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XR75 mystery electrical problem- help!

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First time poster here, so bear with me.

I have a 1975 XR75 that is being restored from the ground up. I came across a running motor that went into the original frame of the same year. After assembly and going through the top end, adding a new carb, gaskets, etc., I could get it to run, but it would "pop" back through the carburetor and would not reach maximum rpm. I decided to change the points and condensor as a precaution because they appeared to be the originals. Got new points/condensor from Sudco, pulled the flywheel, installed the parts, set the point gap, etc. per the manual and put everything back together. No spark. Nothing.

After a day or two of violent swearing, I took the whole bike to the local Honda shop and explained the problem--assuming that they would find a bad connection or something similar. They had the bike for several weeks, and could find nothing wrong. We thought that I might have by chance gotten a bad condensor, so I had them install a genuine Honda unit and resoldier everything. Still nothing. I took a spare parts motor to them with a different ignition and coil. They "mixed and matched" parts and still got nothing. I read on a TT forum that if the washers are mixed up on the points, things will ground out and it will appear to have no spark. I trucked myself back down to Honda and told them to check that out. They found one washer out of place, so they put the washers back in proper order. Still nothing.

At this point, the mechanics and I are clueless. The odds of having not one, but two bad stators are extremely low, and I've never seen one just "give up" after changing points and condensor. We have no idea where to go with this. I'm not an electrical expert, but that ignition is not at all complicated, so I can't imagine what the problem could be. I'll dig up a new stator if necessary, but I'm not certain that would fix the problem based on what I've seen so far.

I'm a Triumph guy, so I'm familiar with electrical issues, but this is ridiculous. Any help would be GREATLY appreciated.

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This is a very very typical story with points ignitions. The first thing I would suggest would convert to CDI (just ask starmoto), but if you're running the stock 4 speed, then I'm not too sure the flywheel would swap. One of the problems that I've notice over the years is the advancer in the flywheel doesn't advance properly. The springs are too weak, just plain broke, or rusted. If it's a 4 speed which is stock, you're going to run into problems getting parts. Unless you want to keep it stock for restoration purposes, you may want to look into a xr100 to put in there. Otherwise just keep an eye on ebay for parts.

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While the CDI was a great step forward for ignitions, there was life long before they came along. Points required regular and proper basic maintenance, CDI set and forget. Sorry socalxr but in the North West not a typical story at all to change points, loose spark and not even the dealer be able to figure out why. :thumbsup: Didn't the dealer check stator output........??? Check points to ground with a ohm meter when open, and for continuity across contacts when closed.......??? (New points can have a film on the contacts!) Check coil and condenser on tester....??? Man this is basic stuff for a dealer mechanic! :ride: Get yourself a Honda repair manual and it should walk you through how to check out the ignition components.

On the advancer springs I agree, and add you may have this problem with any well used advancer. The XR200 uses a advancer with CDI and can have this problem.

On after market points beware, there are some that will not allow you to get engine in time. Have a hunch distance between pivot shaft and contacts may be different then OEM. A friend of mine ran into this on a 69 SL90, and another guy on a SL100, OEM points cured problem.

Old School Al

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I've run and worked on point ignition vehicles for years with no issues, here is what you need to do:

1) Pick up a good shop manual and the bike

2) Don't worry about converting to CDI, as the XL engine has a different crank than the XR engines and you'll run into even more problems.

3) Make sure you don't have a coil from the wrong year of bike that has a condensor attached to it instead of having the condensor under the flywheel

4) Using the shop manual and an ohm meter make sure all wiring connections and wiring is in order.

5) Pull the flywheel and start over, make sure the points are clean by using a small peice of paper and squeeze the paper between the contacts as you slowly pull the paper out [don't rip the paper]

6) The wire must contact the contact points but must be kept from being grounded, [look at the diagram in the manual ]

7) Make sure the plug wire is making good contact with the plug wire

8) PM me if you have any questions

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2) Don't worry about converting to CDI, as the XL engine has a different crank than the XR engines and you'll run into even more problems.

It's a XR75 not and XL.

However, It may or may not be the original motor. That's why I suggested the swap. Depending on what motor is in there, I can't understand why anybody would suggest putting in any more time, grief and money into something that he and a $100 an hour Honda shop couldn't figure out. I'm pretty sure the Honda mechanics are more than capable. It takes about 20 minutes and $100-$125 to do the conversion and it will start first kick every time depending on the condition of the carb. I understand some people would rather work on bikes than ride them, but I would rather fix the problem permanently and ride.

Back to the problem, popping through the carb at high rpm is a more than likely a timming issue. Like suggested before OEM points might work. (I might even have a set lying around) But I would still check out the advancer inside the flywheel. Also, take a pic of the motor so I'll know version xr75 motor it is.

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Wow--this is a lot of info, and I appreciate it all. A few questions:

1. If I go the CDI route, what brand should I go with?

2. Again, if I add the CDI, is it a simple change, and can the stock flywheel be used without modification?

3. If I dig into the advance spring problem, what am I looking for? How do I tell if the springs are shot if they're unbroken and appear otherwise normal?

4. Which Honda repair manual should I use if I check the wiring/stator/etc. myself? I've got the Clymer manual for that model, but I don't think it gets quite that deep into ignition issues (but I haven't referred to it in awhile, either)?

My major problem at this point is cost. As it stands, I'm stuck with an ever-growing bill at Honda each time I ask them to tear into it again. I know the CDI may not be cheap, but if its a mod I can do myself, then it might be worth the investment. I'm just a little nervous because this bike started as a dirt-cheap project and its getting out of hand.

Again, thanks for the help.

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Forget the Honda Shop, like Racer suggested, just PM him with questions. Being a Z50 guy, he probably knows his stuff and is willing to help. :thumbsup: The correct manual ist the one with an old photo of a kid railing a berm on a XR75. His helmet say's "Matt" on it. The only way you can go the CDI route is if some stuck a five speed in it. If not, you can't do it. The brand of CDI is just a Honda CDI that came on all xr80's and 100's after 1992 (93 for the 80). You can get them on ebay all the time. I have two extra. You have to get them complete, cdi, coil, loom, stator, and flywheel. But pretty much everything is always on ebay at least 2 or 3 times a month. Being a Triumph guy, I'm sure you're a decent mechanic and these bikes are easy to work on. So forget the Honda shop. Just get that manual. If it's a four speed, I'm not the best guy for that. But there are a few four speed guys out there who know them like I know five speeds.

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Don't forget... It worked (kind'a) before you took it apart. Now it doesn't. When in doubt, start over. Get a manual, pull it apart, and reassemble very carefully.

Todd

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Ya I've got a few things kicking around here that are still running points, I didn't have enough room in my sig. to list them all :applause:

I may be a bit jadded, as I've seen alot of really shoddy work come out of dealerships :ride: so I wouldn't be too suprised if they didn't put alot effort into finding the problem. Just pick up the bike and go through everything methodically and take a break for awhile if you find you're getting frustrated. The ignition systems on these little bikes are about as simple as they get, so take your time, go through the manual and once you understand how they work I'm sure you'll have it up and running in no time :thumbsup:

If you want to know the year your the engine just let me know what the serial # is and I should be able to tell you.

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Boy...........I'm glad to hear there are a few people with enough mechanical aptitude to have a good basic idea of point ignition systems! What would some of these guys do if they actually had to figure out and fix something! :applause:

Man at the dealership level if a mechanic can't even figure out how to trouble shoot a point ign. system on a XR75 WHAT IN THE HECK is he going to do when a real problem comes along??? :thumbsup: For a non mechanic at home I can understand.............and with a little help and patience even they can figure it out! :ride:

By the way CDI ignitions are great..............but still need to understand the basics!!! :applause:

Old School Al

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Socalxr is predjudice against points ignition guys :ride: He tries to convert everybody.... lol

Ya, I'd have to agree with him, CDI is pretty nice to have on those little bikes. :thumbsup:

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Boy...........I'm glad to hear there are a few people with enough mechanical aptitude to have a good basic idea of point ignition systems! What would some of these guys do if they actually had to figure out and fix something! :applause:

Man at the dealership level if a mechanic can't even figure out how to trouble shoot a point ign. system on a XR75 WHAT IN THE HECK is he going to do when a real problem comes along??? :thumbsup: For a non mechanic at home I can understand.............and with a little help and patience even they can figure it out! :ride:

By the way CDI ignitions are great..............but still need to understand the basics!!! :applause:

Old School Al

Last winter one of the guys I snowmobile with took his snowmobile into the local Yamaha dealer complaining that it was missing. It was there all week and when he went to pick it he asked me to go with him. We get there and they tell him they haven't been able to figure it out the problem yet, they said it's got fuel, compression and spark but it still won't run. I ask him if they'd checked to see if the piston skirt was broken b/c the sled has rather high milage and when the cylinder gets worn, the skirt will eventualy break from the piston slapping around in the cylinder causing those symptoms. The mechanic just looked at me and "Oh, ah, no, umm... we'll check that right away." :applause: I told him not to bother we'd fix it ourselves and when we were about to leave they handed him a bill for $460, my friend payed the bill and we got back to my place and I pulled the cylinder and discovered.....Gee, big suprise, a broken piston skirt! My friend then brought the piston in to show the dealer what the problem was but they still wouldn't refund any of his money :applause:

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I've decided to get the XR back from the Honda shop. They insist that the shop "must have" checked stator output, continuity, etc. They seemed a little peeved that I asked such a question.

I'll attempt the fix myself. Does anyone have a copy of that manual that is mentioned? I can't seem to locate that particular one. My Clymer manual is good, but it makes it clear that it doesn't cover the '75 and earlier XR ignition repairs. Even if I could get just those pages on ignition troubleshooting, I'd be back in business (I hope).

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You should be the one that's peeved.......................hope you never paid them!!! This shop sounds like a real good place to stay away from!

Sorry no manual, someone should have one.

Old School Al

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Got the bike back from the shop today. I had them take off the flywheel again before I took it back so that I could look for myself or show someone photos of the stator plate, flywheel, etc.

Based on you guys' advice, I asked them if they had tested the stator, points continuity, coil, etc. They said that they had tested the coil with an "electrical tester" (I don't know if they mean an ohmmeter or what exactly), and it checked out fine. They also said that they checked the points for continuity a number of times, as well. I asked about the stator, and didn't get a clear answer on how they analyzed it. They said they checked all connections, etc., but that when a stator goes bad, there's really no way of confirming that. They also told me that all of the spacers and washers holding the points were in the correct order per Honda's manual.

I may take some photos of the stator plate, etc. and pm them to someone if it might help to actually see the stator and flywheel (?). I'll check the advance springs, too, to see if anything's obviously wrong.

:thumbsup:

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