They need a little cleanup but are runners. The red DT actually has a wrangler jean jacket made into a cover with a serious fade.

And if you needed any more reason to get psyched on the old enduros check out these guys instagram accounts. Tons of great old photos.

I spy Vic Eastwood and Hakan Andersson. #motocrosshistory #motocross #worldmotocross #realmx#natualterrain#70’smoto

A photo posted by DG’s Vintage Motocross Garage (@dg533) on May 6, 2015 at 12:48pm PDT

Sliding r in MXA style. #motocrosshistory #motostyle #motocross #mxa

A photo posted by DG’s Vintage Motocross Garage (@dg533) on May 3, 2015 at 7:57pm PDT

The great Joël Robert holding the high line on his Factory Suzuki at the 1971 Saddleback Park Trans-AMA @dirtbikemag #Legend #BeerSmokesAndHaulingAss #Motocross #70sMoto A photo posted by Tony Blazier (@tonyblazier) on Apr 26, 2015 at 6:15am PDT

The Toyota SR-5 Sport Truck -the official truck of the 1978 AMA Supercross Series. #MikeBell #JamminJimmyWeinert #WhatEverHappenedToLowTrucks #Motocross #Supercross #70sMoto

A photo posted by Tony Blazier (@tonyblazier) on Apr 20, 2015 at 7:23pm PDT

First off… Why do you care and what’s the deal?

On 2 stroke dirt bikes, there is a rubber seal on either side of the crankshaft. Over time these dry out.

The seal on the magneto side (left side) prevents air from getting into the combustion chamber. If the seal on this side goes bad, you’ll get air leaks. Your idle will hang and/or the bike will rev erratic randomly. Bike will run lean and trying to tune it will be pointless.

The seal on the clutch side (right side) prevents crankcase oil from getting into the combustion chamber. If the seal on this side goes bad, you’ll burn a ton of oil and eventually foul plugs and suck the crankcase dry of oil.

Ok.

Things you’ll need to change the crank seal which you most likely do not have or own:
– air compressor set up and air gun to loosen certain bolts for the first time in 30 years
– 26mm / 29mm / 30mm socket
– yamaha magneto puller tool

Magneto side crank seal

1. Use OEM yamaha seals. Get them from BikeBandit.com
2. Pull the cover off
3. Bolt will be a 19mm. Unless it’s recently been loosened at some point, absolutely no way you’re getting it off without an air compressor set at above 80psi.
4. Once that bolt is off, screw on the yamaha magneto puller tool
5. Tighten it on there and then start to use the 2 wrenches to pop the magneto off. If this is the first time your magneto is coming off, be prepared to feel like you’re going to strip threads, or break something. Every time that it’s the first time i’m blowing off a magneto that’s been stuck on there for 30 years, it’s blows off with a crazy loud noise. Shit is seriously scary.
6. Use an impact driver to get the stator screws out.
7. Then take a drywall screw and hammer it gently into the old seal. Only poke it through a tiny tiny bit. Then screw it in only until it grabs. Then use a hammer to pry, and pop out the old seal. Side note – if you can get the seal out with a pick instead of a drywall screw, do it. Good luck though.
8. Wipe everything dry with alcohol. Then, since this side is prone to air leaks, I use Black Gasket sealer on the outside of the seal. Never gotten air leaks by using this method.
9. Push the seal in gently. Tap it in gently if you have to. Also, once the seal is pushed all the way in, put a thin coating of gasket sealer around the outer edge. Someone once recommended this. Works for me. Again, gasket sealer is up for debate but I like it on things that are prone to air leaks.
10. Since it’s all apart, wipe the contact areas of the stator and magneto clean with a rag and alcohol.
11. You’re done this side. Reassemble. Important note – when you put the magneto back on make sure you tap it on super hard with a rubber mallet. It needs to sit all the way into the woodruff key and the bolt needs to be tight as shit or the woodruff key will sheer off.
12. Last note. These seals are directional. So put them in the right way which is little round spring facing into the combustion chamber. My images show it going in backwards, sorry. However. I put them in backwards in my IT and never had a problem … actually think it makes more sense to put them in backwards so the little spring can’t fall into the combustion chamber. I dunno, it’s your call. 

Clutch side crank seal

1. Pull the cover off
2. Undo the clutch spring bolts
3. Those 2 bolts I’m pointing to will definitely not come off unless you have an air compressor set up. Maybe if you have a clutch basket holder. Still they prob won’t come off.
4. Once you do get them off, it’s easy. Pull off the clutch, and pull off the primary gear. Take a photo to ensure proper reassembly if you need to before pulling shit all apart.
5. Popping the seal out on this side is the same as the other side you just did
6. Wipe everything clean with alcohol, and put this seal in dry. No gasket sealer.
7. Reassemble. Make sure you tighten those 2 big bolts back to the torque spec or at least make them tight as shit. Then… Drink a beer.

So so much damn fun. Little 2 strokes are the best.

All were 69-71 era, piston port motors, before Yamaha really knew what dirt bikes would become. And all were relatively about the same dimensions, just different weight.

Lately I’ve been regretting buying my 71 CT1 since it’s lacking the newer technology compared to the late 70’s. I really wish I had bought a 78-82 dt175 instead; way better suspension and faster.

Regardless… I’ve been looking at ways to make mine better from a performance and suspension standpoint and after finding all these cool images, it gives me some solid inspiration. Some of these bikes below are badass! This is what I’m thinking:
– already have pod filter and jetted carb
– GYT expansion chamber exhaust
– aluminum rims. small front hub. no front brake
– plastic front and rear fender
– smaller front gear. bigger rear gear
– front end from a YZ or MX
– maybe take all my lights off and put a number plate on it

Yamaha had a power kit from the factory called “GYT”. (Genuine Yamaha Tuning)

You could walk into a Yamaha dealer in 1970 and get a new piston kit / carb / gear / exhaust (all yamaha parts) to make it go faster. I’m trying to find some of this stuff on eBay but its super rare.

FYI – the hot exhausts were:
– GYT
– hooker
– DG performance
– torque engineering
– bassani
– moto tech

Check out the map below. Zoom in/out to see it all.
As far as I’m aware, these are the only locations to ride dirt bikes. None are legal. All are sketchy, and be prepared for someone to probably try and mug/stab you or call the cops.

• A – kenzo trails
  I rode back here all weekend. It’s awesome. Super sketchy though. Watch out for booby-traps and someone trying to mug you.
• B – airport trails
  Has anyone actually been back here? I went there yesterday, and now there’s a big fence. It has an electric open gate portion which was open, so we went in real quick. I heard this is the most sketchy, ghetto spot in philly. Is it shut down now?
• C – fairmount mountain bike trails
  There’s really only one or two trails. Basically you’ll ride through it… pop out and then go on your way. Don’t expect to spend too much time back here I don’t think.
• D – river road trails
  I haven’t been back here yet, but I heard it’s good? Anyone know?
• E – wissahickon fishbowl trails
  This used to be crappy mountain bike trails behind the baseball field down in the bowl like area. It’d be fun to hit this up again.

Also… watch this video below. Philly cops don’t / won’t chase dirt bikes if you run away… Just saying…

Read this article too.

As I said earlier, the clutch slips like a mother fucker. It’s horrible.

I really wanted to do Barnett springs and plates. I found the plates easily on eBay but I couldn’t find ct1 Barnett springs anywhere. On a whim I ordered dt175 springs since they are available… not knowing if they would fit.

Well… They do fit.

Just wanted to put this out there in case anyone else with a ct1 has the same issues.

I took my top end off.

From what I can tell… Some dip shit before me put in a reed-valve piston into a piston-port engine.

Let me back up a step if you know jack like me.

Apparently in these old shitty jap 2-strokes, there are piston-port heads and reed-valve heads. Reed-valve is the newer style of the two.

Basically it means what style of air / fuel intake is it. Piston-port uses the piston as the intake valve and the exhaust valve. Reed-valve uses flaps and piston as the intake valve and the piston as the exhaust valve. I’m sure my explanation is ultra generalized but from a beginner understanding it’s probably fine.

Anyway, my engine is the older piston-port but when I took the head off the piston in it was a reed-valve piston since it has the holes on the intake side.

The holes on the intake side of the piston lets the intake flow draw more air in which is something reed-valve heads want / need.

No idea why someone put a reed-valve piston in a port-piston head. The holes would draw too much air from my understanding. I’m assuming it was a dip shit and this is one of the reasons the bike ran like total garbage. Anyway, I’m putting in a wiseco piston and doing the crank seals. Plus I’m going to try shaving down the bottom of the intake skirt a tiny bit as the dude in one of the bottom images suggests since I have a pod filter and jetted carb.

Overall I’m cleaning this thing up a bit because it’s a piece of junk right now.

Anyone know 2-strokes and have input / suggestions for me?

Oh… and this thing is a joke to work on. Took like 5 mins to rip off the little shit it had on it. And another 5 mins to take the top end of the engine off.

Piston on the right is the wiseco piston and the correct type of piston for a piston-port head.

The good:

• It runs… kinda
• Cosmetically… it’s pretty nice… but just rough enough.
• The wheels are straight… kinda
• The seat is original and really nice.
• Inside of the tank is perfect.
• Carb is clean.
• Motor has 90psi compression. Probably do the Wiseco piston kit anyway since it’s like $40.

The bad:

• No title. Looks like I’ll be doing the Vermont shit.
• Guess how many quarts of oil were in it… Zero.
• No wiring on the bike is connected at all, except 1 wire. It comes off the magneto, runs directly to the coil, from the coil, the spark plug wire goes to the plug. That’s it. Does anyone understand how or why that works? Seems like the magneto creates enough current to make the coil fire. There are no grounds… no other wires at all. No battery. Just that 1 wire which goes from the magneto directly hard wired into the coil. Definitely some sketchy shit, but it works. I’m going to make a custom minimal wiring harness.

I just rode it to the grocery store in the snow. Pretty darn fun.

The oil-injection pumps too much… or the engine seals are letting oil by, and the jetting is too rich with the pod filter.
So basically it runs like shit.
And the clutch slips like a mother fucker.

Still cool, and for the price… can’t go wrong.

I’ll say it again… who wants to build dirt bike jumps with me in the sketchy woods near Huntingdon and Richmond street?