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Biggest reason (I've found) for inherently stable bikes - like RD's - to 'wobble' when getting light in the front end or the wheel coming off the ground at speed is improper rear wheel alignment. When the wheel comes down full force it tries to align with the rear and is snapped one direction or the other until the two wheels are playing as a team again.

The list of culprits can be anything from worn swingarm bushes, loose rear wheel bearings, loose steering-head bearings, cupped front tires, or improper chain puller adjustments. Checking bearings and bushings is done static, but since I've found adjuster hash-marks that are off, I check alignment at speed - get your body as straight on the bike as possible and let go of the bars; if the bike goes perfectly straight alignment is good. If the bike pulls to one side, move that side adjuster back until it tracks true. If the hash marks are in fact off, remark the puller to match the opposite side.   

Since your wobble went away toot-sweet, it sounds like an alignment issue; most wobbles don't resolve on their own and often get worse, until you get the bike slowed down. Worst wobbling vintage bikes I've found to be short-frame BMW /5's, especially with handlebar fairings; they wobble easiest when the front tire cups - I've has some frightening tank-slappers on Beemers, but so far have never been spit off - 60 years and counting! 

Warren

Thanks for all the encouraging replies! Luckily there were no real stoppers, just lots of challenges.

I did submit a request for one of the Rubbers Kits, but was rejected even though it was one of the first received. According to the response, they made 5 kits but will only sell them to verified Japan resident owners. They were very nice about it though...

I failed to attach the picture of the tool to cut the clutch inserts to the correct shape so here it is.

Warren

Bottom end is done! The crank with new OTC main bearings and seals went together fine, with the drive side seal sandwiched between two main bearings (the outer oiled by the gearbox, and the inner by premix), and only one timing side bearing with the seal mounted in a carrier much like a YDS/TD. The bottom-end is all done and the cases are Yambonded shut. The gearbox was originally shimmed a little too tight - the synchro clearance in neutral  was 0.002" at the C-shaft gear, so was relieved of a few shims. Shifts like butter now!

Interesting that there are no Phillips Head screws anywhere on the motor or chassis; all engine screws were Cheese Head. Even though the DKW RT125 they copied almost exactly used a center-case gasket. The actual engine case is slightly (maybe 5%) larger than the DKW; a DKW qasket set was obtained and the base and head were exact matches - the center case and clutch cover gaskets were too small. All tolerances and fitments were very tight; reminded me of the British.  

The clutch was a problem; the fibers welded themselves to the steels over the last 60 years, and was stuck into a big chunk. The disks had to be pried apart, leaving much fiber bonded to the steel faces. There were no equivalent fiber plates available, but luckily the fibers (48 cork inserts) were replaceable, like many British bike clutches from the 50's and older. Fortunately working in a British shop back in the 60's gave OJT to re-corking clutches. 

To recork, the friction disks were thoroughly cleaned and wire brushed, and a sheet of 4mm thick (0.3mm thicker than the originals measured) cork was obtained to cut the inserts from. The inserts should be 1mm oversize/OD all around since there is no adhesive - tolerance fit. Make a metal template on a stick to use as a pattern , then cut the pads (48) out with a utility knife. Cut the pads slightly larger than the template to allow for sanding the edges smooth and true; a flat sheet of 150-grit sandpaper taped to a board works well - match them to the template.

The inserts were then softened up for pushing into the holes by soaking them for about 20 minutes in near-boiling water (a shallow bowl in the microwave), 8 at  a time.  A bit of panache is needed, but after mastering the technique, they go in pretty fast. Bare fingers worked best (for me). Finally, sand the entire face or each side using the board and a metal disk to insure a full contact patch and solid engagement; when saturated with oil, cork glazes instead of wearing in.

Once complete, the corks must be sanded flat to insure maximum contact - same 150 grit flat sandpaper with the disk held true with a flat piece of wood; both sides. Sand until all faces make contact.

Warren 

To the vintage TZ racers, being competitive is of little consequence compared to actually being out there on their beloved machinery. The comradery among the vintageists is amazing. Chances are in the USA at least, a TZ750 rider is going to be the only 2T out there anyway.

When racing a vintage TZ in a modern class, the fun is surprising the modern-bike riders by staying with the front pack on that smoky old fossil!


Warren

Hopefully the buyer is a racer too; sadly (for us) Europeans are more likely to ride their vintage racers than we are.

Well, prices sure are not on the rise:

Hey SoCal250, sorry about the mis-directed accolades. I have found myself doing dumb crap like that too much lately ... as much as I hate to admit it, age takes a toll, and dementia runs in our family anyway    Thank you for the info, pics, and understanding!

I remember Kel from some of the major races in the Southeast region, but never dealt with him directly; he was wall-to-wall busy helping the expert class riders at Daytona and Road Atlanta, which were the events I saw him at in the 1970's. Never had much time for social endeavors back then - keeping my lowly RD's running at the track usually ate the entire day(s). I remember once at Moroso in West Palm Beach I lost a rod bearing, and changed motors between the heat race and the Final; the 'Consolation' race actually, I was way novice.

Which brings up an interest point - the age factor, not the bike. Too many of the 'senior' mechanics and racers I know have met their maker, and taken vast amounts of knowledge, experience, and stories with them. On too many occasions I have tried to connect with old friends and associates to brainstorm fixes, source obsolete parts, or just say hi, only to find out they had passed.

Racers Bobby Winters and John Buckner come to mind; Bobby (a 1960's Yamaha Works rider), and John (an Expert TD1 racer from the '60's), had some fascinating stories. Bobby, beat John (2nd place) in the 1966 Daytona 100-mile AMA Championship ... barely. Bobby admitted that even though he was on a Factory TD1, John's privateer TD1 was just a little faster, so required some finesse to cinch the win, by just a few feet:
John and Bobby swapped leads more than a dozen times during the race, but for the last few laps Bobby drafted John and resisted any passing attempts; on the last turn of the last lap, Bobby, who had been watching John's line like a hawk, sandbagged him, dove the corner, made the pass, and managed to stay ahead of John for the win. Bobby said if the finish-line had been 100ft further down the short straight, he would have been passed and lost. John is #155 in the Mag pic, Bobby #20. The 2nd picture below is Bobby Winters standing by the John's bike, 55 years later.

John Buckner has an encyclopedia of stories too; he was a fantastic story teller, and had a great sense of humor =) We had many conversations about the nuts and bolts of making  TD1's fast, but the race reports were the most fun to listen to. He told about how the Honda Factory team was always so secretive and protective of their bikes, but always had their nose in everyone else's stuff, so at a race at Willow Springs with his good friend and race buddy Tony Murphy (Yamaha Factory rider) pulling in the night before, they decided a little payback was in order:
They pitted right across from the Honda team who had left for dinner, unloaded their bikes, boxed them in with their vans, and covered them just like the Honda guys ... Except, before covering they tie-strapped 2 loose expansion chambers above the bike's pipes, and left just enough cover off the rear to see the 4 stingers; the Honda guys had a royal fit trying to figure out what the Yamaha guy had - they thought Yamaha gave Murphy some experimental 4-cylinder 2T or something! There was quite the crowd when they finally pulled the cover off the next morning, and everyone (except maybe the Honda team), got a big laugh because the never let on and surprised everyone with their fakery.

But time marches on, and takes so much history with it. Back in the 60's and 70's nothing much 'Motorcycle Racing' was documented except what made it into Magazines or newspapers, a few short film clips, and zero interviews. If it wasn't for home movies, even big races like Daytona went unrecorded - what's on YouTube is about it. The real stories are going away with the people who actually lived them.   

Warren

A friend of mine here in Phoenix is way interested; he repops and sells RD and CZ soft parts. If he buys it, he said I can use it any time =)

Preben, thanks for the location info and extra pics; nice to see the bike isn't in some black-hole collection never to be seen again. The chambers on the TZ750 were the among the earliest that Kel Carruthers (the designer and first builder of X-over pipes) made in 1975 for Mike Ninci. The silencers were installed in the initial build, probably because there were virtually no others available at the time.

I have previously had 2 other vintage 'original chambers' TZ250's with those VW silencers welded on, and also on the early (screw cap) TD2 I'm currently restoring, so possibly they were the least restrictive available early on (un-silenced TZs have claimed more than a few racers hearing, myself included). I'll post a picture of the TD2 pipes before I painted them when I find it.

Thanks again; I'll drop them a note and try to tag the owner - lots of history that never made it into the Iconic listing.

Warren
 

SoCal250: That picture is the TZ750A I sold through Iconic recently - Mike Ninci was the original owner. The lengthened aftermarket (unknown Mfg.) swingarm on that bike was very stout; the frame was reinforced too. Wondering where it went... where is that??

Warren

This is everything needed to go into the cylinder boring business, and a good price considering all the extras. Boremasters are the best in the industry :)

Boremaster Boring Bar Setup

Warren

Had an XT225 a few years ago - swore by it, not at it! Even rode it above the timberline up Mt. Adams in WA State - never missed a beat; no idle or jetting issues, even going 8K feet higher in altitude and into the snow.

Wondering, seeing you didn't have a chance to give it a good shake-down with the old electrics, could it be a timing advance issue? A hanging electronic advance curve (I think all XT225's go from 9 degrees retarded to 31 degrees advanced) can cause wonky idle and hanging low throttle RPMs.

Being an Early American and British bike enthusiast, many bikes I've had were manual advance, and for-instance my '27 Indian could be ridden using a static partial throttle (1/8 to 1/4), and rev from a low idle to in-town speeds using only the manual-advance twistgrip. My '53 BSA does the same, but not to such a drastic extent; kinda like what you describe.

Easy to check with a timing-light and it's probably just fine, but maybe...

Warren

Hi Preben,
Saw that - strange adjusters; the arm itself looks like a little on the light side. It'sa bit'sa for sure; 700 top end with replacement cases.
Warren

Deep pockets required:


Warren

RD crankshafts plus all the rebuild parts fit in a USPS Medium Flat Rate box: $18.50 'Click and Ship,' $21.05 OTC.