on, you just need to adjust them more frequently than the later years where the carbs are linked via a shaft.

I agree with carb synch being out. Also check for vacuum leaks (carb boots especially if they are original)as it can produce high frequency vibration.

ofreen · « **Reply #21 on:** November 20, 2005, 09:20:38 AM »

Actually, carb sync doesn't have much effect on vibration at higher throttle openings, such as at cruising speed, a least at the typical variation you are likely to see. If you are getting excessive vibration now that you weren't getting before, it is likely to be something else. Check all the motor mounts for tightness. Check the exhaust mounting on the engine and chassis, as well. Check the rest of the bike's fasteners while you are at it.

Has the bike been down at all, even something minor as falling off the stand?

Greg
'75 CB750F

Jonesy · « **Reply #22 on:** November 20, 2005, 03:03:41 PM »

Quote from: Dennis on October 20, 2005, 02:22:03 PM

Quote from: Bob Wessner on October 20, 2005, 01:58:31 PM
Your bike is a '70 750, you have four separate cables to the carbs right? ...... They are easy to work on, ........

"They are easy to work on, ........"

Did Bob REALLY say THAT?

...If he keeps telling himself that, he'll eventually believe it!

Buffo · « **Reply #23 on:** November 21, 2005, 05:42:41 PM »

I "played with my timing about a week ago and got a high speed vibration in the bars at 75 mph...I have the Dyna S...

I didnt realize that being a little out of sync or time would give a vibration like that...I thought that I had a front end problem from trail braking or a road hump...

I have sense resored my timing to normal but I have not been above 60 mph yet...My carbs could use a sync as well...

Buffo The Magnificent

6adan · « **Reply #24 on:** November 21, 2005, 06:31:18 PM »

The more I hear from you guys the more I think the problem is in my hands being older,the mirrors are clear when riding. I baught a set of gel grips from Dennis Kirk that were said to be 5.00 in. but they were too short only 4.75 in.Anyone know where I can get a set for a 750? Dannie

Lumbee · « **Reply #25 on:** November 22, 2005, 07:20:21 AM »

...might want to try tightening u'r engine mounting bolts...

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Author Topic: vibration (Read 4808 times)

eldar

ElCheapo

eldar

Buffo