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I want to fit tapered steering head bearings for my narrow case Monza. I did a quick search on this forum about this procedure and the results were several years old...What are you guys using?...what's easy?...and what should I look out for?...

Thanks in advance...I'm not especially lazy...I just don't want to reinvent the wheel...You guys have already done that...

Mike

I made some taper roller steering bearing adaptors for a racing friend's single.
The pair were identical, but talking about the top one:
The lower part of it pressed into the steering head, as per the original bearing cup.
The upper part of it was dimensioned to house the TR cup.
The new bearings had ID to match the steering stem.
Holes were drilled in the adaptors to enable the cups to be pushed out.
I think the wall thickness was 3mm everywhere.
I doubt the modification made any improvement to the bike's handling, but it made servicing easier because the balls didn't fall out.

I picked this dwg from the web, long time ago. It's possibly helpful.

Hans

These are the bearings I used, with a built in seal. KOYO 32005JRRS Narrow Section Steering Head Set Taper Roller Bearing 25x47x15mm

This require machining facilities, as do Jordans suggestion.

The inner bearing races have to be bored to 26 mm.

I knurled the adaptors to simulate the original cones, also slots to facilitate bearing removal. Both yokes require a small amount of machining to accommodate the seals, and the frame head stock tube needs to be reduced by 3mm at both ends, to keep things at the original dimensions.

Hi Mike

Ducati uses a 26 mm steering stem . there are 2 tapered bearing that have a 26 mm inside diam .

Honda motocrossers like the XR 400 R uses a 26 / 47 mm bearing .
Ducati beveltwins and some belt driven camshaft engines used a 26 / 52 mm bearing

the drawing Hans provided is for the 52 mm outside bearing

both size bearings could be found on E Bay fairly cheap .

Eldert

Hi Eldert, thanks for flagging up the 26mm stem, it was quite some time ago now when I did the conversion, and I had totally forgot I bored the inner races out to 26mm. (Tempus Fugit) I will update my post.

Thanks to all of you guys for your information and input. I know more than I did before, but it is clear that there is no easy solution. Every solution requires machining and I'd just as soon avoid long discussions with machinists who have no idea what they are looking at. It looks like cups and balls at this point...I'm sorry that I can't machine stuff...just another failure of my Catholic education!!

Thanks again for informing me.

Mike

Hi All,

I wasn't sure whether to start a new thread or revive an old one but I figure the questions continue on from this thread...

I'm working through upgrading my rolling stock on what started as a Monza Jr 160. I've got a Honda TLS Hub, 18" Akront Rims, Stainless Spokes, Avon RoadRider tyres, Marzochi 32mm forks (That are currently too long but I will cut down in time) and yokes from a Benelli I think - took a lot of modifying in the end, and new stainless wheel spindle I finished making today in the style of the original.

I'm now at the stage where I need to make this setup fit the frame, I'm going to go for a taper roller setup and I now need to make a new stem to suit. From the outside it looks like the headstock is about 138mm long and from the drawing ducwiz kindly shared it seems that the inside diameter of the headstock is 38mm. Can anyone confirm these dimensions so I can finalise my design in CAD without striping the front end off my bike?

Thanks very much

J

Hi I am in the process of fitting the same fork type to a 250 Monza frame, the ID of the headstock is 38mm but the headstock length on my frame is 145mm so obvious difference with the 160. Did you manage to find new seals for your forks ?