Topic: pulling to the left, bent frame or messed up front end??

[ntm1974]

I picked up a 72 cb750 that is in pretty rought shape.  It pulls to the left pretty hard when I take my hands off the bars.  The front end looks messed up for sure which is ok because i was planning on replacing it anyway.  However, before I sink a decent about of money into the bike, I'd like to make sure the frame is straight.

I have the frame completely stripped and was hoping that there is a way to make sure that the frame is straight before going any further.

Any ideas?

[Frostyboy]

I found this using the search function http://forums.sohc4.net/index.php?topic=41557.msg428652#msg428652
I'm sure you'll find more if you have a good look around.
btw: did you happen to check the rear wheel position before you pulled it down? Maybe the back wheel was in there crooked to start with.
Good luck, I'm sure you'll get more responses, 

[KingCustomCycles.com]

Look the frame over for obvious kinked tubing or dents.  Since the frame is stripped, place it on a workbench and level the top frame members under the seat.  You can then measure the neck for misalignment.  Honda frames were seldom spot on from the factory but it should be close.  Post pictures of anything you suspect is not right here. 

[dtmmil]

I agree with frostboy, did you check to make sure the rear tire was straight? If thats off a little it will pull one way or the other.

[754]

Start at the front, check forktubes (out of the tree) in 2 or more places.. with straightedge or each other.. check once then turn 90 degrees.
 Quick check of the frame..eyeball the two front frame down tubes, from the side, see if they appear even.
 Look at the forkstop plate on frame, is it damaged.

[TwoTired]

I agree with frostboy, did you check to make sure the rear tire was straight? If thats off a little it will pull one way or the other.

+1
I like to start with the simple things first.  If rear wheel isn't in alignment then bike will always want to turn.  That's what those axle adjusters are for (beside taking up chain slack).

Cheers,

[ntm1974]

I'll preface this by saying that I have no idea of what I am doing of if this is an acceptable way to do this:

I put a 4' level on the frame going from left to right.  I then put a 3' level on the steer tube and made sure that the levels were parallel.  The steer tube showed slightly out of level, pictured in pic1.

I put a level on the rear swingarm also showed slightly off. Pic2

I also checked the downtubes for damage and didn't see anything to bad.  There were symmetrical indentations that look similar to my 76 frame damage that occurred when someone torqued down a crashbar to hard.  I put a straight edge on it and it didn't look bad Pic3

Do you guys think the amount the frame is off could be causing it to pull hard to the left?  Is there anything else I need to check or a better way to check for alignment?  Thanks for looking.

[KingCustomCycles.com]

Those level indications are slight, and could be just errors in parallelism or tool alignment.  Crushed downtubes are common for the reasons you mentioned.  Usually the neck is checked with a long rod centered where the steering stem would rest in the neck and the frame leveled.  Plumb bobs can be dropped from each end of the rod and then compared for alignment with the frame.  If it is twisted, there will be some wrinkling, dents, or twists, however subtle, somewhere.  Wrecks normally produce a center of impact with twisting stretching or crushing of the surrounding area.  Did you hold the handlebars lightly when the bike pulled?  Some riders have a tendancy to try to pull bent or twisted bars straight, without even realizing it, thereby introducing a pull. 

[754]

pull the forks out of the trees, takes 30 seconds to check them against each other, and to see any bend..