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Lord Gruntfuttock

LG's 1985 Yamaha TT250 Thumper

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So despite having no money, multiple other projects, and house renovations to finish, I bought this recently, a 1985 Yammy TT250.
Was watching a few old trailies on the tard when this one didn't sell, and he offered it at $350. Was local so I immediately pulled the trigger knowing nothing about it.



Good things: it's a new bike project :)
Plus, they're a decent old model, all plastics are there, overall in not bad shape, throws a spark, and suspension seems sound. Also eligible for VMX racing I believe...
Bad things: front wheel fucked, seat cover ripped, no idea on condition of motor (has a patched hole in cyl head) front brake needs work, some plastics are cracked, and not a Honda (purely for parts availability)...

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So, teardown and bagging things as they come off, fairly straight forward, noticed a few frame tabs missing and cable ties holding things together, and seems to have compression (of a sort).



Managed to get it in bits and dispersed around the place pretty smartly to conceal purchase, and once down to the frame got the welder out for some patching. 



Bit hard not knowing what the missing bits looked like, but got there by looking at frame pics on the interweb. Plan is to get it blasted and spray with Durepox red epoxy  as I have a tin of this left after doing up an old kids bike. Paint means I can make repairs/touch up when required rather than make sure all is perfect before powder coating...

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The front caliper pistons were stuck. Really stuck. And because it is a pretty model-specific caliper there weren't many around.


After compressed air failed I looked at swapping to another model caliper, then thought bugger it, nothing to lose, so drilled and tapped an M10 fine thread bolt to take a grease nipple,  screwed that into the banjo bolt hole, then used a grease gun to push out the pistons (can get thousands of psi).  Worked a treat... :thumbleft:





Some notes, pump grease through with bleed valve open to displace air first so you don't make a brake piston slug gun, and retain each piston with a c-clamp as you ease them out in turns so you don't blow one out and lose all pressure... Worked really well, would use this method again - cleaning out old grease was the biggest hassle, but Brakleen was half price at supercheap... :)

Anyway, pistons cleaned up ok, and bought new caliper seals and a used master cylinder on eBay. Toyed with a cheap universal m/c but found the correct model for $24 so grabbed that instead. And now the waiting for parts begins...

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Typical old trail bike, lots of bits missing or bodged, so tidied it up a bit...



Just made up replacement tabs and welded them, then welded on captive nuts and tidied up some previous repair work...






Will take for blasting next week and throw some paint on when weather allows...

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The kickstand hole was flogged out, hate a wobbly stand so I cut a plug out of some 10mm waste, chamfered both sides and welded it in place. Used a hole saw so there'd be a hole bang in the centre for drilling out to fit the pivot bolt...



Bloody pleased with that weld, nowhere near as much grinding req'd as normal.  :)

Then realised I didn't have a 14mm drill. So ground down a stupidly large drill bit I had. Test drilled a piece of alloy and it seemed to work ok...


And it's round again. Slightly undersized hole so will  test with the new pivot bolt I've ordered, and ream if required to make a neat fit...


And drilled the cross piece I welded in earlier (I realise there's one less hole than there should be). Now frame should be ok to get sandblasted...


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Frame went to be blasted yesterday so I looked at carb last night. These use the Yamaha Dual Intake system (YDIS) essentially a vacuum secondary, and theory is that from half throttle the secondary carb opens up. Unfortunately they are a weird Teikei model and not easy to get bits for.  This view is from the engine side looking out...

Looking at the port colours it seems the secondary side may not have been opening too well...? 

Toyed with replacing whole carb but no real information on any bolt-on options, and can't be arsed working it out, so decided to give this one a clean and see how it goes (ordered a simple gasket, o-ring, float needle kit). Pulled float bowl and doesn't look too bad, have definitely seen worse...

Separated the primary and secondary sections easy enough...

And got the pilot jet, main nozzle, jet, and pilot screw out ok, although the float needle seat doesn't want to move, didn't want to force it till replacement arrives...

Main vacuum diaphragm looks ok...

As does the enriching system diaphragm...

And the drain plug on the secondary was a right bitch to get off. Didn't want to file flats in it as these are unavailable, so gentle heat, a bit of tapping and the right sized screwdriver got it out (don't think it has ever been off, looking at it). The main jet however will be a problem. Hit it with lots of spray and tried unscrewing it, felt and sounded like it was coming but when I looked I had just twisted the head slot off. Bugger... :(

Think these are #136 sized too for this model (looks a fairly big hole) and none of these seem available. I've ordered a 120 and 125 so at least I'll have something to put back in if I manage get it out. The nozzle behind this is unavailable too (naturally) so will be a bit tricky. I can see an ezyout being carefully used trying not to fuck anything...

And at least I can clean up all these bits to get ready for reassembly while I wait...

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Wheel bearings...

Was really struggling to get the rear wheel bearings out, I usually manage to tap them out with drifts I've made up out of big old screwdrivers, but these ones refused to budge, and I had bugger all lip to drive against. Looked at blind bearing pullers (spendy)  then realised it was a 20mm bearing, so tried a 20mm dynabolt...

Worked a charm. Just inserted bolt, tightened the nut to expand it a bit, and bosh, one smack on the other side and bearings popped out on the ground. Great result for a tool that cost $7.42... :thumbleft:

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Nice love a good quick progress build. 

I sent a few emails to mikuni oz re carbs and the man there has a wealth of knowledge. Might be worth having a yarn with him about replacements?

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It's the twin port and airbox setup that worries me if I changed carbs. Think there is a Kwaka set that fits the 350? Really cant be bothered setting something new up.

Had a go at drilling out that jet tonight, need a M8 x 1.0 tap to run thru it to see if I can clear the remnants and recover the nozzle. Trouble is I can't tell where the jet finishes and nozzle begins so don't know how deep to go.

Good news is I scored a damaged 250 carb on Aussie eBay so should get something sorted...

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So picked frame up yesterday and warm today so thought I'd get some primer on at lunchtime, which was a bit optimistic. By the time I'd found everything I needed I had to get back to the orifice. Also, my hardener had, well, hardened, so had to grab some more on way back thru town...

Still, managed to tidy up some old and ugly repairs that were noticable with the paint off, will try to get some colour on it tonight while weather is cooperating... 

And wife away so can use handy backyard rotary frame (prob should take washing in first). I'm sure the kids can feed themselves while I'm chucking paint...

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And got a coat on after work,  the durepox sticks bloody well, I'll just put a few coats on and see how it goes as a top coat. It's only a trail bike, will just touch up as it get dings and scrapes.
And frames are buggers to paint, all nooks and crannies. Balanced it on the old cable drum and did the under side before hanging up to get the top and sides done...

And it's red again. Not a bad match for the original colour either... :)

That's a win, always good to get paint on a blasted surface asap, hopefully I'll get another couple of coats on tomorrow and it'll be all good to start putting bits back on...

[edit] and finally mixed just the right amount of paint, usually run out or have far too much. Made up mix to150mls then added 20% reducer to 180mls. Almost the perfect amount...

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Misc parts 

So this model was a bit obscure, seems most of the world had the  SOHC TT225, whereas Aus/NZ/Japan had the DOHC TT250, similar to the 350/600. Aussie websites have part number listings for the 250, appears most chassis parts seem interchangeable with the 350, the SRX250 used the same engine, and many parts appear to be common with the XT. So I've ordered a bit of gear from all over the place - gaskets, grommets, sprockets, etc, plus a clutch cable from Aus, and assorted missing/worn bits. Surprisingly, Youshop works out ok when you're buying a lot at the same time, a large consolidated package costs around $40 delivery, which isn't bad for 12-odd packages...

Swingarm seems in pretty good nick so far (haven't looked at bearings/bushings yet) but the plastic chain guides need replaced and are hard to find/$$$. I found an entire swingarm on eBay for $39 with all plastics on it, so bought that and was $50 to forward it to NZ (not too bad). Looks pretty good and the plastic parts are in great nick...

Wheel = well poked, obviously split externally but was amazed at the corruption inside after I finally wrestled the old tyre off (was hard AF)...

Tried to get all old spokes out in one piece to re-use if possible and was going really well using sprays and heat (plus a good spoke spanner) till I snapped one, so gave up and grabbed a new spoke set. Then after looking at what was available locally I bought a 21" rim from Aliexpress, will see how that goes after it arrives and I lace it all up...


Some parts are stupid expensive or unobtainable, so looked at what I could use instead. The rubber cap on the steering stem will keep water out, so after a measure up I found rubber bike bar ends will fit, 83c on Ali for 2... :thumbleft:


A rear fender tool bag would be nice to have, but I'm not paying $50 for one. Found this though, a red cosmetic bag the perfect size for $12 from Ali. Just have to remember to replace the lippy with a plug spanner... :)


Ordered a full set of brake pads (Fr and Rear) for $22 from Ali, and high capacity Koyo headstock bearings from eBay. You can get cheaper bearings but they're something I don't mind spending money on. Bought a seat cover and bash plate on tardme, and this spare parts carb from Aus, looks to have the bits I need...


So doing what I can while parts are in transit, hopefully it won't get parked up (like other projects) and I'll get it running reasonably soon to hoon. there's quite a following with old dirt bikes now and they seem to have some good runs...

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[Now with added two stroke]

So was trying really hard not to get distracted, but heard of a bike run coming up and since the TT won't be ready, dragged this old girl out of the shed, a '74 TC100. Had it for years, just been sitting there unused and thought it'd be a hoot to ride. Bloody thing burst into life on third kick... :thumbleft:


And a test run round the block indicated some issues, wouldn't get past 72kph, and was hesitant on acceleration, so ripped into a cleanup/service.
Plug was wrong type but was a good colour...

Pulled oil tank and carb. Discovered original tool bag and spare fuses all there...

Drained watery old trans oil and put fresh stuff in...

Carb looked bloody clean, but disassembled, cleaned and blew out passages anyway. Discovered there was no spring on the pilot screw and the whole carb was a bit loose on the intake. Bodged a spring, set float level and reassembled/installed...


And also cleaned/lubed the throttle and choke cables, and cleaned old oil tank. Hope to take for another run this weekend to see if it goes any better...

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