Stretched/ovalized head tube

eng2007

eng2007

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So in finally getting to my neglected 85 GSXR750 project I've been on a path of bad news since I started tearing it down: Broken lower engine mount, engine-mounted oil line leak (that can only be serviced with the head coming off), stripped countershaft sprocket nut threads, and a whole whack of other PITA, but more manageable issues. This brings me to the least managebale issue: the head tube. After pulling the front clip I happened to touch the top bearing race and to my amazement it spun freely in the bore. "Wow, they must've done things differently back then" Im hoping to myself and then I lift up on it and pops right out and falls on the ground with the most dreadful ringing sound Ive ever heard.
Upon inspection, the head tube is ovalized - big time. I can physically move the race about 5mm backward and forward in the frame and it fits snug against both sides - clearly an epic front end impact (this bike has more rash than reusable Pampers). What are my options? Can I use this frame (its meant for the street)? This project is now fenced on this frame being usable.
Also, assuming theres a solution for the steering, can someone recommend an aluminum welder? I would like to take the frame and the engine mount bracket prepped and ready to weld and get some nice quality TIG beads on there.
Sorry about the lines, my Enter key does not seem to be creating new paragraphs.
 
Yes it can be used. I had a similar problem from a previous owner of one of my bikes. What I ended up doing was machining an insert to remove the play and then TIG welding it in place. It worked and held up for 3 years of track abuse (I inspected it after each session because I was paranoid).

That was when I had access to a full machine shop to play in. I can not recommend a place to do it for you :(
 
Or have the ovalized secion welded top and bottom, and then machined to be round again to pop the bearing races in.
 
The correct fix would be to replace the steering head tube.
It is a simple, but time consuming process IF you are equipped to do the job.

Talk to Denis at CMR racing. He has a frame jig and the necessary experience to do this job.

It is actually easier to replace the head tube than to repair and align bore it... even if you do have access to a machine shop.
 
As much as I would like to implement a proper, longterm fix, it just isn't in the cards for this build. Theres too much to do as it already and I don't have the budget for all the fab and welding.
What I was thinking was this: Years back I drive a forklift in a an old warehouse. Whenever the very smooth concrete floor would chip they would come back and fill it with some sort of epoxy resin-type stuff which would take, literally, tons of abuse from forks and pallet jacks every day for years. Would I be able to drop in a new bearing race, clamp and wedge it against the 'good' side of the steer tube and fill the gap with some magic filler?
 
I wouldn't. The (hardened steel) bearing race is meant to be a surface load against the (aluminum) frame. Awkward-shaped spacers jammed in there to take up the gap will act like point loads (stress concentrations), and probably do more damage.

Do it right, or don't do it at all. If you can't afford to do it right, wait until you can.

Talk to Denis at CMR Racing about your situation. Get a cost estimate to see what you are in for.
 
If it were me and I really didn't mind cheesing it - I'd drop new races in and then use tapered bearing drivers top and bottom pulled together by threaded rod, very tight. Then gently beat the aluminum back to the races. Then cut out rings out of aluminum plate using hole saws to suit. Tap those around the outside of the race holders. Have Professor stitch weld around underneath. I've never done this, just putting myself in your shoes.
 
from all the repairs required you listed, this is the one that could produce a speedwobble and put somebody into the buckwheat, at high speed. Sloppy head bearings are not good, i'd park this thing till its in the budget to get it fixed (properly)
 
Let me elaborate on my quick-fix idear with the some visual aids. As I understand it, the idea with steering bearing races is that theyre a tight, friction fit so that theyre preloaded against the frame to efficiently transfer steering/braking/wheelie forces to the chassis. To this effect, the races need to be held tightly by the steer tube and aligned with the rest of the frame to maintain the intended behaviour dynamic. In this case I have a reference point; the back of the steer tube, which would have been unaffected by the accident. Looking at the bottom race (not pictured), the bearing is held firmly in place and the offset is equal all the way around ie no damage.
What I want to do is preload this top bearing race against the back of the steer tube with some clamps and fill the gap left by the accident with some very hard-wearing epoxy. The filler would flow into the cavity and take up any remaining space between the new bearing race and steer tube. After it cures, the clamps would be released and you would have a preloaded bearing race set into the frame, ready for the stem.
irst two photos show the bare stem, third has the bearing dropped in showing the gap caused by the stretch.


 
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That looks a lot less than 5mm stated earlier. Anyway, the epoxy idea has some merit but with the clamping it's a one shot deal that the race will be perfectly circular. I'd think that be important. Maybe using an old set of tapered bearings top and bottom held tight by long bolt would help there also to keep both races square.

Another option, in addition to epoxy might be drilling and tapping small set screws.

edit, I glued a wheel bearing into aluminum hub years ago. Never had a problem with it. Can't remember the product.
 
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Let's make this simple.
Suzuki thought there was going a large load transmitted into the steering head. This is evident by the mass of metal around it... and the distortion you gots.
The 10mm of aluminium that Suzuki gave you couldn't take that load.
There is no glue available to us mere mortals that will take that load.

Your problem now is that the metal around that bearing cup is stretched, at the molecular level. When the metal is stretched like that the metal is weakened. To fix it you have to change that metal at a molecular level, by welding it or replacing it. Those are your only real choices.

Take a step back and think about this for a minute; Do you really want the steering of your bike changing geometry at speed?
 
Brian P said:
I wouldn't. The (hardened steel) bearing race is meant to be a surface load against the (aluminum) frame. Awkward-shaped spacers jammed in there to take up the gap will act like point loads (stress concentrations), and probably do more damage.

Do it right, or don't do it at all. If you can't afford to do it right, wait until you can.

Talk to Denis at CMR Racing about your situation. Get a cost estimate to see what you are in for.
Click to expand...

Yup Denis is your guy. Nice man he wont bite,
 
I would weld and re machine the bores, or I would also try making a hardened steel sleeve. I would re machine the bores large enough to make them 100% round again, then make a sleeve that presses in, then the bearings press into them

Your neck tube is part of an aluminum cast section, so people suggesting you cut off the head tube and weld in a new one are not taking that into account, its not a simple neck tube that can be turned out on a lathe....

So your best be IMO is to repair it with a sleeve or welding and re machining. Or get another used frame with good neck race bores and use that

People may question that fix, but I have done it with front wheels that needed larger bearings for them to fit another bike....And I have been able to successfully rebore them dead center.
 
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kneedragger88 said:
Yup Denis is your guy. Nice man he wont bite,
Click to expand...

That's for sure. Had a great chat with Denis early December when I dropped my old BMW frame off. He's going to do some fairly extensive mods. When I left, I knew it was in good hands. A good feeling.
 
It turns out that I have a VIN ending in ...100030 on this frame. I am currently corresponding with Denis.
 
Looks to me like you have a nicely cold forged (pounded) steering head. Consider what that did to the aluminum, and surrounding area, joints, etc. Also consider that welding introduces even more molecular stresses. Next, consider what your life is worth, if something unforeseen lets go at the right moment. I've been a steel mill machinist a long time, in my opinion a safe repair in that area would be very extensive, and should include an engineers advise.
 
I wouldn't reccomend sleeving this to correct the ovalization.
You will correct the dimensioanl issue. But you will end up with a weaker head tube.
There will be less material holding your sleeve.
I woruld reccomend either a weld repair to the existing bore, which may/not be practical.
Option 2 is a new head tube welded on.
 
Brian P said:
Talk to Denis at CMR Racing about your situation. Get a cost estimate to see what you are in for.
Click to expand...


That's good advice. Just a heads up for anybody interested in frame work, I put a CMR review into the Review forum.
 
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