excess vibes

[pa23driver]

my '77 650 standard engine seems to be vibrating excessively. in the last couple days my forward and rear motor mounts have vibrated loose, i lost the bolt that mounts the left head pipe to the frame and a muffler rattled free of the head pipe. i realize these motors vibrate but i've seen harley's running like complete ass vibrate less. my girlfriend recently bought an 81 special that i got running and the things runs as smooth as a Goldwing compared to mine. the bike climbs through the power band pretty smooth but on decel and cruising it rattles.

List of mods i've done to my bike:
fresh top end
fork brace
clubmans
tx750 swing arm
needle bearings
cleaned and synched carbs
timing adjusted properly
valves adjusted
cam chain adjusted
commando mufflers on stock headpipes

So do the specials have better rubber mounting than the standards? does the electronic ignition smooth things out that much more? something wrong with the motor? or do i need to just suck it up and buy a bottle of locktite?

 

[pa23driver]

i should add it doesn't matter if it's in gear going down the road or in neutral running in my driveway

 

[bergoff]

I've always just used blue locktite on almost everything. When I got my bike from the PO all of the screws on the brushes and seat pan were loose. And on my first xs my points came apart on me. The specials I think have more rubber mountings so its some what better.

 

[grizld1]

There's no rubber engine mounting on any XS650 production frame, period. Torque the motor mounts to spec and in sequence, check ignition timing and function, check valve lash, check compression, recheck synch. If that doesn't do the job it's time to get into the motor: inspect camshaft and camshaft bearings, rods (side play and play at wrist pins), main and rod bearings, runout on crankshaft.

 

[retiredgentleman]

I'm not aware of any different mounting on Specials as compared to Standards.

This vibration thing seems to have varing effects on these bikes. A while back I kept reading posts from riders saying there licence plates were cracking through from the high vibration. Many had to add backing plates.I would go and check mine, but never found any damage.

I think its important to have the engine mount bolts tight ( don't have any missing). Some of the chopper lads leave the top engine mount off and seem to get away with it. I would not remove the top engine mount from mine, although I have left it off for a few hundred kms while I was re-torquing the head studs.

If the engine mounting bolts are tight, you should not need any locktite. Good idea to check al the bolts on the bike occasionally.

I use a u-tube manometer (homemade) to sync the carbs..............that may help to smooth the beast

I also believe in the dead cylinder method to adjust the mixture screws................again this may help smooth things out.

I also suspect that the guys doing the final crankshaft balancing at the Yamaha factory may have had different abilities and attention to detail. Some cranks may just be better balanced than others.

 

[pa23driver]

There's no rubber engine mounting on any XS650 production frame, period. Torque the motor mounts to spec and in sequence, check ignition timing and function, check valve lash, check compression, recheck synch. If that doesn't do the job it's time to get into the motor: inspect camshaft and camshaft bearings, rods (side play and play at wrist pins), main and rod bearings, runout on crankshaft.

i knew there was no rubber engine mounting, i was thinking that maybe the specials had better rubber bushings on the chassis and/or maybe the high bars helped take away the feel of the vibes as compared to maybe clubmans which are considerably more sturdy.
the top-end is fresh with new rings, cam chain, guides and fresh valve lapping. cam shaft and bearings looked great. didn't notice any play in the wrist pins when they were installed into the rods and the small ends looked good for wear. didn't tear into the bottom end though. timing should be good since i put in a new dual output coil with dual lobed cam only a couple miles ago. carb synch was re-done yesterday, probably won't get a good compression reading until the rings seat a little better but it has a nice firm kick over. I'm going to retorque all of the engine mounts today with a torque wrench. i'll keep an eye on the vibes to see if they get worse, if they do guess i'll have to tear into the bottom end. Thanks for the reply

 

[pa23driver]

I'm not aware of any different mounting on Specials as compared to Standards.

This vibration thing seems to have varing effects on these bikes. A while back I kept reading posts from riders saying there licence plates were cracking through from the high vibration. Many had to add backing plates.I would go and check mine, but never found any damage.

I think its important to have the engine mount bolts tight ( don't have any missing). Some of the chopper lads leave the top engine mount off and seem to get away with it. I would not remove the top engine mount from mine, although I have left it off for a few hundred kms while I was re-torquing the head studs.

If the engine mounting bolts are tight, you should not need any locktite. Good idea to check al the bolts on the bike occasionally.

I use a u-tube manometer (homemade) to sync the carbs..............that may help to smooth the beast

I also believe in the dead cylinder method to adjust the mixture screws................again this may help smooth things out.

I also suspect that the guys doing the final crankshaft balancing at the Yamaha factory may have had different abilities and attention to detail. Some cranks may just be better balanced than others.

funny you should mention the license plates cracking, i got a crack in mine after only 20 miles . i synched the carbs with the old style motion pro mercury sticks yesterday and a set of zerk fittings (i think you suggested zerk fitting idea to another member, worked great btw), the carbs were definitely off, but didn't seem to settle her down. i told the old lady to grab a handful of throttle while it was parked, looked like she grabbed something hot by the way her hand shot off the handle bars, she's like "oh my god, how can you ride that thing"
i'll re-adjust the mixture screws today while i'm retorquing everything.

yeah there's no way i'd leave off a motor mount on this thing, but that '81 special i mentioned might be able to get away with it.

she gets real smooth in the upper mid-range as long as i got a good handful of throttle, i guess i just gotta ride her a little harder

 

[5twins]

Did you check each cylinder individually with the timing light? You need to with that dual lobe cam. Some of them aren't machined correctly and don't fire both cylinders on the "F" mark as they should.

 

[pa23driver]

actually i think i just static timed it, my idle was off due to an off carb synch and i have excess play in the advance rod that i'm going to be taking up with some shims - made it damn near impossible to use a timing light. once i shim out the advance rod, probably today, i'll put the timing light on it.

Thanks for the tip

 

[5twins]

Shimming the advance rod may smooth it out as well.

 

[retiredgentleman]

I think the Specials were manufactured to a higher standard................better balancing etc........................Ha Ha just razzing the Standard guys.

 

[pa23driver]

I think the Specials were manufactured to a higher standard................better balancing etc........................Ha Ha just razzing the Standard guys.

they better be to make up for their looks

well just finished all of the above suggestions and got back from a quick ride around the block, would've went further but it's raining (i can see why front fenders are so popular). she's running about as smooth as she's going too without a rephase.

after i was able to put the timing light on it i realized the right cylinder was outside of the "F" marks by a couple degrees towards TDC, so i had to set it so the left cylinder was just inside the "F" marks towards advance. the right cylinder was still a bit hard too read with the timing light but the shimming definitely helped.

I think i'm going to incorporate a motor mount re-torque into every oil change, couldn't believe how loose those things were.

she runs great, just a few minor carb changes (incurring a little break up around redline), but i am confident i can take this thing on a long ride finally.

Thanks for all the help, you guys are awesome

 

[CDNTX650]

they better be to make up for their looks

well just finished all of the above suggestions and got back from a quick ride around the block, would've went further but it's raining (i can see why front fenders are so popular). she's running about as smooth as she's going too without a rephase.

after i was able to put the timing light on it i realized the right cylinder was outside of the "F" marks by a couple degrees towards TDC, so i had to set it so the left cylinder was just inside the "F" marks towards advance. the right cylinder was still a bit hard too read with the timing light but the shimming definitely helped.

I think i'm going to incorporate a motor mount re-torque into every oil change, couldn't believe how loose those things were.

she runs great, just a few minor carb changes (incurring a little break up around redline), but i am confident i can take this thing on a long ride finally.

Thanks for all the help, you guys are awesome

But buckhorn bars and stepped seats look so good....

 

[XSLeo]

That much timing difference between the cylinders might be why the vibes are more. The TCI fires both plugs at exactly the same time. The Pamco and the Boyer does. With careful adjustment the stock dual points do.
On my dual lobe points cam they were quite far apart. I got two seperate flashes at idle. One was just outside both of the F timing marks. I think the marks are 3 degrees apart. My flashes were out maybe 5 to 7 degrees apart. I think thats way too much. It ran pretty good that way. Didn't notice the extra vibes.
I put in the Pamco and i'm very happy with it.
The 750 kit smoothed it out noticably. Most as a 650 the power comes on good at about 4000-4500 rpms, and the vibes jump up as well. On the 750 that don't happen.
Thats my $.02 worth.
Leo

 

[5twins]

You can fix that dual lobe cam by filing and wet stoning the approach ramp on the lobe that fires more advanced. I made mine right by doing so but then went to a Pamco shortly afterward . There's another short-coming to the single points set-up. Those Yamaha points weren't designed to do double duty like that, firing twice as much as normal. They wear faster as a result. I have several other bikes with a factory single points set-up and they hold up fine - because the points set was designed to be used in this manner. Mark your mileage down now from the install and throw a timing light on the bike in 500 miles or so, you'll see what I mean.

 

[pa23driver]

i kinda figured the points would wear a little quicker. all this is just a hold over until next year when i can afford a Pamco - thus the dual output coil. I'm so over budget on this build it's hard to justify another 100 bux to replace an ignition that works well enough, for right now.

filing the advanced side of the cam is a good idea, i'll probably give that a shot after i've got some saddle time - kind of tired of working on points for a while.

a 750 kit would be nice... might be a couple years down the road though.