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74fj40
05-17-2007, 08:17 PM
We are now the proud owners of 3 non-working 70's era dirt bikes - 2 DT125s and a DT175.
Thought after working on a cruiser, these things would be easy - NOT!!
Anybody out there with any experience on these guys?

Beater
05-17-2007, 08:38 PM
I've been known to play with a 2 stroke once or twice...

not that particular one, but they are real simple, yet subtly complex

74fj40
05-17-2007, 08:42 PM
Interested in helping a noob learn?I've been known to play with a 2 stroke once or twice...

not that particular one, but they are real simple, yet subtly complex

MDH33
05-17-2007, 09:48 PM
Cool, Vintage Japanese is in your system full-on now! :D

I collect and restore 60's and 70's era Honda Street bikes. No experience with the 2 strokes though. I have some good connections for vintage japanese mc parts which might help you out.

Oh yeah:

THIS THREAD IS USELESS WITHOUT PICS!

:thumb: :D

gcmandrake
05-17-2007, 10:43 PM
<flashback>
Gosh, I remember having an old Yamaha 125cc Enduro back in my college days. It was a serious beast. I remember taking it apart in my frat's basement and getting harassed by the Fire Marshal. I finally managed to sell it and replaced it with a Yamaha RD400. Now, that was a fast two-stroke, it was a replacement for the RD350. You would leave a stop sign on a wheelie without intending to. I was putting so many highway miles on it that I finally replaced that bike with a Yamaha 850 with direct drive. :cool:

A conspiracy then developed by the women in my life to separate me from my motorcycles. So ended an era.
</flashback>

I probably don't remember enough to help you out. If I remember correctly, servicing a two stroke isn't too difficult. The first thing I would do is clean everything. Plugs foul quickly on a two stroke and on certain bikes, that have magnetos, you would need to clean the points.

Second thing I would do is get a service manual for each of them. The DT125 was very popular, it shouldn't be too hard to find manuals. Have fun.

the Other Matt

RockRunner
05-17-2007, 11:14 PM
Nice pick up, I used to ride the 175, most likely the start of my back problems;)

Never really tore into it to much back then, bought it running and sold it running so no real wrenching, sorry I could not be more help.

Enjoy your new money-pit..............:thumb:

nuclearlemon
05-17-2007, 11:34 PM
don't know about the dt.

had an it175e for years. no lo end for a dirt bike, but the price was right. traded it for a bar.270 with a leupold scope.

Red_Chili
05-18-2007, 09:48 AM
I have messed with ring dings for years. Used to work for Vickery Yamaha in the 70s. Currently I have a KDX220, just freshened the top end. The rest of my garage's residents (some owned by my kids and wife) are thumpers: Honda XR650R, Yammie TTR250, Honda CRF230F, BMW R100LS, and of course a Buell Ulysses.

Whatcha need? Note: most likely you need to thoroughly clean the carbs and perhaps even replace the jets (especially the pilot) due to corrosion by now.

Beater
05-18-2007, 11:54 AM
also the reeds.. boysen is a good brand.

74fj40
05-18-2007, 12:06 PM
Thanks for all the replies - we do have a manual for both the 125 and 175 - what we really need is some basic learning on what does what and a brief look over of the current condition of the bikes to see what parts and work might be necessary. We need a kick start.....hahaha

Red_Chili
05-18-2007, 12:45 PM
Time is my least plentiful resource right now... well, money isn't exactly falling out of the sky either. But if I get a moment in the next week or so I could pop over.

Check the spark, pull the float bowls and look for varnish, smell the tank for bad gas. If you have bad gas and varnish in the carbs, but have a spark, you just need to overhaul the carbs - THOROUGHLY - and clean out the tanks, and fill the oil injection reservoirs with good Yamalube injector oil, and give the kickstarter a whack. Then listen for excessive piston slap or motor noise.

A new piston kit is no big deal, if the bore is clean and not scarred. Even if it is, a first over rebore is no big deal. Get a service manual. Very easy to work on.

74fj40
05-18-2007, 01:48 PM
That would be way cool - I see some 1554 in your future.....
Time is my least plentiful resource right now... well, money isn't exactly falling out of the sky either. But if I get a moment in the next week or so I could pop over.

Check the spark, pull the float bowls and look for varnish, smell the tank for bad gas. If you have bad gas and varnish in the carbs, but have a spark, you just need to overhaul the carbs - THOROUGHLY - and clean out the tanks, and fill the oil injection reservoirs with good Yamalube injector oil, and give the kickstarter a whack. Then listen for excessive piston slap or motor noise.

A new piston kit is no big deal, if the bore is clean and not scarred. Even if it is, a first over rebore is no big deal. Get a service manual. Very easy to work on.

Beater
05-18-2007, 02:02 PM
I am probably too far away.. and quite busy these days, but you are welcome to reach out.. you're probably better off will r.c. (redchili)

here is my basic list on every 2-stroke I get:

clean piston/head
soak/clean/rebuild carb
de-coke exhaust (google it - you can use lye or a torch)
tighten every bolt

usually this takes care of most issues, and will lead you to any real problems

SteveH
05-18-2007, 04:08 PM
I had a '70 CT-1 and a '73 CT-3 and the things I had to figure out with help (and a manual) were how the oil injection works and the carb needle deal.

There's a wobble-plate pump and when the engine is running, oil is slowly pumped in. When you open the throttle, you increase the excursion of the wobble plate, and oil is pumped in faster. It's a clever design, and all goes on under the right-side engine cover.

The carbuertor should be cleaned and inspected, and the needle that hangs down in the middle of the sliding sleeve deal has three positions - this controls mid-range mixture. I think there are either jets or screws for idle and wide-open throttle. If any of these are plugged, you'll get a bike that either won't run wide open or won't idle.

Neither of my bikes were fast, but when you drive an FJ40, anything you can wind up to 6000 rpm is fun. If they smoke a lot under throttle, you can back off the oil a bit on the pump adjuster - they shouldn't look like a mosquito fogger. If you suspect the entire auto-oiling thing is messed up, you can premix oil and gas and just put that in the tank. HAving said that, if there is no blue smoke at all, you could be running the bike with no oil, and that is badness.

My '70 had electric start, and like most bikes of that era, the battery charging by the combined starter/alternator was weak, and even a new battery had trouble starting the bike.

One of my bikes only had 1200 miles and looked like new - it was very sharp after I resto'ed it. Have fun - these bikes are a good low-cost way to expand your gearhead skills.

74fj40
05-21-2007, 08:06 AM
Had a dirt bike weekend - we're concentrating on the 175, so pulled the engine, cleaned it up inside and out, checked the piston/rings installed new gaskets - all looked pretty good.
Cleaned the carb - it was already pretty clean, and put everything back together.
One of the studs in the exhaust port had previously been broken off and one of the pos had tried to get it out - messed it up pretty good - a little jb weld and a new stud and it seems to be holding fine.
Also, the lower throttle cable is old and brittle - Martin, I may have to use one of your connections for parts....
Anyway, tried to start it, but no spark...do you need a battery to start? I didn't think so, considering it's a kick start, but going to buy one today and try again.
Checked the plugs and the wire - both ok - will install battery and check points tonight - keep you posted....

Pics coming....

Red_Chili
05-21-2007, 08:14 AM
No battery required. Possibly a toasted CDI?

Beater
05-21-2007, 12:57 PM
be careful there bill, some require batt for signal completion...

Red_Chili
05-21-2007, 01:38 PM
Not the DTs IIRC

74fj40
05-23-2007, 10:33 AM
Have ordered a flywheel puller so we can clean the area behind the magneto and access the points. Also ordered a bettery to check the electricals. Hopefully will receive the parts towards the end of the week and update the thread then - pictures are coming......

74fj40
05-28-2007, 01:43 PM
Pics.....

Red_Chili
05-28-2007, 09:45 PM
Brings back memories! Never owned one, worked on a few. Friends rode them. Some were very good woods riders - amazing when compared with machines of today!

74fj40
05-28-2007, 10:03 PM
Bill - really sorry to hear about your rig....if you need any help at all, please don't hesitate....
Brings back memories! Never owned one, worked on a few. Friends rode them. Some were very good woods riders - amazing when compared with machines of today!

wesintl
05-29-2007, 09:47 AM
Wow.. they cleaned up nice fella's

74fj40
05-29-2007, 10:45 AM
Yep - still scrounging around for some parts and trying to get them running, but they're getting there...

Wow.. they cleaned up nice fella's