Crooked engine ?

Back story: I had the bike ( 1970 Roadster with the centerstand on the frame) completely apart over the winter. Engine, gearbox, and cradle out. Installed new rubbers in the isolastics and a Dave Taylor headsteady with MkIII (?) style spring gizmo.

There is a noticeable amount of vibration up to 4000 rpm at least. Checked the clearence on the isolastics and it appears that the engine is leaning to the left. At the front, on the left, 0.010" at the bottom, tight on top. On the right 0.010" on the top, less than 0.005" at the bottom. Right rear is 0.005" at the bottom, 0.008" at the top. The ball end link in headsteady is loose when I'm sitting on the bike and tight when it is on the centerstand. Rear springs are set the same. There is no good way to quantify loose and tight with the DT headsteady link. And I have not checked the isolastics when I am sitting on the bike, but I suspect that they are tight at some point.

What do you think ? Grab the head and yank it to the right ? How can it be off ?

Greg

Are you missing the spacer on the right top side of the gearbox maybe?

EDIT=Sorry it is on the left side!

No, that's in there, but I did add a left side transmission adjuster.

Greg

FYI The engine is naturaly offset aprox 3/4", i believe this is to the left. I pulled my Dave Taylor type headsteady for stabiliy sake (no support for up and down movement). I got over a ton yesterday with plenty left. Solid, straight, and smooth with srock headsteady. DT steady in the ebay bin.
Verify iso numbers .010 total, .005 per side. Review proper procedures.

Its deeper issue than mere gearbox spacer, which would not bother
engine set anyway just primary and drive chain aligning.
I don't understand what you measured.

Isolastic rubbers with a side stand set might cause some L lean.
Some will just flip em over to even our cradle stance.

Unbalanced swing arm spring force might tweak engine-cradle L.

Cradles can get tweaked.

Of course frame tubes and tabs must be suspect too.

Might try a ride w/o the top link for more clues.

hobot

The vibration made me think that the isolastics were too tight. I had set them up for 0.008" - 0.010" off the bike. The bike has mostly been on the center stand since I put the new rubbers in.

When checking the isolastic clearence I measure all the way around the mount since I have never had a consistant gap. The bike was wrecked by the original owner (something about qualudes, beer, and a curb), but had been proffessionially (sp?!) straightened.

I'll try disconnecting the head steady, but it is loose with me sitting on the bike, so I don't think is is pushing the head to the left and causing the binding / vibration. The spring gizmo is supposed to take care of the up / down support. The isolastic rubbers that I removed had settled a lot (>1/8"), so I thought that the spring was a good idea.

Maybe I should be pulling the down tubes to the right...

Greg

pvisseriii said:

FYI The engine is naturaly offset aprox 3/4", i believe this is to the left.

Click to expand...

Its near 1/4" (6 to 8mm) is typical.

Mick

Greg, I need ya to figure it out and report back as I'm about to face
similar
but '72 Trixie factory head steady alignment is at least 1/4" to leftward.
[ok i'm in denial flash backs, more like 3/8" ugh]
I don't know its prior New Orleans history but do know it got clobbered
by a deer knocking it out from under me.

I almost couldn't get the front mount in d/t skewed and too close
together frame tabs. Banging wood in to spread and pry bars to ease in,
then cranked out the iso adjusters for average gap and it smoothed
out about as expected. Bind tension did transmit side/side combustion
issues like plugs or one carb gasket leaking etc, than a more true
Commando. But once all normal then felt just delightful.

I'll take the magic carpet ride over excessive speed handling.
Rod steady should be as you do it, ball end neutral loose slack
in road loaded state. BUT, if rod radius long enough it should not
bind on or off stands. Very interesting report to me thanks.

Double check the cradle, I may have skewed my first Combat's
rolling off a rear tire at a drag strip, straight up wheelie then
slam down on R side and me. The instant hook up as 2S cam
hit its 3rd piston kick in after 6800 is what I suspect jerked
cradle and even even cases to L and backwards, or CW facing
the drive side.

Maybe just too tight a set, so get too and give nice ride report,
as implies that's all I need do once assembly fight done.

hobot

How does the spring gizmo look? Equal tension/length on each side? This will show if things are grossly off centre.
When replacing my spring after the original broke i noticed that the new spring was tensioned noticeably more on one side than the other - looking quite lopsided.
I am sure this was not the case when i first fitted the DT headsteady but all had since been apart for frame painting among other things, and reassembled by a shop. Shortly after the bike was back on the road the spring broke. For a number of reasons i have not yet tried to sort this.

ML said:

pvisseriii said:

FYI The engine is naturaly offset aprox 3/4", i believe this is to the left.

Click to expand...

Its near 1/4" (6 to 8mm) is typical.

Mick

Click to expand...

Usually its closer to 3/16".

Have you fitted the front adjuster on the right (timing side) and the rear adjuster on the left (drive side)? If you have, then the next step is to check the mount itself. Remove the front isolastic mount, which is easy, and check the clearance all round on the bench. If the clearance differs at various points, then you know that the ends of the large tube are not flat and parallel with the hollow threaded tube to which the rubbers are bonded, and therefore with the adjuster. That might be your problem. If you have a lathe that will spin the tube, you can machine the ends flat. Otherwise, a machine shop will do this for you.

I know that old rubbers can deform, which can give a tight clearance at one point and loose at the opposite point. Since you have new rubbers, that shouldn't be an issue, although you cannot assume this with new replacement parts and you can visually check that the inner threaded tube is centred in relation to the large outer tube. In a previous thread, I mentioned getting a new rear isolastic mount with a threaded tube which was way too sloppy for the engine bolt. I had to make a sleeve so that the bolt fitted snugly. If both your new mounts are sloppy, this might allow the engine to twist off-centre slightly.

I believe the problem is a bent frame.

1) jacked the bike up by the lower frame rails (both 8 3/4" off the floor).
2) hung a plumb bob from the center of the steering stem.
3) put a strip of masking tape across the frame tubes just above the front engine mounting plates
4) put a strip of tape across the frame tubes just below the steering head
5) measured and marked the centerline between the down tubes
6) lined up string with top mark

The bottom mark is to the right (facing forward on the bike) of the string.

The diagram in the service manual makes it look like the steering head should be centered between the front mounting plates. That does not appear to be the case here. Different opinions ?

Greg

Greg,
You may want to try removing the spring and see what the vibration is like without it. Also check if that has any affect on canting the engine over to the left. Did you slather up the rubber parts of the iso's with silicone lube? It makes it easier for the iso's to center themselves in the tube. The tube may not be square at the ends and the end caps can wear unevenly on the outer surface and where they touch the tube on the inside. You can check the clearances top and bottom after spinning the caps 180deg and see.
P.S. Did you mount the spring before or after setting up the headsteady linkage?

If you left the silicone grease out get a spray can of the stuff for sunroofs , door seals etc and spray into the isos with the sideplates off, it will work its way in once the engine is running.