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Author Topic: 1972 Yamaha DT 250 Enduro to Cafe/Bobber  (Read 19177 times)

Offline CTENG

  • Posts: 23
1972 Yamaha DT 250 Enduro to Cafe/Bobber
« on: Aug 28, 2008, 22:54:10 »
I'm new, thought I would jump right in with a project thread.
This is my first bike, I always have to be different and I came across a Craigslist deal I couldn't pass up.  I picked up this '72 DT2 (DT250) for $300.  It was a parts bike for a restoration, only things removed were the handlebar controls and the seat.  It fired on the first kick and idles great.  Just needed some gas.
Best part of the deal - clean street legal title.  KS isn't great for registering 2-strokes so this was gold to me.



It came with a plastic competition tank, never used just a bit dusty.  After the humidity ruined the first paint job I started all over and I am one polish away from being done with it.  Not perfect, but I learned quite a bit during the process.  As you can see in the first pic, my hobby is 4-wheelin and I don't build for pretty on my 4runner.



I did a lot of research and decided I wanted to combine my favorite aspects of a cafe racer and a bobber.  I have started with the front end.  Cleaned up and rebuilt the front forks, painted the lower tubes to match the tank.



I was surprised under all the haze and gunk, everything is cleaning up considerably well.



Swapped over to black Clubmans, vintage cafe style grips (comfy), and bar-end mirrors.  Needed some risers to get everything in the right position, they have several levels of adjustment I can tweak later.  Some stuff, levers, etc, I was able to clean up enough to reuse.



Front tire came today so I got that mounted up with a new HD motocross tube.  Went with Avon Distanzias, kind of a dual sport tire so the bike keeps just a little of her off-road heritage.



That is about where I am so far.  I have been having a lot of fun with the project...my biggest challenge right now is trying to find some cheap used expansion chambers so I can build one with my own dimensions out of them.  Plans for the rear suspension make using the stock exhaust impossible.  Anybody have any chambers lying around they are looking to get rid of I may be interested.

The back will be a bit more customizing.  I plan to remove the rear frame including the shock mounts, run a bobber-style solo seat and remount the shocks to the seat frame bars.  No front fender and a trimmed harley front fender mounted on the swing arm for the rear.

-AJ

Offline valvesprung

  • Posts: 1059
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #1 on: Aug 28, 2008, 23:53:32 »
I love it so far and your ideas sound wicked...can't wait to see it completed!
'79 KZ650SR
'81 GPz750 (KZ750R)
'93 GS500 (Adv conversion)

Offline dbarale

  • Posts: 45
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #2 on: Aug 29, 2008, 23:08:27 »
Mix between a cafe and a supermotard, a supercafe maybe? Cafe scrambler?
 Either way, looks really good so far!

Offline CTENG

  • Posts: 23
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #3 on: Sep 01, 2008, 22:38:14 »
Got the front rim taken care of, all painted up and finished assembling the front end.  Only thing left in the front is a headlight...anyone know a good source for 6 volt lighting???

I am pretty happy with it so far.  Time to order a seat and drop the swingarm off it.












Offline Ease

  • Site Supporter
  • *
  • Posts: 2124
  • 83 XJ650RK, 77 TS-250
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #4 on: Sep 02, 2008, 01:16:07 »
Front end looks killer.

Offline Jason TEAMSHRALP

  • Posts: 135
    • http://teamshralp.wordpress.com/
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #5 on: Sep 02, 2008, 04:26:54 »
i think honda cl and cb 125's us 6 volt and have cool looking head lights/buckets.

Offline Speed2XS

  • Posts: 132
    • SoCal86.com
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #6 on: Sep 02, 2008, 14:37:11 »
i think honda cl and cb 125's us 6 volt and have cool looking head lights/buckets.

Thats what my cb125s uses.

Offline motofiaccone

  • Posts: 1946
    • Chris' Cafe Racer
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #7 on: Sep 03, 2008, 09:55:53 »
Since you painted the wheel with the tire already mounted, will you talk a little about the process and the materials you used? It looks great in the pics, but I'm curious about the durability/longevity.

--Thanks, Chris
Check out the build projects at www.motofiaccone.com

Offline Brass_machine

  • Posts: 15
    • New School Cafe
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #8 on: Sep 03, 2008, 11:14:28 »
That is about where I am so far.  I have been having a lot of fun with the project...my biggest challenge right now is trying to find some cheap used expansion chambers so I can build one with my own dimensions out of them.  Plans for the rear suspension make using the stock exhaust impossible.  Anybody have any chambers lying around they are looking to get rid of I may be interested.


One of the keys to getting 2 strokes to run well is expansion chamber design. The chamber itself is an important piece of the engine. Chambers for one bike usually will not run very well on another. In fact, if you have a bike that has had engine work and are using tuned pipes, it usually won't work as well on the same kind of bike unless everything else is the same. You would be better served using expansion pipe design software. I know that stuff gets expensive, but MOTA is offering a simple design program for free. I haven't used it yet, but I have used the other MOTA package before and it works well. It might be worth your time to download the free software and give it a try. You can find it HERE. Scroll down to the beginning of the 3rd paragraph and give it a go.

The bike is looking good!

Eric

Offline CTENG

  • Posts: 23
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #9 on: Sep 03, 2008, 11:21:19 »
Since you painted the wheel with the tire already mounted, will you talk a little about the process and the materials you used? It looks great in the pics, but I'm curious about the durability/longevity.

--Thanks, Chris

Sure.  Keep in mind this is a fairly budget minded build.  I am not dropping thousands on a $300 bike, so that is my driving theory.  I try my best to figure out the logistics of everything step by step before hand to minimize screw ups.  One this I knew immediately was, if I painted the rim and then tried to put the tire on I would ruin the paint and have to spray it again anyway.  

Here is how I went about it.  First I cleaned the rim.  I would have polished it and called it a day, but the spokes were rusted a bit and they weren't getting any better.  The rim is still tight and true so didn't want to go replacing it.  I cleaned it with Purple Power degreaser to make sure I would get good contact and then scuffed down the outer rim with a scotch brite pad.  Get it nice and clean again and start taping.  I put the tire on the rim, but didn't seat the bead until after paint.  This lets you put a first layer of masking tape down around the tire overlapping slightly onto the rim.  Then just push the tire inward and the tape slips between the tire and rim.  After that I used newspaper to cover up the tire.  I taped off the parts of the hub I wanted to remain polished chrome and got to painting.

Now, with a wheel that is beat and rusty, there is no reason to go all out with expensive paint and primer and sanding.  I used Rustoleum Hammered paint.  The paint is made to go right over rust and seal it.  To get the hammered texture it uses a mixed in adhesive much like chip-guard, so when the paint sets up it is a thick layer and very tough.  I put on two coats.  It goes on very even, self levels, you really can't screw it up.  The finish is decent and it takes very little work.  I have been using this on suspension parts on my crawler for a couple years and it has proven to last better than any other std paints I have used.  I have been using the hammered stuff as an accent on the bike for all the parts I figured would be high-wear.  It dries fast too.

Let me know if you have any other questions.  I should have teken more pictures I guess.

Offline CTENG

  • Posts: 23
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #10 on: Sep 03, 2008, 11:28:30 »
One of the keys to getting 2 strokes to run well is expansion chamber design. The chamber itself is an important piece of the engine. Chambers for one bike usually will not run very well on another. In fact, if you have a bike that has had engine work and are using tuned pipes, it usually won't work as well on the same kind of bike unless everything else is the same. You would be better served using expansion pipe design software. I know that stuff gets expensive, but MOTA is offering a simple design program for free. I haven't used it yet, but I have used the other MOTA package before and it works well. It might be worth your time to download the free software and give it a try. You can find it HERE. Scroll down to the beginning of the 3rd paragraph and give it a go.

The bike is looking good!

Eric

Thanks for the link!

I have done quite a bit of research into expansion chambers.  I also have a degree in Aerospace Engineering, so I think I am pretty good on the concept, function, and BASIC design parameters.  My need for used chambers is simply for sections I can cut up to reweld into the dimensions I want for this bike instead of cutting and rolling them all myself.  Lazy time-saver really.

My intentions with the chamber will be to elongate the head pipe and expansion cone to lengthen the time to return of the pulse.  I want to keep the peak resonance in a lower RPM band and run a smaller rear sproket to try and get the bike into a street friendly/engine longevity type function.  I am also considering making the head-pipe to expansion cone joint adjustable from the begining so I can tune while I ride and then weld it in once I have it set up the way I want.

Offline Brass_machine

  • Posts: 15
    • New School Cafe
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #11 on: Sep 03, 2008, 11:35:54 »
Thanks for the link!

I have done quite a bit of research into expansion chambers.  I also have a degree in Aerospace Engineering, so I think I am pretty good on the concept, function, and BASIC design parameters.  My need for used chambers is simply for sections I can cut up to reweld into the dimensions I want for this bike instead of cutting and rolling them all myself.  Lazy time-saver really.

My intentions with the chamber will be to elongate the head pipe and expansion cone to lengthen the time to return of the pulse.  I want to keep the peak resonance in a lower RPM band and run a smaller rear sproket to try and get the bike into a street friendly/engine longevity type function.  I am also considering making the head-pipe to expansion cone joint adjustable from the begining so I can tune while I ride and then weld it in once I have it set up the way I want.

Very cool! I am glad to see you have researched chambers. With your plan, the software and your education you should end up with a nice set of working chambers. I will dig through my pile and see if I have any chambers left from a 2-stroke project I have going on. They are yours if I still have them, just pay the shipping.

Eric

Offline CTENG

  • Posts: 23
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #12 on: Sep 03, 2008, 12:19:31 »
Thank you!

I also need to hit the steel yard, probably tomorrow.  Likely I am not lucky enough that they will have thin-walled 4 inch pipe just lying around waiting for me though.  Fortunately I have time.  I can't mount up the exhaust until I have the new rear shocks set up and I haven't even ordered them yet.  Need a seat first.

Offline Kev Nemo

  • Posts: 916
  • Honda Hacker
    • Fallingapartart Streetwear: Destroyed By Design since 2009
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #13 on: Sep 05, 2008, 10:28:54 »
Can you push those forks up in the trees any to drop the front?
Fallingapartart Streetwear: Destroyed By Design since 2009 http://www.fallingapartart.com

Offline CTENG

  • Posts: 23
Re: 1972 Yamaha DT 250 Enduro to Cafe/Bobber
« Reply #14 on: Sep 05, 2008, 10:48:39 »
Yes, but I am not going to start doing final adjustments on anything until I get the seat on and he new shocks in place.  The tree is just snugged down for now, but I can drop it about 2 inches if I want.