Just bought a 1975 Yamaha MX 250

[TRexRacing]

You can remove those little plastic caps holding the floats down.It will ruin them and they are no available.However they don't affect they floats operation.Clean the pin the floats mount on and that should free up the movement and allow them to work correctly.

 

[giggyhurdle]

I took the pins ends off and took the floats off. I cleaned behind the floats and I cleaned the pins. I then sprayed the whole thing down with WD40. I forget how much that stuff smells like bug spray...

I blew out the jetz (My roommate is a VW nut, he rebuilds engines and crap, he said I should take the jets apart and just do a rebuilt, I figured I'd give this a try to see how it goes..)
When I get home today, I'll put it back together and put it back on the bike.
It looks like my bike has an oil resevour on the side of the bike, I haven't looked at it closely. Is there a way to check the oil levels in it? Thank you.

quick note: Should I keep the airbox that's on there now with dual filters, or should I switch to a single filter coming right out of the carb? Any help would be great. Thank you.

 

[gwcrim]

I'd keep the airbox. It's the first level of protection from mud, water and other nastiness.

 

[giggyhurdle]

Cool.
Now, I'll need to replace the attachment for the front brake, as that part is broken.

 

[TRexRacing]

Sounds like progress is happening.Cool.

 

[giggyhurdle]

Next Question.. for today.. I'm looking for the HOLDER, LEVER 2 part (it's the generic name of the hand brake holder).. Will anyone work? Seems like a pretty generic part.

 

[Shaw520]

Next Question.. for today.. I'm looking for the HOLDER, LEVER 2 part (it's the generic name of the hand brake holder).. Will anyone work? Seems like a pretty generic part.

Thats called the "perch" can be found at any bike parts store.



Note the three items Ive marked,.. they should be removed and cleaned with carb cleaner and compressed air. Do not stick anything through them, solvent and compressed air only.

 

[giggyhurdle]

Will any perch do?

 

[giggyhurdle]

Premix or.. is there injection? I've checked bike bandit for the oil injector in a diagram, and I can't find it. Should I pre-mix?
So, I've been scouring the internet to find out if my bike is pre-mix or not. It makes sense that it's not because the 73 and 74 weren't. However, I don't know what the oil resovier looks like. I find an ausie website that has a lot of pictures of my bike, but even on there I can't see the oil resovier..

 

[supernova]

yes your bike is mix whit oil maybe 32:1 i whill start whit that.

excuse me but i thing you d'ont have experience wite dirt bike so ask question here and stick wite the answere you got from here sory for my english is not to good :bang: i am french but i can read you :cool:

 

[Vintagesplash]

The '73 and '74 MX models came with oil injection but the '75 is a premix only bike. I run 32:1 in mine.

Sounds like you have the carb rebuild going fairly well. You can find the exploded diagram for Mikuni carbs at Sudco.com. For cleaning a varnished carb, I buy Chem Dip carb cleaner in the 1 gallon can. It has a basket in it for dipping the carb. DO NOT OPEN THIS CAN INSIDE THE HOUSE.

REPEAT: DO NOT OPEN THE CAN IN THE HOUSE!!!!!!!

I did and my wife nearly killed me.

A good alternative to buying a new perch and brake lever from the dealer would be to go to www.denniskirk.com and order from them. They are a good source.

 

[giggyhurdle]

The '73 and '74 MX models came with oil injection but the '75 is a premix only bike. I run 32:1 in mine.

Thanks so much for this tidbit. I spent many many hours yesterday looking for this answer, as well as the oil injector. I'm gong to be out of town this weekend (which is sort of a good thing. It's supposed to be really cold) so I won't be able to work on the bike again until Tuesday. But, by that time I should have my manual. I'll put the carb back on, hook everything back up filler with the pre-mix, and fire here up!

thanks for everyones help thus far.

 

[giggyhurdle]

As far as oil goes for the case, am I okay using Motor oil? (like 10w-30 or something like that?)

 

[BadgerMan]

Use a four stroke motorcycle oil. Some of the energy conserving automotive oils have additives that can make your clutch slip.......so I am told.

 

[giggyhurdle]

This just in..

She's running. Not idling.. but eh.. no big deal. She starts on the first kick.

I had the throttle in wrong.. it wasn't all the way down in the carb liked it was supposed to be.
The clutch works fine. I push started it down the hill and pushed the clutch in. Works like a dream.
tomorrow it's going to be installing the perch on the front brake, getting new air filters and a gas cap.. and ... she'll be on the trails!!! Thanks for everyone's help!

 

[giggyhurdle]

I'm back again.
I finally got the idle screw, and I left my bike running to warm up yesterday (It was around 55 degrees) and I came back, and it had died. It looks like the idle screw came out. I put it back in and started it up again, this time I reved the engine (the bike was in neutral) and it lurched a bit forward and died.
I tried riding it a bit, but I couldn't get it into first gear and the clutch wasn't engaging (unless I had it in 5th gear). There is no neutral anymore, and when I put it in the lower gears, the bike goes about 4 inches and locks up.
I'm thinking I'll need a new transmission and clutch.
Ugg.