FZR Bits on RD

teazer · June 13, 2026, 05:02:30 PM

Did someone mention TZ top ends on air cooled cases? Back in the day, TZ cases used to wear out and replacements were not always available, so racers took to modifying RD cases to take the TZ crank arrangement. Others bougt TZ top ends and fitted them to RD bottom ends.

This is a set of RD cases with a TZ crank and water pump with RD400 transmission and 40900 (64mm bore) top end with bigger reeds. 40970/40971 66.25 TZ750 C/D/E top ends also drop straight an to an Air cooled bottom end.

I forgot how to insert and image. I'll be right back as soon as I work that out.

teazer · June 13, 2026, 05:08:05 PM

I worked it out

SmokeAddicted · July 27, 2026, 06:03:22 PM

Swing arm swap is complete. Now I'm onto contemplating the front end.

Apparently I was incorrectly under the impression that All Balls offered a "kit" which included bearings, seals AND spacers for a triple clamp swap. Apparently, they do not offer spacers, which now has left me to using a machine shop to press the RD stem into the FZR lower triple.

Did All Balls ever offer a complete kit with spacers for front end swap? I swear I've heard of these kits (with spacers) existing in the past. I also have a buddy that says the same.

mlakritz · July 30, 2026, 12:13:14 AM

So Cognito Moto did a '07 R1 triples conversion for me that included a new stem and the tapered all balls bearings after sending them the lower triple and it bolted right up, perfect fit using all the original R1 hardware and cost very little, just $250 since I supplied my own triple clamp. Side benefit with the R1 front is the gold forks look killer with the original RD paint.

I'm putting on a 2011 FZ6 swingarm (sitting on the work table with some blue masking tape on the pivot tube) for a monoshock conversion, which requires a bit more hacking and machining but it will be 2" longer than stock and have the same wheelbase as a 2008-2025 CBR600RR. So Smoke, you must be using an offset front sprocket to align with the FZR rear, what or who is helping with that? The guys at sprocket specialists said they won't build a tool for a one off but they didn't totally rule it out either. Fast from the Past does 10mm offsets for the RZ350 but I can't find any for the RDs anywhere so I'll probably have to go to one of the many expensive aerospace machine shops in my hometown (Boulder, CO) who can scan the stock sprocket and produce whatever I need but they are expensive AF.

rodneya · July 30, 2026, 12:51:26 AM

MJ Corse will make custom sprockets

mlakritz · July 30, 2026, 12:57:59 AM

Quote from: rodneya on July 30, 2026, 12:51:26 AMMJ Corse will make custom sprockets

Wow, yes they do for pretty much anything. Thanks rodneya, that's quite the resource.

1976RD400C · July 30, 2026, 08:49:07 AM

Back in the early eighties, when pistons were readily available at the dealer for $29, some people went "big bore" with 66.4mm TZ750 pistons. There is no restriction at all as it inhales.

Dvsrd · July 30, 2026, 11:12:02 AM

Quote from: m in sc on June 02, 2026, 10:26:41 PMi still have it. the stem is the right size but too long. swap the rd/fzr stem, mod the steering stops and its good. the forks stick up about 2" thru the tree. however, theres a year or 2 fjr 600 fork tube that swaps in thats shorter. i have those in mine but can not remember the year

Shortening fork tubes is pretty straightforward. Cut off the excess at the top, then into the lathe for machining and single point threading.

m in sc · July 30, 2026, 12:14:02 PM

and recess for the o ring, etc. hard to find a shop here to do it. i can do it and it was easier to find different tubes

Dvsrd · July 30, 2026, 12:38:32 PM

Quote from: m in sc on July 30, 2026, 12:14:02 PMand recess for the o ring, etc. hard to find a shop here to do it. i can do it and it was easier to find different tubes

I never did that on FZ/ FZR fork tubes, but did it on a pair of extended ("chopper") fork tubes for a 72-76 XS 650, for use on my RD. And on a Suzuki GN125 that I modified to a more "standard" stance. Both were straightforward, since the O-rings were in the top plugs.

m in sc · July 30, 2026, 01:07:15 PM

not everyone has access to a lathe.. 0.02. easy is relative especially vs paying somebody to do it vs buying a set that fits. im just saying...

SmokeAddicted · July 30, 2026, 07:55:05 PM

Mlakritz, I paid very handsomely for a German manufacturer's piece. Rebel Gears out of TN that said he has a 15T but also seems like he was open to running a batch.

I had a hang up with the German sprocket, but the guy took care of it for me. In fact, I didn't even have to adjust the drive side wheel spacers at all. Bolted straight up after modifying the caliper bracket.

Thanks for the tip on Cognito. I wouldn't have imagined only $250. This may be a viable option.

News:

FZR Bits on RD