1975 RD 250 tracker build

So I just picked this thing up a couple weeks ago. First bike for me. Not exactly sure where this is headed but I'm aiming for a tracker style build on it.

Got it running(went through the carbs) and took it for a test ride yesterday. Ran good but then the right cylinder crapped out. Fresh plug in it and it will run for a few minutes then stop sparking. Tried the same thing for three plugs.

I'm interested in putting a newer ignition on it. Any way to get away from points? Do they make something that's CDI based for this bike? Carbs looked good inside and when it would spark it sounded good and ran good as well.

I have a leaky petcock. Any idea where to source orings for it?

Took compression readings cold. 110/115
Compression hot was 100/105
Is that where these motors should be or is this tired and in need of a fresh top end?










http://youtu.be/RVj6cAcB4yk

Anyone have any input on this system? I really have no interest in messing with points.

http://m.economycycle.com/site/mobile?url=http%3A%2F%2Fwww.economycycle.com%2Fservlet%2Fthe-13%2FMZB-CDI-Electronic-Igntion%2FDetail

unless your stator is shot, i would get a dyna-s from vintage smoke. no upgraded charging system, but its almost $200 less.
LEDs would help in the tail section for less draw, and a 35w halogen. not much else.
Ricks has a great combo R/R unit as well. fit both onto my rd350. looks like a good start, love the white.

http://www.ebay.com/itm/1975-YAMAHA-RD250-FUEL-TANK-DECAL-GRAPHIC-SET-LIKE-NOS-/360199848996?pt=Motorcycles_Parts_Accessories&hash=item53dd958424&vxp=mtr

some pricey decals for the tank if you wanna re-label it.

The MZB is well worth the money. I have it on my 250 right now. I set the piston TDC, set my timing wheel and tightened it down. Runs like a clock and you don't have to adjust it after. That was the easiest thing that I did on my bike.

Be sure to look after the crank seals they tend to dry out after some years and there youre in big dudu.

I'm not going to promote any one system over another. Good and bad to be found everywhere. All non-breaker point ignitions have the advantage of zero maintenance. Set the timing one time and you are done. Most are pricey, some are very. The stock points system is just fine though for most applications. However, the stock coils were wimpy when new, and age has almost certainly doomed what ever is left by now. I have a box of them, and many are seriously weak, so if you keep the points, just buy new coils out of hand. Points have one great strength: It is almost impossible to be stranded if you carry a spare condenser. You may lose spark for some reason, but not both cylinders if you have a condenser with you. You can always limp home on one cylinder. The points do take maintenance, but it is easy, and actually is reasonably far between adjustments. All the breaker-less iggys don't need adjustment, but generally if they fail, you are doomed. Carrying a spare black box is probably not going to happen. If there is a real reason to abandon the stock system, it is not so much to eliminate the points, but to eliminate the stock rotor. Unless you drive like a little old lady, the rotor halves will eventually loosen up and the rotor will fail. And THAT will definitely leave you stranded, so if you lose the points, lose the stock alternator as well. For the record, I personally prefer fitting a Banshee system (from the Yamaha 4 wheeler) because you also get to eliminate the battery. Lots more spark, no adjustment, no limit on revs, lots of weight savings, no dead battery ever, and as bomb proof as anything I have seen. The big down side is you have to build a hybrid crankshaft to fit it (apart from that, it is practically a bolt on). My own stock RD has points and reproduction stock coils. Runs superbly, but its only a matter of time before (another) rotor comes apart. Someday when I have time, I will make a "transistorized" ignition that uses the points at much lower voltage to trigger a transistor which will switch the 12v to the coils, and put bigger screws in the rotor and rewind it. Right. Project #862. Have to get right on that!

jp do you have any pics of your failed rotors?
you are getting me worried...luckily i have a spare rotor with all 8 of the red plastic-covered screws still intact just in case, but i have never heard of this happening before!

Thanks for the info guys!

Do the compression #'s sound right?

I'll look into crank seals and inspect the top end this winter. Still haven't done anything else with it since running it. Got married and left for a two week honeymoon and now there's house remodeling to do. Hopefully I will dive into this once the cold weather gets here.

Well finally got around to messing with this bike. Fires up and runs nice, idles well. All signals, headlight, tail light, brake and horn work.

Ordered a new master cylinder, caliper and pads for the front brake system.

Re packed both mufflers.

Rebuilt the petcock with a new oring kit. Also added inline fuel filters to each carb.

Ordered fork seals but need to pull the forks to replace and refill with oil.

Most importantly, got it registered yesterday!

Going to put on a set of bars and grips on then ride it once or twice before it gets too cold.

Thinking about pulling the oil injection and running premix? That's the first thing we do on the Jetski motors. Better to know exactly how much oil you are adding than just hope the pump is doing its job. Or have a pump fail and go BOOM!

Plus, the oil mixed in helps stabilize the crappy ethanol fuel we have a bit, when it sits in the tank.

Nice RD you got there i m doing an RD built 1979 with CDI...last aircooled model.

I m not a fan of premix.think about it when you go off the gas the motor will run with just the oil thats left in the cyl.
Going downhill downshifting with no steady grip on the gas hand will do no good.

Ill run my RD with the oil pump.premix is for racing only where you steadily rip the crap out of the stroker.

Oil pumps can fail but it's pretty rare and the motor needs different amount of oil depending on load. Per-mix gives you the same proportion regardless of throttle position and with a closed throttle you get zero oil feed. With a pump there is always some oil feed.

The only time I will get rid of a pump is on a road race bike that will never see the street like my TZ. With that bike I want fresh race gas and fresh oil and in the proportion I decided to run. On my street 2 strokes I always run a pump.

My first bike was a sixties Villiers motor in it and it needed pre-mix and what a royal PIA that was. If I wend more than a few miles I had to carry oil around with me. I quickly learned that there had to be something better and there was - oil pumps and injection. Thank the lord.

The compression numbers seem a little low. Fortunately those motors are so easy to work on and reasonably light too. Pop in new crank seals. No need to strip the crank, but it would be a good time to strip the motor and give it a good clean and inspection and time to check the bores and make it all look fresh.

Cool. Thanks for the insight guys. On the skis we rip the hell out of em. Lots of sustained WOT runs so premix is always safer. I guess I forget on a bike you can still roll at 50-60 and be off throttle. Letting off the throttle on my ski is hitting the brakes. Lol. I have some premix in the tank right now and the oil tank is full with the pump operational.

Today fork seals got installed but the fork tubes have been painted and are very pitted where they slide through the seal. Wondering if I can source some "good used" tubes here?

Put some lower/straighter bars on and mocked it up today also. Will need to move gauges to make them work right without interfering with the master cylinder banjo bolt.

Anyway here's the pics. More to follow in a few day when get back to it. Need to do a fuel pump on my work beater car. Driving the truck right now and it sucks to fill that ga$ tank.

rotate the bars back you don't want them tipped up at the end like that,you can't control the bike

Took it for another test ride up the block today after doing a little more work. It Ran good and I think she's ready for maiden voyage. Supposed to rain all day tomorrow though.

Caliper mounted, brake line flushed, brakes filled and bled.

Gauges moved with some ugly temporary mounts. Used some spare handlebar top clamps to move the gauge cluster. Also flipped the headlight brackets to lower the headlight and have space for the gauges.

Gas tank cap rubbers all replaced. Also ordered a second key. Just nervous I'll lose the only one and be screwed.

Basically just wanted to get the bike all safe and ride it once or twice then tear it all down to build it how I want.

Took it out to shake it down today with poor results.

It started out good. Bike ran fine, much peppier than I expected for an air cooled bike(I came from 250cc single liquid cooled dirt bikes). I guess the whole two cylinders thing helps with torque.

Made it to a local gas station(1.6 miles away according to tripometer) put in a gallon of fresh gas then wouldn't start. Had my buddy ride back to my house to get my truck and we loaded it up and went home.

Battery voltage read 10.2 and I had faint spark, no headlight, no horn, and dim neutral light. Charged it back up and the bike fires right up. Checked the battery with the bike at a high idle and it jumps from mid 12's to 13.8 volts. Is that enough output to keep the battery charged?

My next step is ditch this old electronic junk and buy that MZB system. Worth the money if it keeps the engine running the whole time I want to ride.

One other issue I had was the neutral light stayed lit the entire ride no matter what gear I was in. Neutral safety switch bad? Do these bikes even have one?

Thanks for the help guys. You've been good to me so far.

Bruceski said:

Took it out to shake it down today with poor results.


One other issue I had was the neutral light stayed lit the entire ride no matter what gear I was in. Neutral safety switch bad? Do these bikes even have one?

Click to expand...

had an issue too with my neutral switch.the switch generelly is a plastic piece with a contact brass piece fit into it.when the gears change theres a tiny "pin" that moves and connects,if in neutral with that brass piece.the whole thing is behind the front sprocket.

the brass piece has a ground cable that closes the circuit and lights up the neutral idiot light.

so my guess is that your neutral grounds at any given time....so there must be an electrical problem,since you can switch trough the gears.

There are a few quick things to do. Check the two output connectors from the stator. They are the white plastic 3 wire plugs, one located under the carbs coming from the alternator, and another next to the battery in the sleeve with the fuse holder. They get resistive and melt fairly often. Since you are getting intermittent voltage, look at the regulator. It is under the battery, and a bit of a pain to get to. You may get lucky and solve your problem there. Take the cover off (two little phillips screws). Be careful not to damage the seal. The unit is mechanical. Clean the points like you would ignition points. They are adjustable by bending the tang that works against the operating spring. The process is easy, but detailed to relate here, but the factory manual is clear and easy to understand.

Otherwise, barring some simply broken wire etc, parts can fail. Commonly the rotors go bad on RD's, especially if they have seen high rpm. They commonly test ok on the bench, but fail while spinning. Look for exposed (or missing!) screws on the front face of the rotor. They are covered with epoxy from the factory, but if you see little holes where the epoxy has popped out exposing the screw you are doomed. Rectifiers go bad but rarely. See the manual for tests (I know, thanks for the help!)

If you are going to change the ignition, consider an entire system with a new charging system to escape the rotor issue. Very expensive though. The stock system is fine though if you are easy on your engine (right - good luck with that). Keep if below redline and infrequently get close to it and it works great. One of my drivers is totally stock, runs great and charges fine even with a 50 watt headlight, though admittedly carefully assembled.

Last thought, check carefully the brush assembly on the front of the alternator. It's old, so make sure the wires are good mechanically, brushes are working and not too worn (they cam in their housings when worn too short) etc. The factory manual is your friend here. It has one of the better explanations of how your system works, and is not too intimidating.

Your neutral light wire has to be shorted to ground somewhere. Take it off the switch, and assuming the light is still on, trace it back to the instruments and find where it is grounding to the chassis.

Thanks! That was some detailed info there. I have a manual here. I'll do some reading and check it out next week when I get some time again.

I'm really tempted to just order the MZB ignition. I know it's pricey, but it should be a set it and forget it piece.

I'll let you know how it works out once I go over some of the current electronics and the neutral switch.