Author Topic: Yamaha 1974 MX250 (Read 5110 times)

rtbmrgl · « **on:** April 19, 2015, 12:49:17 PM »

Picked up a 1974 Yamaha MX250 Basket case. Got it for $400, included a new Webco piston(not installed) and a fresh bore, new upholstered seat. so figured a good deal.
Heres the bike as purchased, Ive been doing few things with it, Ill post the pics.

ekpent · « **Reply #1 on:** April 19, 2015, 03:24:34 PM »

Check out this original awesome one for inspiration http://lansing.craigslist.org/mcy/4982043682.html

micol · « **Reply #2 on:** April 19, 2015, 08:48:11 PM »

Had one for a long time. Geared down some, it made a pretty good play bike with good power. Had 70's handling and suspension all the way. Will look good put back together.

rtbmrgl · « **Reply #3 on:** April 19, 2015, 10:03:02 PM »

Quote from: ekpent on April 19, 2015, 03:24:34 PM

Check out this original awesome one for inspiration http://lansing.craigslist.org/mcy/4982043682.html

That incredible, all original, including the tires. You never see the little rubber dampers on the fins.

rtbmrgl · « **Reply #4 on:** April 19, 2015, 10:09:02 PM »

Quote from: micol on April 19, 2015, 08:48:11 PM

Had one for a long time. Geared down some, it made a pretty good play bike with good power. Had 70's handling and suspension all the way. Will look good put back together.

Plan on making a nice vintage runner, not a no-ride show piece.
I used to have a '73 SC500, a friend had the MX250, he loved it.
I have the stock gearing now so maybe lower a tooth on primary. I have an aftermarket heavy flywheel, bolts on top of the stock internal rotor, adds little over a pound. Should help trail with slow riding

rtbmrgl · « **Reply #5 on:** April 22, 2015, 06:06:31 PM »

Cut the spokes off, getting new set from Buchanan spokes. Will clean up hubs and install All-Balls wheel brgs. The cracked rim, very common, they always crack right at the seam. Same thing on my SC500, $40 at Bast Welding,
FYI the same Bast family that raced and races Speedway bikes. The owner Harlen sr. Sammy, Bart, and there uncles, former world champions Steve and Mike Bast.

Did a little painting.
A little trick when painting the head and barrel, I wanted the edge of the fins not painted, before painting I took a bar of soap
and ran along the edge, after paint took razor blade and scraped off, easy-pezzy.

rtbmrgl · « **Reply #6 on:** April 24, 2015, 10:01:56 AM »

Re-building the forks, dampers are in good condition, cant say that for one of the tubes, has rust pitting. Its not terrible and its have way up the tube. So as far as I can see there are three options,

#1- re-chromed, probably too expensive
#2 Find NOS or one in excellent cond. (yeah right)
#3 my favorite, just wheelie all the time so always extended.

grcamna2 · « **Reply #7 on:** April 24, 2015, 10:48:01 AM »

I've done the old 'sand the nicks,rust pits w/ fingernail' more times than I can count and that always saved a pr. of old tubes unless the stuff was too extreme and I just kept going deeper into the fork tube.
I remember what looked like a tiny rust 'pit' hole near the bottom of the fork tube travel area on a fork I was working on for a long time(couldn't charge for it..)that ended up going 4mm deep

and had to find the guy another "good used cond." fork which worked out good for us w/ only deep scratches to sand smooth.

Have any of you heard of different other ways to fill in nicks,pit marks on fork tubes that are recommended ? New ones are Big $.

rtbmrgl · « **Reply #8 on:** April 24, 2015, 05:48:19 PM »

Quote from: grcamna2 on April 24, 2015, 10:48:01 AM

I've done the old 'sand the nicks,rust pits w/ fingernail' more times than I can count and that always saved a pr. of old tubes unless the stuff was too extreme and I just kept going deeper into the fork tube.
I remember what looked like a tiny rust 'pit' hole near the bottom of the fork tube travel area on a fork I was working on for a long time(couldn't charge for it..)that ended up going 4mm deep and had to find the guy another "good used cond." fork which worked out good for us w/ only deep scratches to sand smooth.

Have any of you heard of different other ways to fill in nicks,pit marks on fork tubes that are recommended ? New ones are Big $.

Thanks for getting back, It will probably be ok, the pitting holes aren't large. My CB500 had a gouge about 8mm long and 1-2mm deep, i filled with JB-Weld and sanded smooth, never had a leak.

grcamna2 · « **Reply #9 on:** April 24, 2015, 07:59:56 PM »

Mark,
Did the JBWeld repair you described on that fork tube need you to prep the fork tube by sanding down to bare steel? or did the JBWeld bond to the hard outer chrome plating on the tube ?

rtbmrgl · « **Reply #10 on:** April 24, 2015, 08:27:37 PM »

Quote from: grcamna2 on April 24, 2015, 07:59:56 PM

Mark,
Did the JBWeld repair you described on that fork tube need you to prep the fork tube by sanding down to bare steel? or did the JBWeld bond to the hard outer chrome plating on the tube ?

No I didn't sand down the chrome, the chrome was in good condition, only the gouge in one place. I filled in with JB Weld and sanded so even. Hope I described to make sense.

grcamna2 · « **Reply #11 on:** April 25, 2015, 06:23:53 AM »

Mark,Yes that helps.
I've used JBWeld plenty and heard of folks using JBWeld to repair fork tubes but haven't tried it myself;it sounds like an excellent way to save fork tubes w/ scratches,nicks or rust 'pits'.

rtbmrgl · « **Reply #12 on:** April 25, 2015, 10:56:43 AM »

Heres the tank, it was painted over the original color and decal, i think 4 times. The bottom layer found it was off a 1973 MX360, . The other colors incl-
red, green, yellow, gray,