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Old 08-17-2012, 11:57 PM   #1
rightone1974 OP
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Cool2 need 1976 Yamaha DT 250C info

I am new to this site so if I make any mistakes please let me know Im trying to get used to it.

I have a 1976 Yamaha DT 250C enduro and I am trying to get any information about this bike that I can find out. I was thinking about bypassing the oil injection and just premix it myself. I just cant rely on the injection system. I live in a very rural area and don't want to get stuck out in the middle of the mountains What do i need to do to get my bike to run right? Can I change the jets in the carb to next size up? or should i leave them stock. what would I have to gain or lose from up sizing my carb jets? I onlyt paid 50 buck for my bike and it runs great now it is pretty quick considering. it was sitting for almost 10 years before i got it. it is hard starting, how can i get it to start easier?
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Old 08-20-2012, 01:16 PM   #2
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If you are going to premix you'll have to go to larger jets since the oil going through the jets will effectively make your mixture leaner. How much larger I couldn't say. Make sure you block off where the oil enters the carb/intake so you don't have an air leak. I have an oil injected Yamaha 2-stroke and I like the injection. I can just ride up to a gas station and fill up, no mixing. In my opinion you should just leave it alone.
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Old 08-20-2012, 03:18 PM   #3
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Pre-mix is a good idea.........as long you remember to add oil to fuel there is nothing to go wrong. If you use 50:1 mix with a proper pre-mix only fully synthetic oil, then I doubt very much you will need to change jets as factory set up is generally always going to be on the rich side as standard anyway.

As to bad starting, carefully clean out the carb, check the reed petals are sealing properly, and fit a new non resistor waterproof plug cap, and an NGK irridium spark plug. If there is any sign of rust/crap in the carb, then you might have a corroded tank, and it would be good idea to clean tank out as best you can, and fit a clear inline fuel filter.
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Old 08-21-2012, 06:08 AM   #4
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I have a 1974 DT250A and have removed the oil injection. I premix 32:1 using good quality two stroke oil. The carb jetting is bone stock, same as original Yamaha spec. Spark plug is always a perfect light/ medium brown color and the bike runs great. I made a small plate to seal the hole where the oil pump mounted and removed and sealed the oil line connection. I removed the oil pump control cable from the cable splitter and sealed the opening in the side cover. This worked fine, but I was concerned about the splitter possibly causing the throttle to stick so I had MotionPro make a custom one piece cable.
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Old 08-21-2012, 07:34 AM   #5
JWhitmore44
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I've had a 73 AT3, a 76 DT250, and a 81 DT175 and never had a problem with the oil injection. the DT250 was my high school bike and my buddy had one just like it. We ran those bikes all over the place never had a problem. There was s site glass on the oil tank so it was easy to keep an eye on the level. Fill up at any gas station. I live in a rural area and I would much rather have the oil injection. If my injection tank has oil I can barrow some gas from a farmer if I run out in the middle of no where. If you are running pre-mix you either have to bring your own gas or bring oil with you.

As far as getting it running, I'd freshen up the top in with at least new rings and a hone. Over sized pistons are fairly economical for 2 strokes. Check the carb intake mount for cracks, make sure there's no air leaks.
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Old 08-21-2012, 05:38 PM   #6
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Old 08-22-2012, 09:37 AM   #7
Shocktower
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The oil injection systems in yamahas have worked for years, they are nearly flawless, I will never remove an oil injection system unless I am going to race a bike at a track..........................................
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Old 08-22-2012, 10:25 AM   #8
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Quote:
Originally Posted by Shocktower View Post
The oil injection systems in yamahas have worked for years, they are nearly flawless, I will never remove an oil injection system unless I am going to race a bike at a track..........................................
Totally agree...Yamaha oil injection has never been a problem for me ... when I blew up my TY175 everybody told me to ditch the oil injection....the oil injection was not the problem..the old ass crank seal was the problem leaning it out.

When set properly the oil injection is not an issue.
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Old 08-23-2012, 08:56 AM   #9
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Running oil injection on any bike not intended purely for road use isnt that great an idea, as it means to more to do wrong, and 2T motors never seem to run as cleanly on injection, when compared to pre-mix.

Removing the injection was always the first thing to do on the old TY Yams, and as well as making the bikes more reliable and better running, the throttle action becomes much lighter.
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Old 08-24-2012, 02:05 PM   #10
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I had probably as many as 30 Yamaha Enduros back in the ld days. I not only never had a problem with an Autolube, I never knew ANYONE who did. I did remove one and had a bitch of a time getting the bike to run right with different mix ratios when I used premix. I also suggest if it is to remain street legal, NEVER remove the Autolube
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Old 08-24-2012, 02:21 PM   #11
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Originally Posted by Sniper X View Post
I had probably as many as 30 Yamaha Enduros back in the ld days. I not only never had a problem with an Autolube, I never knew ANYONE who did. I did remove one and had a bitch of a time getting the bike to run right with different mix ratios when I used premix. I also suggest if it is to remain street legal, NEVER remove the Autolube

I agree 100%.. if the OP is not sure he should go ask over at Yamahaenduro.com . just about everybody over there that is not racing their bike will tell you keep the Autolube and make sure it is adjusted properly. I have been on some pretty crazy rides with those guys and know a few that rack up major miles on their vintage yamaha's and they all keep the autolube.

good luck convincing Twin-Shocker from what I have seen on ADV Rider he knows everything dont ya know
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Old 08-24-2012, 02:32 PM   #12
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I was a service manager at a Yamaha shop for ten years covering that model. I can say with some confidence that I've never experienced a failure from a Yamalube system. They are bullet proof! Simply keep quality 2stroke oil in the tank. Bleed the system (simple) and forget it! Mixing will let you down sooner or latter. Mixing does not take into consideration the raising and lowering of the RPM's.
Yamalube does! This is a very simple decision, leave it alone!
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Old 08-24-2012, 09:44 PM   #13
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Premix will limit your travel to 1/2 a tank from home, unless you carry extra oil and a ratio-rite cup. I have a bike that's pre-mix and carry the right amount of oil in a container for exactly two gallons of gas. I would leave it alone.
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Old 08-25-2012, 05:44 PM   #14
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Originally Posted by WRW9751 View Post
I was a service manager at a Yamaha shop for ten years covering that model. I can say with some confidence that I've never experienced a failure from a Yamalube system. They are bullet proof! Simply keep quality 2stroke oil in the tank. Bleed the system (simple) and forget it! Mixing will let you down sooner or latter. Mixing does not take into consideration the raising and lowering of the RPM's.
Yamalube does! This is a very simple decision, leave it alone!
If Autolube works so much better than pre-mix, I wonder why no serious 2T competition bike has ever been fitted with it?

Some of the main reason serious comp 2T's all use pre-mix, is down to the fact bikes run more cleanly, mix ratio's can be adjusted to suit race conditions perfectly, and there are no extra mechanical parts to go wrong and add extra weight.
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Old 08-25-2012, 09:01 PM   #15
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Originally Posted by Twin-shocker View Post
If Autolube works so much better than pre-mix, I wonder why no serious 2T competition bike has ever been fitted with it?

Some of the main reason serious comp 2T's all use pre-mix, is down to the fact bikes run more cleanly, mix ratio's can be adjusted to suit race conditions perfectly, and there are no extra mechanical parts to go wrong and add extra weight.
You are really talking apples and oranges here. The DT's were designed to be play bikes. They work great to ride trails on the weekends,, run errands during the week, and even take you to work or school. You don't have to worry about pre-mix or carrying 2 stroke oil with you. If you are running low stop at 7-11 and top off. No need to worry about trying to figure out how much oil to put in 1.35 gallons of gas. They were also made for longevity, you don't have to do a top end every third race or so. You also have lights, turn signals, horn, some even electric start, I don't think there's concern about the little bit of weight the injection adds.

Compare that to an MX bike that is being ran at mostly the higher RPM's. It's not that big of a deal to re-do a top in between a race or two. You have your premix already mixed up in the spare gas cans back at your pit, tuck, van what ever. I never rode trials, but I can see why yo may want to get rid of it on the TY's. You're probably never too far from your can of premix. You're typically ridding trails or at a track. I'm not saying you can't make a non-injection into a play bike, I would love to plate my son's KDX. But if I did it would be so much nicer to have oil injection on it.

If you need to disable the auto lube you probably started with the wrong bike for your intended purpose.
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