Old School Yamaha.

[Rustydog2010]

This is a old Yamaha bike I was just given! The guy I got it off said that it ran a couple of years ago. He reckons its a tt420 2 stroke. But I cant find any info on it.

Anyone help with the model?
The numbers above the clutch cover are 547-000722.
Still searching google, but to no avail.

Going to go clean the carb and give it some fresh gas, and see what happens.

The thread would be usless without some of these






Jeremy.

 

[Rustydog2010]

Okay so its 396cc, and it looks very similar to a Yamaha DT.

The best news of all is that all I did was chucked in some fresh gas, and she now runs beautifully.
Not to sure weather to do her up, sell it as is or chuck the motor in a go kart chassis I have?

Jeremy.

 

[bighead]

Interesting. I did not think Yamaha ran the pipes under the bike? DT run them out the side. I would guess 1970 71 or 72 from the pipe style. Really got me stumped on this one.

Check the motor mount brackets. It looks like they are not factory. Shifter arm does not look right as well. And I do not see Yamaha on the cases.

Also how does it kick start with the pipe right there?

Sorry if I am wrong. Just stumped right now.

 

[Rustydog2010]

Thanks for the input, the pipe is quite obviously not stock. A very shoddy homemade one. The shifter arm looks standard, the yellow you can see is just a bit of hose on it.

Kick starting is a bit of a pain when it forces your foot off of the kicker, but I suppose I cant complain, it was free.

I think if I can be bothered I might make a new pipe for it.

I suggested DT, mostly because of the rear end.

Jeremy.

 

[bighead]

Okay that explains alot. You can see on the head where the fins are shaved. Thats where the original pipe would have gone.

DT is a later model. I would start with DT1. But most of the DT and DT1 has that chrome flip top gas tank. Does the tank look stock or plastic aftermarket.

Also search RT2 and LT2 will get you close. Enduro as well. The enduro dt1,rt2 and lt2 all get called DT's over time for the later same models were all DT's but look the same. Hope that makes sence. Also all DT has electric start I think.

Those are bullet proof motors. Thousand and thousands of them are still running today in stock condition. All most all the old yamaha's enduros I can get running. You can't kill them. We ave a GT80 enduro in the family for 30 years and it still runs. I also restored the family MX80 last year. Motor still runs like new. Yamaha did these right.

If you can find a model you can ebay a pipe pretty cheap. Lots of sellers parting these old bike out.

 

[Russ2251]

And I do not see Yamaha on the cases.

On the opposite side...the magneto cover will identify it as Yamaha.

 

[bighead]

Willing to bet you have a YZ400

The small gas tank lid and big fat padded seat put it into the off road model for sure. Your heads looks more like the YZ. Also notice the larger rear brake arms are the same as the MX and YZ. Also notice the tops of the shocks? (looks like speedo and tach) I think you have a YZ or sure.

If the tank is original paint I would guess YZ model. All YZ back in the day were yellow like that.

Look here. http://home.comcast.net/~vintagemxbikes/yz400c.htm

 

[88s10Durango]

Iknow its definately not a TT engine , I have one ( TT 600 ) engine for my kart , all TT models are 4 stroke ,yours is for sure a 2 stroke and the MX is looking like thats what you have , you should have a proper exspansion chamber close to the head for that engine to perform correctly ,your pipe looks more along the lines of a 4 stroke pipe . as far as starting it try to slowly pust the kicker tell you are on the compresion stroke , once there stop ,then give it a good solid kick following through till the kicker is down low, don`t give the kicker a general jab kick from any position, this usually leads to a broken kick lever and or a kickback which you will feel or throw you off the bike lol .heres a pick of my 4 stroke TT 600 , big difference in the design of the engines .

 

[bighead]

Pretty sure it is a YZ. Check out the fork tops. What ever those are at the top of the forks by the bars. Same fender as well on the bottom one. I say 1976 YZ400C with an aftermarket Clark tank.

And maybe it has a YZ175 tank. Thats the only model I can find with the lid on the side.

If it's a YZ400 then it should be a screaming engine. Thats a big two stroker. The bike look to be okay condition. I would get a pipe and air box. Some side plastics. Paint and put it back. I love bringing these old bikes back to life. Would be hard to start on a kart. There is also money to be made on Ebay. That tank is $100 easy with no rust and dents. Is that a aftermarket or original tank? Looks nice to the rest of the bike.

Also looks like the seals are out on your forks?

 

[Rustydog2010]

Cheers Guys.

Russ: Yes it does, it says Yamaha on the clutch cover.

Bighead: I think you may be onto it. The things on top of the forks are air reservoirs I presume. Its where you fill the shocks with air. Will snap a pic tomorrow.

Durango: It seems that if tts are only 4 stroke this isnt one, the kick start method is good, but this seems to have very little compression, or the kick start gearing is perfect. Will get the gauge out tomorrow.

Jeremy.

 

[newrider3]

but this seems to have very little compression, or the kick start gearing is perfect. Will get the gauge out tomorrow.

Jeremy.

In my experience with old DT's and YZ's is that they are very easy to kick over, even on a fresh top end.

 

[Rustydog2010]

If it's a YZ400 then it should be a screaming engine. Thats a big two stroker. The bike look to be okay condition. I would get a pipe and air box. Some side plastics. Paint and put it back. I love bringing these old bikes back to life. Would be hard to start on a kart. There is also money to be made on Ebay. That tank is $100 easy with no rust and dents. Is that a aftermarket or original tank? Looks nice to the rest of the bike.

Also looks like the seals are out on your forks?

Wow totally missed this part of the post.
I dont think it would be to hard to start on the kart I have, but then saying that it has the horsepower but a lot of unusable torque.
Ebay isn't that popular down here in NZ. We use trademe.co.nz, I had a look and couldn't find any old YZ400's like this one? The tank looks original, same mounting holes and brackets etc. But as you say the condition of it looks to good. It has a few dents and scratches, but clean as a whistle inside.

The forks are something I don't understand. They are air shocks, but how many PSI do they need? I put some air in them yesterday and they seem to be holding it.

Cleaned the carb today, could see the piston and rings and looked to be in good condition.

Jeremy

 

[Rustydog2010]

Oh My! This thing goes like a cut cat! Seems to be a 4 speed. The throttle seems to be starting to stick, so I think ill check that out before I do to much more.

Jeremy

 

[88s10Durango]

Should be a 5 speed >> 1 shift down to first .. then 4 shifts up ..

 

[Rustydog2010]

Yea thats what I wasn't to sure about. I go one down then there are three up shifts. If you go for a forth it feels like it goes into neutral. Must be missing a gear or something?

This is IIRC, will go have another go later.

Jeremy.

 

[bighead]

In my experience with old DT's and YZ's is that they are very easy to kick over, even on a fresh top end.

I would agree with this but not the big bore YZ's. They can be a mother to kick over. 490's are not easy to start.

 

[Rustydog2010]

You can turn this thing over by hand! Tried the compression gauge but couldn't get it between the tank and head...

Jeremy.

 

[Rustydog2010]

Its hay making time!!





Havent really been able to open her up yet, because of the long grass. Now we have cut for hay, I got straight out there.

OMFG this thing is nuts. Have only got to 3rd gear! Think I might have to keep this new toy.

 

[Rustydog2010]

All done, tomorrow morning there will be no more obstacles. I really like the look of Bigheads restored MX80. So I think Bighead may have convinced me to restore the old girl.





Jeremy.

 

[Rustydog2010]

Oh well, took the piston out. Only to realize that it has absolutely stuffed rings.

I took the numbers into my local Yamaha dealer and he found out that the frame is a 1976 YZ250 frame, the motor is a DT400.

The sad thing is that they cant get parts for them. So will have to look at getting rings made and getting new locator pins put in the piston. That will be tomorrows job.

Jeremy.