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Discussion Starter #1
I wasn't sure where to post this so I'm posting here.

I'm about to get this old '68 Yamaha 2-stroke dirt bike that has been converted to dirt only. The guy tells me he also made it to run off premix only. I would like to restore this bike to it's stock functionality, but I have never really worked on a 2-stroke. What do I need besides the stock oil tank to convert it back?

Edit: This... bike.... is.... to...sweeeeeet. I'm getting cavities just thinking about wrenching on that.
 

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To get back to oil injection (no pre-mix) you'll need the tank you mentioned, the oil pump, and the stock 'Y' throttle cable. One branch of the 'Y' cable goes to the carburetor throttle slide, the other branch goes to the oil pump.

The cable might be hard to find these days, but you can probably kludge something up if you can't find it. You'll be able to find the oil pump on eBay as there are probably a million of them out there that were hardly used, still sitting in some drawer for (holly crap, is that right?) 40years!

There is a soft spot in my heart for the early Yamaha enduros. My first bike was a little 1972 100cc. :happy3:

The first thing a lot of people did to those old bikes was to turn them into "MXers" by stripping off anything that wasn't' essential. The oil tanks and oil pumps were the first things to go. The other must do mods of the time were knobby tires, expansion chamber, new Preston-Petty plastic high front fender in place of the low metal one, front fork brace, MX bars, and of course number plates to look like a real racer!

Let me know if I can help you in any way. Those bikes are easy and a lot of fun to tinker with!

What model are you getting?
 

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I are confused are there two strokes not on premix? Is there an engine oil compartment that slowly dries up or something? Ok explained above...
 

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I are confused are there two strokes not on premix?
Those bikes had separate oil tanks for the 2 stroke oil which was injected into the intake by a small pump. No need to premix.
 

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most snowmobiles now are ran off oil injection. just put gas in the tank in the tank. sleds have become much more efficient in terms of oil use. i barely have to add any to my 700cc sled after riding a weekend.
 

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Keep it the way it is, if the oil pump gives up there is nothing that will stop a seized engine. Pre-mix is easy and guaranteed safe(when mixed right). Unless you have to have it perfectly stock in every way leave it.
Just my 2cents
 

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Keep it the way it is, if the oil pump gives up there is nothing that will stop a seized engine. Pre-mix is easy and guaranteed safe(when mixed right). Unless you have to have it perfectly stock in every way leave it.
Just my 2cents
Not to mention something less to maintain
 

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For a dirt only setup I would just keep it running premix. If it were still on the street the oil injection would be nice so I wouldnt have to mix my gas at the pump. Even that wouldnt be terribly troublesome I just wouldnt like keeping good 2 stroke oil with me.
 

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Discussion Starter #10
Keep it the way it is, if the oil pump gives up there is nothing that will stop a seized engine. Pre-mix is easy and guaranteed safe(when mixed right). Unless you have to have it perfectly stock in every way leave it.
Just my 2cents

If the oil pump goes out, all I have to do is run premix to prevent seizure, correct?

This bike is going to be largely a restoration project. I may do the paint in a non-factory color but with factory "patterned" paint scheme. I may just stick with the premix for the short term. Eventually I want to restore it to it's former 1968 glory. (Man, this bike is almost as old as my parents.)
 

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Discussion Starter #11
To get back to oil injection (no pre-mix) you'll need the tank you mentioned, the oil pump, and the stock 'Y' throttle cable. One branch of the 'Y' cable goes to the carburetor throttle slide, the other branch goes to the oil pump.

The cable might be hard to find these days, but you can probably kludge something up if you can't find it. You'll be able to find the oil pump on eBay as there are probably a million of them out there that were hardly used, still sitting in some drawer for (holly crap, is that right?) 40years!

There is a soft spot in my heart for the early Yamaha enduros. My first bike was a little 1972 100cc. :happy3:

The first thing a lot of people did to those old bikes was to turn them into "MXers" by stripping off anything that wasn't' essential. The oil tanks and oil pumps were the first things to go. The other must do mods of the time were knobby tires, expansion chamber, new Preston-Petty plastic high front fender in place of the low metal one, front fork brace, MX bars, and of course number plates to look like a real racer!

Let me know if I can help you in any way. Those bikes are easy and a lot of fun to tinker with!

What model are you getting?
For sure, man. It's a DT-1 250 in a faded, rusty, yellowish color. I think it was orange. I'm not sure if black was an option, but the white ones looked sweet. I'm sure it'll look pretty sweet in a metalic black like my old '02 naked and silver pinstripe.

to get the stock look, I'll have to get a stock oil tank. It's not ever going to look stock without it. The bikes also missing gages, lights, the cool looking exhaust shield, and whatever else they took off to make it a MX bike in the 60's. I really like the way it looks stock.

Edit: Oh and it's also missing the cool looking stock fender. A high mount MX style fender is installed in it's place. I got to find me a stock fender too.

Here it is in it's former glory:


hmmmmmm..... I can fabricate a tail light bracket like that... expansion chamber.... I can get some fancy shocks for the back. Dude... I dont think I'm capable of "restoring" anything.... :tard:
 

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If the oil pump goes out, all I have to do is run premix to prevent seizure, correct?
Sure, but how do you think you will know it quit until it's too late? If it quits while riding, you're done.

I love the old Yamaha AT's and DT's. I had an early 70's AT-1 125 and really regret selling it.
 

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Discussion Starter #13
Sure, but how do you think you will know it quit until it's too late? If it quits while riding, you're done.

I love the old Yamaha AT's and DT's. I had an early 70's AT-1 125 and really regret selling it.
Oil pressure sensor with light? Or even better wired to a kill switch.:bom: (isnt there a light bulb emoticon?) Good idea, dude! *patting self on back
 

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The oil pressure put out by the pump is variable dependent on throttle. If the DT-1 is setup like my CT-1, the oil pump is ran by the engine so that it ramps up as the engine ramps up (driven by a plastic gear ran off of the fly wheel iirc). If it's in running condition great, if not, parts are hard to find!
 

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nope, the only way to find out if the oil pump isn't working is a seized motor!!

we had a guy come in to a shop i worked at with an RD200[73-74] and it had quit running, still had the temp tag on it, about 300 miles, and it had seized, well, the 1st question we would ask is, "did you do ANY work on it??!!" and of course the answer is no, well, this guy had the carb slides in BACKWARDS [but, HE didn't touch it!!] now remember, it had around 300 miles on it, and it IS stuck.. so, we pull the cover for the injection pump and what do ya know, there's a bubble in the line, which means he ran it out of oil.."but the tank is full!!" yeah, after the fact, so, just 'cause it's got an oil pump....
 

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The oil pressure put out by the pump is variable dependent on throttle. If the DT-1 is setup like my CT-1, the oil pump is ran by the engine so that it ramps up as the engine ramps up (driven by a plastic gear ran off of the fly wheel iirc). If it's in running condition great, if not, parts are hard to find!
they were adjusted by shimming the pump, lean/rich...
 

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Discussion Starter #17
nope, the only way to find out if the oil pump isn't working is a seized motor!!

we had a guy come in to a shop i worked at with an RD200[73-74] and it had quit running, still had the temp tag on it, about 300 miles, and it had seized, well, the 1st question we would ask is, "did you do ANY work on it??!!" and of course the answer is no, well, this guy had the carb slides in BACKWARDS [but, HE didn't touch it!!] now remember, it had around 300 miles on it, and it IS stuck.. so, we pull the cover for the injection pump and what do ya know, there's a bubble in the line, which means he ran it out of oil.."but the tank is full!!" yeah, after the fact, so, just 'cause it's got an oil pump....
Oil pressure actuated ignition kill switch(OPAIK-- yeah I invented it foos. I get to name it) would prevent that wouldn't it?
 

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I'm staying with the oil pump on my GT380. It's a more accurate way of putting oil into the engine.

When you use premix, you are using only ONE oil "setting" for the engine. You'll likely foul plugs if you idle for a long periods, because the oil mix will be too rich. Premix is mixed for your typical throttle setting--3/4 throttle.

Proper maintenance will ensure that your oil pump won't die. Note that the pump is VERY simple. There isn't much to it, and not much to fail. It's not much more complicated than a rock.

You strike me as some one who is MORE than capable of maintaining a simple thing like an oil pump. Hell, I think it was you who many months ago posted pulling valve springs from a car's engine and using them in a bike or something?
 

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Discussion Starter #19
Quick Opinions Needed!!!

I have approximately 4 hours to decide what fender I want to go with. E-bay auction for a stock fender.

Stock fender or something different? Restore or mod? Please help!!!







I think it was you who many months ago posted pulling valve springs from a car's engine and using them in a bike or something?
hmmm... I don't think I did anything like that, but I did extract broken studs and port polish a pair a heads for my Xterra.
 
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