shooter308 Posted June 30, 2008 Report Share Posted June 30, 2008 I've got a 74 Yamaha TY 250 that my best friend owned and used to ride frequently. Then he sold it to a mutual friend of ours last summer and it sat for a year. I got the bike after he passed away last Labor Day Weekend. When my best friend had the bike, we put a new condenser on it and it seemed to run fine. He did have to change the spark plug fairly often because his plug would be fouled out. It seemed to have a weak spark. Would this be a problem with a bad coil or just the points need to be changed? I cleaned the carb a couple of weekends ago and it has fuel getting to the spark plug, but I don't have any spark at the spark plug. Is there a place to change it over from points to an electronic ignition type setup? Your help is greatly appreciated. Thanks, Doug Quote Link to comment Share on other sites More sharing options...
dgshannon Posted June 30, 2008 Report Share Posted June 30, 2008 Is there a place to change it over from points to an electronic ignition type setup?B & J Racing http://www.bjracing.com/id115.html sells a top notch electronic ignition kit, for the TY 250. Quote Link to comment Share on other sites More sharing options...
swooshdave Posted June 30, 2008 Report Share Posted June 30, 2008 Could be bad ignition or just the wrong plug. Or too much oil in the fuel (is the automatic oiler still on the bike?). Quote Link to comment Share on other sites More sharing options...
shooter308 Posted June 30, 2008 Author Report Share Posted June 30, 2008 (edited) Oops.....Sorry I guess I should've mentioned that stuff also. I put a brand new NGK B7ES spark plug in it. I put a brand new mix of 32:1 Castor 927 pre-mix into the tank as it was bone dry when I got it. I would think that the spark plug and fuel mix should be good to go now, just no spark. The factory automatic-oiler is non-functional, so I just pre-mix the fuel with a ratio rite bottle - I have an 85 Honda atc250R so it's easy to just make enough mix for both. Was there a common problem with the factory coils on the TY bikes going out? What would cause a weak spark and plug fouling? My wife wants to learn how to ride a motorcycle again (she hasn't been on a dirt bike in over 10 yrs) so she can get her motorcycle license. I figured that you can't get much better balance control than from a trials bike, so I want to get this bike running ASAP. Thanks, Doug Edited June 30, 2008 by Shooter308 Quote Link to comment Share on other sites More sharing options...
swooshdave Posted June 30, 2008 Report Share Posted June 30, 2008 Check points gap. Check points. Condensers can be bad from new. So not unusually to replace what you think are good ones. Quote Link to comment Share on other sites More sharing options...
shooter308 Posted June 30, 2008 Author Report Share Posted June 30, 2008 I figured I'd check the points, but I have to wait to get a flywheel puller first. What is the gap on the points for these old bikes? When my best friend had the bike, he sold it to our mutual friend and gave him the title to the bike, a Yamaha service manual, and a flywheel puller. But since he passed away last fall, his wife doesn't know where they are...... Looks like I'll be selling the custom water cooled gaming desktop pc I just built to afford to buy the electronic ignition from bjracing.com...... Quote Link to comment Share on other sites More sharing options...
tony283 Posted June 30, 2008 Report Share Posted June 30, 2008 Very unusual for there to be much wrong with the top coil on any of he 70's TY models. With an older bike remember the gaps on the ignition system need to be set acurately. 15 on the points and 22 on the plug. A lot of plugs, even the correct one that you are using, come new with a much wider gap. New points sometimes come with a coating on that needs to be polished off before they will spark correctly. In your case before you go to all the expense ($300 +) for an electronic system start by cleaning the points, a small nail file will do if you are not taking the flywheel off. They will often have a "blackspot" on them so file back to bright. Check your plug gap and then the plug cap to lead which often goes rusty on the wire. Next check the wiring loom where it comes out of the case and feel along it. This will often become hard and brittle in which case just replace the wire, the black one is the hot wire. Disconnect the kill switch wire. If you still have no spark it will either then be the top coil (unlikely) or the source coil on the stator plate (left side) lower or the condenser. Always change the condenser and the points at the same time. Good luck. Tony Quote Link to comment Share on other sites More sharing options...
shooter308 Posted June 30, 2008 Author Report Share Posted June 30, 2008 Thanks for the info Tony..... So if I read your post correctly, I can check the points gap and clean them without taking off the flywheel? That would be nice to be able to at least get it running while I wait for the new tune up kit to show up that I ordered. Thanks again, Doug Quote Link to comment Share on other sites More sharing options...
02-apr Posted June 30, 2008 Report Share Posted June 30, 2008 I assume the 250 is the same as the 175 in that the specified points gap is given as a tolerance between a maximum and minimum gap. The timing is adjusted solely by changing the gap. When the points go beyond spec to get the correct timing then you put new points in. All this is from 30 year memory so may not be correct for the 250. Timing is 1.8mm BTDC (I think). No doubt there are plenty on here who can correct me if I am wrong. I can't remember what the tolerance was but it could be that the "traditional" 15 thou points gap is nowhere near correct. Quote Link to comment Share on other sites More sharing options...
shooter308 Posted July 1, 2008 Author Report Share Posted July 1, 2008 I was just wondering if anybody here on the forum has tried to convert the TY points ignition over to electronic via parts from another yamaha bike i.e. DT, IT, etc.? I was just wondering if it could be done any cheaper than say the $410 kit from bjracing.com? Quote Link to comment Share on other sites More sharing options...
swooshdave Posted July 1, 2008 Report Share Posted July 1, 2008 I was just wondering if anybody here on the forum has tried to convert the TY points ignition over to electronic via parts from another yamaha bike i.e. DT, IT, etc.?I was just wondering if it could be done any cheaper than say the $410 kit from bjracing.com? If you are looking for a cheap solution I'd suggest getting the stock system working. That has to be horribly less expensive than either a electronic kit or hacking something up. As for converting another model to the TY you need to check the flywheel for compatibly. Quote Link to comment Share on other sites More sharing options...
shooter308 Posted July 6, 2008 Author Report Share Posted July 6, 2008 Okay, I've got the flywheel off and I'm gonna clean the points. How do I gap the points? I can spin the flywheel around, but I cannot see the points open and close. At what point should the flywheel be for the points to open up? Thank you very much for all of your help. Doug Quote Link to comment Share on other sites More sharing options...
shooter308 Posted July 6, 2008 Author Report Share Posted July 6, 2008 I got it figured out. I don't have a manual for the bike yet, but I cleaned the points up really nice, and then adjusted them to where they would at least open up. Then I adjusted them to .015" and re-gapped the spark plug to .022" and it has a nice healthy blue spark to it now. It seems to run really good now, so I'll be teaching my wife how to ride a motorcycle again..... 1 Quote Link to comment Share on other sites More sharing options...
tony283 Posted July 7, 2008 Report Share Posted July 7, 2008 Well done, you figured out the holes in the flywheel are there for a reason. Sounds like you have done a good job, very satisfying and a whole lot cheaper than the electronic option. If it has the oil injection disconnected run on a good mix of 40:1 and bear in mind that our current fuel is not that good and quite often has to be completely replaced with fresh. Other problems to frustrate you will be the old carb. Clean the inlet plunger for the float with a very light emery as these will stick closed or open and make sure you have a new in line filter between the carb and the tank. Remember the Carb rules 1 No start = blocked Choke/Enrichment circuit. 2 Starts but won't run off choke= blocked Pilot. 3 Poor pick up= airscrew or pilot jet size ..... you need a 30 or 35 ITS FUN! Tony Quote Link to comment Share on other sites More sharing options...
Tillerman6 Posted March 12, 2021 Report Share Posted March 12, 2021 On 6/30/2008 at 12:24 PM, shooter308 said: Oops.....Sorry I guess I should've mentioned that stuff also. I put a brand new NGK B7ES spark plug in it. I put a brand new mix of 32:1 Castor 927 pre-mix into the tank as it was bone dry when I got it. I would think that the spark plug and fuel mix should be good to go now, just no spark. The factory automatic-oiler is non-functional, so I just pre-mix the fuel with a ratio rite bottle - I have an 85 Honda atc250R so it's easy to just make enough mix for both. Was there a common problem with the factory coils on the TY bikes going out? What would cause a weak spark and plug fouling? My wife wants to learn how to ride a motorcycle again (she hasn't been on a dirt bike in over 10 yrs) so she can get her motorcycle license. I figured that you can't get much better balance control than from a trials bike, so I want to get this bike running ASAP. Thanks, Doug Doug- I had one problem like that last time and it was a corroded ground connection at the high voltage coil where the wire attaches to the frame. Another thing to check is to be sure there is no ground on the kill switch wire- If you have the stock kill switch you want the red square not to be showing when starting. also leave the throttle closed to start- that works better for me. And make sure the points are clean and dry. The voltage at the points is so low that any oil or residue on the points and it will not make any sparks. I will be trying to make sparks on mine tomorrow- may run into the same problem- I changed most of my wiring around and eliminated the lights completely. By the way- you need a very sensitive low ohms range ohm meter to check this stuff out. The stator coil windings are thick and few, and the resistance to ground only changes about 0.1 ohm when the points open- impossible to catch with a garden variety ohm meter. Some guys use a battery and a 6 volt tail light bulb across the points- when you see the light change color- that is when the points open- very subtle. Anyway, the stator coils and the HV coil primary are in parallel all the time to ground. When you ground out that line on the handlebars, it prevents that tiny voltage from reaching the HV coil primary. The kick comes from the magnetic field collapsing when the points open about 3 degrees before top dead center. There is no spark advance on the stock TY 250 A if you were wondering. A timing light is really not useful. Good luck! Quote Link to comment Share on other sites More sharing options...
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