Bad Vibrations? READ THIS

alfredo

1978 xs650 Special
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Some of you might know that I have spent some time rebuilding my motor, running my motor, rebuilding my motor, running my motor and rebuilding my motor over again. It's been a few years since I jumped on here knowing absolutely nothing (haven't come far from that btw) and really made an effort to dive in. I won't say much about the community that Travis built (xs650.com) because I know everyone here gets tremendous benefit from it. Wheter you just browse and never post, are an active asshat to everyone or an active contributor. You all get value here. No question.

What I do want to take a second and talk about is vibration. There are a lot of things that you can do to your xs that make it more reliable, sleek, sexy and fast. Most of these things are very well covered in other posts, but the one thing that I personally feel is understated is the RePhase. I have had the fortunate, and unfortunate, pleasure of experiencing the very same xs motor in various states and configurations. Now, if you are a professional racer or motor builder then I am sure this luxury is afforded to you all the time. I just don't think thats what makes up 80-90% of this community. I think there a lot of guys and gals like myself who are budget and time conscious and really want to get it right out of the gate. No time to test and test and just want to cruise.

When I first started riding the first rebuild (360°) it vibrated like a wild angry animal at speeds of 60+. If I tried to go up to 70+ the vibration was REALLY bad, sometimes I could barely keep my hands on the bars. I actually felt like it might shake loose, despite others saying it was normal. I was able, through the help of loads of forum members, to tune out some of this. The problem was it was still there. Lots of suggestions that would certainly do the trick to tone it down; squishier grips, bar snake, etc., but nothing that made a huge difference without a good amount of kit/add-ons. The vibration always felt wrong to me. I mean, I get the mechanics and why it does it, but it never really felt like something I could look forward to experiencing when riding the bike. And to me, I wanted to look forward to riding the bike. Enter the rephase. I read a ton about it and it seemed like the holy grail. So, I did the hard thing to do after spending all that time and cash on rebuilding the motor and tore it down again for the winter to do the rephase.

Saving the money and the time took awhile. I went all out this time. PMA, 5th overdrive, rephase crank/cam, but kept my bore from the original rebuild. No 750 kit in the budget and from all of what I could read the 750 just gets you to the max speed quicker. Doesn't really do too much for you unless you are racing or are really interested in getting to your cruising speed a little quicker. Neither of which are my interest or worth the $$$ to me personally.

To start to shorten this story up, I put the motor together twice with all the newly worked parts. First time I had the cam off one tooth :doh: and the base gasket was seeping. Once it was all together I ran it for about 50 miles, but even then I could tell the dramatic reduction in vibration. I never got it above 65, because of my past experience with the bike starting to vibrate like crazy before. Because the bike still vibrates a little more around that range, so naturally when it started to vibrate a little more I got scared and thought it was going to be as bad as the first rebuild.

Enter this past sunday. I was meeting up with some friends to take a ride to Nags Head (about 110 miles one way) to give the bike a proper shake down. This meant getting on the interstate which in my area means a posted speed limit of 70mph. Needless to say I clinched my butthole and went. The bike ran incredible the entire way. There is a spot where the vibration gets a hair more around 60mph (I am assuming its about 4.5k, but have no tach hooked up) but its an incredibly smooth vibration compared to the 360° phase. All went well barring some slight clutch cable adjustment needed. Even at speeds of 85-100 it barely vibrates more than a subtle hum. I have solid grips, solid mounted bars and also have all motor mounts hooked up and tightened down. I never maxed it out, but it certainly felt like it wanted to keep pulling even at 100mph. I was scared and impressed at the same time. My little xs was pulling away from a 70s ironhead and a 2000s harley 883. There were a few times when I just rolled on the throttle for a few minutes and got up to around 100+ and would look back and those guys were gone. They were right beside/behind me pulling and then they just vanished. None of us could really fathom that they couldn't keep up. Both of those bikes will get to 60+ faster than mine, but neither can keep up. I never maxed it out, but it always felt like it would go more and more and more.

So, long story short; While there is a lot that you can do to remove the vibration from the stock configuration, there is nothing you can bolt on that gives you as much of a dramatic improvement as doing a rephase does. Also, the 5th gear overdrive is an absolute MUST if you are doing a rephase. The benefit of the rephase, I feel, is dramatically understated on this forum. From my personal experience. I don't want to start an argument, just state what my experience has been.

Lots of thanks to Hugh and Pete for teaming up to offer such a great/painless upgrade available for this motor. If it's within your means to do this now or in the future. Do it. And give Hugh and Pete your money. Others may be able to do it, but these guys are certainly the top shelf.

:cheers:

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You know, I get emails like this all the time- but very few folks preach it on the forums. I'm glad you decided to give it a shot - and glad you are out there burning up the roads a bit...

Hugh
 
I haven't done a rephase yet, but I did Mike's 750 kit. One of the first things I noticed was the reduction in vibes. From Idle up to around 4000 rpms the vibes are just a bit stronger. You would need to jump back and forth from a stock to 750 to really notice the difference. Once you reach the 4000 rpm range the stocker starts a rapid rise in vibes. The ones everyone claims is too much, just aren't there with the 750.
The engines vibes are the same clear across the rpms.
I plan at some point in the future doing a rephased 750 on the spare 82 engine I have. Then I can compare the vibes between the two.
Leo
 
alfredo,havent heard it put quite like you have.have been gradually gathering the parts for a rephase etc upgrade and have been worried if the moneys been well spent.thanks for the boost
 
This may not be the proper place to ask this but I will anyway. A rephase job, which will also include at least a freshening up of the top end (and of course could include more if needed) will cost approx. what dollars? I am well aware that there are variables involved but a ballpark figure will do.
 
I haven't done a rephase yet, but I did Mike's 750 kit. One of the first things I noticed was the reduction in vibes. From Idle up to around 4000 rpms the vibes are just a bit stronger. You would need to jump back and forth from a stock to 750 to really notice the difference. Once you reach the 4000 rpm range the stocker starts a rapid rise in vibes. The ones everyone claims is too much, just aren't there with the 750.
The engines vibes are the same clear across the rpms.
I plan at some point in the future doing a rephased 750 on the spare 82 engine I have. Then I can compare the vibes between the two.
Leo

Might just go this route! More power and less vibes.
 
This may not be the proper place to ask this but I will anyway. A rephase job, which will also include at least a freshening up of the top end (and of course could include more if needed) will cost approx. what dollars? I am well aware that there are variables involved but a ballpark figure will do.

Like any other mod to these old bikes, the more you are willing to do yourself, the more money you can save.. :thumbsup:

gaskets and seals - $100 or so

Rephased Crank and Cam from us at HHB - $485.00 (if your OEM rods are in good shape, if not, then replacement rods are about $180.00 from MikesXS)

If the bore/valves/etc.. are all in good shape, you can do it pretty inexpensively. Listening to Alfredo - you can see that the 650cc is plenty capable, and you can rephase just about as cheap if not cheaper than a Big Bore Kit if you do the labor yourself and aren't afraid to tackle the engine build.

We build a TON of 277 crank and cams - and lots of beginning wrenchers have found the XS rebuild to be a simple enough task using the manuals, and this forum for help when they get stumped..

I don't like to try and be a salesman on the forums (or at all really, I totally hate a salesman! :laugh:) , so if you need more advice or help, feel free to email HughsHandBuilt@gmail.com

We also have a TON of information about the rephase on our Blog - http://hughshandbuilt.blogspot.com/2011/01/re-phased-goodness.html

Hugh
 
Great write up. I smiled a bit about the others not keeping up. Certainly would like to Rephase/BigBore one day
 
And even I have budget constraints when it comes to a build - believe it or not :laugh:

I have this bike (it's finished now, but just an example) and I built a really nice 360 (oem crank/cam) engine using a set of Wiseco 750cc Pistons, Brand New Pamcopete Ignition, Web Cam, Mikuni Carbs, upgraded clutch, etc... During the shake down rides and testing/tuning of this bike I simply could not stand the vibes in the engine... It was a total bummer... I had less than 50 miles on this freshly built 750cc engine and I just couldn't bring myself to tear it down to rephase it. But I knew I'd never be happy riding that bike with the 360 crank in it... So out it came :banghead: The shake down riding before paint/powder and final details was literally shaking me down :yikes:

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So I tore it down, rephased the crank and cam, did the 5th gear OD (Might as well while I'm in there) and built it back up proper as a 277. I swapped out the Pamco for a 277 pamco and fired it right up... The bike is sooo much more rideable now, and I'll likely put a ton of miles on it as it's way more comfortable to ride. And it has the power to do fun stuff too! :thumbsup:

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So yeah, even though I had a beautiful and powerful 750cc engine with practically no miles on it, ready to go and ride - I just couldn't bear riding the bike without doing the 277 mod... Yeah, it cost me some money, but the mileage I'll put on the bike now compared to before will more than make up for it. I literally couldn't stand the vibes at hwy speeds. I even tried every possible combo of gearing and nothing was gonna make it better... So yeah, I tried like hell to not sell myself on the 277, but I just had to do it...

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When you can run them on a solid mounted test stand and they don't walk all over the shop - you know it's good stuff :laugh:
 
Honest, I am not trying to be a contrarian or argumentative, but I have never really experienced really bad vibrations, and I have ridden a few different XS650s at sustained 70 MPH. Whenever I hear about bad vibrations, first I wonder if they are talking about the early years before Yamaha reinforced the frames, or if they are talking about 1975 and earlier with the 34 mm forks, neither of which I have ridden. Then, I wonder if they are talking about hardtails, which I also have never ridden. Alfredo, great post, and I'm glad your bike rides good. Is it an early frame or a hardtail?
 
The more OEM your bike is, the less vibes it will have. The OEM seat alone makes it much more bearable. The lighter the chassis becomes, the less it will absorb the vibrations and they will be transferred to the rider. The oem side covers, grommets, rubber mounts, fenders, seat (that thing is THICK!) and general weight of the bike helps absorb a ton of the vibes.

I have an 81 Heritage Special here that is not modded at all, and it's actual quite pleasant to ride in its OEM configuration. I don't take it on the highway much, but it's completely tolerable in town as is.

Hardtailed, Bobbed, Chopped, Cafe'd or stripped down all tends to start showing the vibes pretty good once the weight is stripped off..

Think of it like hooking up with a chic who as some meat on her bones, compared to a scrawny lil' gal... One is built for speed, the other for comfort :)
 
The more OEM your bike is, the less vibes it will have.


That makes sense! I've been reading this thinking about how much I like the 360 engine. My SK is a joy! It is not any fun on the super slab, but for back road blasting, I love it!

I took a ride on a friends 277 cafe. I didn't think it was for me. The vibrations were very heavy at low RPM, but up near redline it was fantastic. I thought it a good mod to go like stink all the time, but not for leisure. Maybe it was the bike I was riding, or it could just be my preference. I've only ridden that one 277 bike. I would not advise anyone either way. It's just different. Does it not move the powerband up to higher RPM?
 
That makes sense! I've been reading this thinking about how much I like the 360 engine. My SK is a joy! It is not any fun on the super slab, but for back road blasting, I love it!

I took a ride on a friends 277 cafe. I didn't think it was for me. The vibrations were very heavy at low RPM, but up near redline it was fantastic. I thought it a good mod to go like stink all the time, but not for leisure. Maybe it was the bike I was riding, or it could just be my preference. I've only ridden that one 277 bike. I would not advise anyone either way. It's just different. Does it not move the powerband up to higher RPM?

Vibes will all depend on tuning as well. Just like any XS650 engine. If the carbs aren't perfectly sync'd - you'll still get vibes in the low end (less than a 360 engine, but still vibes regardless). But if you look at my videos on Youtube, you'll see that these engines barely vibrate at all at Idle, and even with a flick of throttle they don't do the "XS650 Dance" across the floor like a stock engine does. Tuning is everything, 277 or not. Not to say your buddy didn't have his just right, but the gearing, piston mods, chassis weight, etc.. all play into how the bike rides and feels of course...

Nothing wrong with a well tuned 360 bike - sometimes it's just perfect - sounds like yours is just right for you. If you ever make it to Asheville NC, come on by, I'll let you take a spin on a few of our bikes if we have them available.

One of my goals this season is to have 2 identical specials but one of the rephased so that people can take a spin and see the difference for themselves... I have the bikes, now i just need the time :)
 
Nothing wrong with a well tuned 360 bike - sometimes it's just perfect - sounds like yours is just right for you. If you ever make it to Asheville NC, come on by, I'll let you take a spin on a few of our bikes if we have them available.

Careful! I'm close enough to show up! :D
 
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