Vintage Dirt Bike Q & A

What is a good duel purpose tire for the mt. Still have the original brigstone on right now.

trying to decide which tires i like. Will a 4.00x18 fit correctly in place of a 3.50x18. Since i have the tires and rims off the bike, i dont know how much clearence there is. this is the 74 mt 125.

ordered the kenda270. looked like a good duel purpose tire.

I bought the same tire for my MT250 project a few weeks ago. Haven't mounted yet, so I can't really offer an opinion.

making progress a little at a time.

The bike's looking good!

I ran the Kenda 270's front and rear for most of 2011 on my MR, 40% street / 60% trails. It's an excellent tire for hard surfaces like pavement and hard-packed dirt, and wears pretty well. The rear is a fairly large-diameter tire and noticeably affected my gearing, adding maybe 3 or 4 mph top speed. After the Kendas I went to the Dunlop 606 front & rear (much better on the dirt but didn't seem to wear as well, especially the front), and right now a set of Bridgestone M403/404's are waiting to go on. These tires are super light and work great on my YZ, I hope they wear OK.

I've had left-side clearance issues with every replacement rear tire I've put on the MR (4.00-18, 120/100-18, etc.), so I imagine the MT125 is similar. Even with the tire rubbing the chain guard, the wheel is still cocked slightly to the right. Last week my chain came off for the first time, and though there were several factors involved, the misaligned sprocket surely didn't help.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I got the 3.50x18 for the rear and clearance looks good. but i had to go with the 3.00x21 for the front instead of the factory 2.75. I dont see any future problems on the difference.

Now to figure out my timing issue, still have to fix a pin hole in the fuel tank and paint it. I have vinegar in it soaking to try and clean the rust out.

I've got spark but not sure if my points are set right as i dont have a light set up to check them yet.

Anyone know what compression should be on a new piston and ring job?

for setting the ignition timing,i would get timing checker at HVC Cycles.
http://www.hvccycle.net/ignition-timing-tester-buzzbox/

i use a similar unit on all my bikes and it is called a Okuda Timing checker 2030.
you hook up one lead to the black or black wire with a white stripe coming off of the ignition and the other lead to ground on the engine or frame itself.

here is my okuda in action with a dial indicator being used but if your MT125 is like my MT250,there is a plate on the magneto cover with a arrow in it and you align it with the mark on the flywheel so no dial indicator is needed on a MT250 and possibly the 125 as well.


if you have the eyes of a eagle,you want the points to crack open when the marks align.i use the testor as my eyes are not the greatest.

the timing on my example reads 2.7 mm BTDC.
also if your crankshaft rotates Counter Clockwise,you want to turn it clockwise to set the timing.

the Okuda beeps when the points are open and it goes out when the points close if memory serves.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

the mt 125 is the same as the mt 250. i'll pull the flywheel and make sure the key is in the slot .

i just dont know why the spark quits when i increase the rpm. it starts out looking good at very slow rpm and gets weaker till it quits as i increase the rpm turning the flywheel with drill.

sounds like a feasible option there Rob.that is indeed strange!

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!