Loose top headset cup
 

Hi,

Recently bought an old MBK super sport on ebay and am fixing it up to teach myself bike mechanics. As I took the forks off the bike the top headset cup came out without any force - is this normal? I thought they were a tight fit and had to be hammered out. So my question do I need to replace this or is it not a problem. Sorry for my ignorance...

Thanks in advance,

Martyn

The cup coming out would be very unusual as yes normally they are hammered out and pressed in-- not talking about the upper race that spins down onto threaded fork are you? If the cup did just fall out check to see if any damage to headset or tubing and you may need to buy another headset to get a correct cup. Pictures always help.

No, definitely the cup that came out. I will order a new headset. Can't see obvious damage. I'll try and upload pics (I'm on my phone right now and can't see how to upload)

Martyn

Assuming it's a pressed headset and not some kind of integrated version, a cup simply dropping out is less than ideal. But it isn't all that rare on used bikes because of things that can happen.

The most likely (and best from your standpoint) possibility is that someone used a JIS 30.0mm cup in an ISO 30.2 headtube. That's an easy fix, get the right headset.

The other possibility is that the tube is oversized. If it's now JIS, ream it properly to ISO (both top and bottom). Otherwise, the tube can be "shrunk" by painting the inside. Nail polish works fine for this. There's also a bearing-grade Anaerobic (Locite) that swells as it sets, made specifically for this kind of thing, but it's pricey and overkill for one time use. Over the years, I've had very good results with paint or nailpolish.

http://bikeforums.net/attachment.php...hmentid=379078http://bikeforums.net/attachment.php...hmentid=379079

Here are some pics. The paint inside the tube has worn away which could make a difference. My calipers tell me that the cup is around 30.1 mm diameter. I have ordered a new headset from wiggle and will look into adding some varnish.

I plan to get the frame shot blasted (£10 by local company) and then I'm going to respray myself.

Thanks for the helpful comments - a very friendly forum...

Martyn

Don't do anything until you have the new headset. 30.1 is an odd size, but I suspect it might be JIS, and the new headset will fit fine. If so, then mask the inside of the tube if you're painting it, so you don't have to ream out any overspray.

OTOH- is the new HS is also a sloppy fit, don't mask when you paint and the overspray will be your friend.

Thanks, I'll let you know how it goes