OzVMX Forum
Marque Remarks => Yamaha => Topic started by: Nathan S on January 20, 2010, 04:53:13 pm
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Not that this is a super rare or special rebuild, but creating a blog-style thread seems to help me stay focussed.... If it bores you, then fair enough - just ignore this thread!
I bought a pile of MX250 and DT250 stuff from JimG in the second half of last year. After selling off some stuff, I reckon the remaining pile owes me around $600. The contents of the pile werea bit random - there was a correct MX-A rear wheel (with Mudcatcher rim), but two incorrect front wheels, for example.
The pile was ignored for several months, until I got sick of stepping over it. So rather than try to find places to put about 2.5 bikes worth of bits, I figured that the easiest way to get rid of the pile was to turn it into a bike.
The philosophy has been to make a solid, race worthy bike for as little money as possible.
The motivation is a mix of things - first is that as a kid with a DT250A, I always viewed the MX as some sort of holy grail (ha!) so buying the pile of parts was satisfying a nearly-20-year itch.
The second part of the motivation is that I'm building a 74 Montesa Cappra VR250 race bike - there's no doubt that the Cappra will be a much better race bike, but its also costing me enough (in both time and money - I want it to be 100%) that I'm not sure it will make it to the 2010 VMX Nationals. So the MX250 is a project that I know I can finish in time.
The final thing is that with the Montesa owing me so much money (by my standards anyhow), and the relative difficulty in getting hold of parts like pistons, that I'm feeling reluctant to thrash it around at every VMX club day - I suspect that I'll try to keep it nice for the big events like the Crawford River Classic and future VMX Nats.
Work so far:
I've stripped the frame back to bare metal, welded up a small crack, and paint it with (quality) aerosols:
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan20-10Camera003.jpg)
I was 95% of the way through stripping the frame when I discovered the crack. I was literally thinknig "Jeez, this frame is awesome - dead straight, no cracks, no rust, and... oh..." when I saw it... :D Still, easily fixed!
I pulled apart the rear wheel, and gave the hub a clean and light polish. For such a scabby looking wheel, it came apart beautifully and had no dramas like flogged out bearing holes.
The Mudcatcher rim was replaced it with a non-catcher rim that I had. And the spokes were painted black. All of this made the rear wheel match one of the front wheels which I'd built up several years ago before selling it to Jim in another deal... :D
It still needs the spokes tensioned and the wheel trued, as I greatly prefer to do this in the bike.
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan20-10Camera004.jpg)
Lots of other bits have been bead-blasted (there's a decent sized blasting cabinet at work, and rather than sitting on my arse at smoko/lunchtimes, I make use of the workshop). Some of these bits can be seen on the ground behind the frame in the frame pic.
Last night, the re-assembly began:
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan10-20Camera001.jpg)
Tonight, I'll refit the swing arm, and finish building up the rear wheel.
Maybe start bogging up the fuel tank.
The tank was a freebie from Vandy, before I even bought the pile of bits... It was suitably rough, with lots of bog and a few rust holes. I attacked it with the MIG welder and is now watertight. In keeping with the low-cost philosophy, it will remain full of bog. :)
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan10-20Camera002.jpg)
Costs so far:
Pile of bits $600.
Seat $50 (purchased long ago in the vain hope it would fit my RT1).
Paint $50 (all aerosols! A local hardware store is closing down and has 20% off everything).
Bars $50 (purchased long ago because a pair of quality alloy bars can always find a bike to be fitted to).
Grips $15.
Killswitch $7 (inc postage - I bought a dozen when Ballards were selling them for $6 each).
Filter foam & glue $20.
Fork seals $24 (no oil in the forks yet, so that's why its not on the list!).
Rear wheel bearings $15.
RHS side cover $20 (bought from Betric years ago, just because).
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Engine bearings and seals $60.
Other stuff that you'd expect to pay money for (like the very good front tyre), was a freebie from a mate. There's also a lot of new nuts and bolts on the bike, because I have a very cheap supply. ;)
I'm hoping to have it on the track for under $1500, but that will depend a lot on what I can manage for rear shocks.
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Hi Nathan,
What did you use to clean up the hubs, or did you blast them?
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Blasted, then some 180 grit Wet & Dry to get rid of the nastier casting marks, and then 240 grit W&D, and then car "Heavy cut and polish".
The intention was never to bring the wheels to a mirror finish or anything - just to make them like new(ish).
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Thanks for that, they come up well.
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mine owes me about $1500, bike was $600 then I threw a good set of shocks on, swingarm of the gods etc, though recent purchase of Webco head has blown my budget.
But what you get for your money is pre 74 bike with limitless supply of spares so well worth it. I am just changing to YZ ignition and giving the barrel some love with the dremel/
(http://i245.photobucket.com/albums/gg71/marcFX_photo/P2210013.jpg)
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Nice!
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I like your uncluttered work environment Nathan, and what's with the low fat beer? You on a diet Rick? ;D
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Having a bit of a blather about colour. I know that it should be either yellow or silver, but am failing to be inspired by the thought of either.
I'm really liking the way it looks now - everything is black, plated steel or raw aluminium. The idea of bringing any colour into the equation seems gaudy, but I know that the racing number plates will bring green and white whether I like it or not...
Current thoughts are:
Metallic grey (ie darker than silver).
or
White with a dark green stripe on the tank (like the red on the twin shock YZ works bikes).
or
Black, maybe with a yellow stripe.
All my MX plastics are pooh, so they all need to be painted regardless.
I like your uncluttered work environment Nathan, and what's with the low fat beer? You on a diet Rick? ;D
:D While i am trying to get my weight down, I don't compromise on my beer! Actually there aint no beer in that box - its full of Toyota Crown front springs (long story, don't ask... I have never been a Crown owner).
As far as clutter goes, this is a nice clear space by the standards of my shed.
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Black tank, normal red YZ stripe ?
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Slow progress - a mix of being busy with real-life and avoiding the frikken heat.
Here's how she sits now:
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan21-09Camera003.jpg)
Yeah, basically the same as last time, but the rear wheel is finished now, and it has a throttle assembly and cable...
And here's a misleading pic that is good for my motivation:
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan21-09Camera005.jpg)
The cases are completely empty, and its all just been 'plonked together' - obviously there's a lot of work before it will actually be this complete again.
I've also decided to fit a longer DT250A swingarm, because they're supposed to make the bikes handle better.
Here's the DT 'arm and a pair of lower fork legs drying:
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan21-09Camera006.jpg)
Some detail pics, because stuff looked good in the shed tonight (although the camera wasn't particularly kind to me, and the photos make it all look a lot less pretty than it actually does... :D ):
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan21-09Camera012.jpg)
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Jan21-09Camera014.jpg)
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Good paint drying weather hey Nat ;) :D.
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Hey Nathan, that zerk fitting on the rear backing plate looks a little dodgy ;D, seriously she's looking good. Since you seem to be having a shed clean up/clear out I've got a handy tool you can build out of "junk" you'll probably have lying around. Here's the recipie ......Take 1 used wheel rim (preferably Volvo-nice Swedish steel and I'm pretty sure there's one next to your shed), add a pipe ( approax 50 mm diameter, 1.2 to 1.5 high), weld at the bottom, then weld some bit's of 10mm round bar to the top at 120 degree spacing's. These can be whatever length you choose (600 or700 mm is good) The reason for using 10mm bar is so you can bend it to any shape you need, you can also add a couple of bars down low. Now you have the perfect painting stand that you can move around without anything falling off, paint in the shed, let it flash off, take it out to the baking oven (sun), bake it, bring it back in. You'll be amazed how much easier it is to paint shit, even tanks, we've made a couple at work and there brilliant.... you can even string a frame between 2 and it wont fall over!!!....get to it son ;)
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Nathan the MX swing arm is the same length as the DT, only diferrence between arms are the mountings for the pillon pegs on the DT ??? ;)
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Nathan the MX swing arm is the same length as the DT, only diferrence between arms are the mountings for the pillon pegs on the DT ??? ;)
I'm glad you mentioned that, that's my understanding but I wasn't confident enough to say anything. I think the RT1/DT1 swing arm is 25mm longer and swaps.
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the square DT1 swingarm is real close in dimensions to the MX250/360/SC500/DT250/360 arm but it's the round RT/DT2,3 arm that is a little longer.
i think the square DT1 arm may also have a slightly smaller pivot bolt diameter.
i have all 3 swingarms here as well as the XT500c arm which again is the same dimensions as the MX250etc arm{just with heavier gusseting around the rear axle}.
cool tank 8)
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Interesting... This means that my old DT250A has a DT2/3 swingarm - and had it waaaay back in the past (it was an unloved paddock bike when I got it in 1990).
And it means that my freshly painted swingarm is a DT2/3 item.
Edit: My DT's swing arm is same length as the DT2 swing arm, but has a grease nipple in the same spot as MX250 swingarm.
The freshly painted swing arm for the MX is obviously a DT2 arm, as the grease nipple is in the bolt rather than the arm. And has the early style dust caps over the swingarm bushes. Duh! Its funny the evidence your brain can ignore when your brain has already decided that it knows...
Edit2: MX250/DT250 swing arm is ~445mm from pivot to middle position of axle slot. DT2 is ~470mm.
Interesting bit is that there seems to be about 5mm of variation in lengths between examples of the same type of swing arm!
Edit3: Sometimes I really don't understand Yamaha...
The DT2 (with its longer swingarm) handles better than a DT1.
The YZ125X (with its longer swingarm) handles better than a YZ125C.
The YZ125E (with its longer swingarm) handles better than a YZ125D.
Why were they so obessessed with fitting short swing arms, when they obviously knew that the longer arm improves handling?
My inner cynic suggests that it makes it really easy to make the updated model significantly better...
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Posted by: Nathan S
Insert Quote
Slow progress...
You're kidding aren't you ;D you should have the bloody thing finished this weekend at the rate you're going.
As far as tank schemes go, were the any other private hop-up companies from the era (eg. Noguchi) that you could use for inspiration?
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photos from Jan 22nd look very nice,,, Well done on your progress!!
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Slow progress... Been stupid busy at work, and gotten involved in rally politics again*, which have combined with the heat and kinda sucked my motivation for going out into the shed...
Anyhow, the bike is to be metallic charcol. Figured that the grey would keep the pesky colour business to a minimum, while the metallic would stop it being entirely drab and business like.
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Feb10-04007.jpg)
I screwed up with the read guard, somehow. Cleaned up a really awful looking old guard (scraping, sanding, more sanding, etc) and painted it.
Then realised it was a 125 guard... ::)
Went to put the bearings into the cases tonight, then realsied it was 10pm, and decided against hitting stuff with a hammer...
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Feb10-04006.jpg)
While its got the usual chain damage in front of the sprocket, this case is the only MX/DT case I own that has the rear sprocket mount intact.
And another detail pic because it looked good in the shed - but looks shit in the photo! >:( Honeslty, there's no red dust anywhere on it - just something the camera has invented to make me look bad! :D Note the low-cost lower bearing seal, made from air-ilter foam - it supposed to be a rubber seal, but I've somehow managed to lose all of mine that aren't fitted to bikes...
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Feb10-04008.jpg)
*But the planets seem to align, for I'm on the right council, at the right time to actually make a positive difference.
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Ah nothing like a bike of metallic in the fram paint, always works for me. Bright yellow tank would top it off nicely. ;)
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shouldn't joke about hammers/crankcases/mainbearings late at night,some might take it seriously :P
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geezas,you wern't joking!,the bloody seals are in place :o, Nathan when you took the "baked" cases out of the stove (to post cure the black case paint??),then would have been the time to take all the bearings out of the freezer and neatly drop them into their respective holes, ;), :P
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Hey Nathan hows the re-build going.
This has totally grabbed my interest,and am looking forward to the next installment of pics,and words.
Looks like it going to be one sweet bike.
Cheers,Mark.
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Hey Nathan hows the re-build going.
Slowly! Spent a fair bit of the evening 'tinkering' in the shed, rather than getting stuck into it - doing stuff like sorting out bolts and tidying up.
Been trying to sort out gearbox stuff. In the pile from Jim, there were two complete bottom ends, a set of empty cases, and another two gear-sets. I'm using the empty cases and spare bits to build the motor, rather than pulling down either of the MX bottom ends (they've both got sub-standard big end bearings, so cannot be used as-in).
The first gearset turned out to be DT250 ratios, and the second gearset has an exploded 2nd gear.
Managed to confuse the hell out of myself, trying sort it all out... I've got a DT250 bottom end in pieces, and it appears that all three gearsets have different ratios to each other. But I really need to sit down and have a proper look when I'm less sleep-deprived.
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Feb10-06009.jpg)
Also spent some time working out which bolts go where and stuff. Doesn't make for a particularly interesting photo, but...
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Feb10-06008.jpg)
The aluminium tube at the bottom will be the body for the muffler. Can't really do anything more on it, until the engine is in and the pipe is fitted up properly.
Gear lever is an IT folding tip welded onto a mangled DT lever - pretty pleased that I turned two bits of rubbish into a useful gearlever (the IT lever had stripped splines).
Discovered that the barrel is currently 1.7mm over size. I'm pretty sure that Wiseco make a +2.00mm piston, but I'm officially on the hunt for a less-rooted MX250A barrell...
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Coming along nicely,the gear lever looks factory.
Keep it up.
Post some more progress when you can.
Cheers,Mark.
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Wiseco makes it up to 2mm, it will be a 234-P8 (72mm), im sure but i would have a few here so can double check if needed.
Im not sure if that takes you over the 263cc though..... 8)
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Long overdue update!
(http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/MX250A/Photo0079.jpg)
(Crap photo because our camera died, so this was taken with my bat-phone).
Lost motivation for a while there - mostly because work has kept being stupidly busy and I arrive home exhausted most evenings. Seeing one of the two other guys at work who do the same thing as me put a router into his thumb, and put himself off for a fortnight, its been super busy.
Anyhow, there's been some trials and tribulations since the last post:
1. The MX gearset I've got doesn't fit into the MX cases I've got - when the cases are bolted together, they lock the gearbox solid. This happens with either or both shaft in place.
Lacking time to sort it out, I slapped a well-used DT250A motor into it. Its not rad or sexy, but it will work (I hope!). I also discovered that the top rear mount is too wide on the DT motor, due to the rubber mounting - of course, you only discover this after you've painted the bloody thing. Some careful hack-saw work had it under control.
Has been fitted with the MX ignition, 34mm carb and MX pipe, so it should still go OK.
2. The forks needed more work than I wanted to think about - or have time for... so I've 'borrowed' the forks & front wheel out of my DT125.
3. The tank was put into the too-hard basket, and I simply fitted a nice DT tank that came in the pile of bits from Jim - well, after welding in an MX filler neck (eagle-eyes might notice the MX cap and DT tap in the photo). After I did it, I realised that there's a simpler, quicker, neater way to fit thescrew-in cap to the DT tank.... Oh well, there's always next time, right?
4. Rear guard is awful... but should do the job!
5. Poverty forced me to fit a TT500 rear wheel that was ear-marked for my DT250, as I don't have the cash spare to buy a new sprocket to suit the MX wheel (TT wheel is same as YZ250A etc, so is pre-75 legal, BTW).
6. The flywheel removal (from the donor motor) was a nightmare. I owe Marty from Wright's Motorcycles a big thank you for his efforts, easpecially as I dumped the jobon him this morning, expecting it to be 5 minutes work... :-[
There's been a few 1am finishes and other such idiocy, but it might even make it to Broadford this weekend - and if it doesn't make it to Broadford the following weekend, then I'll be very unhappy.
The good news is that it fired on the first kick - but did not start. Getting it to run is a job for tomorrow evening.
I'm suspicious of the carby (seems like the float level is too high and/or the needle & seat is leaky), and there's some wiring to tidy up.
Beyond that, there's just a couple of little things to do: Fit the LHS hand grip (after the bar is plugged), mount the CDI box, and a few other trivial things.
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And a HUGE thanks to vmx157 for the LHS side-cover at a very generous price.
:) x 1000000
(And my apologies for not thanking you earlier - I've "Been being a self-obsessed wanker" as my wife so generously put it...).
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Dairy Farmer's won't be so kind when the Flying Squad catch up with you..... ;D
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another quality whackittogetheratthelastminute bike.
i mean that as a compliment by the way.
i reckon i've seen those shocks on more than one of your bikes too Nathan. must be the best value for money shocks going.
a stock DT motor with the MX carb,pipe,ignition etc should still be sweet enough for most riders.
my MX is stock with a DT piston and external flywheel and i love it just the way it is.
smooth as...
cool bike 8)
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Ah yes, those shocks... For a while I owned three of them, and I'd swap the third one between two bikes. :D Somehow I kept one silver and one orange one, rather than a pair!? So now they're a mis-matched pair, which adds to the "no expense spared" look of the whole project! :D
I got it running this morning. Was difficult to start from stone cold - sometimes it would fire, other times it would ignore you.
Once warmed up, the mixture screw makes no difference across the normal range of adjustment - just before it bottoms out and just before it falls out will have it faltering, but anywhere in the middle is exactly the same.
Any suggestions on what I should be trying?
Still, once warm it starts easily, idles happily (perhaps a bit fast) and free revs fine. Test ride this arvo.
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I got it running this morning. Was difficult to start from stone cold - sometimes it would fire, other times it would ignore you.
Once warmed up, the mixture screw makes no difference across the normal range of adjustment - just before it bottoms out and just before it falls out will have it faltering, but anywhere in the middle is exactly the same.
Any suggestions on what I should be trying?
Are you running a DT barrel and head with an MX chamber? If you are I would think it is a mismatch of chamber to porting (lacking back pressure at low RPM). You might be able to achieve something with jetting but I think you are pushing shit uphill with a pointy stick ::).
The 'bees knees' is MX barrel and head, carby and chamber with DT ign. I think you have it arse about.
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There's lots of things that are 'non-ideal' at the moment - no time, no money!
I've sourced another MX barrel, but it won't be fitted until after the Nationals. FWIW, the bolt-on MX pipe spigot lines up beautifully with the DT exhaust port (ie: Its 'port matched' without being touched) - far better than most of the YZs do from the factory... The MX pipe is still 'milder' than the aftermarket DT pipe I've got here, so I don't think that's an issue.
I'm also running the MX head - mostly because I don't think a DT head fits under an MX pipe.
Yes, the heavier ignition is almost certainly a good thing - but I don't own a spare functional external rotor ignition.
And for all of that, it goes a LOT harder than I expected - admittedly everything feels fast in the backyard, but it still impressed me that it lifted the front wheel in second gear on moderate throttle application alone (not threatening to loop out or anything, but still better than I expected).
My shoulders are about three inches higher than they've been all week - the weight has been lifted!
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FWIW, In terms of timing the DT barrels are quite advanced (esp for a trail bike) & not far behind the MX & YZC. eg DT Exh duration is 180deg. However the MX/YZ ports are considerably wider.
I'd have tho't yr combination would have been quite decent Nathan, tho it'll proably run out of breath a bit on the top end esp up against the gun machines of the class. But don't be psyched out by using a DT barrel.
Probably 'tailor made' for short-shifting.